Show Clipped Pixels

Moderator: jsachs

Marpel
Posts: 320
Joined: September 13th, 2009, 3:19 pm
What is the make/model of your primary camera?: Nikon D810
Location: Port Coquitlam, British Columbia

Show Clipped Pixels

Postby Marpel » December 8th, 2017, 9:05 pm

I have a couple photos where the sun, or edge of the sun, is shown in the image with rays extending out (some are of a sunrise at Mesa Arch while the others are of a rising sun showing through a morning fog in a grove of trees).

I used the "Show Clipped Pixels" button in the tool bar in an attempt to determine how much of the images were clipping, as I adjusted brightness etc. And I'm trying to understand what I am seeing.

The clipping overlay colour (red) is only showing around the edge of the sun, where there is a very light yellow colour. I had presumed that the (blown out) sun itself would have the clipping overlay on it as well, and I am wondering why the sun itself isn't included.

I checked the manual for the explanation of this tool and found "...displays pixels that have a maximum of minimum intensity in a solid color."

I am wondering the definition of "solid color" and whether this means that the tool will not show a bright white as clipping because it must be a "color" (i.e. something other than pure white or pure black)?

Or am I misinterpreting things?

Marv

jsachs
Posts: 1379
Joined: January 22nd, 2009, 11:03 pm

Re: Show Clipped Pixels

Postby jsachs » December 8th, 2017, 9:13 pm

In file preferences you set the threshold values for highlight clipping. If any channel has this value or greater, it is considered a highlight. My guess is that for some reason your white highlights don't go all the way to 255. (For 16-bit images, clipping is at the 16-bit equivalent of the threshold value). If you post a bit of the image which has the highlights, I can check it.

Also, you can try using the readout tool to check the values.
Jonathan Sachs
Digital Light & Color

Marpel
Posts: 320
Joined: September 13th, 2009, 3:19 pm
What is the make/model of your primary camera?: Nikon D810
Location: Port Coquitlam, British Columbia

Re: Show Clipped Pixels

Postby Marpel » December 9th, 2017, 6:32 pm

Thanks Jonathan,

Had the clipping value in Preferences set to 255, but did not realize that only one channel had to meet that limit. For some reason, just assumed all 3 channels had to meet/exceed for the clipping to show up when using the tool. Nice to know.

Also, followed your advice and checked the images using the readout tool, and discovered that the centre part of the sun (in all three images) is less bright than the yellowish edges. Would have thought the opposite, go figure.

Learned something new today.

Thanks again,

Marv


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