eyal wrote:
I reached out to Lloyd to ask about the nonagonal bokeh balls. He confirmed them on his copy and has reached out to Zeiss for their thoughts. In his hands it appears these will show up at 'everything other than infinity':
Yeah, I messaged him as well. Looks like I was wrong and unlike Batis 25mm in this thread https://www.dpreview.com/forums/thread/4022440
the 40mm has it by design. It's unusual for sure. I also changed my mind after a while because it indeed looks ugly. If that's not sample variation and you actually have to live with it, I don't want to make the tradeoff.
Moreover, it looks like the lens is stopping down aperture as you focus closer, so it's not just an optical illusion due to moving focusing group. I don't know any other lens that links aperture mechanism and focusing mechanism. It could be related to Close Focus abilities and some design optimizations for best quality @ infinity and MFD. It can also be an unintentional firmware bug.
And when I said that I'd been tracking down differences in performance at different focussing distances, I meant on lenses that do have some kind of CRC/floating element. I think that what floating elements do is certainly to improve things overall, but also to introduce a "wavey" pattern of getting better and getting worse IQ across the distances, rather than a lens without them which is just best at wherever it is optimised for, and then gets worse as you go away from that. Just possibly the Batis 40 is better corrected than most floating element lenses to minimise that effect over a large range.
And when I said that I'd been tracking down differences in performance at different focussing distances, I meant on lenses that do have some kind of CRC/floating element. I think that what floating elements do is certainly to improve things overall, but also to introduce a "wavey" pattern of getting better and getting worse IQ across the distances, rather than a lens without them which is just best at wherever it is optimised for, and then gets worse as you go away from that.
That's interesting as that article was written by Bernd Ritschel (Zeiss Ambassador?) but it's not mentioned anywhere on the Zeiss official page for the Loxia line. When lenses do have FLE, Zeiss makes sure to list it as a main feature just like they do in the case of the Milvus, Otus, Batis lines. That's absent from any Loxia official description. So, it's still unclear to me.
I get your point about similar resolution from MFD to infinity even with FLE...I know many lenses with optimal distances even with the help of the flotation group.
Fred Miranda wrote:
That's interesting as that article was written by Bernd Ritschel (Zeiss Ambassador?) but it's not mentioned anywhere on the Zeiss official page for the Loxia line. When lenses do have FLE, Zeiss makes sure to list it as a main feature just like they do in the case of the Milvus, Otus, Batis lines. That's absent from any Loxia official description. So, it's still unclear to me.
I get your point about similar resolution from MFD to infinity even with FLE...I know many lenses with optimal distances even with the help of the flotation group.
Hi Fred the official pages have an icon which I think is for floating elements; it's the one between asphere and declick on this page for the 21mm:
Interesting article over at mflenses, 'who made the first floating element design' will get you there. Looks like the design was adopted in prime photographic lenses from fast wide early cine lenses, dating from the 1960s. Nikon made one in 1967. Canon's very fast FD 85s had it in the 1970s. CZ's first prime for photography came in the form of the 28/2 'Hollywood' prototyped around 1970.
Zeiss are notoriously very spare with lens commentary. Phillip Reeve's review of the Loxia 21mm and several other sources indicates it lacks FLE, others say it does have the system. The 25mm will likely be the same. I've not seen comments on the Loxia 85mm that it has FLE.
The wide Loxias may also lack internal focusing (I've never seen one). The D/SLR Distagon 21s have both IF and FLE, carried over from their CY ancestor.
philip_pj wrote:
Interesting article over at mflenses, 'who made the first floating element design' will get you there. Looks like the design was adopted in prime photographic lenses from fast wide early cine lenses, dating from the 1960s. Nikon made one in 1967. Canon's very fast FD 85s had it in the 1970s. CZ's first prime for photography came in the form of the 28/2 'Hollywood' prototyped around 1970.
Zeiss are notoriously very spare with lens commentary. Phillip Reeve's review of the Loxia 21mm and several other sources indicates it lacks FLE, others say it does have the system. The 25mm will likely be the same. I've not seen comments on the Loxia 85mm that it has FLE. ...Show more →
I think that Phillip now thinks that the L21 does in fact have FLE; if we can confirm that we'll change the article.
I think the 85 doesn't, though it's not a unit focussing lens: the rear elements stay fixed while it front group focusses. That may help with evenness across distances a bit.
Back to the 40mm. I’m starting to get a little off on it with diaphragm bokeh I’m seeing. I do need to look into this lens more as I have not had a chance to yet.
Fred Miranda wrote:
I know someone at Zeiss that can confirm this for us. I will send him an email.
Can you ask him about this 40mm Batis aperture issue as you focus closer? It's the first time ever I see this kind of behaviour. If the lens is closing down the iris as you focus closer (causing stop sign bokeh), it could very well be a software issue and not intended by design.
If it's, however, done on purpose, it'd be interesting to know why and what'll happen if you focus at MFD without stopping down.
Last option is that it's just an optical illusion that changes the way aperture is seen based on focusing distance, but it's very unusual and I still think that blades don't keep their orientation relative to each other.
maratus wrote:
Can you ask him about this 40mm Batis aperture issue as you focus closer? It's the first time ever I see this kind of behaviour. If the lens is closing down the iris as you focus closer (causing stop sign bokeh), it could very well be a software issue and not intended by design.
If it's, however, done on purpose, it'd be interesting to know why and what'll happen if you focus at MFD without stopping down.
Last option is that it's just an optical illusion that changes the way aperture is seen based on focusing distance, but it's very unusual and I still think that blades don't keep their orientation relative to each other.
If the effective focal length changes as you focus closer, as is often the case with close focussing internal focus lenses, then the actual aperture size required for the same f-stop is smaller.
That might explain it.
I suppose they could design it so that it's f 1.7 or whatever at close focus, with no change in the iris but
(1) the quality mightn't be as good as they planned and
(2) It's a bit of a record keeping nightmare and could seem "messy"
But I agree it's not a desirable behaviour, not without more blades...
DavidBM wrote:
If the effective focal length changes as you focus closer, as is often the case with close focussing internal focus lenses, then the actual aperture size required for the same f-stop is smaller.
That might explain it.
I suppose they could design it so that it's f 1.7 or whatever at close focus, with no change in the iris but
(1) the quality mightn't be as good as they planned and
(2) It's a bit of a record keeping nightmare and could seem "messy"
But I agree it's not a desirable behaviour, not without more blades...
1. Effective aperture is also getting smaller when you focus at MFD. Almost all lenses have it, mixed with focus breathing. But only macro lenses at close to 1:1 magnification actually report lower effective aperture to camera. It's common to drop from f2.8 to f5.6 at 1:1 magnification
2. Lloyd Chambers has just confirmed 2 stop difference in exposure, which shouldn't happen at 1:3.3 magnification and can only be caused by stopping down mechanically.
3. Aperture geometry at MFD visually resembles typical f4 from other lenses. You can clearly see it if you compare the blades curvature with the opening size. I'm now almost 100% sure that it's being stopped down gradually by the lens itself due to a mistake.
maratus wrote:
1. Effective aperture is also getting smaller when you focus at MFD. Almost all lenses have it, mixed with focus breathing. But only macro lenses at close to 1:1 magnification actually report lower effective aperture to camera. It's common to drop from f2.8 to f5.6 at 1:1 magnification
.
Effective aperture reduces as you focus closer with extension, but less so with internal focus.
And internal focus lenses are the ones that are most likely to reduce focal length at close focus, and thus need a smaller absolute aperture the get the same relative (f stop) aperture.
But your other points sound interesting and do incline me a bit more to think there is an error here.
I certainly hope so. If it is then it can be fixed, and it’d be more attractive...
That behavior discovered by Lloyd Chambers is quite unusual indeed, I do not know if I'd prefer a lens that at close-up reduces its FL but retains its nominal aperture and round bokeh balls or one that keeps its FL at the expense of being 2 stops slower and yielding nonagonal bokeh balls..
SPOILER: in fact I know, definitely the first option..
GMPhotography wrote:
Back to the 40mm. I’m starting to get a little off on it with diaphragm bokeh I’m seeing. I do need to look into this lens more as I have not had a chance to yet.
Me too, I'm not keen on the idea of the aperture blades automatically closing gradually at any distance closer than infinity, and having effective f4 at minimum focus distance... If that's the intended specification, it seems strange that Zeiss would not provide any information about it in their specs/announcement as it might put off many who have pre-ordered the lens without expecting this behavior. Anyway, need to wait for some official word from Zeiss on this first.
maratus wrote:
1. Effective aperture is also getting smaller when you focus at MFD. Almost all lenses have it, mixed with focus breathing. But only macro lenses at close to 1:1 magnification actually report lower effective aperture to camera. It's common to drop from f2.8 to f5.6 at 1:1 magnification
2. Lloyd Chambers has just confirmed 2 stop difference in exposure, which shouldn't happen at 1:3.3 magnification and can only be caused by stopping down mechanically.
3. Aperture geometry at MFD visually resembles typical f4 from other lenses. You can clearly see it if you compare the blades curvature with the opening size. I'm now almost 100% sure that it's being stopped down gradually by the lens itself due to a mistake....Show more →
I have just emailed Zeiss' Sr. Director, Americas about this. He seems to be very knowledge in exchanges we had in the past.
