Newcomer question: focus error on Summaron 3,5cm/3.5 and RD-1s...

[jvr]

Hi!

I'm new to this forum (although I've read a lot here before) and I have a question for you: I have an Epson RD-1s that I've been using without any problem with my Zeiss Biogon 21/2.8 and CV Ultron 28/1.9 but that shows a small (but visible) back focus error on an old Leica Summaron 3,5cm/3.5 that I used for ages on my Leica M3 without any concern.

That does not happen with either the Zeiss or the CV lens (and DOF is much smaller with the CV at 1.9 than the Summaron at 3.5). Strangely enough, it does not even happen with an old collapsible Summicron 5cm/2 (although old 'cron picture quality is severely impaired by an aging coating 🙁 ).

Both the Summicron and the Summaron are from the 50s.

Also no problem whatsoever focusing a new Summicron 35/2 Asph and a new Summicron 50/2 (and yet, much smaller DOF).

When focusing the Summaron, the better focused plan is a bit further away than the plan that correctly aligns the rangefinder patch. It's off by a good 5cm on a 1.3m distance and at 3.5 is very noticeable (I can post some pics). It can be off by 15cm at 4m.

So that should be a problem with the Summaron. Funny that I nevcer noticed it on the M3... Maybe the fact that the CCD surface has almost no thickness explains that the error is much more visible on the RD-1s: focus has to be dead on.

Has anyone had a similar problem?

I like very much the Summaron rendering on the Epson RD-1s (good detail, low contrast, excelent for sunny days!) but it's frustrating to use it in low light.

Best regards,
Joao Ranito

 

[garethc]

I too have used a 35/3.5 Summaron with my R-D1.

I was going to send my R-D1 away beacuse of close focusing problems but they disappeared when I got my Summicron.

I know that doesn't help your problem, but it might make it clear that it isn't a 'one off'.

 

[jvr]

Nope, I used the naked M3. The M3 viewfinder (forgetting the framelines) gives you an idea of the 35 field of vision. But I got my share of cut off feet in the beggining... 🙂 But I got used to it and when I travelled I always carried the M3 + Summaron. Very compact outfit and fantastic rendering with Tmax 400.

I also used it on a M6 TTL (sold the M6 because it scratched all the films...): framelines but a very, very tight fit. Maybe manufacturing tolerances were not that great in the 50s, after all... 🙂

Now I would be very happy to use it on the RD-1s (like all my other lenses) but it looks like I have to be careful when focusing wide open and adjust a tiny bit.

 

[jvr]

You're right, it does not solve it but it helps to know I'm not alone... 🙂

 

[jvr]

Thanks for the info, Roland.

Unfortunately, I'm sure it's not a focusing issue (several tries) or camera shake (sturdy tripod and remote shutter release, several tries).

I used a setup just like (at least in spirit...) your tape: a bookshelf and several similar books, each one slightly pulled more than the one to the side (about 1cm each). Camera parallel to the shelf (well, as much as possible, anyway, no scientific experiment!). This is the same setup I used to adjust the focus on my Nikon D70s (which had a big back focus issue: pictures were much softer than those I got from my D100, before adjustment).

This is mainly curiosity: I keep the Biogon 21/2.8 (+viewfinder) on the camera almost 80% of the time and the Ultron the other 20%... 🙂

For typical pictures with Summaron (outdoors and f11), this is not a real issue, anyway... I was just afraid that maybe something was wrong with the camera.

But as it works quite well with all other lenses (including some from the same period and more dificult to focus)! and garethc had the same problem, I guess it's ok and the lens is the culprit. Maybe the curved focal plane has an impact...

It just shows that we can't take anything for granted: the Summaron is still one of my favorite lens on the M3 (even without the eyes) but I have to be careful with it on the RD-1s!

garethc, thank you for your input, again!

 

[jvr]

Hi Joao,

so I was thinking a bit more about this and was wondering.
Let's say the lens focuses accurately, has a curved focal plane,
is adjusted not to the picture centre but to 1/3rd line intersections or so.

Due to the RD-1 crop factor, if you compose in a similar way, you will
actually move away from the optimal distance points on the curved focal
plane, by a few centimeters, which might account for the few
centimeters inaccuracy that you are observing.

Roland.

That makes a lot of sense. And the fact that the CCD has almost perfect flatness could also add to explain why that's an issue with the Epson but not the M3...