Konica Hexanon Dual 21-35mm owner question: focus behavior

[marduk]

I got my hands onto beautiful Konica Dual 21-35mm lens, beautiful user (easily 8+/10 condition, 9+/10 optics and smoothness), but I wanted to understand if the other owners noticed a following problem in their lenses too:

When shifting the focal length ring from the 35mm to 21mm position, the plane of focus moves forward quite significantly, which is well visible on mirrorless cameras (SL 601). For example switching FL without changing position of the camera means that if some object 1.8m away was in focus with 35mm, at 21mm I should rotate the ring towards 1.2m mark. Which is not a big deal on DSLM, but since the RF cam position does not change, it will back-focus on rangefinder bodies.

I have not photographed on film with it yet and don't have a digital M body. I might shoot some test shots on the film to confirm, but I can not see how it will be different than on DSLM, since even with all the DoF that one gets at the 21mm, it is not just few centimeters off and as expected it will not be ideally sharp on the SL at infinity. However, the rangefinder spot (on my M2) aligns perfectly with inifity with this lens (of course in its both positions).

Hence questions to the owners of the lens:
- have you seen the focus plane shifting on the mirrorless when changing the FL?
- is it spot on in the 21mm position same as in 35 on your rangefinder? If so, it means that the lens is able to move the rf cam with the FL switch action which is not that straightforward 🙂
Many thanks 🙏

 

[das]

The Dual Hexanon definitely has some focus shift. With digital, I would definitely confirm focus with liveview. On film, it really is not a big deal, and I do not notice any ill effects.

 

[marduk]

I was a M262 user for a bit, now I only have a M2 and mirrorless 🙂 It makes great pictures but I would be surprised if nobody has suffered from this issue (and yet at the same time i can not imagine what is wrong with my sample. It doesn't look like it has been tampered with).
I would keep it if it's within tolerances, I guess I have to make more tests tomorrow in daylight (I'm in Austria).
I have adapted myself a Contax G 21mm to M-Mount but would prefer the Konica for handling and clear corners without magenta shift.

 

[shawn]

When shifting the focal length ring from the 35mm to 21mm position, the plane of focus moves forward quite significantly, which is well visible on mirrorless cameras (SL 601). For example switching FL without changing position of the camera means that if some object 1.8m away was in focus with 35mm, at 21mm I should rotate the ring towards 1.2m mark. Which is not a big deal on DSLM, but since the RF cam position does not change, it will back-focus on rangefinder bodies.

I have not photographed on film with it yet and don't have a digital M body. I might shoot some test shots on the film to confirm, but I can not see how it will be different than on DSLM, since even with all the DoF that one gets at the 21mm, it is not just few centimeters off and as expected it will not be ideally sharp on the SL at infinity. However, the rangefinder spot (on my M2) aligns perfectly with inifity with this lens (of course in its both positions).

I don't recall seeing that when I had a 21/35 but I also don't think I shot it much on mirrorless, mostly on a M240. Didn't have focus issues there.

Do you have another M mount lens that you know has accurate focus at the infinity stop? If so try it on your SL and see if you have sharp infinity at the stop on the SL. If not, your adapter is not the exactly the correct length. That will impact 21mm more than it would 35mm and might be why you are seeing the shift?

I typically shim my adapters to get them so that infinity is sharp at the stop.

 

[Freakscene]

It’s a non-parfocal zoom lens. The focus point changes when the focal length changes. But the depth of field at 21mm should cover the difference. I never tested it formally, but I never got any out-of-focus photos (on film) either. The cam does not move when the focal length changes.

I didn’t look in the 21-35 but early KM lenses had a shim in the mount to change the backfocus for Konica’s slightly different back focus standard and, at least in the mind of some, to make them less suitable for being used on Leicas and Leica lenses less suitable for the Hexar. Some later KMs, made after the late Erwin Puts pointed out the back focus difference, appear not to have the shim. I’m not sure if the Hexar ever changed. If the back focus is off it will exaggerate other problems, and it is more important to get the back focus correct with a wide angle because rear focus is more critical the wider the field of view. It is worth noting that back focus is notoriously hard to measure.

A 21mm lens at f3.4 has a depth of field, assuming a normal circle of confusion, of roughly 0.8-2.1m, so assuming everything else is working it covers a lot.

Maybe try it and see if it works.

 

[marduk]

Hi @shawn I have a Leica 35mm 'Lux ASPH and different kids of adapters (Novoflex LET/LEM and several Urth), both kinds of adapters as well as the Lux and Konica at 35mm show exactly the same behavior. The Konica at 35mm is spot on.

@Freakscene thanks for your comment, it is rather extreme variation from what I can see. Interestingly, the Konica at mfd of 0.8m is sharp on 21mm as well as 35mm. The focus collimation difference between the two focal length grows as you focus closer to infinity, for example object 3m awat would be 2m by the 21mm scale and the one which is 5m away would be only 2.5-3m by the 21mm scale.

The DoF scale can be used to estimate focus, because the far end of the focus zone according to the green numbers is where the sharpest focus is actually placed. So it is not impacting so much in practice because it is easier to get used to than it sounds, it is also easy to refocus given the extremely short focus throw but if you depend only on the rangefinder style photography it is noticeable in practice, it might leave one wondering where the focus is for example in many typical people shots or if you go to photograph the market stalls in the middle distance (which i would not do wide open in most cases anyway).

Also David B. from Macfilos replied that he does not see this problem in his lens: The M Files (13): Three Konica M-Hexanon lenses – one of them is a real gem and truly exotic

 

[marduk]

@Freakscene you might be right about the focus point change and the depth of field. Starting from f4.5 the shift when going from 35mm to the 21mm position is diffusing. Shooting wide-open with focus towards infinity is not very typical, but it is just a hair away from the ideal focus point at 21mm, while focus is perfectly collimated for the 35mm. I was quite busy today but took some test shots, it may be a keeper, but relying solely on the rangefinder for photographing people on 21mm wide-open is going to produce images with slight back-focus. The zone focusing can be used with a simple scale-based adjustment technique. What i saw in fact is that if you note the distance when focused with 35mm or you guess estimate the distance then you need to rotate the focus ring slightly more so that not the red center mark but green f4 letter on the barrel is aligned with that distance number.

 

[marduk]

I am quite impressed with the sharpness, it is just a tiny bit less sharp than the Leica 11 874 ASPH, as well as Contax G Biogon 21, but still more than enough very uniform across the frame including corners and has nice flare resistance. Plus the vignetting and color shift in the corners in much better on the SL than the other adapted wide-angles I have got (tested the G21 and the CV21/4) and the price was less than all prior ads I could find on the fredmiranda. However to justify keeping it i would like it to be perfect on the M bodies, because for mirrorless there are many other lenses available too.

 

[KoNickon]

Hi @shawn I have a Leica 35mm 'Lux ASPH and different kids of adapters (Novoflex LET/LEM and several Urth), both kinds of adapters as well as the Lux and Konica at 35mm show exactly the same behavior. The Konica at 35mm is spot on.

@Freakscene thanks for your comment, it is rather extreme variation from what I can see. Interestingly, the Konica at mfd of 0.8m is sharp on 21mm as well as 35mm. The focus collimation difference between the two focal length grows as you focus closer to infinity, for example object 3m awat would be 2m by the 21mm scale and the one which is 5m away would be only 2.5-3m by the 21mm scale.

The DoF scale can be used to estimate focus, because the far end of the focus zone according to the green numbers is where the sharpest focus is actually placed. So it is not impacting so much in practice because it is easier to get used to than it sounds, it is also easy to refocus given the extremely short focus throw but if you depend only on the rangefinder style photography it is noticeable in practice, it might leave one wondering where the focus is for example in many typical people shots or if you go to photograph the market stalls in the middle distance (which i would not do wide open in most cases anyway).

Also David B. from Macfilos replied that he does not see this problem in his lens: The M Files (13): Three Konica M-Hexanon lenses – one of them is a real gem and truly exotic

Thanks for pointing out that review -- I hadn't seen it before. Something the reviewer said was very interesting -- that the aperture is embedded within the rear lens group, and that group (along with the aperture) shifts position when switching between the two focal lengths. Presumably that accounts for the focus shift? Sorry if I'm stating the obvious here.

 

[marduk]

@KoNickon I think that is causing the variable aperture, but not sure if it can contribute to the focus shift. In that link, there is a fresh comment today with a reference to a Japanese whitepaper with lens diagrams and text where Konica said that they used a washer (FC adjustable plate) to adjust the distance between the front and rear groups so that the focus position at each focal length is the same.

 

[KoNickon]

@KoNickon I think that is causing the variable aperture, but not sure if it can contribute to the focus shift. In that link, there is a fresh comment today with a reference to a Japanese whitepaper with lens diagrams and text where Konica said that they used a washer (FC adjustable plate) to adjust the distance between the front and rear groups so that the focus position at each focal length is the same.

Ah -- fascinating! A pretty formidable technical achievement, this lens. I have all of the other M-Hexanons (other than the fast 50) but I don't see myself finding one of the 21/35s anytime soon.

 

[shawn]

Hi @shawn I have a Leica 35mm 'Lux ASPH and different kids of adapters (Novoflex LET/LEM and several Urth), both kinds of adapters as well as the Lux and Konica at 35mm show exactly the same behavior. The Konica at 35mm is spot on.

@Freakscene thanks for your comment, it is rather extreme variation from what I can see. Interestingly, the Konica at mfd of 0.8m is sharp on 21mm as well as 35mm. The focus collimation difference between the two focal length grows as you focus closer to infinity, for example object 3m awat would be 2m by the 21mm scale and the one which is 5m away would be only 2.5-3m by the 21mm scale.

Do your other lenses hit infinity sharply at their infinity stop with those adapters? The Novoflex M mount to GFX adapter I had was *way* off. If the adapter is not correct it is going to mean the Konica's lens focus will be off more at infinity then it will be in close and it will be more off at 21mm compared to 35mm.

 

[Freakscene]

The FC adjustable plate can move; as the name indicates, it is 'adjustable'. Put the lens on a tripod, work out how much the focus is moving between focal lengths using a distance scale that you are looking at in the subject of the photo through the lens, don't measure distance using the distance scale on the barrel of the lens. If there is a substantial difference you have a problem - talk to a lens repairer.

It would also be useful if you can explain clearly what you find and what happens in the end. It is a very nice lens. It's one of only very few that I wish I hadn't sold on.


Random comments:
This is not focus shift. Focus shift happens when the focal point moves as the aperture changes. This is non-parfocality - the focus point moves when the focal length changes. They are different.

Adapters only make a difference on cameras with the different mount and they won't make any difference with this lens to the change in focus distance between the focal lengths. Have you tried the lens on an M mount camera?

Are you seeing the actual focus distance move or are you referring to the distance scale on the lens? Or both? It is unclear. The distance scale is very approximate, and designed for film, which means it was calculated with a circle-of-confusion larger than for digital.

KM lenses do not have an adjustable infinity stop on the helicoid like many lenses, and a vast majority of M mount lenses, have - the only thing that stops the KM lenses at the end of their travel is the mount/external part of the lens. They are designed to be able to focus slightly past infinity, and you need to focus for infinity if you want to focus at the distance.

Marty

 

[shawn]

Adapters only make a difference on cameras with the different mount and they won't make any difference with this lens to the change in focus distance between the focal lengths. Have you tried the lens on an M mount camera?

If the adapter isn't the proper width the resulting difference in actual lens position will have a greater impact on a wider angle lens. It will throw it further out of position compared to more telephoto lens. As an example I had a 21mm that on an M body hits infinity at the infinity position on the lens and a DAG'd 50mm Elmar that also hits infinity at the infinity position on the lens.

When used on a mirrorless with a Novoflex adapter (that was too thin by a little over 0.5mm) to hit infinity on the 21mm I was focused at roughly the 2m mark on that lens and on the 50mm it was about the 10m mark.



.


The -0.5mm shift from the adapter has a bigger effect on the shorter focal length compared to the longer focal length. When I then shimmed the adapter both lenses properly hit infinity at the infinity mark.

Likewise on a zoom lens with a bad adapter I'd get focus shift when zooming and after shimming the adapter that went away.

 

[Freakscene]

If the adapter isn't the proper width the resulting difference in actual lens position will have a greater impact on a wider angle lens. It will throw it further out of position compared to more telephoto lens. As an example I had a 21mm that on an M body hits infinity at the infinity position on the lens and a DAG'd 50mm Elmar that also hits infinity at the infinity position on the lens.

When used on a mirrorless with a Novoflex adapter (that was too thin by a little over 0.5mm) to hit infinity on the 21mm I was focused at roughly the 2m mark on that lens and on the 50mm it was about the 10m mark.
View attachment 4832272


.View attachment 4832273


The -0.5mm shift from the adapter has a bigger effect on the shorter focal length compared to the longer focal length. When I then shimmed the adapter both lenses properly hit infinity at the infinity mark.

Likewise on a zoom lens with a bad adapter I'd get focus shift when zooming and after shimming the adapter that went away.

Yes, it will affect the wide angle more; I hadn't considered that, but unless it is extremely close but not quite right, it should totally mess up the back focus at 21mm.

It would provide much information to put the lens on an M mount camera, particularly one with live view.

 

[marduk]

Thank you Marty and @shawn those are very good points about the adapters and angle of light. I will measure the distance to sharpest focus for both FLs with a measuring band after putting the camera on the tripod.
Might also walk in the afternoon and shoot some film with my M2, because I do not have a digital M currently. I will test it outdoor and indoor actually focusing on the piano, with my 35mm Summilux lens as well as Konica lens to make sure I am not overseeing some issue at the 35mm as well (see below).
Another alternative is walk to one of the shops in Vienna around Leica shop and see if they have another adapter and talk to staff. A digital M would have been good of course but I can not make it within free return period, being too busy during the week.

What I see with my in the EVF of the SL handheld for example object 3m away would be 2.2m by the 21mm scale and similarly focused on 2m with 35mm you need to turn it slightly back to the 1.6m mark, the amount of correction needed roughly corresponds to the distance on the ring between the focus mark and the first green f4 mark on the hyperfocal scale so not much.
I observed actually bigger deviation on first evening when using Urth and other camera:
- SL with Urth adapter
- Fuji X-H1 with Metabones adapter (but i will not post the data from that because the thread will get confusing).
Yesterday I changed the adapter to Novoflex and in direct comparison I can definitely the Dual lens fares better with Novoflex than with the Urth adapter, infinity with Urth is way more off and the lens requires extra turn. If the focus drift effect when switching the lens between 21/35 is also less on Novoflex I could not tell with 100% certainty, as I said I should measure it with a tape, but this seems *subjectively* so, as refocusing needed with a cheaper adapter is (as approximate as the distance scale can be ) consistently more than the other one. If it will still be there on the M240-M11 that would eliminate one variable from the equation.

About shawn's question:

Do your other lenses hit infinity sharply at their infinity stop with those adapters? The Novoflex M mount to GFX adapter I had was *way* off. If the adapter is not correct it is going to mean the Konica's lens focus will be off more at infinity then it will be in close and it will be more off at 21mm compared to 35mm.

Another wide lenses I tried on the SL were ZM 25/28mm, the ZM25 just as Minolta at 21 do not hit the infinity at the hard stop but before it. The ZM28 is perfect. That's the widest manual lenses i have. The Contax G21 is adapted and shimmed by myself so skip that. I put the C/Y Planar 50/1.4 on the SL(through Urth C/Y-L Mount) and it also must be stopped way before.

As Marty said it may be best to shim the adapter if you want to hit the infinity stop sharply. I still have a second Urth so can try to modify one of them for the KM.

 

[marduk]

Another thought
I just wonder can it slightly front-focus on 35mm and slightly back-focus on the 21mm? I had always thought it is because of adapter thickness, but when i focused the Summilux 35mm on 2m distant object on the M2, on the SL i had to refocus it to the 1.8m. Same goes for the KM at 35. On the Novoflex adapter the 'Lux focuses infinity sharply at the infinity stop.

Among other systems I have tried the APS-C fuji body and I can see that when the adapters cause poorly converging infinity focus, with any lens, it is probably somewhat aggravating the focus drift on Konica Dual lens. This is the subjective thing which needs to be confirmed through measuring, but I'm just saying that some adapters may cause poor performance in terms of more focus driting on 35/21 not only at their infinity but closer distances as well.
I see that ideal focus could be there when operating the zoom ring, just a few mm before it clicks into place at 21mm. That means a little internal problem in the lens but the question is how much impact will it have. I do not have a digital rangefinder, on one hand I would not expect it to perform tack sharp wide open in both focal lengths when you rely on the RF for focusing, on the other hand I don't know how much unsharpness the drifting focus point is causing in practice.

The bigger the crop factor and the worse the quality of an adapter the more of an impact it seems to cause, e.g. on the X-H1, focus will converge during "zoom" action roughly 1cm before the lens clicks at 21mm but on the SL this is hardly perceptable at least without critical inspection on the PC. Viewing test shots on the PC previously I could see you are mostly good stopping down half stop or full stop.I noticed this may be a thing when I mounted the lens on the camera with bigger sensor for first time - when, after the @shawn's comment, I took out my GFX50s (first model).

Initially, there with the highest mignification factor using the live view or the display of the GFX with focus peak highlighting I am struggling to see any focus drifting but I shall take photos from the tripod with the GFX for for closer lens inspection because its display and the EVF gives plenty of "zoom" but not much resolution for critical focus. So confusing but definitely a worthy data point!

I must add that I have used GFX for the critical focus like that because the M-GFX adapter which i have from 7artisans has some wobble, it is a cheap brand after all and i generally didn't care about more expensive stuff because I don't have any usable M-mount lenses which cover 44x33mm (btw, the Konica's 35mm end seems to cover full sensor with no vignette, other Zeiss and Leica glass doesn't do that).

 

[shawn]

So if your other lenses aren't hitting infinity at the stop your adapter is too thin, which is pretty common. That will be throwing the Konica out more at 21mm than at 35mm and the difference in the adapter will affect all focus points. The reason I was asking about infinity is it is the easiest way to check to see if the adapter is accurate or not. To shim them most adapters have the lens mount side be able to be removed such as in this Novoflex. I used copper tape to shim out the lens mount side to get it all proper. If you have lenses with floating elements your performance should increase with a properly shimmed adapter too since the element positions will be wrong if at the wrong flange focal length due to a thin adapter.

 

[marduk]

Hi, I developed some test film (APX 100) on the weekend with my piano and ruler test and if there is a back-focus in 21mm position it is certainly not much maybe 10cm in the 1m focus position, when shot wide-open (btw, the 35mm one has noticeable wider angle than the Summilux 35asph, quite a pleasant surprise). The infinity photos wide-open came sufficiently sharp, once can see that the 21mm wide-open performs a tiny bit sharper when focus on the hyperfocal mark than the infinity itself, but the film grain makes it almost imperceptible. All photos on digital (SL) turned out sharp, of course i have not turned the ring fully to the end because i have not shimmed the adapter yet so focused in EVF wide open.

I have strange outliers with my few last frames on the Leica M2. I focused the lens from the hill facing downwards to the city and made 3 shots when the lens was focused, according to my notebook, at infinity, at 10m mark and 5m mark and stopped down to in-between f8- 11. So the difference is aperture which takes me somewhere to f9 and 1/125sec on ISO 100 film, and of these three shots neither one is sharp. I think the focus is in front of the scene (the crown of the nearest tree just starts entering the focus zone) and it could be my mistake but i was carefully setting and writing down the parameters of the lens and the camera, so I don't know. I did not have any of these outliers on digital stopped down so it can not be down to the lens? I rechecked my scanner (Nikon CS 8000) calibration but it focuses where it needs i think. It would have been easier with a digital M camera - now I am out of town for 5 days.