Question re: Summicron-TL 23mm F2

[wsself]

Advertisement (gone after registration)

 

I picked up the Summicron-TL 23mm F2 this evening. I believe that I'm going to absolutely love this lens. I did however notice one slight quirk with this lens and I'm wondering if anyone else out there can explain what's happening?

In the store, I fitted the store's sample lens to my Leica CL body to test it out. What I immediately noticed was that the camera's aperture was only opening up as wide as F2.8, despite the lens' F2 maximum aperture spec. The salesperson and I went through a series of basic troubleshooting checkpoints.

• Is my camera set to aperture priority? Yes.
• Am I using the latest firmware? Yes.
• Do I maybe have the exposure bracketing set to a value beyond 0? No.
• Does the same issue exist on a different Leica CL body? They tried it on one of their store models and it cranked open to F2, no problem.
• Placing the lens back on my camera the problem went away.
• I cracked open the sealed box containing my new lens. My CL body immediately applied a firmware update before I could operate the camera. When complete, I was in business, shooting portraits of sales clerks in the store in full F2 glory.

So, when I'm home further exploring my new lens I'm noticing I'm back to F2.8 again. What I think is happening is that when I get too close to an object, the lens stops down to F2.8. When I pull away from the object I'm back to F2 - a change the camera makes on its own. 

Is this part of the general operation of this lens? I've never encountered anything like this on a prime lens before. I'd just like to know more about it, and perhaps the reason why this aperture adjustment happens?  

Thanks!

 

[adityaw]

I believe this is normal for this lens (if you get too close to your object it won't do F2). Somewhere I read Leica did this to maintain IQ.

[Advertisement]

The Leica Q3 is available for pre-order at B&H Photo Video and Adorama

[wsself]

12 hours ago, adityaw said:

I believe this is normal for this lens (if you get too close to your object it won't do F2). Somewhere I read Leica did this to maintain IQ.

Hey thanks very much! I suppose the lens stops down in order to maintain details in the subject. Like I said, I never encountered this before on a prime lens. 

Great lens though, I wasn't sure what I was going to get in terms of DOF with the F2 aperture but I'm rather pleased with what I'm seeing.

[ropo54]

13 hours ago, wsself said:

 

I picked up the Summicron-TL 23mm F2 this evening. I believe that I'm going to absolutely love this lens. I did however notice one slight quirk with this lens and I'm wondering if anyone else out there can explain what's happening?

In the store, I fitted the store's sample lens to my Leica CL body to test it out. What I immediately noticed was that the camera's aperture was only opening up as wide as F2.8, despite the lens' F2 maximum aperture spec. The salesperson and I went through a series of basic troubleshooting checkpoints.

• Is my camera set to aperture priority? Yes.
• Am I using the latest firmware? Yes.
• Do I maybe have the exposure bracketing set to a value beyond 0? No.
• Does the same issue exist on a different Leica CL body? They tried it on one of their store models and it cranked open to F2, no problem.
• Placing the lens back on my camera the problem went away.
• I cracked open the sealed box containing my new lens. My CL body immediately applied a firmware update before I could operate the camera. When complete, I was in business, shooting portraits of sales clerks in the store in full F2 glory.

So, when I'm home further exploring my new lens I'm noticing I'm back to F2.8 again. What I think is happening is that when I get too close to an object, the lens stops down to F2.8. When I pull away from the object I'm back to F2 - a change the camera makes on its own. 

Is this part of the general operation of this lens? I've never encountered anything like this on a prime lens before. I'd just like to know more about it, and perhaps the reason why this aperture adjustment happens?  

Thanks!

 

I know that the Leica X typ 113 had the same behavior, by design.

Rob

[hoppyman]

Yes it’s not a fault, it’s a feature of the firmware functions 😉 You can reproduce it by test if you want. Nothing wrong with your camera or lens.

[DwF]

As an X 113 owner/shooter, a camera that received bad press for the same issue, I am fascinated to read this.   In practice, the difference between f 1.7 and f2 for portraiture on the 23mm in APS_C is really negligible for me. Reviews said that the lens would stop down to f 2.8 but if I back away to a comfortable few feet and so that facial distortion is not an issue, I find the camera stops to f2 and sometimes 2.2  Of course we shoot Leica because we want control of these parameters. The X113 is a wonderful camera for me so I put up with it. I imagine if I get a CL, I'll be doing the same.

David

[wsself]

Advertisement (gone after registration)

Thanks everyone for confirming that this is an intentional behaviour in this lens. I actually made a point to e-mail the sales guy to bring him up to speed on your feedback. 

I can see how this 'feature' of stopping down the lens based on its proximity to the subject can be considered something of a letdown to some. Those few stops between F2 and F2.8 can be considered rather substantial to many. From my initial shooting with the lens though, I don't see this being an issue. It is a wonderful lens!

I sold my Sony/Zeiss 24mm F1.8 equivalent this afternoon - an APS-C lens I used on my Sony A6300. It was a fantastic little lens. I did mention to the buyer that the one feature I will miss on the Zeiss is its close-focus ability. I wish I can get in closer with the Leica, but other than that I have no complaints - fantastic little lens!

[Keith_W]

I don't have the 23mm f/2, but I did borrow a copy and can confirm that this behaviour is intentional. It is very annoying though - I think that I should be able to choose whether I want to shoot at f/2 or f/2.8, and I don't want the camera to make that decision for me with no way to over-ride it. Leica should change the firmware so that if f/2 is selected, f/2 is what you get. 

[cdekter]

Some lens designs lose brightness as you focus closer - macro lenses in particular are known for this. I'd be curious as to whether this is actually what is happening - that the loss of aperture at close focus is a feature of the optical design. The way to tell for sure would be to put the camera in manual focus mode and turn the focus ring to close focus while watching the iris inside the lens. If the iris closes down as you focus closer, then it's a software feature. If not, I would suggest that this is an optical property of the lens design.

Edited December 1, 2018 by cdekter

[ruskkyle]

15 hours ago, cdekter said:

Some lens designs lose brightness as you focus closer - macro lenses in particular are known for this. I'd be curious as to whether this is actually what is happening - that the loss of aperture at close focus is a feature of the optical design. The way to tell for sure would be to put the camera in manual focus mode and turn the focus ring to close focus while watching the iris inside the lens. If the iris closes down as you focus closer, then it's a software feature. If not, I would suggest that this is an optical property of the lens design.

I have just bought this camera & lens combination yesterday and can confirm, yes, the lens stops down at close focus even in MF mode. I’m a little disappointed in this behaviour tbh.

[scott kirkpatrick]

Leica doesn't work the way you might like.  Someone in the lens shop has decided that the performance of the 23/2.0 meets Leica's standards down to f/2.0 at most distances, but when focused closer than about .5 m the sharpness and whatever else is being controlled falls off, and these standards are met at f/2.8.  You could avoid the feeling of being ordered around by having the maximum aperture be f/2.8 at all distances, but I wouldn't want that.  And I know from watching these arguments in the past, that if your standards are lower than Leica's standards, that's tough.  Leica's standards will be applied.  The folks who want to make their own decision whether to do immediate dark field exposures or go ahead and take the next shot after a loong exposure have been losing this argument with Leica for many years.

[frithjof.b]

22 hours ago, scott kirkpatrick said:

Leica doesn't work the way you might like.  Someone in the lens shop has decided that the performance of the 23/2.0 meets Leica's standards down to f/2.0 at most distances, but when focused closer than about .5 m the sharpness and whatever else is being controlled falls off, and these standards are met at f/2.8.  You could avoid the feeling of being ordered around by having the maximum aperture be f/2.8 at all distances, but I wouldn't want that. 

The question is not so much the "Leica standard" rather the physics behind it since Leica cannot beat the laws of physics.

Prior to your post I was only aware of such a behavior in macro lenses. People on the net write about a "bellow factor" even though they do not have a bellow but a off-the-shelf macro lens. I remember checking that hypothesis with my Zeiss ZF f2/100mm Macro Planar 7-8years ago, by focusing at infinity, aperture at f2 fully open, and setting a fixed exposure time in manual mode. Then I changed the focal distance up to the closed distance: all images were correctly exposed, although according the "bellow theory" I should have lost 1/2 a stop at 1:2. This bellow effect might be more relevant with full frame view cameras with film size of 8x10cm or larger. Definitely irrelevant for the 2/23mm since Leica states a magnification of 1:12.6, which does not explain the change to 2.8.

Modern AF lens designs often focus by shifting a small amount of lens elements which might leads to a change of the focal length at short distance. 70-200mm zooms are known to reduce the focal length closeup as a price for a fast AF, one Nikon 2.8/70-200 has a reported 140mm equivalent field of view closeup for the 200mm settting. There is a claim that most all AF macro lenses increase their focal length closeup. Since the opening diameter stays the same, the  aperture would increase.

I sadly do not own the TL 2/23mm, but I would check whether the field of view is changing when focusing close. If you see a narrowing of the field of view when you are manually focusing closeup coming from infinity, you have your answer. Simultaneously one should get a longer exposure time if the physical f stop is shown.  I suspect it has to do with the very compact lens design with the constrain of supporting a fast  AF with a very small AF motor. 

I found this observation fascinating since the MFT diagram for the Summicron TL 23mm show a Aperture stop 2.0 MFT for close focal distance on Leica's info sheet of the lens. Somehow this appears to be inconsistent.

 

[nicci78]

It is by design. Leica reckons that image quality is not sufficient at f/2 in close up range. Therefore they prefer to limit by software max aperture at f/2.8. 

It is the same behaviour with the X typ 113

Leica’s MTF close up range is 1m, no data for minimum focusing distance 

 

[frithjof.b]

3 hours ago, nicci78 said:

ILeica’s MTF close up range is 1m, no data for minimum focusing distance 

 

Thanks for pointing that out. I the data sheet I could not find the definition of "close focal distance".

[SrMi]

4 hours ago, frithjof.b said:

Thanks for pointing that out. I the data sheet I could not find the definition of "close focal distance".

Leica's Datenblatt in the download section:

"Focusing range: 0.35 m to ∞"

[ramarren]

My Leica X 113 closed down the aperture when in the minimum to 1m range and I read about a thousand amusing whines and moans about it. In use, it never made a single bit of difference to me. Lens performance was excellent throughout the range, and at close distances like that one tends to stop down the lens anyway to obtain enough DoF.

[DwF]

I tried the 23mm lens on a CL about two weeks ago. I got in very close and the DNG when I opened it showed f2. Is this for certain a design issue?

[SrMi]

1 hour ago, DwF said:

I tried the 23mm lens on a CL about two weeks ago. I got in very close and the DNG when I opened it showed f2. Is this for certain a design issue?

What do you mean by very close? You have to be closer than 20" to the subject to notice gradual aperture change f/2.0 -> f/2.8.

[DwF]

I wondered and no, not 20 inches close more like 24-27 inches. Still shorter distance than with X 113 for stopping down to activate.  Thank you for clarifying.

[Advertisement]

Hallo,

Look here: Leica L-Mount

[lanetomlane]

Mine does exactly the same, be assured you don't have a problem