colour cast in shadows with IT8

[Alex Ramsay]

I've just upgraded to v6.4.2r9. I've calibrated Silverfast using the 35mm target supplied with my original Silverfast 5 CD. This is a C-ROES target, 1999:10. When I try auto-adjusting the prescan, the shadows take on a strong red-brown cast. I can take most of this out using the auto colour cast function, but that tends to leave the contrast too high (shadows block up). I'm mostly scanning 6x7 Fuji transparencies on a Sprintscan 120 & Mac. I've been careful to follow Ian Lyons' directions (I think). What can I do about this?

Alex

[LSI_Noack]

Dear Alex

I suggest you configure the automatic image adjustment tool to your taste. This can be done on the "Auto" tab of the SilverFast "Options" window.
More information can be found in our documentation (PDF, 2.58MB).

Best regards
Sonny Noack
- Manager Technical Support, LaserSoft Imaging AG -

[Alex Ramsay]

Thanks, I'll try this. I still don't understand where the shadow colour cast is coming from, though. And should I be using a more recent IT8 target for more precise results, perhaps a medium format one as I principally scan 6x7?

Alex

[degrub]

Is your CRT calibrated ? Do you let the scanner lamp settle for 15 minutes or so ? What does a scan look like if you scan the target under your settings , same issue ?

Using Velvia ? You might email Gregory C on this forum as i think he has used a lot of the Fuji films.

A new target wouldn't hurt. But if the old one has been stored in the dark. low humidity, moderate temp., it probably hasn't shifted much that would matter.

[LSI_Noack]

Dear Alex

if SilverFast's IT8 calibration routine finds the colour values read from the target's patches deviating from the values put down in the corresponding reference file to be unusable, it will tell you so.

Until then, I am not sure that recalibrating with a different target will help much. Size generally is of no big importance... i.e. of a target, mind you
However, it can well happen that the surface of the target reflects light in an "odd" way, e.g. long-waved (i.e. red) light is deflected differently than higher frequency (short wave length) (i.e. blue) light.
This may ultimately lead to a cast, however, the deviation should have been experienced in the lab, too, and thus reflected properly in the corresponding reference file - at least in theory.

Best regards
Sonny Noack
- Manager Technical Support, LaserSoft Imaging AG -