so I tried to set my RF according to the Nokton 35 and...

[mooge]

Hello friends,


I tried to align my RF to the Nokton 35/1,4 I just got. standard procedure- lens on camera, shutter held open (B), focus through RF, check on groundglass (actually a Spotmatic focusing screen) taped on the film rails.

I set the RF according to the micoprisms on the focusing screen... but the negatives show that the RF is definitely out and the lens is in focus closer than the RF says it is. and same deal with the distance scale- it would read something like 5m when the subject I focused on was something like 10m away.


so I'm curious why the microprism stuff would indicate that the lens was in focus when it was not- is this some sort of optical trick (pretty sure the '70s Spotmatic was not designed with 35/1,4s in mind) or something? it's NOT focus shift and it's NOT sample variation or getting a crap lens or whatever. the lens is okay. my RF is sort of okay. and that RF adjustment procedure has worked fine for me with a 50/1,8 and a 90/2 before...


any ideas? hopefully what I wrote is somewhat comprehensible...

 

[Krosya]

Your screen may be taped not flat enough or try turning screen around - that may make a difference. Minor error make a difference in RF calibration.

 

[pvdhaar]

The shorter the focal length of the lens and the wider the aperture, the more critical it is to have the focus calibration correct. And here the SLR viewfinder screen itself might become the issue..

I'm not sure what exact type of screen you're using. but if it's a bright-screen, there's a Fresnel pattern present, whose micro-grooves may prevent the screen from sitting close enough to the film gate to calibrate the 35/1.4..

 

[Rob-F]

Why not try it with film before drawing any conclusions, or placing too much reliance on the microprism.

 

[mooge]

well, the screen is out of a Spotmatic- there are two plastic bits; the fresnel screen (grooved) which I don't use, and the focusing screen which is frosted and has the microprism stuff on one side and a bit of a dome on the other. I'm using the second one. and it's always taped down pretty well when I do that stuff.

Rob-F-
I knew my RF was out somewhat before I got the lens, so either way, I'd probably get out of focus photos.

but I've re-set the RF to the Canon 50/1,8 so it should be somewhat correct... I'm just wondering why my RF adjustment method works for 50 and 90 lenses but not this 35...

thanks.

 

[Steve M.]

Doesn't make a lot of sense, does it? Makes sure that the ground glass side of the screen is facing the front of the camera. Make sure that it's laying in the film channel exactly where the film is laying, not on some higher point above and below that channel. First, set the focus at infinity. Make sure the lens, ground glass, and RF all agree there. Then, ck it at around 6 feet. That is certainly the drill on every camera I've ever done this with, and it's always worked fine. The only other thing it might be is that because your lens is what it is, a very fast lens, you may need a better way to set the focus than a ground glass (focus screen).

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