What caused this vignetting?

[raid]

I used a W-Rokkor 21mm 4.0 via an adapter on a Canon RF camera. All images show some serious blackening on one corner only.

What is the reason?

No lens hood was used and no filter was used. Most images were taken at F 16.

Was it some internal optical problem?

Was it the Minolta-Leica adapter?

http://i162.photobucket.com/albums/t261/raidamin/167413-R1-00-0A.jpg

 

[Benjamin]

It can also be seen in the bottom, left hand corner.

Looks pretty severe, like an obstruction as opposed to light fall off.

Good luck!

 

[Beemermark]

Are you sure it isn't a finger or camera strap? Things like that happen with a wide angle on a RF.

 

[raid]

A finger or camera strap would not be causing the same exact effect in all images. I fear that someone has worked on this lens and that it was not properly put back together.

 

[raid]

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[raid]

photos have been removed

 

[raid]

It can also be seen in the bottom, left hand corner.

Looks pretty severe, like an obstruction as opposed to light fall off.

Good luck!

Benjamin,
It is much more blackening on one corner than the opposite corner. I fear that some repairman caused this problem.

 

[squirrel$$$bandit]

stuck aperture blades?

 

[Benjamin]

I fear that some repairman caused this problem.

Yes, it doesn't seem unlikely..

Is it worth having it looked at though?

 

[raid]

It cost me $200 Plus, so I think that it is worth it. Some people sell it for $700.

 

[raid]

stuck aperture blades?

Would this cause such blackening?

 

[squirrel$$$bandit]

Would this cause such blackening?

I'm not sure. In fact, probably not...it would have to be closer to the film plane, or out in front of the lens--at least you'd think so.

You'd think the answer would be obvious...

 

[raid]

I'm not sure. In fact, probably not...it would have to be closer to the film plane, or out in front of the lens--at least you'd think so.

You'd think the answer would be obvious...

It is a definite "no" since I used the lens with an adapter in closed aperture mode. There would be no aperture blade movement.

The shape of the protruding lens glass in the back and the flower cut of the holding piece of the glass requires careful positioning of the glass if someone worked on it for a CLA. Any changes will result in serious blackening.

 

[squirrel$$$bandit]

Well, are the hood petals out of alignment? If the hood was twisted a bit off true, the petals would intrude like that.

 

[raid]

I may be on to something here. I took a magnifying lupe and inspected the back glass. Then I wetted a soft cloth with cleaning liquid and I wiped it clean. At one stage, two black smudges appeared on the cloth. Could there be oil from the blades plocking the light ? If so, a CLA may take care of it.

 

[petebown]

I think mabelsound has the answer, or the adapter is causing the lens to sit slightly skewed.

 

[raid]

Well, are the hood petals out of alignment? If the hood was twisted a bit off true, the petals would intrude like that.

How can I check this out?

 

[raid]

I think mabelsound has the answer, or the adapter is causing the lens to sit slightly skewed.

I don't have a Minolta SLR body (SR) to check out the lens without the adapter in place. Is there another way ofdoing such a check?

 

[raid]

I took a 10x lupe and I reversed it when looking at the lens from the front. I now see two areas corresponding to the two areas appearing as black in the images. These two areas appear like shining crystals. Is this decementing or broken optics or what?


edit: A second look shows me smudges and not crystals. Oil?

 

[squirrel$$$bandit]

The petals should be parallel with the frame of the photo. Those cuts in the petal shape are for the corners of the image; the small petals for the sides, the large petals for the top and bottom, get it? The petal hood maximizes the amount of flare control possible without intruding onto the frame, but it has to be precise. That's why there are no screw-on petal hoods. So if you look at the camera head on, and the petals seem off true, that's your problem there.

BTW, Raid, this would all be easier to read without seventy huge photos to scroll through!