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If I look back over the past few years it's just astounding how much the "Digital Revolution" has changed photography and the photographic industry.  And the speed at which it's done it has left more than a few people wondering what on earth happened. My first "serious" digital camera was the Canon 30D and what a revelation it was. It's 3 mega pixel sensor was astounding and we're still using the pix I shot on it in Africa Imagery today. Now, of course, it's almost impossible to buy a 3 mp camera with the norm around 5 or 6. It is soooo easy to get caught up in the pixel race and and many cases a 3mp camera would be more than enough.

Let ' s have a look at some of the technical things to with the digital world and see what differences there are to shooting digital as apposed to film. Well, to start with there is absolutely no difference between film and digital when it to the visual issues. Composition, style, visual complexity and all those things that go into making a great picture all remain the same. So to do things like shutter speed and aperture selection, lens focal lengths exposure values and filter choices. So what does change? Two things really: the first if really the type of " film " is being used and the other is a mind set change regarding what happens after you have pressed the shutter release button.

Let's deal with the “film” first. With digital cameras, instead of the image being recorded onto light sensitive film it is focused onto an electronic “chip” called (depending on which camera is being used) either a CCD or a CMOS sensor. These sensors are made up of (again depending on which camera is being used) hundreds of thousands, or millions, or in the case of Canon's latest little effort, tens of millions of light sensitive points called pixels. Each of these pixels can record various bits of information about the light at its particular spot – colour, intensity and a bunch of other things. This information is written to some storage device in the camera and it can (usually) be downloaded to a computer or (sometimes) directly to a desktop printer. So the digital image is made up of many, many dots, in a very similar way to the way pictures are printed in a magazine. Take a reasonable powerful magnifying glass (or look through your binoculars the backwards and move them very close to the page) and you will see that the picture is made up of cyan, yellow, magenta and black dots. It stands to reason that the more dots the picture is made of the smoother the picture will look until it seems to be a continuous tone. The two pictures below illustrate this. In the first I have used 72 DPI (dots per inch) and the picture looks really great. In the second picture I dropped this down to 20 dpi and you can easily see how the image is being broken up or pixelated.

So what does all this mean? It means (and here we get into that “it depends what you want” thing again) that if you are going to want to print out photographs on your computers printer or at a photo lab you should really think about getting a reasonably high number of pixels in the camera – something in the region of 3 or 4 mega pixels, 6 is better though. On the other hand, if all you need is to e-mail a few pictures to g reat aunt Mildred and do a few slide shows on the computer, then something in the 2 or 3 pixel range would be just great, and considerably cheaper. Computer monitors are generally capable of resolving only up to about 72 dpi so there is little point in displaying a picture at 300 dpi, which is generally what is needed to make photographs or print in magazines. And, Mildred is very quickly going to alter her will if you send her a 30Mbyte image file of the family on holiday that takes 3 hours to download!

While the quantity of pixels if certainly an indication of the quality of the final image there are many other aspects that influence quality too. It's a bit like film… The fewer the number of pixels the more “grainy” the images becomes. In film the higher the ISO rating (generally speaking) the more “grainy” the film becomes. If one compares two ISO 100 films from different manufacturers the graininess may very well be similar but the colour palette, contrast, tonal range etc will almost certainly be different. So to with digital cameras. When purchasing one have a look at the final prints and make your choice. Do check very carefully for noise (looks like grainy areas) particularly in the shadow and out of focus areas. In low end cameras this tends to be more pronounced and can detract from an otherwise great picture.

When shooting pictures with digital cameras always shoot at the highest quality settings (least compression) and the largest images size. (The one exception to this is if you're shooting specifically to e-mail pictures). If your camera has the facility to output TIFF or Raw files use this. Most cameras though output jpeg images and this is a compresses form of image. We normally use Tiff format in our work which is a non-compresses image and so the file sizes can be quite large – approximately 25 mega bytes (mb) for an A4, 300 dpi image and up to 47mb from the Canon 1DS I use . Converting the tiff format to a jpeg compresses the image to around 4 mb or so depending on how much it is compressed. But, as the Texan once said, “there ain't no free lunches”. There is some loss in quality - the higher the compression the more information is lost – but used properly this can be really useful.

The second “difference” between film and digital cameras is what happens after the picture is taken. With film you simply hand the roll of film to the lab and say, “get to it”. With digital cameras it's over to you. There is still work to be done on a computer, although with some cameras/printers you can go directly to the printer. But if it's quality you're after then it's to the computer that the images must go .

If there's something that you would like to read about in this column or questions you have , feel free to contact me on e-mail at info@africaimagery.com . I will try to get back to you but things sometimes get a little hectic around here so please forgive me if I don't. It will, though, help to give me an idea of what you want to know.