Focus problem - nd grad filter?

[Christopher Hansen]

I just my film back from the lab from my Labor day weekend shots. The one shot I made with no filters is razor sharp everywhere. However, every shot I made with nd grad filters seems to be generally sharp, but have one spot (roughly 1" square) on the right center of each frame that is out of focus. I don't get it. Could it be the filters? Why is is localized to one spot? Is this a common problem? What can I do about it?

I thought I saw something like this before, but I thought it was insufficient depth of field issue with a front tilt. Looking back on it, maybe it was the same problem. This time I used no tilts at all.

All my equipment is decent quality - Singh-ray filters, schneider 180 lens, toyo AII camera.

Thanks.

[C. D. Keth]

Filter do, on occasion have bubbles or uneven spots. Check your filters. Lay them flat on a page of printer word. That will make any uneven spots very obvious.

[Christopher Hansen]

Thanks. I just checked my filters and they look fine. No bubbles or scratches. I haven't used them very much. I'm wondering if it is flare off the combination of 2 filters and the front of the lens.

[C. D. Keth]

Any way you could post one of the images?

[Christopher Hansen]

I don't have a scanner at home that can handle 4x5 film, so I trimmed a section out of one frame and scanned it with my medium format scanner. I scaled it down and sharpened it a bit in Photoshop to make the problem stand out.

Look right above the big rock. You will see a section of the frame that is fuzzy. Any ideas? It just doesn't make sense to me.

[William Stone]

Perhaps a water drop on the filter ... ? Bill

[Christopher Hansen]

That would make sense, except that I was up high above the water - like 50 feet up - where I took the shot. This was taken from the walkway at Julia Pfeiffer Burns State Park in Big Sur, CA. I don't remember getting anything wet.

I'm wondering if down at the surf there was more mist in the air. It really doesn't look like lens / filter flare.

[Glenn Thoreson]

I have gotten defective filters in the past. The worst one was a new UV filter that made it impossible to get a sharp image. It was not just bad, it was horrible. I would return the filter.

[Shailendra]

Check the inside of your film holder as well, make sure its clear of any dust or something that could make the film not completely flat.

[Uusilehto]

Hard to say from a small picture like that but it sure looks like something was distorting the optical path. I think I've gotten something similar with waterdrops and a large aperture (on small format but large format has a narrow DOF by nature). Too small an area to be a smudge or a bump on the film.

Are you absolutely sure it isn't a smudge on the scanner?