Histogram Stretch (and Shift T) does not work

[Randlov]

Activating Histogram Stretch or the hotkey Shift T does not have any effect on the image.
(Histogram Equalize works fine).
I have to handle a very large number of old scanned b/w underexposed glasnegatives, so batch processing with Histogram Stretch is necessary.
I have tried to reset workspace and database without any change.
Windows 64, 64bit, PSP X8 64 bit 18.2.0.61.
Any suggestions?

[Forriner]

Theoretically (mine, I'm not an expert), histogram stretch is used to stretch a histogram from lowest values higher than zero to zero, and/or and highest values lower than 255 to 255.
If there already is a zero value present, the histogram can't be stretched to the left, and if there's a 255 value it can't be stretched to the right.

Perhaps Levels?

[Jean-Luc]

Hi Randlov,
for me, Equalize does a better job. I tried on an underexposed photo.
Streching works when pixels are grouped in the center of the histogram. If many pixels are grouped on the left or on the right, this command (Stretch) will be useless.

[Randlov]

Thank you very much to both.
I checked with an image with a narrow histogram in the middle, and Shift T worked fine.
The images I am working on right now are scans of old underexposed glasnegatives where the histogram is concentrated at the right. In this case Shift E gives an acceptable result in 3 out of 4 cases.
Problem solved!
Peter