Some of the key recommendations
arising from the information contained in these notes are summarised below:
• Don't store an image on which
you are constantly working in JPEG format. Use the native file type for
your imaging software or a lossless format such as TIFF.
• Try to perform all modifications to an image in Photoshop (or whatever
imaging software you use) rather than in scanner or printer driver software.
• Think of image size in terms of pixels (because this gives an absolute
indication of the relative sizes of different images - monochrome or colour).
For example, if you use 'rulers', set them to indicate pixels.
• Avoid using the interpolation option in your scanner software. If you
need to increase or decrease the image file size, use Photoshop — it is likely
to be much more accurate.
• Whatever size you are printing, always make sure that the output resolution
does not fall below 120 dpi (otherwise you are likely to see pixelation
in the printed image).
• To produce reasonable quality results from a 35mm original, use an input
scanning resolution no lower than 960 ppi if printing to A4 and no lower
than 1320 ppi if printing to A3.
• Remember that a small print will be viewed at a closer distance, so it
may be inadvisable to use a lower input scanning resolution. In fact, scanning
a 35mm original at 2700 dpi gives excellent quality at all output sizes
when taking this into account.
• Never re-size an image with the 're-sample' box checked unless
you have a really good reason.
• Don't apply the 'transform' tool repeatedly - it is equivalent
to re-sampling and quality will deteriorate each time it is used.
• For photographic quality prints, always set the printer to the maximum
number of dots per inch regardless of the paper type being used.
• Don't worry too much about obtaining the highest output resolution if
your image mainly consists of continuous tones with no important fine detail.
• Don't worry - have fun!
Let me end by comparing digital
imaging to driving a car: you should be able to get from a to b without
understanding too much about vehicle mechanics. But this lack of understanding
can get you into bad habits - riding the clutch, inappropriate speed for
given gears, and so on - which will,
sooner or later, cause you problems. The background information provided
here is intended to reduce the number of occasions when your visual trip
from a to b will be punctuated by breakdowns (physical or mental!).
Dr Roger Moore DIGITAL PHOTO ART Feb/Mar
1999