I have a problem that I can't seem to resolve. A polarizing filter is stuck on a UV filter so tight that I can't separate them.
Can anyone suggest a way to loosen them?

Would using cold water help? Possibly putting them in the freezer section of the refrigerator is another possibility (like we used to loosen a tripod in the winter after it was brought indoors and the heat swelled up the leg locks--actually we just put the tripod outside on the porch for an hour our so depending on the temperature). The two filters were given to me by someone with "very strong" hands! I don't want to damage them as they cost quite a bit to replace.

You boys seem to have drifted from the original thread significantly. It started by asking about the noise comparison between a cropped 24 MP and the Full Frame 24 MP Sony sensors (which BTW, do not have the same size photocell receptors). Now you're arguing about the definition of a pixel.

As the originator of the Question raised, yes, things seem to have gotten out of hand.

In summary, simply what I was trying to find an answer to was -

" But, all else being equal, is there a significant difference as to whether the ISO comes from the base range or the extended range?

Stated another way - Is there a differnce if I use (say) an ISO of 12,500 from the Base range, or 12,500 from the boosted range?"

I have received some responses that directly addressed the question raised, although some a a different slant on their response.

As things developed, responses have gone out in all directions. :-(

Excuse me, there is no big ND filter out there that does not provide a color cast, and for that matter all polarizers do as well. Blue is the color and easily correctable and expected. The yellow and magenta casts found in Cokin are from inferior production. You should also add in distortion and vignetting as well. Beginners can't tell the difference. Many will respond, "It works for me". "I don't have a problem with them". However, if you expect great results and visit wonderful places in outdoor and landscape photography. You really don't carry Cokin.

Lee's clip-on foundation system is great and beats the screw-on/push-on filters. Let me explain further. It is nearly impossible to focus let alone view an image through a 10 stopper. With Lee you focus, view, set and then clip-on the ND, snap and clip-off. With a Cokin type, you screw on the adapter and then push on the ND. If your lens has any creep that push on action will change your settings. I am not going to risk that.