Jump to content

Focus shift or a rangefinder calibration problem?


gammarART

Recommended Posts

Advertisement (gone after registration)

Hello everyone,

As I'm currently experimenting to find something more suitable than my black Voigtländer 35mm 1.7 Ultron, I have here on my desk the 35mm 1.5 Nokton Type II and the Thypoch Simera 35mm 1.4 – both in silver. The compact, silver Nokton looks visually stunning on the silver P – it's a sight to behold. The Thypoch is larger, but it's already a head-turner with its not-so-ordinary rangefinder lens design. Despite its size, it weighs just as much as the Nokton without the caps and also looks great on the P.

However, I've noticed the following issue: When I focus wide open with the rangefinder (+ 1.4x magnifier) on a fixed subject at about 1.2 meters away, the focus in the final image isn't optimal. On the other hand, focusing via the display or EVF with focus peaking results in perfect focus. The focus always needs to be adjusted slightly closer to the camera than set through the rangefinder. I confirmed this from a tripod with a timer release.

With my 21mm 1.4 Nokton, the difference in sharpness is so minimal that it would only be noticeable on an M11 with its 60 megapixels.

Now the question arises: Is this a focus shift with all three 35mm lenses, or is the rangefinder not correctly calibrated? And how can I determine the latter?

The enthusiasm is naturally dampened when I have to think about the absurdly long wait times at theLeica Service. Especially since I have trips planned for the week after next and in August, during which the 240P will definitely be coming along.

Who can offer advice on this? 


Sunny regards,
Oliver


 

Link to post
Share on other sites

It sounds to me as if the Simera is not adjusted properly.
Have you checked with the lens set to infinity that the rangefinder coincides properly? To check if my camera needs adjustment this is the first test I do. 

  • Like 1
Link to post
Share on other sites

Posted (edited)

I have only tested at a distance of 1.2 meters so far.
It affects all three 35mm lenses, not just the Simera.

Unfortunately, I don't know anyone with a Summilux in the area. Then I could test if it also has the same issue.

Edited by gammarART
Link to post
Share on other sites

Focus shift is a change in the sharpest focal plane as the lens is stopped down. so what you describe is not focus shift. However, because some lens designs do have focus shift, some lenses are calibrated for most accurate focus one or so stops closed, to make focus "good enough" over a wider range: a bit off wide open and less far off stopped down. Many of my older Leica lenses have best focus 1 stop down.

Since you see the same effect on all your lenses I'd suggest getting the camera rangefinder checked and adjusted if needed.

  • Like 2
Link to post
Share on other sites

Advertisement (gone after registration)

I'm with TomB__tx on this one. IMHO do you know where your lenses were calibrated for best focus near or at wide open. The Nokton was often optimized at f/2.0 instead of wide open. But I do think your rangefinder probably needs to be tweaked given if the issue persists with all three lenses. One other consideration is whether your eyesight perfectly accommodates the rangefinder diopter. I had this issue years ago and it disappeared when i added a diopter lens.

Link to post
Share on other sites

Posted (edited)

Perhaps you should first check if your rangefinder is correctly adjusted at infinity. To do so take your camera to a spot where you can focus on a very distant object, at least one kilometre away. If the image and rf patch do not match, then you can quite easily adjust the roller with a 2 mm hex wrench.

This image is from a member some years ago. There are probably youtube videos hon this too. The adjustment is very easy to do 

 

See:

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

Edited by Jean-Michel
Link to post
Share on other sites

Before taking any drastic steps you may want to shoot actual images with the lenses at various stops and distances. If you perceive an issue in image quality it’s worth having the camera checked.  If your images look good I would leave it well enough alone. 

Link to post
Share on other sites

6 hours ago, gammarART said:

focusing via the display or EVF with focus peaking results in perfect focus. The focus always needs to be adjusted slightly closer to the camera than set through the rangefinder. I confirmed this from a tripod with a timer release.

The EVF test is a good one. Your rangefinder needs probably some calibration. Easy job generally. There are good repair shops in Germany so no need to send the camera in to Leica IMHO.

Link to post
Share on other sites

vor 7 Stunden schrieb TomB_tx:

Focus shift is a change in the sharpest focal plane as the lens is stopped down. so what you describe is not focus shift.

Though you don‘t know whether the lens is exact fully opened and „shifts“ focus when you stop down, or whether it is exact at a smaller f-stop and it shifts when you use wieder openings.

The Zeiss ZM Sonnar 1.5/50mm is notorous for focus shift. Zeiss described that the lens is usually calibrated to be exact at f/2.8 as they assumed that most users would use it not fully opened but stopped down at least two stops. They offered to calibrate it at f/1.5 though with the caveat that it wouldn‘t be exact stopped down.

I had the same experience with the 35mm Summilux asph (first version) which also showed strong focus shift. When I bought it during film times it was calibrated for f/2.8 or even f/4. When I had it coded I got it back calibrated to f/1.4. 

So please do not assume that a lens has focus shift or not, when you neither have seen the results, nor have any information about the f-stops the results were taken with and don‘t know to which f-stop a certain lens is calibrated. 

Link to post
Share on other sites

Posted (edited)

If you want to check the accuracy of focus you could purchase a focus calibration tool, or make one yourself. A few years ago I made this tool by printing the targets and building the tool using mat boards. Easy enough to be accurate in building the tool. It is available for download at: https://squit.co.uk/photo/focuschart.html

 

Edited by Jean-Michel
typo
Link to post
Share on other sites

44 minutes ago, UliWer said:

So please do not assume that a lens has focus shift or not, when you neither have seen the results, nor have any information about the f-stops the results were taken with and don‘t know to which f-stop a certain lens is calibrated. 

Valid point. Unless you test a lens at different apertures to see if the focal plane is consistent you can't determine if the lens design has focus shift.

Link to post
Share on other sites

1 hour ago, TomB_tx said:

Valid point. Unless you test a lens at different apertures to see if the focal plane is consistent you can't determine if the lens design has focus shift.

A few years ago I put a dozen or so non APO/ASPH/FLE lenses through a tightly controlled studio-based test whilst shooting a Focus Calibration Test Card and every single one of them showed focus-shift when using different apertures and using different focussing distances. Some, admittedly shifted more; some shifted less. But all exhibited focus-shift to some extent.

I even mapped-out their results on graph-paper. Good Grief!...I wish I hadn't. Studying - and interpreting - these results in great detail was so confusing that I just accepted the fact that, from time to time, such lenses will be faced with circumstances under which they will perform 'less-than-perfectly'.

However as the OP states in post #5; "It affects all three 35mm lenses, not just the Simera." this does hint at a body-calibration failure assuming the focus-shift is similar for all three lenses.

Philip.

  • Like 1
Link to post
Share on other sites

Focus shift seems to depend on cameras too. My Sonnar 50/1.5 has focus shift on my M240 for instance but i cant' seem to see anyon my M11. I did not do side by side comparos though.

Link to post
Share on other sites

Posted (edited)
3 hours ago, lct said:

Focus shift seems to depend on cameras too. My Sonnar 50/1.5 has focus shift on my M240 for instance but i cant' seem to see anyon my M11. I did not do side by side comparos though.

I saw the same things on my cameras and lenses.

A m10-r plus a Summicron 50 and Noctilux 50/1.2 demonstrates an obvious focus shift at f/2.8 to f/4, but not with any other lenses.

However none of my lenses, including the above 2, show focus shift on a m11.

I have learned to live with that.

Edited by Rollei35
  • Like 1
Link to post
Share on other sites

Posted (edited)

@gammarART Thypoch lenses are designed to be adjusted by the user, so after testing for infinity with other lenses and supposing the camera is ok you can then adjust the lens. Here is a tutorial. Do not have the camera adjusted if it works with other lenses.

 

https://youtu.be/s2hs81K36j8?si=zPvhvE8yJNlp-zaK

 

 

Edited by 250swb
Link to post
Share on other sites

Posted (edited)

So, lots going on these days. The Nokton and the Thypoch are going back for now. I might conduct the aperture series today with the 1.7 Ultron. The 240P will be sent for adjustment after the vacation.

Then we'll see.

Edited by gammarART
Link to post
Share on other sites

2 hours ago, UliWer said:

Evidently the M11 defies physics: it freezes even though electronics are supposed to produce warmth and it cures spherical aberrations of glass elements.

Do i sense some sarcarm here 😄 Hard to believe in the current mood of M11 bashing but this body has rejuvenated lenses i did not use or with difficulty like Sonnar 50/1.5 and also, for other reasons, Super-Angulon 21/3.4, Heliar 15/4.5 v2, Skopar 21/4 or Biogon 21/4.5. FWIW.

  • Like 1
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...