Sunday, April 22, 2007

Film or Digital: Part -2 Technical Issues

Image Quality

Few photographers would now dispute that in most or all respects the quality from digital cameras can equal or surpass that available from film. However digital quality is largely dependent on the camera and to some extent you get what you pay for.
Few of us want or need to spend a fortune chasing after the ultimate in quality. All we need is something good enough for our purposes.

If you only want to view and share your pictures on screen, the requirements are fairly low. Most current screen displays are less than 1600 pixels wide, and a good quality image that size needs only a good 2 or 2.5 Mp image. If you are only interested in images for web sites or e-mail use, then even smaller sizes are necessary; a typical 'large' image on the web is around 600x400 pixels, or 0.25Mp.

So almost all digital cameras - even most phone cameras - are good enough for images used on screen.

Most film cameras now use the still widely available 35mm film, and this can provide high quality prints up to 8" x 12" and considerably larger if you have a camera with a good lens. Prints or negatives can also be scanned to give images on screen at any size required. If you are on a low budget, film is still the cheapest route to high quality.

Making prints needs more pixels than a screen image - typically about ten times as many for a picture the same size. Screen displays have around 70-100 pixels per inch, while around 250-300 are needed for optimum prints, although you can do a good job with slightly lower figures.
Image quality depends on the sensor and lens quality, but the most important factor (and the easiest to give a number to) is the pixel count in Mp. The actual size print you can make that will still look great depends on these other factors as well. With high quality digital cameras (such as digital SLRs) and good lenses you can make good prints larger than these figures suggest.

Print Size (inches) and recommended minimum image size.
4 x 6 inches 2.0 Mp
5 x 7 inches 3.0 Mp
6 x 9 inches 4.5 Mp
8 x 12 inches 6.0 Mp
10 x 15 inches 8.0 Mp

If you decide the largest you will ever need your pictures to be, then there is no particular need to buy a camera that has a higher pixel count than this table shows you will need.
If you can afford it, having more megapixels than you need isn't usually a problem, and does allow you to play with the pictures more on your computer, for example by cropping off parts of the picture you don't want. However larger images do take more storage space on cards and hard disks, and are also slower to edit.

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