UP2516D, Weird behaviour at 75% contrast

That doesn't explain why setting a contrast of 75 makes the brightness much brighter than when the contrast is 74 or 76. Actually after playing with it a bit more it seems like it changes the colour balance! 75 is redder than 74 or 76. How does that make any sense? It seems changing to 75 sets it internally to the 'Standard' preset, and changing from 75 sets it to 'Custom Color', although the OSD isn't aware of this change.

"Factory settings" should just be the default values. I don't see what it has to do with 75 being a weird special contrast value. In any case I tried resetting it to factory defaults. This weird behaviour persists.

Seems like a bug.

No, not a cheat. The factory default for brightness and contrast is 75 which matches the Factory settings for Dynamic Contrast, Sharpness, and Uniformity Calibration. By moving to lower or higher contrast, you are taking the monitor out of Factory settings. You should reset the monitor OSD (On Screen Display) to Factory Defaults under Others. All Brightness and Contrast changes should be made in the video card control panel.

How many have you tested this on? What were the 20 digit serial numbers? Did any not do this? Other users will need to post their results of 74-75-76 to see if they also have this scenario.

I have tested on these serial numbers:

CN-03JV40-74445-592-816L-A00

CN-03JV40-74445-592-908L-A00

CN-03JV40-74445-592-565L-A00

They all had the same odd behaviour at 75% contrast. There are hundreds more I can test on but it's pretty clear it is a software bug.

I also tested my Dell display at home (U2515H). and it did not display this behaviour; nothing unexpected happened at a contrast of 75%.

FWIW, I tested a single UP2516D and see no difference between a contrast level of 74, 75 and 76. I made the contrast changes using both the OSD menu and with DDM, but only tested under Standard preset mode, after a factory reset. Perhaps there is some other OSD setting involved, or a bug in a specific firmware revision?

Timmmmmm,
I would not expect a different model (U2515H) to have this issue.

Swamped,
His three tested UP2516D were all revision A00 built on September 2, 2015. What A0x revision was your UP2516D?

Sorry to jump on the back of an old thread, but I'm having this exact same problem, only difference is I'm using a UP2716D.

Out of the box, I've plugged the monitor in and gone to the OSD, both brightness and contrast are set to 75.  Changing the brightness has minimal effect, if I put it to 100, is ever so slightly brighter than it was at 75.  It's only when I change the contrast to either 74 or 76 that the brightness change kicks into action.  Going back to 75 on the contrast alone, makes the screen really dull again.  

Looks like this is because the "Uniformity Compensation" is turned off (and the control for it is disabled) if you set the contrast to any value other than 75. 

Uniformity compensation seems to work by reducing the RGB values in different sections in different amount to match the intensity of the darkest part. So in this mode intensity gets as dark as the darkest part. As soon as you set the contrast to something other than 75, UC becomes invalid (as factory values of the UC are computed for the contrast=75), then the pixel intensities are no reduced.

If your brightness is low, you should no longer see big brightness difference between contrast=75 and other contrast values.