Yes. Each filter will reduce the definition by some percent. So softness will be the result. You may try unsharp mask filter in photoshop to improve sharpness..

Blimppilot2000 wrote:.

I feel more than a little foolish admitting this, but I am trying totroubleshoot some very soft and noisy pictures I took on vacationlast week with my d40x and 18-200vr (I am aware of the softness vs.versatility debate for that lens) with auto ISO..

What I did was stack my tiffen circular polarizer filter on top of mytiffen uv filter. I thought that at worst this would give me slightdarkening and not significantly affect the image quality. Not longinto my journey I found I could not separate the two filters. Onlyafter returning to my camera store was I told to use one or theother, not both together. Could this be a reason so many of mypictures taken of static subjects in broad daylight show an 800 ISOand a lot of softness?.

Keep smiling, Ajayhttp://picasaweb.google.com/ajay0612(Thanks for your precious time & invaluable comments)..

Your polarizer cost at least 2 stops so that may explain the higher than normal ISOs..

Question: When you found that the two were stuck together why didn't you just remove both?..

I recommend using filters only when needed. Especially to people who want perfect shots(color tones, detail). Filter reduces light, distorts (more or less)..

I use CPL filters (during travel or at macro) only when needed. Sometimes at sunsets and sunrises I add ND Grads too..

Http://www.stan-pustylnik.smugmug.com..

Good questionI thought using the lens without any filter was a no-no...

Thanks for the tiplooks like I've got some work to do in photoshop...

Not in my books. I have never scratched a lens in forty years and I only rarely but filter on my lenses. I use a filter only when I have a specific purpose in mind...