Very small clouds?

[Leonard Evens]

I scan my 4 x 5 negatives, color and b/w using and Epson 3200 scanner. Depending on how careful I am I need to do more or less spotting using the clone tool. I keep finding in an apparently clear sky small out of focus 'puffs' which I've assumed are caused by specks of dust far from the plane the scanner focuses on, perhaps on the underside of the glass. I can't see any such specks on the bottom of the glass, and these puffs always appear in the sky and rarely in other parts of the scene. Dust on the top of the glass appears as white spots with well defined edges. I wonder if what I'm seeing are atmospheric phenomena actually out there in reality. A typical 'puff' is about 20 pixels in diameter in an image at 2160 ppi. That would make it about 1/4 mm on the negative if it is indeed there. I can't see anything like that under high magnification on the negatives but, the contrast level is so low that I wouldn't really expect to see anything.

One wouldn't normally see these 'puffs' in a print unless it were very large, and I haven't yet made such prints.

I have been spotting the 'puffs' also, but if they really are out there, perhaps I should leave them there for verisimilitude.

[Bruce Watson]

Hard to say. If after cleaning everything you can find (including the underside of the scanner glass) you still get them, perhaps they are actually there in the scene.

On the other hand, even if they are real, you can still remove them from your image. I find that I remove a surprising number of distant birds from my the skies of my images, for example. Unless I'm making a print that's wall size, they show in the prints as tiny black dots. People notice them - they're distractions. In the interest of making a better image, I clone them out. And I sleep amazingly well at night ;-)

[Paul Butzi]

Perhaps a controlled experiment would give you some info on what's going on.

Why not make a negative of a blank, more or less featureless surface (such as a wall), exposed as zone 7 or so (about where your sky would fall).

If you find clouds on your wall, you can probably conclude the problem is somewhere in your processing or scanning.

You might also have a negative with clouds scanned by someone else, and see if they get the same clouds in the same place.

And yes, I'd be happy to do a test scan for you on my Microtek 1800f, so you can compare.

[Jack Reisland]

Just turn the negative around, end for end, and scan it again. If the same puffs are in the same places, they're in the negative. If you get different puffs, it's your scanner.

[Ralph Barker]

Being as you've already received useful suggestions, I'll just say they might be scanner sprites, Leonard. You know, the ghosts of dead pixels who haven't crossed over yet? ;-)