What caused this vignetting?

I removed the photos.

I think I know where the lens adapter may have played a role here. For whatever reason, when I use the Minolta lenses [35mm and 21mm] with the adapter, the distance scale appears at the side of the lens and not on top where I could easily see the distances. This way, the petals will be misalligned [I know very well why there are petals but I was looking for a reason of the blackening due to other possibilities]
 
I may have to have someone look at the adapter with the lens together.

Thanks mabelsound.

Still, there is/may be decementing in the two areas. I can see the portions covered with something shimmery from one angleand I see smudges from another angle.
 
Last edited:
I wonder how different this new lens is from the old W-Rokkor 21mm 4.5 or 4.0. Most likely, the first difference is the cost, followed by contrast and sharpness.

sometimes new is nice too...
 
back alley said:
I wonder how different this new lens is from the old W-Rokkor 21mm 4.5 or 4.0. Most likely, the first difference is the cost, followed by contrast and sharpness.

sometimes new is nice too...
Click to expand...

Of course, new is nicer. It also costs more. A 21mm Biogon will set you back more than $200 and so would a CV 21mm lens.

Joe, do you have any suggestions other than buying a new lens on the vignetting or ...... ?
 
Raid- it has to be the rear lens guard not lining up properly because of the adapter. If you can have a technician rotate or remove the gaurd, that would probably fix the problem.

Open the camera, set it to "B" or "T" and look through the shutter. You will see if the guard is misaligned.
 
Brian,
The lens is misaligned when using the adapter. I can see this clearly now. With a Minolta 35mm lens I did not have such a vignetting problem because the lens is not that wide, but I see the problems with a wide angle lens like the 21mm. I placed the lens on a camera with the camera back open and speed set to B. The lens guard is blocking the light as it is off by about 90 degrees.
 
The seller is taking the lens back for a CLA first. Then I will start thinking about the alignment issues.
 
Bill Salati mentioned to me that Canon P is incompatible with such a lens. Oh well. I better worry about this next time I use the lens.
 
The lens mounts with the adapter this way [see photo]. The word W-Rokkor should be positioned in the top center where the letter o after W-R is the center to get the lens aligned. Now, the letters QH are positioned where the letter O should be.
 

Attachments

  • rokkor3.jpg
    rokkor3.jpg
    171.8 KB · Views: 0
My local camera repairman inspected the Rokkor 21mm and the adapter. Then he tried the lens out on a Minolta SRT camera. There was no vignette effect with the SRT. He then opened the back of the Canon 7 RF camera, and he placed a piece of ground glass on the film plane. Then he used speed setting B while looking through the back of the camera. His conclusion is that distancing the lens from the film plane via the adapter causes the vignetting. He does not believe that the lens is mounted on the adapter incorrectly.

Why would a 21mm Rokkor vignette but a 19mm Canon does not vignette when used on a LTM? What is the difference in the flange distances between Minolta and Canon SLR cameras?

I am still unsure what the cause of the vignette really is.[the misaligned adapter is my Nr. 1 suspicion]

I placed the two lenses side by side. The 21mm Rokkor is far more recessed than the 19mm Canon.
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom