Zeiss 25mm 2.8 and Zeiss 25/28mm external viewfinder does not match?!?

[MAFW]

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Hi!

I have the Zeiss 25 2.8 Biogon and today I bought the matching external Zeiss viewfinder with 25/28 framelines. First impression: Fantastic optical quality. Bright as hell. A joy to use.

But then: what is this? I took a photo to see how accurate the frame lines are.. and they are absolutely NOT matching. It’s not even close. The lens is way wider than the viewfinder’s frames are showing. 
 

How can that be? I use the lens on a Leica M10 and I am really confused. 
 

Anyone has an idea?

Thanks a lot. 
Matthias

[pedaes]

15 minutes ago, MAFW said:

25/28 framelines.

How does the 28mm frame lines compare with the viewfinders 28mm lines? Are you sure it is a 35mm format viewfinder?

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[pedaes]

27 minutes ago, MAFW said:

How can that be?

This might help

Zeiss Ikon Viewfinder ZI for the 25mm & 28mm Lenses. Unlike 35 mm SLR camera viewfinders, that can only show little more than 90% of what will be recorded on film, the Zeiss Ikon viewfinder lets you see the area that surrounds the actual image giving you greater possibilities and confidence as you compose each image. What's more, the triangulation rangefinder combined with a viewfinder base that is the widest available means that you can expect extreme accuracy and wide-angle focusing precision. All of this and more so that you can follow your passion: creating great images. Vendor Part # 1365664

[MAFW]

vor 53 Minuten schrieb pedaes:

How does the 28mm frame lines compare with the viewfinders 28mm lines? Are you sure it is a 35mm format viewfinder?

Hi pedaes,

thanks for your reply. 
I just set the camera on the tripod and aligned it with some lines. 
The 28mm frame lines of the range finder match perfectly with the frame lines from the external viewfinder. 
 

My conclusion is that the lens copy that I own cannot have 25mm focal length. It must be wider actually. 
But it’s really a big difference. Could it be that it is a 21mm labeled as 25mm?!?
 

That’s weird… 😫

[spydrxx]

Framelines are approximations, not exact. Learn by experimenting with the lenses and viewfinders you have to be able to effectively use the framing and extra space beyond the framelines.

[pedaes]

26 minutes ago, MAFW said:

Could it be that it is a 21mm labeled as 25mm?!?

Interesting question. If it is like a stamp mis-print may be worth a $1m!

Did you buy lens new? Was it boxed?  It could be that if it has been serviced there could be a mix up of front ring. 21mm is getting pretty wide with  converging verticals unless you are careful. If you can post  50mm and '25'mm comparison shots (taken from same spot) I am sure you will get good advice here.

Nikon used to have a useful focal length  / angle of view comparison tool but I could not find it quickly.

Edited May 16, 2023 by pedaes

[Photon42]

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Maybe you want to check the actual angle of view with your camera A 21mm for instance on your M10 has about 90 degrees.

[j.scooter]

Keep in mind that the external viewfinder is not parallax corrected and will not be accurate at all focusing distances especially the closer distances.   

[trisberg]

I find that all external finders I have used are very conservative in the framing. This leads to the lens capturing a much wider image. I have a Voigtlander 21/25 finder and when using it with a 24mm lens the 21 frame lines seem much closer to what I actually end up capturing.

-Thomas

[MAFW]

vor 13 Stunden schrieb pedaes:

Interesting question. If it is like a stamp mis-print may be worth a $1m!

Did you buy lens new? Was it boxed?  It could be that if it has been serviced there could be a mix up of front ring. 21mm is getting pretty wide with  converging verticals unless you are careful. If you can post  50mm and '25'mm comparison shots (taken from same spot) I am sure you will get good advice here.

Nikon used to have a useful focal length  / angle of view comparison tool but I could not find it quickly.

I bought the lens new. I even have a signed certificate from Zeiss that they checked everything. The box also reads 25mm. 😌

I took photos on a tripod from the same spot. 
 

This is the “25mm” Zeiss 

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This is the Summicron 35mm

 

And this is the Voigtländer 50mm

But how can I now determine the actual focal length? Measuring the distances from the point of the camera to the outer spots that are visible in the image and then do some fancy maths? 🙈🤯🤔

 

[Olaf_ZG]

I’m lost about what is wrong now: the lens or the external vf…

[MAFW]

vor 20 Minuten schrieb Olaf_ZG:

I’m lost about what is wrong now: the lens or the external vf…

Hi Olaf!

I compared the 28mm frame lines from the external ZEISS VF with the 28mm frame lines from the M10 built in RF. They are the same. 
 

What else could be the possibility if not the focal length of the lens. 🤔

I mean there are no other variables or am I missing something. 
It is totally strange. 

I contacted the support from Zeiss. Let’s see what they say. 😅

[pedaes]

1 hour ago, MAFW said:

But how can I now determine the actual focal length?

By measuring an approximate angle of view (lines from camera to edge of frames*). Have to say it looks like a 24mm. You could see what viewfinder includes and try a measure that also.

Faulty Viewfinder? They are expensive items so should be accurate.

Zeiss should be able to tell from lens serial number, but suspect that is not problem.

Excellent lens by the way - good choice!

* 50///40 35//54 24//74

Edited May 17, 2023 by pedaes

[wizard]

vor 15 Stunden schrieb MAFW:

The lens is way wider than the viewfinder’s frames are showing. 

 

vor 14 Stunden schrieb spydrxx:

Framelines are approximations, not exact.

 

vor 6 Stunden schrieb trisberg:

I find that all external finders I have used are very conservative in the framing.

All the above comments are correct and are not contradictory. The lines in every brightline finder are a compromise between what any given lens captures at the infinity position and what the same lens captures at the closest focus setting. Usually, the lines are optimized for a focus position of about 2m. Thus, the actual image will show more if set to infinity, and may show less when set to a very close focus position. All of that is normal.

Another factor is focal length variation. I have several 50mm lenses and the MATE, which also has a 50mm position. The MATE when set to its 50mm position has a noticeably wider viewing angle than all of my other 50mm lenses. I suspect that my 50mm lenses are closer to 51 or even 52mm focal length, whereas the MATE seems to have 48 or 49mm focal length in its 50mm position.

So don't worry, everything is in good order. In the old days, one of the advantages of an SLR camera was (and still is) that you won't have those problems, as the camera "sees" through the lens 🙂.

[MAFW]

Soooo…. I made some further tests. 
 

1. Focal length 

 

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The angle must be approximately around 75°.

 

 

I don’t know if that’s accurate and which of the 3 specs from Zeiss are suitable here…🤨

2. Field of view from the ZEISS VF

The minimal focus distance of the Zeiss 25mm is 0,5 meters. At that distance the VF is accurate. In my opinion this is nonsense. You cannot even focus with the range Finder at this distance. And the majority of photos will probably not be taken at that distance either. So why calibrating on that distance?? 😩
 

I have a Summicron 35mm and use it with an VF from Voigtländer. That is way more accurate. Only few millimeters deviation on the final image.

 

I am disappointed because the view is great. But the deviation of the frame lines is a bad joke in my opinion  I mean the VF is built for that very lens…

 

Maybe I should test out the 21mm VF from ZEISS. Maybe this would match better… 🙈

 

[pedaes]

25 minutes ago, MAFW said:

the deviation of the frame lines is a bad joke

You seem to have identified the issue, well done. Remember,  the Leica camera viewfinder framelines aren't accurate at all distances, and the manual explains the variation to inside / outside of the line depending on focus point.

Enjoy your new lens.