Colors change while displaying a file (updated for clarity)

[casterle]

Edit: The colors I am talking about below are RGB values as read from my screen, not the colors read from within AP using the Info Tab. These values are consistent as as expected.

I am following a Histogram/Scope tutorial (https://tinyurl.com/y569lw6z) and ran into something I don't understand. In the tutorial, the instructor is working on an image of sold color squares, croping to select certain colors/color groups and observing the change in the histogram.

I wanted to be able to follow along so I took a screenshot of his image, saved it without compression and opened it in AP. But my histograms were still different from his. Looking closer, I found that the colors in AP were subtly different from those in the screenshot. I understand that the colors I see in the screenshot may not be the same as colors on his computer (due to video compression etc) and thus the histograms would rightly be different. But the colors between my screenshot and those same colors in the resultant file opened in AP should, IMO, be identical.

I opened the same image in IrfanView and PS (CS6) and the colors were identical with pixels read directly off the browser screen. I use an old utility (Zoom+) to read pixel (RGB) values directly off my screen. The values are displayed at the bottom of each screenshot, circled in black. The original screenshot file (as saved by IrfanView) is attached as Color.png.

[stokerg]

Hi casterle,

I've been trying to replicate this and can't, i always pick 118, 89, 75.  I'm using a 3rd part tool to check the picked colour (PicPick). 

Can you just check under Preferences>Colour and check what RGB Colour Profile you have set? 

[casterle]

3 hours ago, stokerg said:

Hi casterle,

I've been trying to replicate this and can't, i always pick 118, 89, 75.  I'm using a 3rd part tool to check the picked colour (PicPick). 

Can you just check under Preferences>Colour and check what RGB Colour Profile you have set? 

Good question. When I open the png file, AP informs me that there is no color profile in the file and assigns my working profile (Adobe RGB 1998). This is the profile I use in PS. 

I opened IrfanView (the program I used to save the original screenshot) and configured it to use Adobe RGB 1998 for all unprofiled files. Reopening the image resulted in the same screen color values.