Help! How do I scan negs in 16 bit?

[pflower]

Well no-one has replied to my previous post so I'll try again with a more specific subject title.

how do I scan colour negs into Photoshop with Silverfast Ai v.6 in 16 bit mode? I am using Mac OS 9.2, PS6.01 and Silverfast Ai v.6 scanning Kodak Portra VC160 6x6 negs on a Polaroid Sprintscan 120.

Problem -the negs scanned as 8 bit seem fine - they reflect the pre-scan and look ok. I have somehow managed to overcome previous problems of mesh screen overlays. BUT if I try and scan in 48 bit HDR Color mode then all sorts of problems occur. (side question what is the difference between 48 Bit Colour and 48 Bit HDR Colour?). I have chosen the right film type in the negafix box.

Main problem - the file is _VERY_ light (when inverted in Photoshop) and suffers from a dramatic light blue cast. Examining the histograms (in Photoshop) shows that all channels (including the master) are highly compressed at the right (white) end. Yes I can get a proper colour cast but only by compressing all histograms at the extreme right side of the screen manually; or by sampling on the high lights and shadow areas with the dropper tools or by using auto-levels - but in all cases the effect of that is to produce very dramatic combing in the histogram.

Yet if I scan an Ektachrome tranny in HDR Color mode then the resulting scan looks fine - a good histogram balanced across the range and only minimal tweaking required and no combing.

I have been through Ian Lyons' tutorials carefully - (yet bizzarrely I notice that sometimes (but not always) when I set the scanner to my calibration file in Profiles for Colorsync section of the CMS dialog the assigned profile is set not to Adobe RGB but to the scanner calibration profile - weird). As far as I can tell all my settings conform to what Ian Lyons recommends and the manual. The same thing happens whether or not the box marked "for HDR Output" is checked or not.

This is driving me crazy. can anyone assure me that they can scan colour negs successfully in 48bit mode and talk me through what I might be doing wrong. Thanks.

[degrub]

48bit HDR is for output to HDR only. It is a "raw" file with perhaps a gamma correction applied. You probably want to use 48 bit color mode. The only reason to use HDR 48 bit is to do all of your correcting post scan. Unless you have HDR, this would not be useful.

"when I set the scanner to my calibration file in Profiles for Colorsync section of the CMS dialog the assigned profile is set not to Adobe RGB but to the scanner calibration profile"

i believe that is what is supposed to be happening. Silverfast should be embedding the profile for your scanner into the output file. Photoshop will then use that profile to convert to your working space, presumably Adobe RGB.

Negafix may be doing all it can do with the film. The profiles are not perfect by any means. You may have to go into expert mode to tweak the profile to get the results you want. Try a search on all of the forums for the Porta film type and problems.

Frank

[pflower]

Thanks for the explanation. I did look but nothing of relevance.

I think I must be doing something wrong but can't work out what. If I scan the same negs in 8 bit mode the scan looks pretty similar to the pre-scan. if I then scan the neg in 16 bit (48 Bit HDR Color mode) the results are horrible although the pre-scan looks great. I have checked and re-checked my settings in CMS against Ian Lyons' tutorials and the manuals and can't see what might be causing this.

Anyone got any ideas - please?