Choosing a digital camera (more added 23 July)

The first thing you need to know is what is on offer. There are three kinds of digital cameras. There are compacts that fit in your pocket. There are SLRs (single lens reflex cameras), and there are bridge cameras. Bridge cameras are smaller than SLRs but bigger than compacts. They try to make out like they are as good as SLRs but nearly as small as compacts.

There are super-compacts, but we don’t want to get into all the advertising stuff about super-slim, super-compacts, super this and that. There is a place for super-slim, super compacts, and it is in your shirt pocket.

There are also rangefinder cameras but there are not many of them (two to be precise) and they are not cheap so I will refer to them in passing but not discuss them in detail.

So apart from size, what are the differences? Well SLRs are called ‘single lens reflex’ cameras because when you look through the viewfinder you are looking down via a series of prisms and a mirror, right out through the lens. They are called ‘reflex’ cameras because the mirror flips up out of the way for a fraction of a second, when you take a shot and then back again.

It seems pretty obvious that there must be something better about SLRs, otherwise everyone would buy super-compacts. After all, who wants to carry around the extra size and weight. And that is the first thing you need to decide. How big a camera are you prepared to carry around? And in order to decide that you have to know what you are going to sacrifice by not having an SLR.

Seeing what you are shooting – the viewfinder
And the first thing you need to know is that the viewfinders on compacts or Bridge cameras are generally pretty bad compared to the view you get with an SLR. In fact, as we all know, lots of compacts have no viewfinder at all. You just look at the LCD on the back of the camera and compose your shot that way. Which is OK if it suits you and if you can see the LCD. The problem with LCDs is that in sunlight they are very difficult to see. You need to go find a dark corner to see properly; but that is no good if you want to take a shot outside on a summer’s day.

So if seeing the subject with a good viewfinder is top of your list, then it has to be an SLR. If you are not sure whether it is that important to you, test it. Look through the viewfinder on an SLR and look 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 it with a compact or a Bridge camera. Ho ho, now your loved one is a dot at the end of a long tunnel. How are you supposed to check that he/she is smiling or that he/she is in focus? You can’t. And it is no easier looking through the LCD. Which is not to say that compacts are no good; and they can take some very good shots. But you need to know their limitations before you put down your cash.

Image Quality
Digital cameras have an array of microlenses 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 microlenses in a compact camera. A six megapixel camera has six million lenses laid out in an array on that chip. The fact ought to make ones 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 you would have thought that the more pixels the better.

How microlenses work
Here is how it works. Each microlens reacts to the light that falls on it. The bigger the microlens, 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 in mushy dirty yellow-black areas in the darker parts of the image. We see it as a sort of speckling of color and grit 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 4×6, but make a bigger print and you will see it.

So the best microlenses are big, and they work best when they are not boosted to receive a stronger signal. Now it should be clear that if we have a chip that is as big as my thumbnail, the more lenses I cement 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.

SLRs have bigger chips – about eight times bigger. So they have better image quality. It’s as simple as that. Sooner or later some manufacturer is going to make a compact camera with a bigger chip, but not at the moment. And the leading manufacturers make SLRS and compact cameras, and you can see what that means without me spelling it out.

All about sensitivity
In the days of film, you went into the shop and bought a film suitable for daylight, or for indoors. The manufacturers rightly 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 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.

That standard has carried over into digital cameras. They almost all 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. 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 sensitive the chip is or the more we boost the sensitivity by turning up the dial, the more ‘noise’. And noise is the digital ugly sister of grain. in fact it is a lot worse than grain because it looks worse.

One more quick piece of information. With the ISO standard, when I go from 100 to 200 ISO, I am doubling the sensitivity. It’s that same going from 200 to 400 ISO. I am doubling the sensitivity. That is how the ISO standard was set up. So from 100 to 800 ISO is eight times more sensitive.

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.

Image Quality Part 2
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 microlenses produce. And some camera manufacturers are just better at image processing than others. That is not to say that there are no differences between chips, and Canon has established itself as a first-rate manufacturer of chips for its professional SLR cameras, using a technogy within the chip that works well with its image processing technology. Canon also makes a range of SLR cameras that use bigger chips than any other manufacturer. This is not to say that Nikon is left in the dust, and it also makes excellent SLR cameras.

Many well-regarded individuals have tested and compared all kinds of cameras – comparing image quality, features, and useability. And the marketplace has voted with its checkbook so that there now some new players in the marketplace, and some gaps where well known names have disappeared.

So what happens after the signal hits the microlenses? Well all cameras ‘process’ the signal that come from the array of microlenses, and the technology is a fine blend of science and art. 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’ files. They are finished files. They can be downloaded and read by computers, and by some photographic printing machines. They are universal formats.

RAW files on the other hand are ‘digital negatives’ and they cannot be read by computers or the web or whatever. They have to be 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.

Why would I want RAW files?
One reason is that you can alter things about the image much more freely with a RAW image than 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 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. 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 is 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

Ceiling of the Church of the Holy Sepulchre, Jerusalem




A black cat at night
For example, how can cameras tell whether what they are looking at is a black cat against a white background, a white can against a black background, a white cat against a white background –you get the idea. And the camera has to know these things or it is going to get the exposure wrong.
In fact all cameras are standardised 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 scenes programmed into them and if they ‘recognise’ 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, that photographers learn to recognise, 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 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, is what the quality of the light is, 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. 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. 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 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?

Why RAW? The question asked again
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. That ‘someone’ is going to be you or a photo lab.

The local Photo Lab
Photo magazines run tests from time to time, comparing the services of different photo labs. The compare them for price and speed of service, and for how well they develop the digital file you give them. Which goes to show that not all labs develop and print digital files the same way.
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.
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.

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

The home lab
Of course you can develop and print your own digital files at home, 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 (see below). 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.

Which cameras allow you to save RAW files
There are very few compact or bridge cameras that allow you to save RAW files. Leica, Panasonic, and Ricoh make compacts that do; Canon used to but stopped, even on its high-end compacts – a fact much lamented by photographers. All SLRs allow you to save RAW files.

Because they are compacts, the Leica, Panasonic, and Ricoh models have small sensors. And as we said above, smaller sensors mean more noise for a given ISO. An additional reason that argues against the Ricoh, is that it takes a long time to produce a RAW file (14 seonds according to one reviewer), and you cannot take another shot until it has finished doing that. In comparison to that, many SLRs produce RAW files instantly. The Leica D-Lux3 is quicker than the Ricoh but not blindingly fast. For a very good review of that camera I recommend reidreviews. It is an online subscription site, but if you are seriously thinking about a compact that shoots RAW, then it is worth looking at that review. Panasonic make a similar mode

First Conclusion
if image quality is your absolute number one priority then you have get an SLR. The files will be cleaner (less noise) and the ablity to tweak images without degrading them will be better than with a compact or bridge camera.

If it is to be an SLR, then which one?
There was a time, three or four years ago, when making a decision about which SLR to buy was difficult because the gap between the really high-end professional cameras and the consumer ones was so great. There were problems with the image processing ‘engines’ in the typical consumer SLRs.

Then in 2003 the Canon brought out the EOS 300D (called the Digital Rebel in some parts of the world) and Nikon brought out the D70, and things were suddenly different. Since then all the major manufacturers have made great strides in bringing out good quality SLRs but in the process, some manufacturers have disappeared because they simply could not compete in the marketplace. Canon has the biggest share of the market today, with Nikon the only real competitor in terms of units sold.

The other manufacturers who produce SLRs are Pentax, Sony, Olympus, Leica, Panasonic, and Fuji. Minolta has gone. It merged with Konica, and then was taken over by Sony. Some afficionados were very sad at Minolta’s demise because it was the only manufacturer that made a camera that had anti-shake built into the body. Now they can like the Sony version. Canon and Nikon have some anti-shake lenses, but they are expensive, and of course you only get anti-shake with the lenses they produce that have anti-shake, which is with the longer focal lengths.

Leica also makes a rangefinder camera (the M8). Epson made the RD1 but it is no longer in production, though in some parts of the world it has released an updated version. Both are good cameras and there are those who believe that the image quality from the Leica is as good as it gets.

Of the SLRs, Fuji has a following among wedding photographers because of its processing engine’s ability – according to some – to capture a wide range of tones and get the colors right with the minimum of tweaking. It is easy to see how this is important for wedding photographers who will be many hundreds of photographs at one time of brides in white dresses and grooms in black or grey jackets, and in various lighting conditions.

Focal Length
Look at a compact camera and the lens may say somehting like 5.8 – 23.2mm. Ask the salesperson and he/she might tell you the lens is 34-140mm at 35mm equivalent. What that means is as follows.

What is actually within the view of a given focal length of a lens, depends on the size of the sensor chip. That’s not so hard to imagine. After all, if you were to place a penny on the kind of chip that compact cameras have, it would cover it. But if you were to place the penny on a bigger chip, it might not.

Compacts have small chips so the lens is onlt required to cast a circle of light over a small area. If the chip were bigger, a longer focal length would be required to cast a circle of light that would cover the greater area of that chip.

There has to be some standardization, and the way this is done is to give the equivalent coverage for a 35mm size frame of old-fashioned film (remember film?). 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.

Small sensors are easily covered by short focal lengths. And therein lies another factor in the search for the best digital camera to fulfil your needs, and that is the question of 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 that if you like photographing people, then your background (that might be twenty feet behind the subject) is going to be in focus. And you probably don’t want that and would rather have a nicely out-of-focus background. Well one thing you can do to minimize that ‘problem’ is to stand back, zoom to the longest focal length and frame the subject. That is as good as it is going to get with a compact.

Of course longer focal lengths mean the effect of camera shake is more noticeable. Imagine holding your finger out and watching the shake. Now imagine holding a long stick in front of you and notice the effect of that shake. See what I mean?

Size, Weight, Focal Length, and Image Stabilization
If it has to be something that fits in your shirt pocket, then it’s game over, and it has to be a compact or super compact. Canon and Casio make good cameras. Canon has a number of different lines. The PowerShot SD700 IS (Digital IXUS 800 IS) is small, has image stabilization, 6 million pixels and a lens that zooms from 35-140mm.

Casio has some super-slim models that have had good reviews.

Topics to come

dials buttons and menus – useability
lens interchangeability
batteries

This is a work in progress – more to come – bookmark it for future updates

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