Color shift with (i)SRD with Plustek 7500i and 7300

[nigel_q]

I was wondering if anyone else has encountered this... It's happened with 2 different Plustek scanners for me now, and it's quite frustrating. Basically, what seems to happen is that the colours shown on the preview scan and the final resultant image are drastically different... But after some experimentation, I've narrowed it down:

On the PC version of SilverFast 6.6 AI Studio, at 5000 dpi scan, using a Plustek 7500i with iSRD/SRD fully off, everything works out fine (except there's scratches, dust, etc.). But if I turn iSRD OR SRD (as in scan with just infrared and software off, or infrared off and software on), the resultant image has very different colours from the preview scan... It's almost like there's a green cast, or the colour temperature becomes much colder...

What's so awesome about this is that it just started happening mid-way through scanning a roll of film... Things were working out, then they stopped. And deleting the preference file doesn't seem to help...

Anyway, before, on both Mac and PC, using SilverFast 6.5 SE with a Plustek 7300 (with just SRD, since it didn't have infrared), the same thing was happening... I thought the scanner was defective, so I replaced it at great expense... But now that this is happening with the new 7500i, and seems to be reproducible, I'm thinking that maybe something is up with the software or my settings...

Has anyone out there come across this? Why would my iSRD/SRD settings affect colours of a scan? The problem is much less obvious when I use SE 6.5 on the Mac, but SE doesn't offer the same degree of 'awesomeness' that AI does for dust and scratch removal...

In both cases, the negafix profile is Kodak Gold 100...

Any ideas?

[LSI_Muenier]

Dear Nigel,

this seems strange behaviour.
Did I understand you correctly that the phenomenon at first wasn't observable, but turned up later on?
Did you also try to scan at different resolutions like 3600, 2400, and 1800 dpi?
What is the exact version number of the Ai and SE you are using (you can find it in the window title of the main floating dialog).

Best regards
Martin

[nigel_q]

Hi Martin,

That's correct, it wasn't doing it at first, then it was...

As far as versions, SE on the Mac is 6.6.0r2, AI Studio on PC is 6.6.0r4c

The problem seems to go away at DPIs less than 1000, but...

I'm back using the PC one, and after deleting the preferences and the serial, it seems to be working normally again, but I'm not sure for how long this will last...

[LSI_Muenier]

Dear Nigel,

please update your Mac version to the current one (v660r4c or newer), too.

If the problem should occur again, then please check different resolutions, especially 3600 dpi and 2400 dpi (as 5000 dpi normally is more than can be extracted from the film).
Please also check if iSRD or SRD really matters, or if the same appearance is seen with a normal scan.
Thank you very much for your help.

Best regards
Martin

[nigel_q]

Hi Martin,

It started happening again on the PC. As you suggested, I tried moving back down to 3600 dpi and that seems to make things 'proper' again, even with the iSRD/SRD on... What causes this at higher dpi?

Thanks,

Nigel

[LSI_Muenier]

Dear Nigel,

does (i)SRD really matter or does it also occur in scans without it?
In the past I had seen slightly differing colors at different resolutions,
which is easier seen with negatives as the color space expansion is much stronger.
Working with 3600dpi resulted in both: a color appearance close to the preview
and a resonable resolution for this scanner.

Best regards
Martin

[nigel_q]

Hi Martin,

It did make a difference before I deleted the config file and serial file, but now it doesn't seem to. I'll play around with it some more and let you know...

As far as colour space expansion, would using 48-bit colour help? Is this related to a calibration routine that the scanner does before it starts scanning?

Thanks for the great insight!

Nigel

[LSI_Muenier]

Dear Nigel,

48-Bit mode might make a difference because the scanner is then forced to supply SilverFast with the full bit depth, in any case.

Best regards
Martin

[Peter Thor]

Hi Martin and Nigel

I know it has been a while sine these posting, but I am having the exact same problem on the Plustek 7500i Ai system now. I upgraded the software to the latest version but it didn't help. Now my big hope is that by now somebody solved the problem. Could you tell me how to solve it?

Peter

[LSI_Morales]

Hi Peter

The cause of this color shift issues is not in SilverFast but the scanner driver itself. You might want to ask our colleagues from Plustek if they are planning to create a new driver for your scanner model which eliminates the issue.

Best regards