Contax RTS & RX Focus question.

MrBrowning · Apr 29, 2017

I just bought a RTS and a RX and the are focusing differently with a 50mm lens. With the RTS infinity is just back from the mark as shown in photo 1. The RX infinity is in focus in the viewfinder further back. What could cause this? I tried using the eye correction on the RX but it didn't help.

michaelorr · Apr 29, 2017

Funny you should point this out - i just looked at my RTS II (with 50/1.7 planar) and focused using the center spot microprism to focus, and the distance indicated is at exactly the leading of the 0 in the 10m mark.

But to your point, it is a bit disconcerting that whatever this point would be, it is different between the two bodies. Obviously the focal point at the film plane has to be the same

MrBrowning · Apr 29, 2017

That's what I was thinking. It seems to me something must be off on the RX body. I'm considering just sending it back to the seller and ordering a different one. Unless it's a super easy fix.

michaelorr · Apr 29, 2017

Do you develop roll film at home? could you sacrifice a roll? i may take mine out to the park and close focus at 1.7 on a brick wall of the blacksmith shop, and then find a suitable "at infinity" subject that would be suitable to see what this camera does. I do know everything i have ever done with it is good, but sure that it is done at > f8. I have to send film to lab so it is of no help to you at the momentEdge in making the "send back" decision.

I bought a RTS before i found the RTS II from a local camera store selling on consignment. I took photos at that same park, same building, did an off-angle exposure to determine if the focus was in the right place a la Barry Thornton Edge Of Darkness. I took the roll back to that camera shop and asked them to develop and print. I went back to collect the prints and invited them to look at the prints with me while i was there. The camera was not focusing correctly. All 36 images were messed up. They returned my money. They also had a Contax G2 kit there they tried to convince me i would like. If i had any blasted idea what i was doing...
I had no interest in a camera i did not understand! I am sure many of us have regrets in stuff like this - i would have loved that camera from the get go i suspect.

Forgot to mention above, i focused on a canopy of woods that are >300ft away when i looked at the RTS ii a little while ago.

MrBrowning · Apr 29, 2017

I have developed a roll from my RTS and they looked fine through a loupe but I haven't had time to print or scan them yet. I was shooting a quick test roll through the RX when I noticed the focus difference and that will be developed later tonight. If I had a second lens (the seller hasn't shipped my 35-70 yet) then I'd test the side by side and see how far off the RX is.

It was suggested on facebook to test the closest focusing on each camera. With the RTS from the font of the 50mm lens to an objejct is 20 1/2" and the RX is 23 1/8". That woud put the RTS very close to the 2' make from film plane to object and the the RX 2'-2 5/8.

The G1 and G2 do look like nice cameras and I will admit to having considered them in the past.

michaelorr · Apr 29, 2017

Maybe you can calculate the difference with the lens equation of u given V for both. Then from the difference in u figure out some sort of delta in circle of confusion to see if those 2 5/8 inches means anything at f1.7

Thinking through this, i guess you know the u is 50mm. Then work out the M for the RTS, hypothesizing it is accurate, to check the equation. Then from the RTS M and the RX v calculate the RX u - it should be different since u is different. somehow the circle of confusion must be able to be worked out for the two values of u at f1.7. Not exactly sure how without further research. but that difference in v is 8% seems high at these close distances. That may be 5mm off at the film plane or perhaps the square root of 5mm probably. Either seems huge on 35mm film.

I had to edit above - from the RTS M and the RX v calculate RX u. The lens never changes so the M of the lens is the same, so need to use the RTS M

MrBrowning · Apr 29, 2017

It does seem large but I had expect it to be off more than it is. Either way I'm think that it would be best to return it and get another one. That seems the safest and simplest solution. I will say just the little shooting I did the with RX it seems nice. I'll enjoy that and the RTS.

Thank you for your help.

GarageBoy · Apr 29, 2017

Could be mirror slip

shutterfinger · Apr 29, 2017

I would verify that the focus screen is correct for the model and installed correctly. The mirror position would be second.
Instruction manuals are available at http://www.butkus.org/chinon/contax.htm if you need them.

MrBrowning · Apr 29, 2017

shutterfinger said:
I would verify that the focus screen is correct for the model and installed correctly. The mirror position would be second.
Instruction manuals are available at http://www.butkus.org/chinon/contax.htm if you need them.

The focus screen is one of the proper ones. It's an FW-1 which is the standard screen. So that seems to leave the mirror position.

Is there a simple way to tell if the mirror is not positioned correctly?

shutterfinger · Apr 29, 2017

Although mirror position is not a problem I've had to deal with I would trip the shutter on B, lens removed, and inspect the mirror resting pad for obstructions, debris, or deteriorated/missing stop pad be it rubber or foam.
Upon release I would check to see if the mirror was returning fully against the stop pad/resting pad. Some cameras have been reported to have stop adjustments. Also look for mirror separation from the backing plate.

charlemagne · Apr 30, 2017

I also had a focus problem with my RTS. In the viewfinder it looked sharp, but the negatives came out unsharp. The pictures I took with my 137MA and the same lens where fine.
Cause: the mirror fell back to far in the down position because on one side a tiny hub/bushing/ring was missing from the bar/catch it falls back on.
I was lucky enough to find that tiny hub/bushing/ring inside the camera. I glued it back on, and the RTS has been focusing fine ever since.

MrBrowning · May 9, 2017

So I ended up keeping the RX in question. Can anyone recommend me a place to send it to have the focus issue fixed?

TheFlyingCamera · May 9, 2017

To be honest, I'd have them both checked out, and also make sure there's not a hidden diopter installed somewhere - I've had an RX, a pair of 167MT's, and an RTS III, and in all four of them, infinity was infinity on the lens. These were very precisely made, well-built machines and they shouldn't be off like that. I'd also have the lens checked out- the lens elements could be out of alignment if you're seeing an issue on both bodies, just more extreme on one than the other.

MrBrowning · May 9, 2017

TheFlyingCamera said:
To be honest, I'd have them both checked out, and also make sure there's not a hidden diopter installed somewhere - I've had an RX, a pair of 167MT's, and an RTS III, and in all four of them, infinity was infinity on the lens. These were very precisely made, well-built machines and they shouldn't be off like that. I'd also have the lens checked out- the lens elements could be out of alignment if you're seeing an issue on both bodies, just more extreme on one than the other.

That's a very valid point. Any recommendation on where to send them off too?

Jeff L · May 9, 2017

I have seen good reviews about Nippon in NYC for Contax repair and service. I have never used them.

MrBrowning · May 10, 2017

Jeff L said:
I have seen good reviews about Nippon in NYC for Contax repair and service. I have never used them.

Thank you

Contax RTS & RX Focus question.

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