filmscanners_owner@halftone.co.uk <> wrote:
> Subject: [filmscanners] Correct/best methods of scanning
>
>
> I have recently spoken to various people about scanning and it
> appears that there are two methods of obtaining a scan for a specific
> size output (that we all use anyway!). If, for instance, a 10x8 image
> at 300ppi is required from a medium format film. Now this can be
> scanned at the exact output size required or the image can be scanned
> at the highest quality of the scanner, providing a much larger file
> than required, then resized/scaled to the required output size. I use
> both these options depending on whether I need the larger file later.
>
> The question is: Is a better image produced from one method than the
> other? Is it wrong to have a large file then scale down? Or is the
> image slightly sharper, better resolved (or whatever the correct
> terminology may be...), any thoughts? Ideas? Anyone produced any
> tests?
>
I have done no tests per se; but from my understanding of what you have
written, both of your two options are basically doing the same thing. The
scanner is scanning at the maximum optical resolution that it is physically
capable of; and, in method 1, the scanner software is downsampling the
scanner raw data and outputing an 10x8 at 300 ppi file, while under method
2, the scanner software in not resampling the scan data but leaving that for
the user to do manually at a later time in an image editing program so it is
exporting a 6x7 cm at 1200 ppi file. In either case - method 1 or method 2,
depending on the several factors, if the original image is say, for purposes
of example - scanned at optical 1200 ppi at the same size as the original
medium format film (for our purposes 6x7 cm), it can be resized to 10x8
inches without engaging in any actual resampling so as to produce an
effective optical resolution of 300 ppi just by changing the dimensions
without touching the resolution via downsampling. However, if the resizing
is not an even multiple of the film size 2x, 4x, 6x ...(i.e. transforming a
35mm film frame into a 10x8 inch imagebeing an example of a non even
multiple), you would obviously have to crop to get the proper aspect ratio;
but in all likelyhood, you would both have to resize the image as well as
engage in some resampling of the resolution if the original film frame was
scanned at 1 to 1 at an optical 1200ppi (as per our illustrative example) in
order to get a 10x8 300 ppi file resolution.
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