monochrome prints in 24bit - highlights blown out

[riotstar]

I'm having problems scanning monochrome photographic prints in 24-bit colour on a Umax Powerlook 2100XL using SF Ai.
The scanning is for archival purposes so the scan has to represent the original image.
I've calibrated the scanner and full colour photographs are fantastic but when the CMS is on and I'm scanning monochrome photo's the scan is quite pale and very green. When the CMS is off the scan has a much better overall colour appearance but the highlights are blown out with a yellow/red cast to them.
I can reduce this by darkening the highlights down in the histogram and bringing the top of the curve down in the gradation curves and finally reducing the contrast of yellow in selective colour correction and then calming them down a bit more in photoshop.

I just feel that this isn't the best practice. While my settings give me ok results which pass, as the photographs are rarely seen next to the screen, I know that highlight detail is being lost and the settings I use are only greying the white down and not fixing the problem. It's as though the lamp is too bright but there doesn't seem to be a way of controlling or compensating for this. Plus I've recently had my scanner replaced and the problem is now even worse.

I've scanned a test image with quite bad highlight problems on an Epson Perfection 4870 and the difference is quite noticeable. The Epson handles the whole range almost perfectly, unfortunately most of our prints are A3 so the Epson can't be used.

Is this a case of limited dynamic range in the Umax Powerlook? Is there any way to reduce the brightness in the highlights or are we stuck with what we've got?

[LSI_Noack]

Dear riotstar

please experiment with setting a blind color channel for your scans.
This can be adjusted in SilverFast Ai > main dialogue > general panel > options dialogue > special panel.

Do you achieve better scan results for your monochromatic scans then?
Which channel worked best for you?

Kind regards
Sonny Noack
- tech support, LSI AG -

[riotstar]

Hi, thanks for your reply.

I tried your suggestion but the problem with the clipped highlights still happens with all the channels.

Anything else I can try?
Thanks
Emma