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Posts: 537
Joined: September 13th, 2009, 3:19 pm
What is the make/model of your primary camera?: Nikon D810
Location: Port Coquitlam, British Columbia


Post by Marpel »

I am processing a couple images of a prism and the rainbow colours it produces. The prism is set on a white paper, and I have been playing with blocking light on part of that paper, so the colours fall on a shadowed area.

Because these colours are spread out over a shadowed area, they appear considerably more pronounced than across the white surface.

In processing, I am experiencing a bit of a dilemma over the saturation level, not wishing them to be overly saturated. Currently, the intended purpose is on screen but printing may occur in the future, which I suspect adds to the saturation issue.

In looking for a way to objectively assess saturation, I came across a method for Photoshop, which includes using an inverted layer, blend mode set to "Colour" and opacity set at 50%. The result is a grayscale image, and anything that shows up as coloured indicates that area is oversaturated.

I am trying to figure out how to do this same thing in PWP. The Invert (and subsequent Composite at 50%) is straightforward, but I don't know the equivalent Colour blend mode.

Any help would be appreciated in figuring this out, or insight into how to assess/measure saturation in PWP, excluding a visual subjective method.

By the way, just used the updated Crop tool and the recent changes are great.


Posts: 3201
Joined: January 22nd, 2009, 11:03 pm

Re: saturation

Post by jsachs »

You can use Extract Channel to extract the Saturation channel as a black and white image. There is no single definition of Saturation as it depends on the color space you are using.
Jonathan Sachs
Digital Light & Color

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