strange color in Zerene output

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BugEZ
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strange color in Zerene output

Post by BugEZ »

Processed a stack with a lot of "dark area" in a hole inside a leaf tube rolled by a caterpillar. While I recall the caterpillar in Alice in Wonderland smoking a hookah, I don't think this caterpillar or I enjoyed similar indulgences. So where did the red color in the empty leaf tube come from? Definitely not hallucinations.

Thanks

Keith

Image

Lou Jost
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Post by Lou Jost »

It never dawned on me until now that the hookah-smoking caterpillar in Jefferson Airplane's classic song "White Rabbit" came from Alice in Wonderland.
Now the whole song makes sense....
https://www.youtube.com/watch?v=WANNqr-vcx0

Beatsy
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Post by Beatsy »

That's very interesting. It looks similar to the over-saturation of chitin that I get on some insects, though clearly a different mechanism. Unless metamerism works on empty space too :) I've no idea what caused it here, but looking forward to an explanation. Thanks for bringing it up.
Lou Jost wrote:It never dawned on me until now that the hookah-smoking caterpillar in Jefferson Airplane's classic song "White Rabbit" came from Alice in Wonderland.
One of my all time favourites. When I lived and worked in the USA, the local radio station (93.3 WMMR) used to play the same 3 songs in a row every morning as I was travelling to work - White Rabbit being the last on the list. I often pulled into the office car park wailing "feed your heeeeeeeead" at the top of my voice :)

Lou Jost
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Post by Lou Jost »

I wonder what would happen if you turned off the option to automatically adjust exposures in Zerene.

Beatsy, I've been doing that all day....it is a persistent ear-worm :lol:

rjlittlefield
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Post by rjlittlefield »

Problems like this always turn out to be due to Brightness adjustment, often combined with one or more frames that have dramatically different brightness from the others.

A good way to isolate the problem is to process the stack, then put a checkmark on "Show as adjusted", and look through the source files from beginning to end.

If the strange colors appear suddenly on one frame, then un-check "Show as adjusted" to see what that frame looks like without the adjustment. Often it will be something like a flash that did not fire. The workaround in that case is to remove the offending frame, reprocess the stack, and live with the out-of-focus band that may appear as a result of the missing frame.

If the strange colors appear gradually from one end to the other, then it is just a matter that the appearance of the subject changes in a way that Brightness adjustment cannot handle. In that case the workaround is to uncheck Options > Alignment > Brightness and reprocess the stack.

--Rik

BugEZ
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Post by BugEZ »

Thanks Rik,

The redness in the shadows in the output frame developed gradually as the stack processed. I use LED lights and no flash. I will try unchecking the options >alignment >brightness as suggested.

Beasty,

When a freshman in college at UCLA my roommate’s clock radio ticked on at exactly the same time each morning playing Rod Stewart singing Wake Up Maggie.. We did not sing along...

Keith

BugEZ
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Post by BugEZ »

turning off the auto brightness fixed things as Rik suspected it would. Many thanks!

Keith

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rjlittlefield
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Post by rjlittlefield »

Keith,

I'm glad to hear that your problem is sorted now.

Here is some further explanation of what was happening to you:

Image

Notice that the dark shadow is almost pure red: R=25, G=0, B=1 at the indicated point.

When ZS brightens that area it preserves the ratio, eventually resulting in colors with lots of red, and still not much green or blue.

The same thing happens in Photoshop when I add Exposure using the Camera Raw Filter.

But it does not happen in Photoshop when I add Brightness using a Brightness/Contrast filter, or when I make corresponding adjustments using curves or levels.

I have never figured out why the discrepancy between Camera Raw and the other filters, or exactly what model Photoshop uses for its Brightness/Contrast/levels/curves filters. If anybody knows those things, I would like to know too!

--Rik

Beatsy
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Post by Beatsy »

rjlittlefield wrote:...I have never figured out why the discrepancy between Camera Raw and the other filters, or exactly what model Photoshop uses for its Brightness/Contrast/levels/curves filters. If anybody knows those things, I would like to know too!
I don't know the details, but suspect the "brightness" filter in Photoshop uses the L-A-B colour model under the hood and only affects the luminance (L) channel. It does produce significantly different results to the "exposure" adjustment.

As a general tip, switching to L-A-B colour mode for sharpening and contrast ops generally works better than applying them in RGB space. They should be applied to the luminance channel only (disable the other two). The result is almost always more natural looking and you have more leeway to push the processing a little further than usual too (without causing artifacts like halos or colour bleeding). Don't forget to switch back to RGB mode when done though.

mjkzz
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Post by mjkzz »

ah, just about to post something similar to this, but after turning off that checkbox, it is normal now. :D

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