Help! Wollensack lens weird sharpness (unsharpness)

[rodorod]

Hi, I got a Wollensak Seneca DUO Rapid Rectilinear 6 1/2"x 8 1/2" lens that has

just been serviced to work on all speeds available.

I did a first test, and it made me crazy to look at the 5x7" neg, and find some

weird unsharpness-kind of moving subject- around the center bottom of the image.

I know small image circle lenses do not cover the whole image, resulting in

unsharp corners, but this is definately not the case for two reasons: First,

the image circle on this lens covers more than 5x7", and second, the unsharpness

is not seen on the corners...it is more a center bottom unsharpness, looking as

if the subject was moving.

If you check on both zoom-ins of the image -unsharp01 and unsharp 02 (

http://www.photo.net/photos/rodorod ), you will notice the strong problem I am

having. Rocks should not move at all...shouldn't they?...

What could be the cause of this problem? Is there a way of solving this?

Any thoughts will be helpful.

Thanks

rod<div></div>

[rodorod]

second zoom in:<div></div>

[rodorod]

full image<div></div>

[michael_darnton1]

If I had to guess, I'd say the film buckled and popped in the middle of the exposure, maybe from heat build-up in the camera. Do you have more than one image that looks like this?

[kelly_flanigan1]

My guess; wager; bid :) is that the negative was flatbed scanned and the "exposure" of the scan bar caused heat that made the negative buckle; a variant of Michael D's answer. If the negative is too tight in a scan holder the expansion of the negative can cause it to buckle during a scan. The "blue" area might be higher than the optimum point above the scan glass. Alas I might be all wet; Please clue us in how the image was scanned.

[rodorod]

Kelly, the film was flatbed scanned, but the negative has actually this unsharpness.

I have three other images with this same problem, on the negative also, and on the same area.

About Micheal's opinion, the weather was not hot enough to think that heat build-up could happen, but as I do not understand the cause, this could be taken as a possibility...

any other thoughts?

thank in advance

[User_503771]

I wonder a couple of things:

 

1) Are the elements screwed in straight, into the shutter? (As a problem, that's a super long shot really.) Also, when you unscrew the elements from the shutter and gently shake them, is there any rattle? Any separation or other weird-looking artifacts in the elements that would indicate some sort of misalignment?

 

2) What f-stop were you using, and did you use camera movements? A lens that focal length could give you problems of focus; it's a complex scene you shot there. This combined (or not) with...

 

3) Rapid Rectilinear lenses are not real well color corrected. And shooting a close subject like this with lots of varied color might have caused problems, especially if your camera movements weren't spot on. If you focused with the lens wide open, then stopped down, you might have gotten some focus shift -- you really do have to check your focus at the taking aperture after stopping down with these old lenses.

 

You could also try using a filter -- light green or light orange, or red -- to see if that'll pop things back into overall sharpness. By substantially eliminating the complementary color, you're also eliminating some focus error. Try to check focus through the filter at taking aperture before shooting; if you just can't see well enough to do that, check focus at taking aperture, then apply the filter and make the shot.

 

I suspect it's not a film holder problem, since you're getting this problem with multiple negatives. Which leads me to ask:

 

4) Are your ground glass springs strong enough to hold the ground glass panel tight against the back with no film holder in it? If you've got a little bit of "drift" there, that could cause problems. But if you've been using the camera with other lenses and had no problems, then this isn't a likely culprit.

 

Here's a simple test you can run. Take a small series of shots of one subject, preferably a landscape (or better yet, an urbanscape with tall buildings) where everything is fairly far away and you don't have to use much by way of movements to get everything sharp.

 

Make one exposure as usual, with no filter, checking your focus at taking aperture.

 

Then, for your second shot, use a filter.

 

Then, for the third shot, no filter, but turn the lensboard and lens upside-down -- 180 degrees rotation. If that's not possible because the lensboard only fits one way, try to turn the lens in its flange, 180 degrees. (Hopefully it's not just blank sky at the top of the photo!)

 

For the fourth shot, leave the lens as-is, but use a filter.

 

If the lack of color correction is the problem, this will show up with better overall sharpness in the photos in which you used the filter.

 

If the elements are screwy out of alignment, this will show up in all the photos, but the position of the distortion on the negatives will be at the other side of two of the pictures.

 

One more thing: If it's not the original shutter, it's possible that the elements are not spaced correctly relative to the aperture and to each other. I don't know enough about optics to be able to predict exactly what could occur if this is the case, but I'm sure it could raise some sort of havoc.

 

Good luck, and let us know if/when you're able to find out what's up.

[doremus_scudder1]

This definitely looks like film movement during the exposure (the "double-image" in the area in question clinches it). Since it is not present in the entire negative, part of the negative must have "popped" or buckled out of the flat position during the exposure. Heat and/or humidity can cause this. It is usually a rather rare occurrence, but if you have the problem a lot, you may want to identify the exact cause and deal with it. If heat or humidity is the problem, usually letting the film "settle down" for a few minutes before exposing takes care of things. If there is a film holder or film/holder compatibility problem, you will need to deal with that in another way

 

I once had a batch of film that was cut poorly by the manufacturer and was tight in the holders on one end. This caused buckling and resultant unsharpness along one edge. It took me some time to figure it out.

 

Good luck,

 

Doremus Scudder

[rodorod]

Michael Hendrickson, Thanks for the multipple action suggestion!

I will run some tests that way in order to find out what is going on.

As of the shutter, it is definately the original shutter. It was only fixed to work properly, and the screw is tight in both ends. It looks in good form and condition.

The springs on the groundglass holder are a bit tighter than usual, as I built them myself to replace some loose ones that came with my old Seneca. This unsharpness does not happen with other lenses.

Doremus, I also feel this has to do with some kind of movement, but I really don't see a reason. It was not hot or humid during that scene.

Does anybody know if this kind of old lenses are not crisp sharp regularly?

Thank you all for your feedbacks.

Rod