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Zana
30-Nov-2015, 05:31
Hello everyone,
I came across this interesting forum and just decided to ask for some opinions from the more experienced ones in the field.
Recently I've accepted a challenge of preparing b&w photos for large printing (for exhibition purposes). The material I have is mainly glass negatives (from 1930's) along with some glass positives and film negatives. The scanner I use is Umax Astra 4450 (with Vistascan software) and I started to scan them in b&w 16-bit mode, 1600 dpi which I suppose is enough for printing the images in app 50x70 cm sizes (is it?). My problem is that every image seem to have diagonal parallel stripes which are particularly visible on the uniform part of the photo (such as the cloudless sky for example) (in attachment). The stripes are not visible when I scan them in 8-bit mode but I'm affraid that limits editing process which is particularly needed for some poor, quite faded negatives. Did anyone come across similar effect, what seems to be the reason for it and how should I avoid it?
Many thanks in advance,
Zana

Doug Fisher
30-Nov-2015, 08:11
Can you scan any other film without problems? If you turn this particular negative 45 degrees and scan it that way as a test, do you still get the same lines? If the image appears exactly the same (including the lines) but just rotated 45 degrees, that would at least narrow things down to something with the negative itself.

Doug

Zana
1-Dec-2015, 06:32
Hello Doug,
thank you for replying, I tried rotating 45 degrees, got the same stripy effect, same direction so I guess it's not about the negative. However, when scanning the same image on the glass positive (16bit) the stripes are gone, so it must be about the negative, but in what way and why?
I even thougth it might have something to do with the power suply (electricity, scanners light source frequency bla? since the stripes are so even in repetition) but the lack of stripes on the scanned glass positive totaly confuses me. I'm running out of ideas... :confused:

Zana

Jac@stafford.net
1-Dec-2015, 07:45
It is definitely a problem in the scanner or its firmware.
Does it happen when scanning a grey card?

Zana
2-Dec-2015, 02:48
Hello Doug,

I agree, but that doesn't make sense for the stripeless scans of glass positives. Stripes appear only in transmissive mode when scanning that black emulsion covered glass plates (tried the other side, same thing plus some Newton rings). Stripes are less visible when scanning in lower resolutions, but I need higher than 1200 dpi for large printing.
I don't have a grey card.... or any clue what should I do ....:)
BR
Zana

Michael W
2-Dec-2015, 03:59
I've no idea what is causing the marks and I'm not familiar with that scanner model. The only thing I can suggest is to try scanning in RGB mode. If you are inkjet printing the files will probably have to end up as RGB even for printing a B&W image, so you might as well try that from the start.