Digital

Digital Cameras - What's The Fuss All About?

Digital cameras are rapidly replacing conventional film cameras.  Prices are falling, and pretty good models can be snapped up for under £100.  But whereas film cameras are easy to understand, digital remains something of a mystery.  This leads to distrust of the medium.   It appears too complicated for a lot of people.

So how does a digital camera work?  It uses a lens to focus light, but instead of the light falling onto film, the light falls onto an image sensor.  This is made up of thousands or millions of pixels.  Each pixel records the light hitting it and generates a charge, the brighter the light the higher the charge. The pixel can only record 256 levels of brightness.  It cannot record colour.  The 256 tones range from pure white to pure black.  So how does the camera create a colour image?  For this we have to thank James Clerk Maxwell.  In 1860 he discovered that colour photographs could be made using black and white film, and red, green, and blue filters.  If three photographs of the same subject are taken with a different colour filter over the lens, and then the three images are projected on top of each other, through three projectors, each equipped with the same colour filter used to take the picture, a full colour photograph is formed.  This principle is used in digital cameras.  Each pixel is in fact made up of three pixels, one with a red filter covering it, one with a green, and one with a blue.  This explains why a 4-mega-pixel image is actually 12 million pixels in size.

So we now have 256 shades of red, 256 shades of green, and 256 shades of blue.  If you multiply these together, (256 x 256 x 256) you get 16.7 million.  This means that the camera is capable of producing an image consisting of 16.7 million different colours.  In computer terms, this is 24-bit colour, or 24 bit depth.  Some cameras and scanners can produce an image of 36 or 48-bit depth, resulting in billions of colours.  However, these extra bits are not used to view the photograph, instead they are used to improve the colour in the image as it is processed down to its 24-bit final form.

In addition, all digital cameras have a diffusing filter between the lens and the sensor.  This is to reduce the jagged edges of the pixels, and to reduce noise, or random specks of colour in the image.  The more expensive the camera, the less noise is produced in its electronics, the less of a diffusing filter is needed, and the sharper the image.  There is a balancing act between sharpness and noise.

Digital Cameras have several advantages over their film counterparts.  One of the biggest is that you get to see the results instantly.  When taking hit or miss shots, like sport or action, you know when you have captured the picture you are after.  When I have taken pictures of birds doing what birds do, which is flap about and scarper when you get near, I set the camera on continuous and hold down the shutter. Click—click—click—click—etc.  I figure at least one of the shots will be ok.  This can get you into the habit of being lazy in your photography.  With film, more care is taken when composing a shot.  Ones mind is always aware of the cost of film and developing, so you try not to waste too many, and therefore take more time.  With Digital the only cost when taking pictures is batteries.  Even so, my camera will last a whole week on one set of nickel metal hydride batteries which only cost a few pounds, far cheaper than film and processing.

As for what to do with your pictures, the choice is the same as for film.  Prints can be obtained anywhere.  Take the cameras memory card into many photographic outlets and supermarkets, and they will produce prints for you at prices cheaper than film.  I upload my images to Bonusprint.  Two days later good quality prints have come back.  As for slides, I am indebted to club chairman Alan Foulkes for mentioning the firm that I now use: Micro-quiz, in the club magazine.  They will produce excellent quality mounted slides for £1.25 each.  Images can be uploaded  (a Broadband connection helps here,) or they will accept images on CD.  The results are superb!

There are two ways to view images that have just been taken by a Digital Camera.  The most common is the little screen on the back.  The problem with these is they are no good in sunlight.  The little bellows that attach with Velcro around the screen are utterly useless.  Also, the screens are tiny, and it is hard to judge the quality of the glorious landscape you may have been after, on one of them.  The other method for viewing your freshly taken shots, are cameras that incorporate the LCD screens in the viewfinder.  The huge advantage is that the picture you have just taken is displayed in the viewfinder for a couple of seconds, at exactly the same perspective and size as the scene was when you were composing the picture.  No sunlight problems here.  Also, exposure is easy to get right.  While looking through the viewfinder, the exposure can be lightened or darkened using the controls on the camera.  When it looks right, it is right.  Tricky lighting situations are much easier to manage.

I hope this gives you some idea of how digital cameras do their thing!

Here are links to the two firms mentioned:
Bonusprint and Micro-quiz

Other great places to try: