Heliar 75/2.5 on RD1s

[MaximK]

Hello!
I bought CV Heliar 75/2.5 and just made some tests.
It is underfocusing about 10mm.
My other lenses CV35/1.2 35/2.5 50/1.5 CZ 50/2 21/2.8 does not have this issue.
They are all very sharp were it was intended to be.
I provide some test photos. Please comment if possible it will be highly appriciated.
Book about 40 degrees to the focal plane and camera on tripod.
1034 at 2.5 and 1035 at 2.8
Focus was on the eye.
The area of focus somewhere near beginning of the legs.
Please let me know what you think.
Is it a problem just with this long lens?
Thanks in advance for posting.
Maxim

 

[pfogle]

FWIW, I tried with this lens, got the same result as you did and gave up. I have read posts by others who love this lens, but I didn't want the hassle of setting it up and possibly putting out some of my other lenses. I decided I can live with a max F/L of 50mm with this camera.

 

[MaximK]

thank for sharing!
i am thinking that one option may be is always to focus little behind the eyes of the person to get it in focus.
just trying to find how to go with lens. return or not return to cameraquest?
stephen propose exchange but i am not sure whether other sample will be better.
maxim

 

[jlw]

75mm is a bit of a stretch for the R-D 1's short-base rangefinder. That's probably why Epson didn't include framelines for lenses longer than 50mm. If your focusing problems with this lens are random (some front-focused, some back-focused) that's most likely the issue, in which case an eyepiece magnifier might help.

Having said that... this is a screwmount lens, right? Which means you have to be using a screw-to-bayonet adapter to mount it on the R-D 1. Do you KNOW your screw-to-bayo adapter is in spec? An adapter that's slightly too thick will cause the lens to focus at a slightly closer distance than indicated by the rangefinder.

The correct thickness of the adapter is 0.98-0.99mm. I've found that many independent-brand adapters range from 1.00-1.02mm, with some even thicker than that. If you have access to a micrometer, you can easily measure your adapter yourself to see if it is correct. Take the measurement between the two mounting surfaces on the front and rear of the adapter; make sure you are measuring on the raised "step" on the rear size, not the lower outer surface.

About half the non-Leitz adapters I've bought have been too thick, regardless of brand (and you can't be sure that adapters of the same brand are made by the same contract manufacturer!)

If you bought your adapter from CameraQuest, I'd suggest you look into exchanging that before you worry about exchanging the lens.

 

[MaximK]

thanks for your reply.
my adaptor is from Cosina new one and i bought it from HK.
I bought total 4 adapters and the other lenses focusing fine 35/2.5 12/5.6 50/1.5.
i will try to shift adapters and see if this is the problem.
the front focus is consistent.
thanks again
maxim

 

[jlw]

thanks for your reply.
my adaptor is from Cosina new one and i bought it from HK.
I bought total 4 adapters and the other lenses focusing fine 35/2.5 12/5.6 50/1.5.
i will try to shift adapters and see if this is the problem.
the front focus is consistent.
thanks again
maxim

Shifting the adapters is a good idea for testing. Thickness of the adapter is much more critical with the 75mm lens than with the other lenses you mention (the 12mm isn't rangefinder-coupled at all, of course.) With luck you will find that one of your adapters provides perfect focus with the 75mm lens.

If you still can't localize the problem by shifting the adapters, perhaps you could take them to a repair shop, or a shop that sells machinists' tools, and have them measured for thickness...?

 

[pfogle]

... An adapter that's slightly too thick will cause the lens to focus at a slightly closer distance than indicated by the rangefinder...

An interesting point here - my reading of the issue is that for 50mm lenses, the adapter thickness is not relevant, as the cam and the lens both move by the same amount - the only issue being that the infinity focus may be unavailable.

For wide angles, the lens will be out more than the cam, so a fat mount will front-focus, and a thin mount will back-focus.

For teles (and, of course, the 75mm) the opposite is true, the cam will be out by a greater amount than the lens so a fat mount will back-focus and a thin mount will front-focus.

Well, I might have got it mixed up, but I think that's right, but anyway, the main thing is a mount-thickness focus problem depends on the focal length, and is zero for a 50.

- ps I've found that one answer here (where you need to build the mount up) would be to use a paper shim between the adapter and the lens. I've used it with several lenses - the only disadvantage is that the aperture index won't be at the top any more.

 

[ferider]

Hello!
I bought CV Heliar 75/2.5 and just made some tests.
It is underfocusing about 10mm.
My other lenses CV35/1.2 35/2.5 50/1.5 CZ 50/2 21/2.8 does not have this issue.
They are all very sharp were it was intended to be.
I provide some test photos. Please comment if possible it will be highly appriciated.
Book about 40 degrees to the focal plane and camera on tripod.
1034 at 2.5 and 1035 at 2.8
Focus was on the eye.
The area of focus somewhere near beginning of the legs.
Please let me know what you think.
Is it a problem just with this long lens?
Thanks in advance for posting.
Maxim

With 10mm you are in the range of the RF accuracy of any camera out there,
and in particular the Epson.

Roland.

 

[MaximK]

I changed adapter

I changed adapter

thanks again everyone for help.
i changed adapter from 50/75 to 28/90 and i think it is better now.
i still have to try more test shots but here what i got...
maxim

 

[wintoid]

Looks like a beautiful lens to me!

 

[jlw]

An interesting point here - my reading of the issue is that for 50mm lenses, the adapter thickness is not relevant, as the cam and the lens both move by the same amount - the only issue being that the infinity focus may be unavailable.

That's true. I've said the same in some of my other posts about adapters. I just figured I'd skip it this time as people probably wouldn't want to wade through it again!

The key point is that an out-of-tolerance adapter will affect RF coupling accuracy with non-50mm lenses, and the farther from 50mm they are, the worse it gets.

Somewhere on my computer at home I've got a spreadsheet I made up that relates focusing error to extension error. I made it up to tell me how much I had to change the thickness of an adapter to correct focusing errors. If anyone wants a copy of this, let me know and I'll try to post it.

 

[Rob-F]

But 75mm x 1.5 gives a 112mm field of view. What will you use for a viewfinder?

 

[jlw]

But 75mm x 1.5 gives a 112mm field of view. What will you use for a viewfinder?

75mm x 1.53x (R-D 1 "crop factor") / 0.85 (safety margin provided by R-D 1 finder frames) = 135... so a viewfinder that covers the field of view of a 135mm lens on a 35mm camera should be a pretty good match.

It does depend somewhat on the individual viewfinder, since finder manufacturers used different values of their own for the safety factor (which is needed to account for the fact that a lens' angular coverage decreases at closer focusing distances; without it, a finder accurate at close distances would show more than you'd get in the picture at infinity.)

 

[MaximK]

75/2.5 today in real use...

75/2.5 today in real use...

Hi everyone!
I had edn of the year performance in my daughter school today. 75/2.5 did nice but i still missed some shots due to out of focus. Attaching one of succesful samples. I decided to buy MS-MAG x1.3N viewfinder magnifier to fight my focusing problems. Hope it will be usefull...let you know when it arrives and post some samples with it.
maxim