corners getting soft on 8x10 format

aj-images · May 26, 2006

I just took my 8x10 out for the first time last weekend. B&J with an Imagon soft focus lens. Since I was shooting scenics and wanting max DOF, I didn't use the discs that are usually used with the lens. I stopped down all the way and shot. After developing the film, all four corners were soft. Will a front swing correct this or is there more to it, like not using the discs? Thanks for any help. - Jim

David A. Goldfarb · May 26, 2006

What's the focal length of your Imagon? It may just not cover the format sharply even when stopped down all the way.

The disks don't make the image soft per se. The lens is designed to have a fair amount of uncorrected spherical aberration wide open, so the light rays that enter at the edge of the lens focus at a different plane than the rays that enter the center the lens. If you stop down the lens with the normal iris, the image sharpens up, because you are only using the rays at the center, reducing the spherical aberration. The disks are designed to preserve much of the spherical aberration, while reducing the amount of light entering the lens, so you get a longer exposure than you would shooting wide open, but the image stays soft.

In any case, I just wouldn't use an Imagon if the goal is to make a sharp image. That's just not what it's made for.

Petzi · May 26, 2006

You should use at least a 420mm Imagon for 8x10".

aj-images · May 26, 2006

David- It's a 300mm. It's from an Ansco 8x10 studio camera, so I assumed it would work.

Petzi · May 26, 2006

The 300mm is good for 5x7" at most. They recommended 250mm for 4x5"...

Petzi · May 26, 2006

David A. Goldfarb said:
In any case, I just wouldn't use an Imagon if the goal is to make a sharp image. That's just not what it's made for.

The purpose of the lens is to make a sharp but soft image.

aj-images · May 26, 2006

Thanks for the info Petzi....did some test strips from the center of the negs and they looked beautiful....sharp, but with a soft and smooth look. It's a shame it won't cover. Back to Ebay I guess.

Jim Jones · May 26, 2006

aj-images said:
David- It's a 300mm. It's from an Ansco 8x10 studio camera, so I assumed it would work.

Maybe it did work when focused for head-and-shoulder portraits. Also, the soft corners wouldn't bother some portrait photographers.

Petzi · May 27, 2006

That's right, but he said he was shooting scenics.

corners getting soft on 8x10 format

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