Photoshop And Matlab Gray Levels

Hello.

I'm using Matlab and Photoshop integration to manipulate some images.

I found incompatibility between the two in the gray levels.

Let's say I set Gray of level 30 in Photoshop (R=G=B=30) and use "psgetpixels" in Matlab I get the value of 21.

How can I create a match between the two?

If it's a Color Profile issue, how can I make Matlab read the Gray levels with no effect of the ICC.

Thanks.