color shift on agfa folder

[Kevin Roach]

OK. I been bragging about my billy record but it's got a small problem. When i try to use f16 or f22 i get a blue or purple color shift. I'm using fuji reala 100asa.

At f8 or f11 it works great but smaller appetures cause this color shift. The exposure seems ok, not too light or dark but the color is off.

Any ideas? or should I just consider those settings off-limits?

Kevin

 

[Dan Fromm]

OK. I been bragging about my billy record but it's got a small problem. When i try to use f16 or f22 i get a blue or purple color shift. I'm using fuji reala 100asa.

At f8 or f11 it works great but smaller appetures cause this color shift. The exposure seems ok, not too light or dark but the color is off.

Any ideas? or should I just consider those settings off-limits?

Kevin

Hmm. Shouldn't happen. Reciprocity problems, perhaps? But it still shouldn't happen, I shoot EPP and EPN at those apertures with a variety of lenses without shifts. And the exposures required are almost always shorter than 1/10 ...

 

[Ole]

Could it be a blueish haze from a small light leak? Just a wild thought...

 

[rbarker]

A change in aperture isn't going to produce a color shift in and of itself. I suspect there is some other element causing the problem, Kevin.

Assuming you're adjusting the shutter speed to compensate for the change aperture, the shutter's performance may not be consistent across the range of speeds. You'd need to test the shutter to determine what the real speeds are, and then look at the degrees of variation from the marked speeds. I'm not a lens/shutter expert, but my impression is that the slower speeds tend to be "off" more than mid-range speeds.

Or, there might be some other artifact that shows itself at smaller apertures, such as wear spots that align at the smaller apertures, causing flare.