Clive R. Haynes FRPS
should be ‘photographic quality’
In one respect the one of characteristics of a digitally-captured picture is very similar to traditional film-based photography – that is, the larger the original image size/information is – the better defined the printed picture will be.
can we actually see?
Size is Important.
if the print we are to make is larger than the original image?
in mind the above and with respect to 35mm originals, the following information
will provide a guide to resolution and file size.
at 2,700ppi, a colour 35mm negative or slide will produce some 8,000,000 pixels
(8 mpxl) of picture information with a resulting file size of 20mb to 25mb (the
figure does vary). When expanded to A3 size, the image will look fine at around
200 to 220ppi.
Remember, changing the scanning resolution will alter file size and therefor have a direct bearing upon the maximum acceptable picture quality of the final image - which shouldn't fall below 200ppi.
you’re uncertain as to the size required for the finished picture/print, always
scan in at maximum. It’s too late to change file size later as for quality
the option of ‘re-sampling’ is not an answer.
Many excellent digital cameras are now available but be wary and be aware of resolution/file size for prints larger than, say, A4 (a lot depends upon content, your requirements and needs). Some cameras use clever methods of interpolation to raise the pixel level - look at the specifications carefully.
So as a rough
guide, cameras at a realistic price with a specification of around 6 to 7mpxls
can be considered the lower limit for acceptable A3 prints. The 6 or 7mgpxl image
when 'uncompressed' expand to around 18mb.
upper range of 'consumer' digital cameras is now providing some excellent results.
However many 'consumer' ‘megapixel’ models will struggle to produce quality images larger than A4 (a lot depends upon content, your requirements and needs). Never the less, I have seen excellent images produced by models producing around 4mpxl and upwards.
There is also a big difference in quality (and cost!) between 'consumer chips' and 'pro chips'.
Digital cameras produce texturally smooth and grain-free images, the result of which frequently looks better than scanned-in slides or negs with their inherent grain structure and surface blemishes.
Pro cameras such as the 'full frame' mega pixel SLR's are fantastic but at a price beyond the budget of most most techno-dedicated, enthusiastic amateurs (we're talking about £3,000 to £7,000 price tags here!) They are, after all, aimed at the 'professional photographer'.
What is acceptable is of course subjective and depends upon content and the purpose for which the image is intended.
Quality digital cameras (usually of the 'SLR' type) shoot RAW file format and this allows 16 bit working to carry through into 'Photoshop'. For more information about 'RAW' click on the link below.