Choosing A Digital Camera

Dear Reader,
I wrote this article to help you choose your next camera. I am not going to recommend any specific brand or model: Instead I am going to tell you things that are good to know when you walk into a store to buy a camera.

For example, does the camera focus quickly enough to get the shot and does it have a good viewfinder where you can actually see what you want to photograph?

Or, how good is the sensor at knowing what you are pointing your camera at? Cameras are amazingly good nowadays at working out exposure, but they are not foolproof and they are not all the same.

The Size And Weight Of The Camera

The best camera is the camera you have with you, so you had better be comfortable with the size and weight.

Time and again I read about people who want a lighter camera to replace the one they have. So they must have learned the hard way after they bought the camera that it was just too heavy for them.

How About The Camera In Your Phone

I shot this photo with an iPhone. For some subjects, mainly those that don’t move, it can do the job.

To some extent you can adjust the exposure on the iPhone by tapping on the lighter or darker parts of the scene. And there is a digital zoom on the iPhone, too. But it’s pretty limited as a tool for serious photography.

The point is that there is always a trade-off in photography, and somewhere in the huge range of what is available, there is the sweet spot that works for you. But it will be a compromise. A camera that can shoot a landscape and show the detail on every leaf is not going to fit in your pocket.

Some people have two cameras – one to have with them wherever they go and one for more ‘serious’ work.

So we start with the super-compacts that fit in a shirt pocket and progress up to SLR cameras (SLR is short for ‘single lens reflex’ and I’ll explain what that means shortly).

I took this shot with a dSLR and I don’t think there is any way I would have got the shot without using a camera with an adequately sized sensor. A compact camera with a tiny sensor might take the shot, but the quality wouldn’t be there.

Seeing What You Are Shooting

SLR means ‘single lens reflex’. With SLR cameras, you put your eye to the viewfinder. The viewfinder is about half an inch or so above the lens and the light from the subject comes directly through the lens and up into the viewfinder via a series of mirrors and prisms.

The advantage of that is that there are no parallax errors. What you see is what the camera lens sees.

Looking through the viewfinder of an SLR is like looking through a periscope in a submarine; it’s just that the periscope is only a half an inch tall.

SLRs are called ‘reflex’ cameras because the mirror that diverts the light that comes through the lens and sends it up to the viewfinder, flips up out of the way for a fraction of a second when you take a shot and then back again.

It has to do this because in its normal position it covers the sensor, so it has to flip out of the way to let light fall onto the sensor when you take the shot.

And when the mirror flips out of the way, the scene in the viewfinder goes black for a moment.

Exactly how long that moment is depends on how fast the camera shutter fires.

Rangefinder Cameras

There are other ways of seeing the scene. Rangefinder cameras have they viewfinders to one side of the lens and there is no prism connecting the viewfinder window to the lens. Because that viewfinder window is slightly to one side of the camera lens, you see the scene from a slightly different vantage point to what the lens sees.

Now you may think that having the viewfinder a half inch away from the line of the lens wouldn’t make much difference and its true that for something like a general landscape shot it doesn’t make much difference.

But for subjects that are closer to the camera it makes a definite difference.

You can test that yourself by holding your finger in front of your eye and then moving your eye half an inch to one side. The view you see is quite different.

The viewfinders in top of-the-range rangefinder cameras show an area around what the camera lens sees and they have frame lines projected within the viewfinder that shows you what the lens sees.

And those frame lines are coordinated with the lens focusing mechanism and they slide across the viewing area as the photographer focuses the camera and thus compensate for ‘parallax error’ – the name given to this difference between what you see in the viewfinder and what the lens sees.

The fact that with rangefinder cameras the photographer sees beyond the frame lines is one of the reasons they are popular with some photojournalists.

They claim that instead of, as it were, holding one’s eye to a keyhole and peering through it, the photographer sees more of the scene around what the lens sees and so is able to compose the shot more effectively and more quickly.

Henri Cartier-Bresson

Henri Cartier-Bresson, voted the world’s foremost photographer of the 20th century, used a Leica rangefinder camera.

No one claims that all his shots were world-beaters, but in my opinion he understood the way three-dimensional reality translates into a two-dimensional image, and using a rangefinder and being able to see around the subject may have helped him to frame his subjects so well.

Looking through a book of his photographs (his book The Europeans is a good example), you can see shot after shot where he makes three dimensions come to life on the flat paper.

Leica and Fuji are the only current manufacturers of rangefinder cameras with optical viewfinders.

There are other manufacturers – such as Olympus, Sony, and Panasonic – that make cameras that use electronic viewfinders, and I’ll say more about them later.

Compact Cameras And LCDs

With a lot of compact cameras, instead of a viewfinder, you look at the LCD – the Liquid Crystal Display – that displays the scene electronically on the back of the camera. And that is how you compose your shot. Which is OK if it suits you and if you can see the subject in the LCD.

One problem with LCDs is that in sunlight they can be very difficult to see. And if you want to take a shot outside on a summer’s day, it’s no good if you have to find a dark corner to stand it to see the LCD properly.

Looking Through The Viewfinder

It’s time to put this into practise. Grab a camera from a friend or take a trip to your local camera store. Look through the viewfinder of an SLR at a general scene – nothing too close – a street scene is fine.

Choose something in the scene that you want to be able to see clearly. Imagine it is your loved one standing across the street. Now try the same thing with a compact camera.

Now your loved one is either a tiny dot at the end of a long tunnel (the view you get with the viewfinders on compact cameras) or he orshe is a tiny figure in the LCD. Either way, how are you supposed to check that he or she is smiling or is in focus? You can’t.

Which is not to say that compacts are no good; and they can take some very good shots. But you should know their limitations.

Later in this guide I will talk about how compact cameras with small sensors manage to get the subject in focus, and the advantages and disadvantages of this.

Shooting What You See

Being able to see the subject is important, but so is being able to shoot what you see.

That is easy enough if the subject is a vase of flowers. Then you can put your camera on a tripod or prop it on some books – which you might need to do if the light is low – and gently press the shutter.

But what if the subject is moving?

It is important then that you can choose a fast shutter speed (see below about sensitivity) to freeze the action. However, it is also important that the delay between the moment when you want to take the photo and the time when the photo is actually taken is as near to instantaneous as possible.

The time lag between these two moments is made up of two parts. The first is the time the camera takes to focus. The second is the delay between the moment you press the shutter and the time when the shutter actually fires and the sensor records the light streaming onto it.

The first is easy to detect. Pick up a camera and point it at a variety of subject in good light and in poor light. Point the camera at a blank wall. Can the autofocus mechanism detect enough variation in the wall to be able to focus? Does the camera ‘hunt’ in an out looking for the point of focus?

Does it perform as well in poor light as well as it does in good light? These things are easy to test for yourself.

The second part of this lag – the delay between the moment you press the shutter and the time when the image is recorded – is called shutter lag and is easy to overlook when shopping for cameras and comparing them.

Shot To Shot

And it is not just the time to the first shot that is important. Some cameras are quite speedy in getting off that first shot, but then slow down while the mechanism re-cocks itself or sometimes while the camera processes the image so that you can take a second, a third, and more shots. That is when the shot to shot lag is important.

Just to be clear that we are not talking in seconds here. We are talking in milliseconds. Good quality SLRs might have a shutter lag of around 50 milliseconds. Some compact cameras may have a shutter lag of five or six times as long as that.

Would you be content to have to wait one half second between the time you press the shutter and the time that the mechanism actually records the image?

That is why I think it is a good idea for anyone buying a camera to pick up a good SLR and focus and shoot with it, even if they have no intention of buying an SLR.

That way you can form an impression of how speedy cameras can be. You might be in the relatively low light of a camera store when you do that test, so make sure to set a fast shutter speed on the camera.

Remember, you are testing the focus and shutter lag – everything else (image quality, etc.) are secondary to finding out how quickly the camera can actually focus and shoot.

Image Quality

Digital cameras have an array of micro-lenses that capture the light coming onto them. An ‘array’ is a collection of lenses laid out in a pattern. Imagine a rectangle about as big as your thumbnail. That is about the size of the chip that holds the micro-lenses in a compact camera.

A six megapixel camera has six million tiny lenses laid out in a rectangular array on that chip. That fact ought to make anyone’s jaw drop to the floor. Six million lenses cemented onto a little chip the size of your thumbnail, capturing light that comes into the camera. It’s amazing.

And it goes a long way to explaining why the image quality varies between compact cameras and SLRs. And why cameras with fewer megapixels can still produce good images, when most people’s first instinct would be to think that the more pixels the better.

How Micro-Lenses Work

Here is how micro-lenses work. Each micro-lens reacts to the light that falls on it. The bigger the micro-lens, the better it is at capturing a good signal. Of course the manufacturers can boost the ability of the lens to receive a signal but, along with the boosted signal comes more ‘noise’. We see that noise as mushy, dirty, speckled, gritty-looking, yellow-black areas in the darker parts of the image and as little speckles all over the image.

Manufacturers sometimes process the images in the camera in such a way as to hide that noise, but inevitably, they also hide the signal and produce images that look like watercolor paintings rather than photographs.

You are not necessarily going to see this in a 4 inch x 6 inch print, but make a bigger print and you will see it.

So the best micro-lenses are big enough to allow a nice gentle rake to the angle at which they receive light through the camera lens. And they work best when they are not boosted to receive a stronger signal than is optimum for their design.

Now it is clear that if we have a chip that is as big as a thumbnail, the more lenses one cements onto it, the smaller each lens must be, and the more we have to boost the signal to get enough light to process an image.

Small Sensors And Large Sensors

SLRs have sensor chips with an area that is about fifteen times the area of the chip in a compact camera. And there are some SLRs on the market that have chips that are bigger than that, and are known as FX or full-frame sensor cameras on account of the fact that the chip is the same size as a frame of 35mm film.

And there are cameras with chips even bigger than that, but if you are considering one of those you need to know a lot more than is in this guide, and you are talking about cameras that cost several tens of thousands of dollars.

Compact cameras with more micro-lenses (more mega-pixels) can look better for small prints than shots taken with cameras with fewer pixels. And the reason is that at small print sizes the more micro-lenses, the more resolving power. That is, the more detail they can show.

And as long as the print is not too big, that ability to resolve more detail can outweigh the propensity for more noise because of the fact that each individual micro-lens must be smaller to fit on the sensor chip.

And there is a second complication and that is that whichever way you cut it, lenses are at there best near the center. And if the micro-lenses are bigger, as they tend to be on bigger chips, then there are fewer ‘centers’ and more corners.

But all of this only holds true for shots taken at the lowest sensitivity of the camera, and that’s the next thing I want to talk about.

Sensitivity

In the days of film, you went into the shop and bought a film suitable for daylight, or for shooting indoors. The manufacturers understood that there was likely to be less light for those indoor shots, so they made film for indoors that was more sensitive than film intended to be used indoors.

As with all things, there is a penalty to pay for making a film more sensitive, and that is that there is more grain. The international standard for the sensitivity or ‘speed’ of a film is called ISO, and a typical low-sensitivity film would have an ISO of 100. And a ‘fast’ film with more sensitivity would be something like 800 ISO.

What does ISO 100 and ISO 800 mean? It means that to get enough light onto the film to expose it sufficiently for the image to be produced, you need eight times more light on the slow ISO 100 film than you do on the fast ISO 800 film.

The ISO standard has carried over into digital cameras. Almost all digital cameras have a button or a dial to increase sensitivity, from 100 ISO (or perhaps 200 ISO) up to 400 or 800 or 1600 or even 3200 ISO or beyond.

And you may wonder how it is possible to just turn a dial and make a digital camera more sensitive to light.

And the answer is that as in almost all things, there is a trade-off. More sensitivity means more noise. And in an analagous way the noise problem is the same with digital cameras as it was with film cameras.

No matter how big or how small the chip used in the camera, The more we boost the sensitivity of the chip by turning up the dial, the more ‘noise’ we get. And noise is the digital ugly sister of grain. in fact it is a lot worse than grain because it looks worse.

How Sensitive? And How Much Noise?

So how does this translate into something practical we can say about compact cameras compared to SLRs? The generally accepted word is that 800 ISO with an SLR produces the same amount of noise as 100 ISO with a compact camera. And that tells us a lot.

Because if I was thinking of buying a compact camera because it is supposed to give good exposures without too much noise, that isn’t such a big deal when I know that the noise on a compact camera is likely to be as bad at 100 ISO as it is with an SLR at 800 ISO.

Very few camera manufacturers make their own chips and the fact is that there are very few chip manufacturers. So the differences between the cameras made by the various camera manufacturers is often down to the processing technology they use to process the signal that the micro-lenses produce rather than differences in the chips.

Somewhere in all of this there is a trade-off but the bottom line is that bigger chips mean better image quality over a wider range of sensitivities. It’s as simple as that.

How Images Are Processed – JPEG and RAW

So what happens after the signal hits the micro-lenses? Well all cameras ‘process’ the signal that come from the array of micro-lenses, and the technology is a fine blend of science and art -that is between what ought to look good and what looks good.

But once that signal is processed, we come to a big division between those cameras that allow you to capture and download the original ‘digital negative’ and those that present you with an image that has been processed ‘in-camera’.

Jpegs and tiff files are ‘processed’, finished files. They can be read by computers and photographic printing machines. They are universal formats.

RAW files on the other hand are ‘digital negatives’ and most camera manufacturers have their own proprietary RAW format. And without being converted to a readable format they cannot be read by computers or the web or whatever. They have to be downloaded from the camera and then processed (or to use the jargon – ‘converted’) using a program designed for the job.

Some camera manufacturers make their own RAW converters but there are many programs made by other companies that are widely regarded as being as good as the proprietory ones made by the camera manufacturers.

Adobe Photoshop is probably the most widely known of the RAW converter programs, apart from all the other things that Photoshop can do.

Several cameras that produce RAW files also have in-built converters so that you can download a custom-tweaked jpeg right out of the camera as well as being able to download the RAW file.

As a side-note, all cameras produce jpegs in-camera, even if they are only tiny, low-resolution versions. That is because that is what you are looking at in the back of the camera when you review the shots you have taken.

Why You Want RAW files

One reason you want a camera that allows you to download RAW files is that you can alter a RAW image more successfully than can be done with an image that has been processed in-camera.

You can alter the exposure (in case you or the camera messed it up when you took the shot) and you can alter the colors or the tonal distribution from dark to light areas. You can do that with images that have already been processed in-camera (jpegs and tiffs) but with less latitude and more likelihood of degrading the image.

This is particularly true with jpegs because of the limited range of colors of which they are composed. Change the exposure and color balance and the whole image suffers.

Which begs the question of whether you want to get involved with all this stuff, and if you don’t, then just know that to squeeze the best out of a digital camera you either want to be able to play around with RAW files, or you (or your camera) had better be pretty good at getting exposure and color balance correct when you take the shot.

And there are many brands and modesl of compact cameras that are good at good at getting exposure and colour balance right when the scene is bathed in diffuse, natural daylight and when the distribution of dark and light in the subject averages out at about halfway between white and black , or where there is a slightly lighter subject set against a slightly darker background. And the reason for that is that there are limits to how well cameras are able to detect exactly what they are looking at.

Difficult Lighting Conditions Or ‘A Black Cat At Night’

For example, how can a camera tell whether it is pointed at a black cat against a white background, a white cat against a black background, a white cat against a white background –you get the idea. And the answer is that it can’t and yet the camera has to know these things or it is going to get the exposure wrong.

In fact all cameras are standardized to expose every scene as though the subject is a specific internationally agreed shade of grey. But it is only a starting point.

Many sophisticated cameras have certain standard scenes programmed into them and if they ‘recognize’ that the distribution of shapes in the scene is like one of those in their memory, they estimate that the scene they are looking at has a certain distribution of light and dark in the scene and expose accordingly. But even the best of them are not always correct, and for certain scenes, ones that photographers learn to recognize, they are very often wrong.

So some compact cameras or less ‘expert’ cameras go a different route. They ask the photographer to tell them what kind of scene the camera is pointed by turning the dial to the appropriate ‘scene’ mode.

In fact ‘scene’ modes are often used in compact cameras for another additional reason and I will talk about that when we talk about other settings – speed and aperture.

The bottom line is that cameras have a limited ability to detect how light or dark a scene is, and so they either expose all subjects as though they were grey, or they ‘estimate’ how light or dark a subject is by comparing it with a memory bank of subjects, or the camera asks you the photographer to tell it what the lighting is by flicking to the appropriate scene mode.

So with this knowledge you have got to expect that the exposure will probably be wrong in ‘difficult’ scenes.

The Quality Of Light – White Balance

The next thing the camera has to know something about, is the quality of the light. It needs to know this so that it can reproduce the color in a natural way. But perhaps the light is not natural – perhaps it is deficient in part of the spectrum. Perhaps the scene is lit just by fluorescent light. Or perhaps there is more than one light source – perhaps a flourescent light and a halogen light and some daylight as might be found in a household kitchen.

Or perhaps the scene is lit by natural light but it is in the glare of the sun at midday. Or perhaps it is in bright natural light at midday, but under the shade of a tree; or perhaps it is at the end of the day when there is a yellow-pink glow in the sky.

Perhaps the scene is in Norway or Canada where the light is filtered through the atmosphere and creates a different light to that found in the tropics.

Again, the camera has to detect which of these it is looking at or it will get the color balance wrong. The color balance is called White Balance – setting the White Balance means setting the color temperature to show white correctly as white. All the other colors fall into place around this.

All digital cameras have automatic White Balance detection but it is easy to show this is not foolproof. And the proof is that many cameras have manual settings for daylight, sunlight, shade, fluorescent, halogen, tungsten and others. Why have these if the auto White Balance gets it right all the time?

And this leads us back to look at RAW, because if the camera does not expose the subject correctly, or does not get the color balance correct, then someone is going to have to correct these after the shot has been taken. And RAW files allow more correction, and with less degradation of the image.

Printing The Image

Photo magazines run tests from time to time, comparing the services of different photo labs. They compare them for price and speed of service, and for how well they develop the digital file they are asked to process. What this shows is that not all labs develop and print digital files the same way or as well.

If you as the customer opt for the cheapest service without color correction, then you are relying on a machine to correct the color and exposure in your digital image. And theses machines are very good at doing this. But they vary between brands, and they vary depending on which engineer set them up and how well he/she checks and maintains them. And of course, how well you exposed the shot in the first place.

For a little more money the customer can ask the lab to manually color correct the images. Which means that a technician will sit and check the images on screen and correct the exposure and the color.

The point is that ‘somebody’ has adjusted and printed the images, and if the file is a jpeg, and the exposure or color balance is wildly wrong, even a lab will have difficulty correcting them to make a printable image.

Whereas consumer photo labs will usually only handle jpeg (or sometimes tiff) files, professional labs will handle RAW files or other proprietary files. That gives them more scope for correcting exposure and color balance.

Of course you can develop and print your own digital files at home using a computer and an inkjet or thermal printer, and many people do. And if you want to have more scope for correcting exposure and color balance, then shoot RAW files and invest in a program that will convert those images in the computer so they can be printed.

You don’t have to actually print your images at home, and there are many good reasons not to – one reason being that you have to buy new equipment to keep up with advances in technology.

But what you can do is tweak and correct the RAW images and then save them as jpegs, copy them to a CD and take them into your local lab knowing the files are ready for printing – color and exposure corrected. Just tell the lab not to apply any settings, and instead to print the images as they are.

The fact is that photographers who used film when that was all there was, could never achieve that kind of quality.

About Lenses And How To Isolate The Subject

Look at a compact camera and the lens may say something like 5.8 – 23.2mm. Ask the salesperson or look at the brochure and you might learn that the lens is 34-140mm at 35mm equivalent. What that means is that if the camera were a 35mm film camera, the lens would be described as having a zoom lens that goes from 34 to 140mm.

The short focal length lens (5.8 – 23.2mm) on the compact camera is enough to cast a circle of light on the tiny sensor chip inside the camera.

That’s not so hard to imagine. After all, if you were to place a penny on the kind of chip found inside compact cameras, it would cover it. But if you were to place the same penny on the bigger chip found in SLRs, the penny would not cover the chip.

So only a small circle of light is needed to cover a small chip and shorter focal lengths are adequate to do that. Anything bigger is just wasted light spilling beyond the edge of the chip.

Which is all well and good but how do we compare cameras and lenses when there are cameras with different sized chips on the market? And the answer is that focal lengths are standardized by using 35mm film camera coverage as the reference.

In other words, all chips and lenses are compared back to the coverage that the lens would give if it were asked to shine on a frame of 35mm film. And small sensors are easily covered by short focal lengths.

The reason that 35mm cameras as used as the baseline to describe lenses in digital cameras is that, well 35mm film cameras got there first and there has to be some standard against which cameras with different sensor sizes can be described, and 35mm film cameras is as good a standard as any.

Which leads us to another factor we have another factor to take into account in the search for the best digital camera to fulfill your needs. And that is what is called depth of field. Depth of field means simply how much of the scene from near to far is in focus. The longer the focal length of the lens, the less depth of field. The nearer the subject is to the camera, the less depth of field. And finally, the larger the aperture in the lens through which the light falls, the less depth of field.

Small sensors means short focal lengths and short focal lengths have more depth of field than longer focal lengths. And what that means is compared to a longer lens, everything from near to far is going to be in focus.

And to save cost and weight, many compact cameras do not have lenses with large apertures. So again more of the scene will be in focus.

If you like photographing people, and you want them to stand out against a gently softened and blurred background, then you are going to be able to do that more easily with a bigger lens that has a longer focal length and has a large aperture.

One thing you can do to minimize that ‘problem’ with a compact camera is to stand back a little, zoom to the longest focal length and frame the subject. That is as good as it is going to get with a compact, because the problem is inherent in the small sensor and short focal length.

Of course, standing back and looking at the subject through an LCD means you also have more of a chance of missing focus. That is, that the camera focuses on the wall/tree/building near the subject and you simply cannot see that that has happened by viewing the scene in an LCD.

What’s New?

Things are moving fast. Two manufacturers have made what are called Micro Four Thirds Cameras. The chip is smaller than the DX chip but larger than the chip on a compact camera. But they have electronic viewfinders. That is, the scene is projected into the viewfinder so that one is looking at the scene on an LCD built into the viewfinder.

The advantage is that it does away with the housing of prisms and mirrors in SLRs while eliminating parallax errors.

The elimination of the housing enables the lens to be placed nearer to the sensor and this means physically small lenses can be used. The science behind this has to do with how big the projected image circle has to be but the result is a small camera that can produce high-quality images.

The downside is that one is looking at an LCD in the viewfinder, so the quality of the LCD and the refresh rate as one moves the camera about are key to whether the system is satisfactory. It is early days, but the consensus seems to be that manufacturers are not quite there yet.

One solution to the weight and size problems is to sacrifice the viewfinder but put a bigger chip in a compact camera. There are technical problems in doing this because the lens has to cover the larger sensor, which makes the camera bigger and so defeats the purpose of the exercise, but four manufacturers has done it with some success. They are still more of less ‘compact’ cameras, so you still have the problems with actually seeing the scene when you are shooting, but image quality is better.

Not long ago a DX size chip in an SLR with 10 million pixels that could shoot clean shots at 800 ISO without too much noise and which weighed somewhere around 800g (one and three quarter pounds), was about as good as it got. But there have been several developments that have turned this on its head.

There are now SLRs that can shoot clean shots at 3200 ISO and higher. They are so good that photographers are taking shots in twilight that would have been impossible just a year ago.

There are also SLR cameras with sensors having around 25 million pixels.

Beyond the fundamentals of size, weight, sensor size, and RAW versus jpeg, all the other factors are down to what the manufacturers do. These include build quality, focusing accuracy, focusing speed, buttons in the right places, information readily to hand, parameters easily changed, high ISO noise control, and the ability of the image processing engine to render fine tonal gradation in the image.

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