FF PS color differences

Hi,
Should I expect identical results between FF and PS CS2 when blending? For example, if I do an overlay blend of an image using PS, choosing an arbitrary pixel, I get Lab=87,21,108 then do the same blend in FF the same pixel is Lab=84,8,92. Are small differences expected and I can move on or is there something wrong with my filter design? At this point, for purposes of diagnostics, I am simply taking an image running it to the foreground and background inputs of a blend component that is set to overlay using an opacity setting of 100% and plugging that into result – a pretty simple test.

Thanks,
Ron

Understood - Thank you.