Technical - General - 101 Most Popular Questions

Q1 I've just bought my first SLR and am confused about the way that lenses are described in millimetres. What do these figures mean?

The numbers are actually focal lengths, used to describe different types of lens. A standard lens is 50mm. Numbers lower than this - 35mm, 28mm, 16mm, etc - are wide angle lenses. Higher numbers - 80mm, 135mm, 200mm, 500mm, etc - are telephoto lenses.

Q2 Can you clarify just what the differences are between standard, wide angle and telephoto lenses?

A standard lens shows you the kind of view and perspective that you are used to seeing with your eyes. Wide angle lenses open up the field of view, bringing more of the top, bottom and sides of your subject into the picture. Telephoto lenses are rather like telescopes. They increase the magnification and bring far subjects closer. The longer the lens, the higher the number in its focal length and the greater the magnification. The wider the lens, the lower the number in the focal length and the more the scene is opened out for you.

Q3 Some lenses are described by two different focal lengths, such as 28- 85mm or 70-210mm. Why is that?

These are zoom lenses. Unlike prime lenses, which have fixed focal lengths and a single fixed degree of magnification, a zoom lens has a variable focal length. A 28-85mm zoom, for example, is a useful wide angle lens when set at the 28mm end of its range. At the 85mm end, it's an equally useful medium telephoto. Naturally, you can also use all the focal lengths in between so that, for example, in the middle of its range, it makes a good 50mm standard.

Q4 I want to buy my first accessory lens for my Pentax, but can't make up my mind whether to go for a prime lens or a zoom lens. A friend at my camera club told me that the quality of the picture I get with a zoom lens will be inferior to that with a prime lens. Is this true?

Today's zoom lenses are made to a much better standard than those of only a few years ago. While it's true to say that a zoom lens, in theory, still gives slightly less quality than a fixed focal length prime lens, it's equally true that in practice you'll be hard put to notice any difference in most circumstances. That's providing you stick with the better-known makes. Some of the very cheapest zoom lenses on the market might not be so good.

Q5 I've just bought a 400mm lens for my Canon AE-1 and was really looking forward to getting some great wildlife pictures with it. But every picture I take is blurred. I've never had this problem with my standard lens or the 70-210mm zoom that I've had for years. Is there something wrong with the lens?

Super-long telephotos like the one you mention need careful handling. First of all there is far less latitude for inaccurate focusing than in a shorter lens. You are using a manual focus camera and the merest twitch of the focusing ring can put a subject out of focus. Also, longer lenses are more prone to exhibiting camera shake, so you must use higher-than-normal shutter speeds if you are hand-holding the camera. With a 500mm lens you should use 1/500th second at the very least, and preferably 1/1000th second. For lower speeds, support the camera.

Q6 Just lately it seems that every picture I take has small, dark cut-offs in the corners when I use my 28mm wide angle lens. I didn't use to get this. Am I doing something wrong, or has something happened to my lens?

More likely, something has happened to your accessories. Have you suddenly started using filters that you haven't used before? Or have you bought a lens hood recently? Wide angle lenses, taking in a wider view than others, are more susceptible to vignetting - the cutting off of corners in your picture - because their field of view `sees' the accessory. This will happen if you use a lens hood made for a standard lens on your wide angle lens. It also happens if you add more than one filter to the front. It could also be a lens fault, but if it has only just started happening, it's unlikely.

Q7 I recently went to an exhibition, where I saw some beautiful pictures taken against the light. But when I tried the same thing on some landscapes, the results were flat and a line of funny-shaped blobs appeared diagonally across the print. Why?

In a word, flare. If you shoot directly into the sun, its light bounces back and forth off the elements inside your lens and reduces contrast. Result: a flat picture. Those blobs are probably the shape of your lens's aperture, and they too are caused by this reflection problem. With good lenses that have been coated in a special way, the problem is minimised to the point where you might not even notice it, but with cheaper lenses, it can be a problem. The answer is to use a good, deep lens hood.

Q8 What's the difference between a mirror lens and an ordinary telephoto lens?

With an ordinary telephoto, the elements inside are arranged in a straight line and the light travels straight through the lens from the front to the back. With a mirror lens, the light enters through the front element, is bounced off a concave mirror in the back of the lens, is then reflected back from another mirror behind the front element and finally exits through a small hole in the centre of that first mirror at the back. The result is a lens that is far shorter than a normal tele, but much fatter. Also, they usually have a fixed aperture.

Q9 I have an autofocus camera and thought that meant every picture I took would be sharp. But when I photographed two friends standing side by side, they were both blurred. What am I doing wrong?

When your friends were blurred, was the background sharp? Look through the viewfinder and you'll see a small rectangle. That's the area on which the camera automatically focuses. If, when you took your picture, that rectangle fell between your friends, the camera focused on the background behind them. The answer is to aim the camera so that the rectangle covers the subject you want sharp, then use your camera's focus lock control, re-position your aim so that you have the required composition, and then shoot.

Q10 I started by using colour film, but have just decided to switch to black and white. On a camera club outing, I saw another member, who always shoots black and white, screw a deep yellow filter on his lens. Why would you want to use coloured filters for taking black and white pictures?

In black and white photography, a coloured filter lightens subjects of its own colour and darkens those of its complementary colours. As a quick guide, think of the complementary of yellow as blue, red as cyan (a greeny blue) and green as magenta (a bluey red). So a yellow filter darkens the blue of the sky in a landscape and makes the clouds stand out better by comparison. An orange filter gives an even stronger effect and a red one makes things really dramatic.

Q11 I understood that a polarising filter in colour photography makes the sky darker. I tried it on some sunsets and nothing happened. Why?

First, a polariser only has its effect on a blue sky. Second, you have to rotate the filter, while looking through the viewfinder, until the effect is at its height. Third, a polariser only works well when you are shooting at right angles to the sun, never towards it or directly away from it.

Q12 What's the difference between a UV filter and a skylight filter?

A UV filter removes ultraviolet light. You can't actually see this light with the naked eye, but the film picks it up, making your pictures look a little misty, particularly around coastal areas of if you are in high mountains. Under these circumstances, a UV filter will add clarity to your pictures. A skylight filter takes out unwanted blue. Again, it's something your eye doesn't naturally see, but it's there when you shoot under a bright blue sky, especially in shadow areas.

Q13 A friend and I went out taking night pictures. We took the same shots from the same places, but when I saw his, all the lights had star shaped patterns coming from them which really added to the picture. What was he doing that I wasn't?

He was probably using a starburst filter, more technically known as a cross-screen. It's a clear filter with lines etched into it. In use, it produces flare lines emanating from all point sources of light. It is particular impressive on night pictures.

Q14 I've never used filters because I'm scared of getting the exposure wrong. Surely, if you put something coloured in front of the lens, it will cut down the light and under-expose your pictures?

You're absolutely right. But with cameras today offering through the lens metering, the camera will usually compensate automatically. The only time it might not be too accurate is when you are using red filters, which don't affect all meters the same way. The alternative is to resort to the filter factor, a number which is usually engraved on the filter mount. It signifies the amount by which you must increase exposure. If the filter shows a 2x factor, this means you should double the exposure by opening up one stop; a 4x factor means quadruple the exposure by opening up two stops, and so on.

Q15 I saw some really weird pictures the other day, in which the sky was green in one, brown in another, deep red in yet another. It couldn't have been done with filters because the landscape below was quite normal. So how was the effect achieved?

The effect probably was achieved with filters - graduated ones. These are deeply coloured at one of the edges, fading across the surface to clear on the other side. If you position them correctly, they will selectively colour just one part of the picture - in the case of the pictures you saw, the sky

Q16 My automatic camera gives me correct exposure, but I can't help thinking I'd do better if I knew what was going on inside. I hear people talking about apertures, but as a complete novice, I don't really know what they are talking about. Can you help?

The aperture is a variable size hole situated between the elements of your lens. As it opens and closes, it controls the amount of light that is let through to the film. Apertures are 'measured' in f-stops. The higher the f-stop number, the smaller the aperture; the lower the number, the wider the aperture.

Q17 It would be easier to remember f-numbers if they gave small apertures low numbers and vice versa. Why don't they do that?

The f-number is the result of dividing the actual diameter of the aperture of the lens into its focal length. So, in theory, a 50mm aperture on a 50mm lens would be called f/1. Halve the diameter of the aperture to 25mm and divide that into the 50mm focal length and you get f/2. And so on down the scale.

Q18 OK I now understand what apertures are. So what about shutter speeds?

The shutter controls the amount of time that light is allowed into the camera. The higher the shutter speed, the shorter the time that the shutter is open and the less light reaches the film.

Q19 If the aperture controls the amount of light overall and the shutter controls the amount of time the light is coming through the lens, surely they both control the exposure of film to the light. Why does a camera need both shutter and aperture?

For different types of picture. If you are shooting fast action and want to freeze it, you use a fast shutter speed, coupled with a wide aperture. On the other hand, in some pictures depth of field is important. This is something that can be controlled with the aperture. So you use, say, a small aperture for a great depth of field and couple that with a slower shutter speed. In the end, as you so rightly say, the same amount of light reaches the film, but it has been controlled in different ways for different subjects and different effects.

Q20 I've been thinking of upgrading to a new camera, but all the different metering modes available are confusing me. What's the difference between average, partial and spot metering?

The difference is the amount of the subject that the meter actually takes its reading from. Average metering covers the whole scene, with emphasis on the central and lower part of the subject. Partial metering restricts that view to less of the viewfinder, so it is more likely to react to the main subject, rather than to the scene surrounding it. Spot metering narrows the angle of view down even more so that you can take a reading from one small area of a subject that might be some way away.

Q21 If cameras today all have built-in meters, why would anyone want to buy a separate one, and do I need one to take better pictures?

A separate, hand-held meter is useful for taking readings close to the subject, when it would be inconvenient to move the camera. It can also often take readings from flash, which most camera meters can't. For most amateur photographers, however, the extremely sophisticated meters built into today's cameras are perfectly adequate, and it's doubtful that a separate meter would lead to better pictures.

Q22 Watching professional photographers on TV as they photographed tennis, I saw one use a separate meter and point it over his shoulder, away from the players. Is he mad or am I?

He was probably taking an incident light reading. Most meters, including all those built into cameras, take reflective light readings. In other words, they measure the light bouncing off the subject. By attaching a baffle to the cell of the meter, then placing it at the subject position, facing back towards the camera, you can measure the light falling on that subject. Because the photographer you saw couldn't walk on to the court and hold his meter under the nose of a tennis player, he was doing the next best thing, since the light falling on his back would be much the same as that falling on the player a few yards away.

Q23 But surely, if the photographer was wearing, say, a green jacket and the tennis player was all in white, then the light readings would be different?

No they wouldn't. Remember, the photographer is not measuring the light reflected from the subject, and so affected by its colour or shade, he is measuring the light falling on the subject, which is the same whatever colour is being worn.

Q24 I took some pictures of the sun across a lake, but the prints were all too dark. My camera's meter works okay, because the rest of the film was fine. What happened to the these pictures?

Even the best of meters can be fooled when one part of the subject is extra bright or extra dark. In this case, the sun was probably dead centre on the picture area and the meter, concentrating mostly on this area, was fooled into thinking the rest of the scene was as bright as the sun. Result: underexposure. The answer is to take a meter reading from the sky beside the sun, with the sun just in the corner of the viewfinder. Set that exposure manually and then re-compose the picture.

Q25 For years I've used colour print film, but I recently switched to slides. The results were really disappointing, with all the colour washed out of the pictures. Do all slides look like this or am I doing something wrong?

It sounds like your pictures are overexposed. With colour prints, if the negatives are overexposed, the problem can be compensated for in the printing. With slides, the film you put through the camera is what you end up with in the slide mount. There is no room for correcting the problem. If every picture on the roll is the same, it is possible that there is something wrong with your camera's meter which, when using print film, you've never noticed.

Q26 I was really disappointed with my holiday pictures this year. We went to the Lake District and I took a lot of landscapes. But when I saw the pictures, they all looked flat and boring. How can I improve things next time?

Landscapes that look impressive when you are there often look boring when reduced to the two dimensions of a photograph. One answer is to put back some of the depth by always including some kind of foreground interest - a gate, a large rock, even a person looking out over the scene. The eye then compares the foreground with the background and a sense of depth is conveyed, making a much better picture.

Q27 This is weird. On holiday, a friend and I took exactly the same picture of a tree against impressive mountain scenery. I lined the tree up in the centre of the viewfinder, but he turned the camera slightly so that the tree was at the side of the picture. I thought he was crazy at the time, but when I look at the two pictures, his is somehow much better than mine. The trouble is I can't say why. Can you?

It's all down to balance. A picture that shows a subject dead centre is boring. But put the subject to one side, so that it fills perhaps a third of the total area, then balance it with other smaller subjects in the background and, compositionally, the picture will always look better.

Q28 Whenever I take pictures of people, they always end up too small on the print, with lots of unwanted background. Does my viewfinder show a different scene to the one being recorded on the film?

Slightly maybe, but not enough to make any real difference. The problem is in the way you are using the viewfinder. When we look through a viewfinder, we tend to see only what's in the centre. Very few people can see the whole viewfinder at once, especially if you wear glasses, which means holding the camera further away from the eye than normal. So every time you take a picture, concentrate on looking at what's in the whole viewfinder. Hold the camera still and actually move your eye around all four corners. You'll probably be surprised to find what's being included.

Q29 I went with a friend to a camera club competition night. When discussing entries, the judge kept talking about 'leading the eye'. What did he mean?

Let's say you have a picture that has a pathway, running up to a cottage. As you look at the picture the pathway makes a natural lead for your eye. You follow it and, when you get to the cottage, you stop. Result: pleasing composition. Now take the cottage away and let the path wander out of the top or side of the picture area. The eye is led out of the picture - and that's something that should never happen in good composition. So use natural lines likes paths, fences, trees and the like to lead the eye into the picture, not out of it.

Q30 I've just tried my hand at portraiture for the first time. My model is a pretty girl, but we were both disappointed with the results. She seems to have the same expression on her face all the time and, in fact, looks bored in most of the pictures. She says she wasn't, so how can we both do better next time?

Try this. Get your camera set up and all the technical aspects sorted out first. Then forget the camera and concentrate on the model. Talk to her. Make her laugh. Get her to relax. If you just ask her to smile, chances are, she'll smile with her mouth but not her eyes. She won't realise that she is doing this, so remind her. One way to get a good spontaneous expression is to ask her to look away from the camera, then swing her head back towards you as you take the picture.

Q31 Why does the sun in my sunset pictures always look smaller than it did in real life?

It doesn't. It's just that your eye is being fooled in a way that the camera lens never is. The sun doesn't really get bigger as it approaches the horizon? It's an optical illusion caused by the fact that, at sunset, you can see the sun in relation to other nearby objects. In fact, the sun registers on 35mm film at a diameter of l mm for every 100mm of focal length. So, with a standard 50mm lens on an SLR or, worse still, a wider lens on a compact, it is going to register on the negative as half a millimetre or less. The answer is to use longer lenses. With a 200mm lens, it begins to look the way you thought you saw it originally. With 500mm and 1000mm lenses, it becomes enormous.

Q32 Some of the best flower pictures I've seen have been taken in a studio. But I don't like to cut flowers. How can I get the best results in a garden?

Make a portable background that you can put behind the subject. White or black card works fine. Also make a windshield to put on at least one side of the flower to stop it moving about in the breeze. At the close focusing distances this type of photography demands, it is essential to keep the plant still. Use a tripod, because close-ups increase camera shake. If the flower is not in sunlight, use fill in flash to add sparkle. Try using a fine water spray to add droplets to the petals. That can really enhance this type of subject.

Q33 I've been trying to photograph my dog, but I can't get him to look at the camera and he never looks lively in the picture, the way I see pets in other animal pictures. Any ideas?

Get a friend to stand behind you and hold a biscuit over your head. He'll look at the camera and will probably adopt an interesting expression as he contemplates food.

Q34 I keep reading in books and magazines that the best time of day to take pictures is early in the morning or late in the afternoon, but no one says why.

If you take pictures in the middle of the day, when the sun is high in the sky, the light is harsh and, coming from directly above, not very flattering for human subjects or even landscapes. At the start or towards the end of the day, the sun is lower in the sky. The light is more directional, which always gives a better interpretation of any subject. Also, the colour of the sun changes to a warmer, yellowy light which is more attractive, especially to landscape photography.

Q35 I bought some extra fast film so that I could take pictures indoors without flash, but the resulting pictures all had a sort of yellow-orange cast to them. How could I have prevented that?

Most colour film is balanced for daylight, which is far more blue than artificial light indoors, which tends towards red. Your eye doesn't see it, but the film does. To correct the colour cast, use a blue 80A filter.

Q36 Can you explain why side lighting on a subject such as a building gives a better picture that when the sun is shining directly on to its front?

Frontal lighting is flat. It casts shadows only directly behind the subject. Light from the side, or at any oblique angle, introduces small shadows in the texture of bricks or stone and so gives relief. The result is a far more pleasing rendition of the subject.

Q37 Why does the sun look more red when it rises and sets than it does at noon?

As the sun approaches the horizon, it has to shine through the atmosphere at an angle, and so through more of it - this filters out the blue end of the colour spectrum, allowing red light to get through.

Q38 Why does a polarising filter make the sky a darker blue, why does the ame filter reduce reflections in water, and is there any connection?

Think of light as a series of long, thin tubes, with rays bouncing about inside those tubes at random. When light is reflected from water or glass it is said to be polarised. Now it is as if the tubes have been flattened, and the light can only bounce back and forth in one plane. A polarising filter also polarises the light. So if you point one at reflections and rotate it, there comes a point when one cancels out the other and the reflections disappear. Since the bright blue of the sky is caused by light reflecting from moisture particles in the air, those reflections can also be reduced by the filter, making the sky look a darker blue.

Q39 When I was on holiday, I left my compact camera in the glove compartment of my car for a few days. When I came to use it, nothing worked. Why not?

Cameras have never liked excessive heat - and the glove compartment of a car can get pretty hot when the sun is shining all day. The computerised workings of modern compacts are particularly susceptible, as you've found to your cost. Moral: don't leave your camera in a hot car, especially in the glove compartment!

Q40 I don't use modern cameras. I like the older fully mechanical stuff. Recently, while photographing some river scenes, I dropped my camera in the water. I pulled it out and dried it off, but a mechanic has told me it is now beyond repair. Do you believe him?

Yes. Obviously you dried the outside, but the inside still remained wet and intricate little gears and chains can quickly corrode in the wet. Ironically, since your camera is not an electronic one, the best thing you could have done would have been to keep the camera in a bucket of water until you reached the repairer. Rusting takes place slowly underwater. Once damp steel surfaces are exposed to the air corrosion occurs at a much faster rate.

Q41 What are those little things like tiny bean bags that come packed with new cameras and lenses?

They're bags of a chemical called silica gel, that has the property of absorbing much more than its own weight of moisture. The bag keeps the equipment free from moisture in its packing. Don't throw these bags away. Keep one or two in your camera bag for the same reason. Every month or so, put them in a warm oven to get rid of the moisture they have absorbed and then return them to your camera bag.

Q42 I have just switched from normal batteries to rechargeable ones, but I can't get them to take a full charge. What's wrong?

Rechargeable batteries must always be fully discharged before you recharge them. If they are already half-charged when you start the recharging, they will not take the full charge. You can buy special units in shops like Tandy to fully discharge batteries, but you can get the same effect by putting them in a torch and leaving it switched on until the bulb goes out.

Q43 I am going on an archaeological trip that will involve a lot of dust. What's the best way to protect my camera gear?

Keep everything wrapped in polythene bags when not in use. Every night, clean inside and out with a fine-hair blower brush. Regularly turn the focusing ring on your lenses and feel for any slight resistance that might have been caused by even the tiniest grain of dust. Especially examine the pressure plate on the inside of the camera back to make sure no grains have stuck here to scratch the film. Be very careful with the surface of the mirror in your SLR. It's front silvered and very delicate and can mark at the slightest touch.

Q44 I'm fed up with the look of modern cameras and I'm thinking of buying a second-hand SLR. I have several different models in mind that I would like to compare. How can I get information about them?

Talk to Oldtimer Cameras. This is an organisation that sells photocopies of old test reports and they also have instruction books for a great many older cameras. Call them on 0208-953 5479.

Q45 What should I beware of when buying a second-hand camera?

Depends on the camera. If it's a Nikon, Leica or Canon, there's a chance that it has had professional use, and that's something to steer clear of. Look for tell-tale signs of more than average use: scratches around the tripod socket, lacquer wearing off regularly handled parts, dents in the bodywork. Test the camera on every speed. Make sure the aperture ring moves easily through all its settings. Set a slow shutter speed and a small aperture, then look through the lens as you release the shutter to make sure the iris is closing down and opening up again as the shutter fires. Ensure that the focusing ring is neither too slack nor too tight.

Q46 Even if a second-hand camera appears to function OK mechanically, how can I be sure the meter is working properly?

Put a film through it. Any dealer worth his salt will let you put in a film, take the camera to the door and shoot a few frames down the road. Shoot at all possible shutter speeds and apertures. With one-hour processing facilities available in most high streets, you can soon see if there are any problems before you buy the camera.

Q47 It started when I bought an old folding camera at a jumble sale. Then I found a few more in junk shops. Now the collecting bug has bitten. Where can I find out more about collectable cameras?

Why not join the Photographic Collectors Club of Great Britain? You'll find them at 5 Station Industrial Estate, Low Prudhoe, Northumberland NE42 6NP. They have regular meetings all over the UK where they buy and sell cameras, and produce a fascinating magazine for members. For other places to buy collectable cameras, look out for specialist fairs organised mostly in the south London area. Or visit a specialist shop. One of the best in the country is Classic Collection at 2 Pied Bull Yard, Bury Place, London WC1A 2JR.

Q48 My grandmother has given me a really strange old photograph. It's in a little velvet-lined case and appears to have been printed on a silver-coloured metal. Is it worth anything?

It sounds like you have a daguerreotype, the first commercially successful photographic process. Daguerreotypes were produced as positives on sliver-plated copper. There are thousands still about and an ordinary one fetches about �25. A few particularly appealing or rare examples, however, have been known to sell for as much as �500.

Q49 There has been a camera in our family for years. The name on the front says it's a Kodak and it folds flat when not in use. What I can't understand is the little trapdoor on the back that opens and closes and strange little stylus attached to the flap.

You've got an Autographic Kodak, but don't get excited, they're not rare! Kodak produced them by the million in the early part of the century. With the right kind of film inside, that flap was opened and the stylus was used to write details that then recorded on the film. Rather like an early do-it-yourself data back.

Q50 I have a bet on with a friend. He reckons some of these modern super-small compact cameras are the smallest ever made, but I'm sure there were smaller cameras made some years ago, that took 16mm film. Which of us is right?

You're both wrong! The smallest camera ever made was the Petal. Made by Sakura in 1948, it was only 30mm in diameter. It took six exposures on a tiny circular film.

Q51 I saw some pictures the other day, in which the main subject - a girl sitting on a fence - was beautifully sharp, but the background was completely out of focus. When I take pictures like this, you can still see all the details in the background. What is this technique called?

It's all down to depth of field. That's the zone of acceptably sharp focus in front of and behind the point at which you actually focus the lens. The pictures you saw had a shallow depth of field, so that the main subject was sharp, but the background was blurred. When everything is sharp all the way from the foreground to the far istance, then the picture is said to exhibit a deep depth of field.

Q52 How do I control the degree of depth of field?

Wide apertures give a shallow depth of field, small apertures increase it. Also, telephoto lenses reduce depth of field, while wide angle lenses op en it up. So for the kind of result you are after, you should use a long lens and/or a wide aperture. On the other hand, if you are shooting landscapes and want everything sharp all the way through the scene, small apertures and/or wide angle lenses help.

Q53 Does anything else affect depth of field?

Yes - the camera to subject distance makes a difference. The further you are from the subject, the greater the depth of field; as you get closer, so the depth of field is reduced.

Q54 I was looking at some horse racing pictures and all the riders seemed to be bunched up together, almost on top of one another. I'm sure that's not the way it really was, so how is the effect achieved?

This is a question of perspective, which is all about camera to subject distance. The further away the subject is from the camera, the more the perspective is reduced. So far objects that are behind each other will seem, in the picture, to be closer together than if those same objects were only a few feet from the camera. Now, if you use a telephoto lens to bring that far scene closer, you bring the distorted perspective with it. The short answer, then, is the longer the lens, the more the perspective appears to be shortened.

Q55 So do wide angle lenses do the opposite?

Yes. Use a wide angle lens close to some foreground object and the objects in the background will seem to be unnaturally far away.

Q56 I bought a macro zoom, and it certainly lets me get closer to small subjects than with my standard lens. But how can I get even closer?

The further you move the lens from the film, the closer it focuses. Focusing from between, say, 3 ft and infinity can be taken care of in the normal movement of the lens. But as you get closer, then the lens to film distances become more exaggerated. To get in really close, then, you must separate the lens from the body. Do that using extension tubes or bellows.

Q57 I've tried close-up photography, taking exposure readings with a separate meter because I didn't think the camera's meter would work when the lens was on tubes. But all my pictures were underexposed. Why was that?

Providing the extension tubes had a linkage between the lens and the camera body so that the aperture setting could be controlled in the usual way, you should have trusted the camera meter. Without it, you were setting the wrong exposures because as the lens is moved away from the body, the effective aperture gets smaller. When you are shooting at 1:1 life-size, for example, the effective aperture is two stops smaller than the setting on the lens - f/8 on the lens is really f/16. So work with coupled tubes and bellows and leave the metering to the camera.

Q58 I've been told that if I pan with the subject when shooting action, the results will be more dramatic. What does it mean and how do I do it?

This is the technique you use to get those pictures in which a moving subject is recorded relatively sharp, while the background appears as a series of blurred streaks. For the best results, set a slow shutter speed of around 1/30 second. Focus, either manually or automatically, on the spot.

Q59 I've been trying to take some of those pictures that make moving water look like clouds of cotton-wool. I know I have to use a slow shutter speed, but in normal lighting, I can't use one slower than 1/60 second without overexposing the pictures. Where do I go from here?

Use the slowest possible film, then add filters to cut down the light. Assuming you are using colour film, the filters must, of course, not affect the colour of the light. A polariser will reduce it somewhat, but for the best results use neutral density filters. They cut down the light without colouring it. Get your shutter speeds down to something like 1/4 second, 1/2 or even one full second and you'll achieve the effect you want. If you' re using black and white film, you can achieve the same result by adding red or blue filters.

Q60 What's the difference between slide film and print film?

Print film, which most people use, is developed to produce a negative which, in turn, is used to make a print. Slide, or reversal, film is processed to make a positive image which light shines through.

Q61 Since slides are so small, compared to prints, and since you have to hold them up to the light to view them, why would anyone want to use them?

Slides are really meant for projection. Project one on a screen in a darkened room and you might never want to look at prints again. Because slides are viewed by transmitted light, rather than reflected light, as are prints, the colours are far more saturated and vibrant.

Q62 What is a transparency?

It's another name for a colour slide.

Q63 What gives the best quality - fast or slow film?

Slow. Although the average film speed is ISO 100, many professionals go to ISO 50 when working with 35mm and there is a school of thought that says 35mm should never be used professionally unless it's Kodachrome 25, which is rated at ISO 25. Once you get past ISO 400, grain starts to become apparent, seen as a breaking up of the image with a granular pattern. With those super-speed films of ISO 1600 and above, obvious visible grain can't be avoided, so they should only be used for specialist photography, when you have no other choice, or when you actually want to exploit grain.

Q64 What is infra red light?

Light is made up of the colours of the spectrum, but there are 'colours' outside the visible spectrum that we can't see. Infra red is one of them.

Q65 So if you can't see infra red, why is there infra red film?

Although the eye can't see infra red, the film is sensitive to it and therefore can 'see' it. Consequently, pictures taken with infra red exhibit strange colours. Add coloured filters and the effects are even stranger. Purple trees, green skies and yellow clouds appear as if by magic.

Q66 I've just started developing my own films, but when I make the prints, they are full of little white marks. How can I get rid of them?

The marks are probably on the negatives and caused by minute particles of dust clinging to them as they dry. So always hang your film up to dry in a warm, dust-free atmosphere.

Q67 I find difficulty in focusing my enlarger accurately and, even when I think everything is sharp, the print always looks blurred. How can I cure this problem?

Always focus the lens at its widest aperture, then close it down a few stops to a smaller aperture before printing. It's a bit like the way a small aperture increases depth of field on a camera lens, except in this case it has the effect of widening the zone of focus on the baseboard, thus compensating for any small discrepancies.

Q68 I've developed and printed black and white film for years and want to make the move to colour. But I'm told temperature control is far stricter and that makes me nervous of starting. Is there an easy way of keeping everything at the right temperature?

The cheap way is o put chemicals and tank in a bowl of water with a thermometer in it, then simply add hot water from a kettle as you see the temperature beginning to drop. he more expensive - but much simpler - way is to invest in a processor that does it all for you with a thermostatically controlled water bath.

Q69 A darkroom fanatic I know takes ordinary pictures and produces prints that are all black and white with absolutely no grey tones at all. He won't tell me how he does it, will you?

He probably uses lith film. Kodalith is a good example which, when developed in its own chemistry, gives exactly the effect you describe. Buy it from a specialist dealer in sheet form and enlarge a negative on to it just as you would if making a print. Because the film is orthochromatic and not sensitive to red light, you can use it with a red safelight. You have now made a positive, which can be contact printed with another sheet of lith to make a negative, from which you make your print.

Q70 My black and white prints always look too light and flat without the sort of contrast I really want. Why?

It sounds like you might be taking them out of the developer too soon before the shadow areas have had time to fully develop.

Q71 You may be right, but the problem is that if I leave them in the developer for the full 60 seconds, they go too dark.

That's because you are exposing them under the enlarger for too long. Keep your developing times standard and vary exposure under the enlarger for the best results.

Q72 Why is it that whenever I try to load a developing tank, the film always gets stuck half way?

Perhaps you haven't dried the spirals properly. It isn't enough to merely wipe them over with a cloth because water droplets will remain between the grooves. Instead always leave the spirals and tank to drain naturally after developing a film. If you still get problems, try running the point of a pencil around the spirals before you start to load. It clears away any small obstructions and the graphite in the pencil also helps to lubricate the grooves.

What's the difference between an automatic flashgun and a dedicated one?

An automatic flashgun - and most are automatic these days - measures the amount of light emitted by the tube as it falls on the subject, then quenches the light when it has given enough exposure for a given aperture. A dedicated gun does that too, but in addition it mates with the electronics in the camera to make sure the correct aperture and shutter speed have been set before firing.

Q74 If a flashgun's light is briefer than the camera's fastest shutter speed, why do we need to set speeds at all with flash photography? Wouldn't the aperture be sufficient?

Yes. The shutter speed does not affect exposure in flash photography, only the aperture.

Q75 So why do we have to set a specific shutter speed when shooting with flash?

This is only the case with single lens reflex cameras that have focal plane shutters. With such a shutter, first a blind opens, then another one closes. With slow shutter speeds, one blind is fully across and the whole of the film area is exposed before the second one closes. With speeds faster than the synch speed, the second blind starts to close before the first one is fully open. So the film area is never fully exposed all at the same time and, if you use flash with one of these faster speeds, you'll only record a portion of the image on film.

Q76 Can you set speeds slower than the synch speed when using flash?

Yes. In fact, some very interesting results can be had that way, combining blur from natural light and slow shutter speeds with frozen action from the flash. Try the technique on a dancer.

Q77 What's the difference between first curtain flash synchronisation and second curtain?

The most common is the first. The flash fires as the first shutter blind opens. With the second, it fires just before the second blind closes.

Q78 Is there any difference in the final picture?

Only if you are taking one of those `blur combined with frozen action' pictures. If, for example, you are photographing someone running across the frame, first curtain synchronisation will freeze the runner at the start of their movement and the blur will record in front of them. With second curtain synchronisation, the blur records first and the runner is frozen in front of it. The effect looks far more natural.

Q79 Many modern cameras seem to have built-in multiple exposure devices. But I have an old Praktica. Can I still make more than one exposure on the same frame with it?

Yes, with a bit of a fiddle. Take your first exposure. Now take up the slack in the cassette by turning the rewind knob until it stops. Put your finger on the rewind button, keeping it depressed while you clamp your thumb on the rewind knob to prevent any film movement, and carefully advance the film wind lever. That should have cocked the shutter and freed the double exposure prevention mechanism so that you can now make your second exposure on the same frame.

Q80 I saw a picture recently in which a tree, shot against a clear sky, had been superimposed over a face portrait, shot against a black back-ground. Surely if this had been a double exposure, the brightness of the sky would have burnt out that black background on the second exposure. If it wasn't a double exposure, what was it? Has anyone ever seen those abstract pictures that are made up from streams of light in regular but extremely intricate patterns? What are they and how can I produce them?

Probably a slide sandwich, produced by binding two slides in the same mount and then, if you want to take the technique further, making a print from them. Double exposures put bright subjects from one picture in the dark areas of another. Slide sandwiches, on the other hand, overlay the light parts of one picture with the darker areas of another.

Q81 How do you get that effect where an image looks sharp, but with sort of blurred edges?

Sounds like soft focus. With this technique highlight areas spread into shadow areas, so that although the picture is technically in focus, the boundaries between light and shade are blurred. You can achieve the effect by the simple use of a soft focus filter. A cheaper way is to stretch a piece of black nylon across the lens or even to smear Vaseline on an old filter and attach it to the front of the lens.

Q82 What happens if you use a soft focus filter on the enlarger lens?

Almost the same as with a camera lens. The only difference is that, when you make a print, the 'subject' is a negative, so the effect works in reverse. In the final picture, instead of the highlights spreading into the shadow areas, the shadow areas spread into the highlights.

Q83 Has anyone ever seen those abstract pictures that are made up from streams of light in regular but extremely intricate patterns? What are they and how can I produce them?

They could be physiograms. All you need is a camera with a B setting, a torch and a piece of string. Tie the string to the torch, pin it to the ceiling and position the camera directly beneath. Draw the curtains so that the room is completely dark, then swing the torch in a circle. Open the shutter on B, leave for about a minute, then close it again. With an average speed film of ISO 100, an aperture of f/5.6 makes a good starting point for experimentation, and coloured filters on the lens give different effects. Every time you try the technique you'll get a different result.

Q84 My friend showed me a print that was half positive and half negative. How do you think it was done?

He's been experimenting with solarisation. You get the effect when the film or print is exposed to light half-way through development. The simplest way is to try it on prints. Expose the paper in the normal way. Put it in the developer and, when the image begins to appear, flash the room light on and off, then continue development in the normal way. Sometimes it works, sometimes it doesn't. Sometimes it works better than other times. Keep experimenting for the best effects.

Q85 The most impressive action picture I've ever seen showed a footballer in the centre of the frame with lines of blur exploding out all around him. It really gave an impression of action. How was it done?

By using a slow shutter speed, matching it with a small aperture and zooming the lens during the exposure. Start with the zoom at the telephoto end and zoom towards wide angle as you expose.

Q86 I saw a irthday card recently in which a girl's face had clouds all over it. I'm sure they weren't painted on, so how can I get the effect photographically?

Photograph clouds on slide film, then use a projector to project the slide on to a face. Shoot the resulting image with tungsten-balanced film, or with daylight film and an 80A filter since the light source is artificial.

Q87 Everyone says my pictures are good enough to make money. But where do I sell them and how?

The big thing to remember is that you won't sell the pictures you fancy taking. You have to take the pictures that editors and picture buyers want. So you must do market research. To help you further, there are two books, published by BFP Books, which are invaluable. The BFP Book of Freelance Photography tells you everything you need to know to get started in freelancing; The Freelance Photographer's Market Handbook details hundreds of markets for your pictures in the UK. You can get them both from BFP Books at Focus House, 497 Green Lanes, London N13 4BP.

Q88 How does an amateur go about market research?

First get hold of a magazine that you would like to work for. Look at it very closely to see how they use their pictures. Are they single pictures with no reference to articles? If so the magazine might want file shots. Are the pictures all tied in with the articles? That means they want words as well as pictures. What are the subjects they cover and can you cover something similar? Having worked that out, go out and shoot, tailoring your way of working as close as possible to your intended market.

Q89 What is the best film to use for publication?

It depends on the market. If you are aiming at a magazine that uses only colour, send them slides. A few magazines today are beginning to accept colour prints, but the vast majority still prefer slides for reproduction purposes. If the magazine uses only black and white - and a lot still do - then send them black and white prints.

Q90 A professional photographer told me that it's impossible to sell 35mm. Is that true?

No. Most magazines today are happy to take 35mm for inside pages. For covers, however, medium format is usually preferred. Having said that, the freelance who can supply the larger format always increases his or her chances of success over a 35mm photographer.

Q91 What about other markets - calendars and greetings cards, for example?

These are two markets that do demand the larger formats. Only a few calendar companies take 35mm and almost no greetings card companies take the format. If you want to make contact with them, there is a list of companies in The Freelance Photographer's Market Handbook.

Q92 Is it worth using an agent?

Not at the start of your freelance career. Agents need photographers who think commercially right from the start and you only learn to do that by selling your own pictures first. Also agents won't deal with just one or two pictures the way magazines and the like might. They usually want to see a few hundred pictures from you initially and would like a commitment to say that you can keep supplying similar quality at regular intervals. Agencies are not for the inexperienced.

Q93 Aren't agencies a bit of a rip-off anyway? I've heard they take 50 per cent of your profits.

They do. But they also earn them. Don't forget that an agency has overheads, staff and a filing system to organise and maintain. Also they can find markets for you that you might never find for yourself and they could end up selling your pictures more than once. If you are professional enough to deal with an agency, the commission they take is worth every penny.

Q94 How do I approach a magazine?

Look on the contents page, where you will usually see a staff list and an editorial address. If the staff is small, write direct to the editor. If they have different people for different departments of the magazine, write to the person who deals with your subject.

Q95 Why should they buy pictures from an unknown like me?

Quite simply because they need pictures for every issue. Most magazines are crying out for the right kind of contributions. They won't buy what's wrong for their market. But if you get it right, they'll welcome you with open arms - irrespective of whether they've heard of you before or not.

Q96 Why do the people in my pictures suffer from red eyes when I shoot with flash?

When the flashgun is close to the lens, its light reflects off the red areas at the back of the eye and bounces straight back to the lens. Red-eye reduction systems help solve the problem by giving a pre-flash that makes the pupil of the eye close up before the main flash, so reducing the effect. But the problem never totally disappears unless you move the flash away from the lens - impossible with a built-in flash, but easy enough with an extension cord if you are using a separate flashgun.

Q97 Thinking about upgrading my SLR, my local dealer keeps telling me how much I need one with a depth of field preview button. What is it? Do I really need it? Or can I manage without it?

Of course you can, but it's a useful device when focusing is critical, particularly if you do a lot of close-up photography. Since SLR lenses focus at full aperture, only closing down to the taking aperture at the moment of exposure, you won't usually see the correct depth of field, as it will appear in your picture, when you look through the viewfinder. The depth of field preview button solves that by stopping the lens down to the taking aperture so that you can see its effect before taking the picture.

Q98 As storing film in the fridge prolongs its life, can you also freeze it?

Yes, in fact the manufacturers store it frozen. But let it thaw for 24 hours before use or you'll suffer condensation problems inside your camera.

Q99 This summer, I suddenly got interested in photographing buildings, but I don't like the way the sides of a building seem to converge when I point the camera up. How can I cure this?

You're suffering from converging verticals. The expensive answer to the problem is with a shift lens, which offers a rising movement of some elements, allowing the top of a building to be included in the picture without actually tilting the camera - the major cause of converging verticals in the first place. A cheaper solution is to switch to a longer lens and, where possible, move further back. That way, you might be able to frame the building without tilting the camera.

Q100 I want a longer lens but can't afford to buy one. What are the good and bad points of teleconverters?

A teleconverter fits between the camera body and lens, increasing the focal length of your lens, and does so for less than you'd pay for an extra lens. Buy one from a reputable, top-class lens manufacturer and the quality should be fine. Buy a cheaper one and the quality might not be so good. If you have the choice of a converter with, say, five or seven elements, always go for the one with the more. The few extra pounds you pay will ensure better pictures. And don't forget that using a 2x converter reduces your effective aperture by two stops

Q101 How can I really get to be a better photographer?

Go back to question one and start again!