Slides - Color cast

[gilou]

Hi all,

 

After hundreds of scans, and tens of target calibration, I still have color

shifts. The big point is that the color shift is not always the same across

the rolls (somtimes almost no color shift - somtimes heavy magenta colorcast).

I've seen that some of my slides rolls were much more encline to color shift.

 

So my question is : as I know that my profile is really good (Global dE < 0.4)

and knowing that I still have random color shifts over the various rolls, I'm

wondering if all this would not come from the developpement of the Slides

(chemistry).

 

If So, How do you solve the problem ?

do you take a photo of a white/gray/black target on each film ?

 

Thanks in advance for your support.

 

Best Regards. - gilles

[roger_smith4]

white/gray/black targets will work- shoot them under daylight or flash. If you have a slight cast, in photoshop autocorrections and snapping to midtones will work pretty well, too. If it's consistently shifted, create one levels or curves setting and load it on each affected file.

[peter_langfelder]

Are you letting the scanning software do any kind of automatic correction - normalization or white balance? Calibratingthe scanner just means that the raw data are accurate, but your scanning software may interpret the data in a wrong way. For example, vuescan's white balance can screw up, i.e. add a color cast where there is none in the raw data.

[nigel d]

What films are you shooting? There may be batch to batch variations.

[gilou]

Hi,

 

Roger, maybe that's the good approach. I was thinking of it.

I'm going to test that !

 

Peter, I scan in 16bit linear without any profile (RAW) - Minolta 5400 rev1 - then I open in photoshop and apply the profile.

 

Nigel : Film fuji Sensia 100 / Kodak Elitechrome 100 / ASTIA100

 

Brgds - gilles.