Whats wrong here? CV 21mm f/4

[chambrenoire]

Hi! I just bought a hardly used CV 21mm f/4 lens. But some of the pictures are blurry, something is not right. Please look at this picture for instance, the left part of the image is blurry but the right side is just fine?!
What could be wrong?

 

[BJ Bignell]

Either the lens is defective/damaged, or it's improperly mounted on the camera. Make sure the mount and threads are clean and that your M adaptor (if you're using one) is also in good condition.

I'm assuming you haven't had this problem with any other lenses? Have you looked carefully at some other shots for comparison, just to eliminate the camera as a cause?

 

[chambrenoire]

It's M-mount and mounted on my Minolta CLE. It clicked into place without any problems. Some other pictures look OK, but then some are like this: http://i31.tinypic.com/2qva8t1.jpg

 

[Sparrow]

that's not typical of the lens, it looks like it's not mounted parallel to the film plane.

this is a normal 21, CV21

 

[dexdog]

very odd, that last shot- sharpest in the middle, really bad on the left, sorta out of focus on the right. I would vote for a lens element being installed incorrectly. If the mount was the problem, you would expect the image on one side or the other to be OK, but in this case, both margins are crummy.

 

[chambrenoire]

But then again, some pics are fine... What could be wrong? I think the 21mm was mounted on the camera all of the time, from the time I took the blurry pics to the sharp ones, and so on! http://i25.tinypic.com/rrnyx1.jpg

 

[ferider]

You sure the negatives look the same ? Maybe curved during scanning.

Roland.

 

[BJ Bignell]

But then again, some pics are fine... What could be wrong? I think the 21mm was mounted on the camera all of the time, from the time I took the blurry pics to the sharp ones, and so on! http://i25.tinypic.com/rrnyx1.jpg

Is aperture selection and/or depth-of-field masking the problem? In this latest shot everything looks fairly sharp, but I'm guessing that you weren't shooting wide open. The problem could be verified with a tripod and some static shots at various apertures.

 

[chambrenoire]

I re-scanned the neg and same blurriness.

They weren't shot wide open, but between 11 and 22 I believe.

Thank you all for your help and suggestions. I can't exactly figure out what is wrong.

 

[Paul T.]

Does this occur with many photos? Because my guess is it might be motion blur.

Look at the shape of the white marks on the left hand side of the steps, and the little boy. I suspect that the camera moved as you took the photo, a slight rotation around the axis of the camera's right hand side - ie the left hand side of your camera moved slightly forward or back.

Of course, if you have the same effect on a lot of photos, it must be due to decentering, or similar. (Or a wobbly left hand?)

 

[chambrenoire]

Only on about three negs, on a roll of 36 so it's not too bad but rather annoying when the pictures taken could have been quite good.

But if I moved the camera while taking the picture, wouldn't the whole picture be blurry?

 

[uhligfd]

The lens is probably its best at f/5.6 or f/8. And diffracts heavily at f/22, no doubt.

Subject moving blur or/and camera motion blur can manifest itself differently depending on the angle (rel. to the optical axis of the lens), angular speeds etc.

 

[Sparrow]

Only on about three negs, on a roll of 36 so it's not too bad but rather annoying when the pictures taken could have been quite good.

But if I moved the camera while taking the picture, wouldn't the whole picture be blurry?

Not always, it's relative to distance. Think how a photo from a moving train window would look.

 

[Keith]

What conditions were the very first pic you posted taken under ... from a car, standing etc?

 

[Avotius]

I suggest a tripod and a something that doesnt move, like a brick wall, I hate it when people photograph them but this time it might be called for. I think you might have a lens element that is out of alignment, could it be one of the element's retaining rings is not tight and its moving in the lens? Sounds crazy maybe but try shaking the lens to hear if something inside it rattling around?

 

[Palaeoboy]

Can you hear anything rattling inside the lens like a loose element? The good one minute then blurry the next may be an element coming loose then reseating itself as you move about or tilting the camera up or down.

 

[kbg32]

Have a repair person check out the lens for decentering or any other anomolies. Then go from there.

I have a CV 15 that sometimes acts like your 21. But it's so weird that I like it!

 

[rumbliegeos]

The first photo also displays a feature of the lens that led me to sell the one I once owned: significant light fall-off. It could be I am just not a super wide-angle fan, but I don't think my Nikon 20mm exhibits such an ev range across the frame.

 

[Benjamin Marks]

I'd echo the suggestion to shoot a flat surface with the camera on a tripod so that you can be certain of eliminating certain variables. One thing to consider is that depth of focus on these lenses is not infinite, and performance will drop off at the corners. In the picture of the woman (and man) with their carts, for instance, focus seems like it is on the man, maybe 20 feet away. If that is so, it is not surprising that a bit of store window six feet away would be out of focus. I mention this because in that particular picture, focus seems soft on both the left and right sides of the frame. It should not be hard to check for the kind of decentering that has been hypothesized here. Tripod. Wall. Camera parallel to wall. Try a few apertures. If it isn't that, you might look at the film rails/pressure plate on the inside of the camera and see if the film is not being held flat when you make an exposure. Of course if this were true, you'd notice the problem with other lenses as well.

Good luck with your diagnostics.

Ben Marks

 

[chambrenoire]

I tried shaking the lens lightly to hear if anything was loose inside but not a sound. And as I wrote, most pictures came out OK from that roll, but these two or three. Perhaps it was something temporary.. Thank you again for all your good answers and help! Appreciate it.