Tuesday, May 23, 2006

Secrets of Digital Cameras

Want to buy a digital camera? Confused by all the choices, the hundreds of models, the thousands of opinions? Well, I am here to help! Over the next few days I am going to gift you with the wisdom of a decade of experience. This first article will cover some basics, revealing the key principles that will guide you through the complicated evaluation process. It will focus (ouch!) on compact digital cameras.

First some background. I first learned shooting and film development on a completely manual SLR, mostly for journalism. That was back in the early eighties. Because of my involvements with media and the arts I had a chance to use the early Apple QuickTake digital camera, which had no removable storage, a serial interface (!), 640x480 resolution, and only three focal positions*. But I could still see, in those ancient days of 1994, that the writing was on the wall for chemical photography.

Since then I have used only a few models and would not consider myself a photography expert. Nonetheless, I am good at two things: research and cutting the crap. I hope these abilities will help you!

Your decision-making experience will be a lot easier if you bear in mind some basic principles.

It's all about the light. A picture is a visual representation of the outside world, and the more light that enters the lens and hits the CCD^ the better. This means that the size and quality of the lens/CCD is the first thing to look for in evaluating a camera. With an SLR one can switch lenses, so when purchasing you have the luxury of compare bodies more-or-less equally. But for a fixed-lens compact one is generally stuck with what one gets in the initial purchase.

You can't take a photo if you don't have a camera. Ignoring low-end technologies like camera phones, you need to have a camera with you when that once in a lifetime moment pops up. A small easy-to-carry camera is more likely to be with you when you need it than the large full-featured SLR. I believe in compact cameras for this reason. Even if you own an SLR, be sure to get a companion compact for shots where you just don't have the time to set up the SLR, or happen to have left it behind.

Don't get fixated on the numbers. Marketing folk will blare with triumph the new 4 megapixel, then 5 megapixel, then 6 megapixel models. But simply counting the pixels tells you nothing about the image quality. More megapixels mean fewer images on your memory card, longer transfer times per image, more disk space used, more backup disks burnt (you do back up, right?), longer software processing times, etc. All of these disadvantages must be balanced against the advantages:

1. The ability to print larger images at the same quality. Ask yourself how often you need large size prints? Do you ever need larger than A4?

2. The ability to crop the image to extract details. But if you're the sort of photographer you spends the time to frame in-camera, this will not be a high priority.

3. The ability to do more software post-processing. But you can only correct bad images to a degree. Buying a better camera in the first place will make the process easier and save endless hours at the computer.

At some point there is no valid reason to increase the pixel count, since the light entering the camera through the lens simply doesn't justify it. For compact cameras we have already reached that point. Manufacturers are moving to other attributes in order to distinguish their wares.

You can't add information to an image that is not there. If the CCD is poor, the lens cheap, or the camera firmware deficient, you are stuck with what you get. Noise reduction software and sophisticated software techniques can help to a degree, but do you really want to spend 30 minutes retouching an image?

There are two critical factors that are rarely disclosed by manufacturers, and so can only be inferred by comparing images. First, what compression rate is used in the JPG image? When buying an SLR we have the advantage of being able to shoot a raw image. But compact cameras use JPG and this means that information has been lost in order to compress the file size. This is why 1200x800 pixel images from different cameras will be a different size°.

Second, what in-camera post-processing has been performed? Some cameras allow you to control factors like sharpening, contrast and colour saturation. In my opinion it is best to leave these "off" so that any processing can be done manually in software, if need be. But what setting is "off" and can this even be set? Usually this is a big unknown.

Buy the features you need. Cameras are overloaded with bells and whistles, but no compact will do everything equally well. Decide what you need and make a priority list. Do you need wide-angle? Greater than 3x zoom? Good macro~ performance? Fast response time? A particular memory card format? Manual modes? List what you absolutely need and what you do not care about. This will eliminate a lot of buying decisions (perhaps entire product lines) immediately.

I hope these principles will help you. Coming up soon will be the result of my decision-making process and a review of my latest purchase.

Be sure to look through the Photos category for some of the photos I have taken.

Single-Lens Reflex cameras have the distinct advantage of using the same objective lens for the viewfinder and the CCD (or film), so what you see is what you get. Commonly these offer removable lenses and larger apertures, meaning more light.

* This ancient review calls it "sexy"!

^ The Charge-Coupled Device is the actual image sensor. How this operates is of primary importance to the image quality. The larger the size, the better (all else being equal).

It is unlikely one can see the benefit of more than 6 megapixels for a 1/1.7" CCD.

° Of course one must be sure to be taking pictures of exactly the same image, something remarkably difficult to achieve.

~ Macro is a special mode that lets you get near an object for extreme close-ups.


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