5x4 400PortraNC and blue skies

[Bruce Watson]

I've got a sheet of 400PortraNC that's given me an interesting problem. I'm trying to track it down to find the cause and then hopefully a correction so it doesn't happen to me again. Learning from my mistakes if you will

The image in question is a late fall or early winter scene. Fall color in a snow storm. What I've found is that when I color correct the image, all the colors fall into line like they should with the exception of the blue sky parts. Instead of blue I get cyan. To be specific, this isn't an overall cast across the whole image, all the reds, greens, yellows, whites and grays all are fine. It's just the blue that's off.

Unfortunately I don't have a lot of experience with this film because it's pretty darn expensive - I only use it when I need the speed (and that day it was cold, seriously windy, and snowing so I really needed the speed), and that's typically in the understory where it's shady. This is the only sheet I've got with this film and any blue sky at all. So I don't have anything to compare to.

So, does anyone have a theory as to what might cause this, and perhaps what I can do to prevent it in the future?

[EdWorkman]

How about this
The color of light in cloudy conditions tends toward blue
You corrected blue "out" to get the reds and yellows.
Try a dydimium filter next time

[Kirk Gittings]

what are you going to do with the film? Scan it? IT is pretty easy to correct the hue of blue skies in PS with Hue/Saturation.

[Bruce Watson]

what are you going to do with the film? Scan it? IT is pretty easy to correct the hue of blue skies in PS with Hue/Saturation.

Indeed. I drum scanned it and corrected it. But what I'm trying to figure out is what caused it so that I don't do it again if I can avoid it.

[Bruce Watson]

It's been nearly a year, but I think I'm beginning to understand what happened with this photograph. It seems that one of the characteristics of the Portra films is that the yellow layer (blue sensitive) tends to go cyan when "overexposed." And the sky in this particular photograph was up around zone VIII-IX if I remember correctly (always a gamble with my sieve-like mind ;-).

I'm also trying to ascertain whether or not this could be a UV sensitivity problem. I'm thinking this because I only see this shift show up in blue skies. I don't see it anywhere else, even with white flowers in full sun (zone X+). White stays white and doesn't go cyan. Hmmm...

So, since the sky areas are also UV rich, could the UV sensitivity of the film be contributing to the shift toward cyan? Said another way, would a UV filter help to keep the blue skies blue?

Any thoughts?

[Struan Gray]

I missed this first time around, I have always felt that with 160NC highlights tend to cyan with overexposure - I see it as part of Portra's look.

It crops up with interiors too: any outdoors seen through a window can look more than usually weird when you correct for dim fluorescent/tungsten lighting indoors. Specular highlights can easily get a cyan tinge too.