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Digital Photography Explained

The "Nuts and Bolts" of Digital Photography

Do you KIND of understand it, but would like digital photography explained a little bit more? Well, without getting into the technical jargon, I will try and explain the basics. You see, if you understand digital photography at a certain level, you then begin to understand how to manipulate each and every pixel to your advantage.

With Ye Olde film photography, the light falling through the lens would create a "Negative" image on the film plane, i.e., the brightest light would BURN a darker area onto the film. Then, when printing this image, light is shone through the negative, onto photographic paper which is highly sensitive to light. So, the darker areas on the film would block the light hitting the paper, thus re-creating the original lighter image that was recorded onto the negative! Make sense? No, read it again.

Now digital photography is radically different, but based on the same principles of light. There is no negative image formed, just a replica of what you see through the lens. Each digital camera has what is called a CCD or CMOS sensor in place of the negative, and this is where the Mega-pixel war is fought. Each individual pixel (Up to 25 million at the time of writing this) records the amount of light, including the full colour spectrum, that hits it and converts the whole thing into an image.

Make it Simpler for me!!!

Ok. Imagine you had millions of square Lego blocks covering 256 different colours and all the shades of the spectrum. If you were able to make these into a picture, using say, a football pitch as a template, that is the basic principle. Now, if you were standing on the pitch, it wouldn't look like a photograph at all, just lots of squares, but if you were to fly over the pitch at a great height, it would start to look good.

The reason I am explaining it like this is that when you use photo-editing tools such as Adobe Photoshop or Elements, what you are actually doing is going back to the football pitch, re-arranging the colours, shades and tones of each block, and then floating over the pitch again to check the image! Obviously you don't alter each pixel individually, the editing program takes care of all the donkey work, although for serious work, I have, on occasion, altered individual pixels!!!

If you understand this, it should make your transition into digital a little easier. In order to alter a photograph in the past, you needed to acquire some serious darkroom skills, and that was time-consuming and messy, believe me!

How many pixels do I need?

It is quite important to understand that it isn't the AMOUNT of pixels on a sensor (E.g. 4MP or 8MP), but the sensor size itself, which creates a bigger and better enlargement. For example, the 8 mega pixel CMOS sensor on the now ageing but still fantastic Canon EOS 20D (Digital SLR circa 2004) will produce better results than the 8 mega pixel CCD sensor on a smaller compact digital camera or 12 megapixel camera phone.

Why? I hear you ask! Simply because it is bigger. Let me try to explain...

Imagine the sensor is a net and each pixel is a square in that net and for argument sake, we are comparing two 24 square nets! I.e. Each net has 24 squares, 4 high by 6 long and they are made of the same material. Now you have to imagine this...

One net is 6 inches long, and the other is 12 inches long. How big can you stretch the 6 inch net before it becomes too tense? How big can you stretch the 12 inch net? A lot bigger right?

That is the (Really!) basic way of explaining digital sensors.

When choosing a digital camera for yourself, remember that digital compacts have the smallest sensors, Semi-Professional Digital SLR's are substantially bigger, and most Pro Digital SLR's have the same size sensors as 35mm film. See the diagram below.

For the utmost in quality, medium format digital cameras have the largest sensors of all (up to 80 megapixels at the time of writing), and the quality of prints from these has easily surpassed film quality in many people's opinion. However, unless you have a budget in excess of £20,000+, you may have to start a little smaller!!!