Nikon 50mm 1.2 issuehttp://d.pr/i/PyKZ

[asamimasa]

Nikon 50mm 1.2 issue

Hey all,

I recently picked up a 50mm 1.2 for my Nikon F2 w/ DE-1, and I'm not quite sure what's going on. A majority of the shots are coming out severely misfocused, which initially led me to think the lens might be miscalibrated, as I'd been shooting a 50mm 1.4 on the body consistently. I stuck the lens on several DSLRs and the focusing came out surprisingly fine for the inferior focus screens. Thought it might be focus shift, but DSLR testing showed it to be negligible. I'm working under the assumption that my mirror alignment on the F2 isn't too off, as the multiple other fast lenses should've raised some flags. Tried using another K-type screen as well.

Any other factors that might be involved? Perhaps just sample variation incompatibility between the two?


Some examples, just screenshot snippets, but you get the idea of how significantly off the focus is (before anyone asks, I wasn't shooting film professionally )

 

[MDR]

The 50 1.2 Nikon exhibits some focus shift, if you focus wide open and stop down to say 2.8 there is a certain amount of foucs shift don't know how much but try stop down focussing instead of wide open.

Good luck

 

[dugrant153]

It looks like perhaps one of the elements may have shifted but you said it's fine on other lenses?
If you're shooting at F1.2, nailing focus might be really tough and since it's so thin it's easy to miss it (I shoot at F1.4 and those times I feel like I have to REALLY take my time to nail them... and even...)

Hopefully you figure it out! Looks like you were shooting a wedding?

 

[resummerfield]

At the same f-stop (1.4), do other 50mm lenses exhibit the same problem? How do the pictures appear with smaller f-stops, such as f8?

In your photo of the couple, it appears that the plane of focus is behind the subjects, but the photo of many people in a line appears sharper on the left than the right. But those photos are just too small and low resolution for analysis. You need to make many more pics to help identify any problem.

Obtain some test charts, or just pages of newspaper with fine printing, place them on a flat surface, and make a series of photos straight-on (at a perpendicular angle). Then publish the entire frame, at a higher resolution, and give detailed information as to the focus distance, the f-stop and shutter used. This will show the extent of the out of focus areas, and whether it is consistent across the flat plane.

Then place a ruler or yardstick in front of the lens, pointing away from the lens, and focus on the mid-point. Make a series of photos at various f-stops to determine the depth of focus.

Finally, try stopping the lens down prior to focus. You should be able to focus stopped down in bright conditions to around f5.6.

I doubt there is anything wrong with the lens. At f1.2 the lens will normally be difficult to get exact focus with any camera, but at smaller apertures it should focus the same as your 50mm f1.4. But with more test pics, a mis-aligned camera focus screen, or an out of square camera lens mount can be identified. And if you do comparison shots, at the same aperture and distance, with the 50mm f1.2 and your 50mm f1.4, any problems with that specific f1.2 lens can be easier identified. Shoot some more test pics, and show us the results.

 

[fotch]

When I enlarged the photos, I could not find anything if focus. Maybe its just me or my monitor.... Perhaps set us some markers at set distances and take photos both focus on a particular marker and another photo using the lens distance scall, for a test.

 

[clayne]

Use a ruler and take a bunch of test shots. The lens is either in focus or it isn't - which the viewfinder will confirm. If it can't hit sharp focus on anything but the nearest objects, then infinity is probably off and only that would need to be recalibrated (but you'll need to prove it out first).

 

[resummerfield]

There are many possibilities… the camera eyepiece diopter may not match your eye, the viewfinder screen may not match the actual focal plane, the camera lens mount flange may not be perpendicular, a lens element may be out of alignment…

The only way to narrow the search for the problem is to do thorough, documented testing.

I have the 50mm f1.2 AIS, and I doubt there is a problem with the actual lens. More likely, a slightly out or adjustment viewfinder screen or eyepiece diopter.

 

[Mark Feldstein]

If the focus was good on the DSLRs, I suggest you check the placement of your focus screen on your F-2. Make sure it's correctly seated and your DE or DP1 finder is also firmly seated and locked in place. Also double check the F-2 focus using your 1.4 lens.

If those things don't work try a focusing diopter. I hated to admit it myself, but a while back I was blaming my 500CM when it was my own 20/20 coupled with age-related limitations errr, so-to-speak.
Mark

 

[fotch]

If it was either the viewfinder screen or eyepiece diopter, would not all lens attached have a focus problem?

 

[Vilk]

i had an issue with my F2 that might have been the same thing: severe random backfocus, just like your first sample, one in every six-or seven on average, say, five or six per roll, focus several metres behind what was sharp on the screen (and i was super-careful after the first few). i'm not sure it was the lens as i, ahem, focused on the body: my local nikon guru saw the prints and didn't even want to look at the lens, he nodded, smiled and kept the body only... and he seems to have smiled with a good reason as the problem hasn't reappeared yet in a couple of years



best of luck in your search--i still remember how annoying it was!

ps. just remembered--i think the whole thing started after i tried to fit in an F3 screen (as i had done many times before); this one somehow started doing this, as if the ground glass were loose in the frame??? but then again, i put F2 screens back in and the issue was there... hmmm... i know, useless...

 

[Mark Feldstein]

If it was either the viewfinder screen or eyepiece diopter, would not all lens attached have a focus problem?

You're absolutely right and I apologize for that omission. I imagined I mentioned that after I got distracted by something else. Sure, if you can duplicate the problem from one lens to another then chances are it ain't the lens. Thanks for noting that. Sometimes it could be that the focusing screen itself isn't really the best match for the lens although I've made do with a lot of different F2 focusing screens.
Mark