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focus shift on fast voigtländer lenses

Guest zoz

By Guest zoz
in Customer Forum

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Guest zoz

Guest zoz

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Focus shift is a problem of some fast (not only) voigtländer lenses.

I´ve compared some lenses in this respect:

 

Nokton 1,1/50; Nokton 1,5/50 Aspheric; Nokton 1,2/35 Aspheric; Ultron 2/28

 

VergleichLinsen.jpg

 

100% -crops of the centre of the images made from 1m distance. Focus should be on "15cm"...

 

VergleichFS.jpg

 

The Nokton 1.1 and 1.5 show similar focus shift. The 2/28 shows stronger shift. The 1,2/35 shows none!

Contrary to the findings of Sean Reid the 1,5/50 shows clearly focus shift. This might be an issue of product variation. It is also possible that the shift of the 1,5/50 ist low compared to those of the 1,4/40 and 1,4/35, so that is what he called "little".

The competition of the 1,1 and 1,5 50mm show in my opinion that it that focus shift is not a question of aspheric design.

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christer

christer

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Please describe the test conditions in detail.

 

Was the ruler at 45° compared to the film plane? How did you establish this? How did you focus, rangefinder or tape? What camera did you use. Why did you use the same distance for all focal lengths instead of the same factor times the focal length?

 

Thanks for your reply!

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Guest zoz

Guest zoz

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The Angle to focal plane was about 45°. Distance to focal plane was a little bit over 1m.

I´m shure, that angle and distance are no critical factors if you don´t want precise numerical results, and this was not my intention...

I focussed with the rangefinder.

Camera was an M8.

I don´t think that different focal length can be competed better (if they can be competed at all) by changing the setup.

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jplomley

jplomley

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Its not just voightlander. I had this on my 28 Cron Asph and now have it on my 35 Cron Asph. Fine at f/2 and f/2.8, and than the plane of focus shifts behind the intended plane of focus at f/4 and f/5.6. My friends 35 Cron Asph does the same thing, and his 50 Lux Asph is fine at f/1.4 and f/2, and then shifts, again behind the intended plane of focus, at f/2.8 - f/5.6. Tests were conducted on each of our adjusted M9's (both of which required RF adjustments right out of the box). I might add that in order to achieve performance at f/4 and f/5.6, I had to live with front focussing at f/2 (on the 28Cron Asph). Because of this, I am somewhat reluctant to send in my 35 Cron Asph for adjustment.

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Guest zoz

Guest zoz

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Would be interesting to see if the shift carries over to more commomly used distances such as 5 feet, 2 meters, and more.

 

As far as I can tell the focus shift is there at all distances even at infinity.

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ArtZ

ArtZ

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Focus shift is a problem of some fast (not only) voigtländer lenses.

I´ve compared some lenses in this respect:

 

Nokton 1,1/50; Nokton 1,5/50 Aspheric; Nokton 1,2/35 Aspheric; Ultron 2/28

 

>[img]g

 

The Nokton 1.1 and 1.5 show similar focus shift. The 2/28 shows stronger shift. The 1,2/35 shows none!

Contrary to the findings of Sean Reid the 1,5/50 shows clearly focus shift. This might be an issue of product variation. It is also possible that the shift of the 1,5/50 ist low compared to those of the 1,4/40 and 1,4/35, so that is what he called "little".

The competition of the 1,1 and 1,5 50mm show in my opinion that it that focus shift is not a question of aspheric design.

 

 

 

Steffen,

 

I believe your camera needs to be adjusted. My both M8 needed adjustment at Solms.

 

Here two exemples I've taken few minutes ago, after reading your original post. Both Pictures have only been resized to 960x646 using Photoshop CS5. Ruler is at 45º and shots are hand held (a tripod would have been better... and pictures will be even sharper!):

 

First one, CV Nokton 50/1.1 at f/1.1 and 1m (full image on the left and 100% crop on the right);

 

Second one, CV Nokton 50/1.5 ASPH at f/1.5 and 0.9m (full image on the left and 100% crop on the right)

 

I have also tested in the past the CV Nokton 35/1.2 ASPH and the CV Nokton 35/1.4. All my Noktons (and Leica lenses) are spot on.

 

Cheers

.

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

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Guest zoz

Guest zoz

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Are You sure You have got what focus shift means?

My Noktons are on spot wide open two, or don´t You agree with that?

But the point of maximum sharpness is moving on the 50mm lenses when you stop down!

In my test the camera was sitting on a large tripod with geared head and the focus ring was not touched between the images. Only the f-stop was changed (time on A compensating the exposure).

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ArtZ

ArtZ

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Steffen and Olaf,

 

Maybe my eyes are wrong but I don't really see "15" cm in focus wide open. So I'm not surprised you get focus shift at different apertures.

 

My exemples were just to show how the figure "15" should appear when a Nokton 50/1.1 or a Nokton 50/1.5 should appear.

 

Yes, I should have taken more pictures at different apertures but I though my point was obvious.

 

Regards

.

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Guest zoz

Guest zoz

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Sorry, but I do not get that point.

The focus wide open might be wrong several mm but I would say it is within +/-5 mm. (This I would blame on me not the Camera! :o)

But with stopping down it is moving about 5cm! This is a pure effect of the lens. How should an adjustment at the camera change that?

If Your Images are more spot on 15mm is difficult to judge becaus the bold printed 15 will always look sharper than the not bold 14 and 16.

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zlatkob

zlatkob

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All of the wide open aperture photos look a little soft -- but that is normal for wide open. The silver ruler has more contrast, so that may contribute to the appearance of greater sharpness.

 

Wow, the Nokton 1.1 seems to have a strong focus shift starting at f/2.0. I wonder whether it is a problem in normal, non-test photos? It seems like it would be.

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01af

01af

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So I'm not surprised you get focus shift at different apertures.

Umm ... apparently you still don't understand what we are at.

 

 

My examples were just to show how the figure "15" should appear when a Nokton 50/1.1 or a Nokton 50/1.5 should appear. [...] I thought my point was obvious.

Well, your focus, in both examples, is somewhere between the numbers '15' and '16' on the ruler so your accuracy of focus is in the same ballpark as Steffen's—so no, I really don't see what your point was supposed to be ...

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Guest zoz

Guest zoz

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Wow, the Nokton 1.1 seems to have a strong focus shift starting at f/2.0. I wonder whether it is a problem in normal, non-test photos? It seems like it would be.

 

It will be a problem if You do not know and have it in mind.

Because of that I try to avoid f2-2.8. I mostly use it wide open (f1,1-1,4) or at f4 or more. Then I´m focusing on the nearest point I´d like to be sharp.

 

But with the Nokton 1.5 it is just the same, only one stop shifted because it´s one stop slower. And being on stop slower it has more dof so that the consequences are not so strong.

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andybarton

andybarton

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Focus shift is a problem of some fast (not only) voigtländer lenses.

I´ve compared some lenses in this respect:

 

As someone who doesn't enjoy a 42 inch monitor, and who cannot, therefore, see the whole of your first post in this thread, can you please stick to the forum rules with regards to image sizes in posts in future.

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Guest zoz

Guest zoz

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As someone who doesn't enjoy a 42 inch monitor, and who cannot, therefore, see the whole of your first post in this thread, can you please stick to the forum rules with regards to image sizes in posts in future.

 

I can´t either!

But it´s not necessary to see the image completely, and I think it is much more convenient to scroll then to switch between single images.

I did not make this image for this forum but for my own curiosity. If it is not wished to share this kind of information if it is not 100% conform to forum rules no problem I won´t show them in future...

If You insist I can delete this file too.

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Guest zoz

Guest zoz

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Bloody hell... No ruler is safe with you lot around, is it...? I could understand this sort of behaviour (just) in the depths of Winter, but it's Summer out there! :rolleyes:

 

Regards,

 

Bill

 

We had 24h of rain yesterday (sunday)!;)

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tdtaylor

tdtaylor

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Bill,

 

Evidently you don't understand ;).

 

In Florida (all of my family but me lives there), you stay inside in AC in summer and you go outside in Fall, Winter and Spring. Of course, being a US northerner, and currently in Maine, I find it humorous when they pull out all of their winter gear if it drops lower than 55 degrees F :D.

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