Infinity focus problem of R3A and CV 50/1.5 set

[lichuntak]

Hello, I hv a question about my R3A and CV 50/1.5 asph with infinity focus. the image can't in focus through the viewfinder if my lens turn like photo 1, but the image is in focus through the viewfinder when my lens turn like photo 2. Does anyone know wht's the problem for my set? THANKS..

 

[umcelinho]

Welcome to RFF!

Well, the 50/1.5 is a screw mount lens, so it needs the M mount adapter to be used on the R3A. From the pictures it looks like in picture 1 the lens is not fully screwed into the adapter, what would explain why it's not focusing properly. It's normal for screw mount lenses to not have the "central" mark on the barrel perfectly aligned verticall, it's slightly to the left (facing the camera down, lens forward).

And congrats, it's a great set. The 50/1.5 Nokton is a great lens and in chrome it's really beautiful 🙂

 

[jsrockit]

Which brand adapter are you using?

 

[lichuntak]

i am using CV 50/75 adapter and the lens and adapter are fully mounted to the camera body, but still hv same problem...

 

[kossi008]

Do you have any other lenses to compare with?

It looks like your rangefinder needs adjustment. I just sent an R4A back to the dealer to have it serviced for the exact same problem, but I had 5 lenses to check it with.

If you want to find out if the rangefinder needs adjustment, there are two ways:
1.) Quick and dangerous: Scotch tape across the film gate. Dangerous because you must not get it on the shutter blades.
2.) Slow and safe: take pictures at the lens' infinity setting vs. at the rangefinder split image matching point. You can also take pictures of objects closer by with some depth to them: if your problem is due to a misaligned rangefinder, you should see a consistent front-focus in your pictures. Slow because you need to have the film developed to judge the problem.

 

[mdarnton]

I vote with the idea that the RF needs an adjustment. Check some of your other lenses, but this problem usually only shows up with lenses with particularly long focus throw because of their shallow depth of field--fast lenses, long lenses, etc.

I would not blame the adapter--that's the easiest thing to build correctly, and the least likely thing to have gone wrong.

Adapter threading is totally irrelevant to this problem. If the adapter flange itself is the correct thickness, the threading can end anywhere, since it's the flange that extablishes lens to film distance, not the threads. The lens cannot screw in "too far" as I sometimes see people saying.

 

[lichuntak]

checked from a local camera store, should be camera body s problem...

 

[lichuntak]

thanks all~