View Full Version : Newcomer needs help. Possible Lens problem??

12-Sep-2011, 06:32
Hi, I got my first sheets of 4x5 negative film back from the lab this week. I've only had a chance to scan a couple but they all seem to be losing focus on the right hand side of the image. The left side is sharp but the image gets increasingly soft from the centre to the right edge of the frame and also at the extreme edge on the left. This seems to be the case when viewing the unscanned images through a loupe also. I've discussed this with the technician at my gallery who suggested It may be a lens problem although he's not familiar with view cameras. I've uploaded an example with details from each side of the image cropped at 100%.

The green square shows the sharp area. The red shows the image getting softer on the right out to the edge of the frame.

This picture was shot using a Sinar 4x5 camera just before dark.

Lens: Schneider - Kreuznach Super Angulon 90mm f8. The lens looks clean and free from dust, smudges etc.


1 min exposure.

Fuji Pro NS 160 negative film.

Other than focusing, no camera movements were used. All planes were level.

As this is my first time using a view camera, perhaps I'm doing something wrong.

Any advice would be very welcome before I purchase a new lens.

Image (http://www.patrickhogan.ie/assets/images/image%20diagram%20low%20res.jpg)

Sharp Area (left) (http://www.patrickhogan.ie/assets/images/Green%20area_sharp.jpg)

Soft Area (right) (www.patrickhogan.ie/assets/images/Red area_soft.jpg)

12-Sep-2011, 06:53
If the standards weren't parallel, that would do that.

Kent in SD

E. von Hoegh
12-Sep-2011, 07:03
If the film was not loaded properly it could do this.

12-Sep-2011, 08:31
if it's ALWAYS not sharp in the left side..not matter how much you move the lens in and out, then it's the lens...

if it gets sharp by racking the back in and out, then something isn't alligned right---since you see the dullness on the ground glass, you should also see if it is able to be sharpened up by moving the back back and forth.

if not...the lens is......something wrong....cross-threaded? I've never seen a lens be halfway sharp ever like that--it's usuall all over and uniform all around.

Kevin Crisp
12-Sep-2011, 08:57
I'd guess some inadvertent swing front or back. If you focus on something uniformly distant and check the ground glass with a loupe is it sharp on both sides?

12-Sep-2011, 09:27
I've re-checked the front and back standards to ensure they're parrallel. They seem accurate now, and after focusing front and back, everything looks sharp on the ground glass across the whole image. It seems a slight swing at the back may have been the problem. I'll run a few test shots to make sure. Thanks for all the help. :)

Bob Salomon
12-Sep-2011, 09:55
Turn the lensboard so the lens is upside down and shoot another test. If the same side is still out the problem is the camera. If the problem rotates with the lens then the problem is the lens.

12-Sep-2011, 10:05
YOu may be moving the back when you insert the filmholder?

Peter Gomena
12-Sep-2011, 10:41
Your lens may not be mounted properly in the lensboard. The retaining nut or ring probably has a shoulder on it that fits snugly into the hole in the lensboard. If the ring is not squarely in the hole, your lens will be cocked at an angle.

Peter Gomena

12-Sep-2011, 19:27
Could you have loaded the film wrong and allowed the film to bind on the right side causing it to bow out of the focal plane?

Kevin Crisp
12-Sep-2011, 20:04
The only reason I'm not entirely convinced on the rear swing theory is that f:16 with a 90mm lens should have been enough to cover some error with depth of field on a scene that far away. But hopefully that is the easy answer.

13-Sep-2011, 11:19
Well to start with... the softness is not only on the right part. There is increasing softness towards to the left on the supposedly focal plane as well, but less dramatic.

You know people sometimes use back tilts for perspective correction of distant objects and yes Kevin might be right at his doubts as at f:16 such focal shift due to bending film might not be the case. I would second Bob's idea of rotating the lens to see if the blur rotates or trying another lens if possible.

Ivan J. Eberle
13-Sep-2011, 11:56
It can be rather difficult to focus a 90mm f/8 in other than very bright conditions. You may need to focus using a loupe and darkcloth to diagnose a problem like this if you haven't already.

You also didn't mention what you're using for a film holder, but if it's a standard International back/Graflok style sheet holder, there is a notch in the film holder that may not be fully seated in the film gate (although if you didn't have a darkcloth over the back of the camera you might also expect a light leak if this were the case).

Too, make sure you have everything locked down tight before firmly seating the film holder into the gate. It's easy to introduce an unwanted swing if not snug.