Can a lens be soft on one side?

[Ed Richards]

I am testing a 47mm XL, and it is driving me crazy. One side of the negative is sharp, but the other side seems to soft. I got a recessed board and repeated the test, to make sure that the bellows was not pushing the standards out of line, and got the same result. I cannot really make out where the transition is because it not dramatically soft, just less sharp. This lens has seen some wear and has a few dings, hence the serious testing before I commit to it. I suppose if the elements were knocked loose, they could be in place on one side and, pivoting on that edge, displaced on the other side. Does this make sense?

[Louis Pacilla]

Hi

Check your camera back. make sure your film is not buckling in the holder. Make sure the Ground Glass & Fresnel(if you have one) is in the right place as well as position. Also make sure that holder is setting in back properly.

I doubt it's the lens IMHO

[BrianShaw]

I'm with Louis... it might be more likely that other factors are in play causing your lopsided sharpness/fuzziness and should be checked out and eliminated as possibilities first.

[Mark Sampson]

Camera alignment seems to be more critical with wide-angle lenses; perhaps someone more knowledgeable than me can explain why. I've had what seem like similar issues using a 75mm lens (on my wooden field camera). I've learned to be very careful when using that lens; I'd guess that using a 47 would amplify the situation. Of course if you try different setups, and see your unsharpness on one side or the other,it won't be the lens.

[ic-racer]

Without seeing the negative close-up it is hard to diagnose. One thing to think about is alignment of your detents (your camera has them?).

I know with my equipment I needed to do a precise laser alignment of my camera's zero detents to get a 65mm lens in proper focus from side to side (for typical outdoor use). With a 45mm the alignment is going to be even more critical.

[Ed Richards]

Come on guys, I did not just fall off the turnip truck.:-) I did all that and more already. I think it really is soft - a little - on one side. I also used a 65mm on the same camera and was perfect.

[Louis Pacilla]

Hey Ed.

There is a Finite amount of things it could be. It seems to me you have checked all. So................ return the lens in the turnip truck you did not fall off of ;)




Come on guys, I did not just fall off the turnip truck.:-) I did all that and more already. I think it really is soft - a little - on one side. I also used a 65mm on the same camera and was perfect.

[Ed Richards]

Louis,

You are right, and I probably will because no matter what it is, if it is inside the lens, I am not going to fix it. I am still curious.:-)

[Steve Hamley]

Ed,

Rotate the lens 180 degrees on the board and see if the other side gets unsharp.

Cheers, Steve

[Kirk Gittings]

I once had a 90 Fujinon that I dropped from about 4 feet on cement (with the lens caps on) on the corner of the back element. There was no obvious dent, but the back element was actually bent at the base where it screwed into the shutter. It was not a problem that was easy to see. The lens was usable stopped down at small apertures but in the middle I could only really get good focus on one side or the other. I actually used it for years until it was stolen. It is probably still out there driving people crazy.

[Frank Petronio]

What Steve said, brilliant common sense.

And when I see that "minty" 47XL for only $500 BIN on eBay....

[Ed Richards]

Steve - My recessed lensboard is offset drilled so the lens only goes one way or I would have done that. I may put it back on the flat board so I can try that, now that I know it was not bellows interference causing the problem.

[BrianShaw]

Come on guys, I did not just fall off the turnip truck.:-) I did all that and more already. I think it really is soft - a little - on one side. I also used a 65mm on the same camera and was perfect.

OBJECTION... introduces facts not in evidence: what turnip truck?

:)

If your 65 is OK then I'd agree with your suspicion that the lens might be wonky in some way. Had no idea that the 65 worked well. I like Steve's suggestion of turning it, if possible, and seeing what develops. (I wish I had brilliant common-sense!)

Dumb question: Can you see the slight softeness on the GG?

[Phil Hudson]

Camera alignment seems to be more critical with wide-angle lenses; perhaps someone more knowledgeable than me can explain why. I've had what seem like similar issues using a 75mm lens

I understand that many LF wide angles have very little depth of focus (at the film plane) even when stopped down to a taking aperture, thereby magnifying alignment error. Not sure if this related to lens design or focal length though.

[John Schneider]

Rather than flip the lens 180 deg., flip your camera back 180 deg. -- this will tell you if it is the fault of the film/holder/back/GG or the lens.

[BrianShaw]

Rather than flip the lens 180 deg., flip your camera back 180 deg. -- this will tell you if it is the fault of the film/holder/back/GG or the lens.

Anotehr piece of brilliant common-sense. I aspire to be as sensible as you guys some day.

[Robert Hughes]

One of my cheaper cameras has an alignment problem in the film travel, causing half the frame to be totally out of focus:

http://farm4.static.flickr.com/3049/3093974864_a47f4e89ee_m.jpg