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Why Isn't the Noct 0.95 58MM an Auto Focus Lens

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ZurichPhoto

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I thought one of the virtues of the new Z Mount was that it would provide a platform for produce more exotics like the Noct 58MM 0.95. I read/heard today that it's a manual focus. This surprised me. Is there a technical reason why a 58MM 0.95 can't be an autofocus lens?

It would likely be slow to focus -- I get it. But is there a technical reason this can't be done?
 
I am not an expert in lens design but...

1. Size, it will probably be large already, so adding motor, etc would make even larger and uncomfortable to use, especially on a really small camera like that.

2. It's DoF is going to be VERY thin and so by necessity many pics will be very unfocused or "near focused". If regular people using AF saw this, they would think it is not working and a "bad" lens and would return it and give Nikon a bad review and ruin that lens' reputation. People that use Manual Focus usually would know what is going on and work with that. So to avoid that possibility best not to mess around with it at all.

The situation is analogous to Nikon 58mm lens that the Noct would be take over from. People that know how to use it use it with care to produce something special. People that can't get it to "work" say it is a bad lens and give it bad reviews.
 
Eliot Kramer said:
I am not an expert in lens design but...

1. Size, it will probably be large already, so adding motor, etc would make even larger and uncomfortable to use, especially on a really small camera like that.

2. It's DoF is going to be VERY thin and so by necessity many pics will be very unfocused or "near focused". If regular people using AF saw this, they would think it is not working and a "bad" lens and would return it and give Nikon a bad review and ruin that lens' reputation.
Click to expand...
Bingo. The tweakers would be all over alleged front and back focusing issues.
Selex said:
People that use Manual Focus usually would know what is going on and work with that. So to avoid that possibility best not to mess around with it at all.
Click to expand...
Or shoot at f2.8 like a Christian :^)
Selex said:
The situation is analogous to Nikon 58mm lens that the Noct would be take over from. People that know how to use it use it with care to produce something special. People that can't get it to "work" say it is a bad lens and give it bad reviews.
Click to expand...
 
Well, I asked for a return of the Noct-Nikkor, manual focus and all, and it seems my wish has been granted. Blame me. ;-)

Of course, I did not want the 21st-Century Noct-Nikkor to be Z-Mount. :-( There is nothing else about the Z system that interests me, at this point in time.

I can only guess whether there is a tech reason for the lack of AF, but this lens may well be a boutique product, a halo product, intended as much for collectors as for the devotees of “MFNG.” (Manual Focus Nikon Glass)
 
Eliot Kramer said:
I am not an expert in lens design but...

1. Size, it will probably be large already, so adding motor, etc would make even larger and uncomfortable to use, especially on a really small camera like that.
Click to expand...
Not a good reason. The thing's got a tripod foot after all.
Selex said:
2. It's DoF is going to be VERY thin and so by necessity many pics will be very unfocused or "near focused". If regular people using AF saw this, they would think it is not working and a "bad" lens and would return it and give Nikon a bad review and ruin that lens' reputation. People that use Manual Focus usually would know what is going on and work with that. So to avoid that possibility best not to mess around with it at all.
Click to expand...
58 mm is not a very long focal length. DoF isn't that thin compared to slightly slower but longer lenses at similar focus distances.

Possible reason is that it's a Noct Nikkor, and AF doesn't work at night with very low light.
 
Being a 'Noct' lens ie. In the dark, AF is not expected to perform well. So it's but expectation to manual focus to be reliable. Out where the ambient light is good, a more traditional f1.2 or f1.4 lens would be the choice.
 
Reilly Diefenbach said:
Eliot Kramer said:
I am not an expert in lens design but...

1. Size, it will probably be large already, so adding motor, etc would make even larger and uncomfortable to use, especially on a really small camera like that.

2. It's DoF is going to be VERY thin and so by necessity many pics will be very unfocused or "near focused". If regular people using AF saw this, they would think it is not working and a "bad" lens and would return it and give Nikon a bad review and ruin that lens' reputation.
Click to expand...
Bingo. The tweakers would be all over alleged front and back focusing issues.
Reilly Diefenbach said:
People that use Manual Focus usually would know what is going on and work with that. So to avoid that possibility best not to mess around with it at all.
Click to expand...
Or shoot at f2.8 like a Christian :^)
Reilly Diefenbach said:
The situation is analogous to Nikon 58mm lens that the Noct would be take over from. People that know how to use it use it with care to produce something special. People that can't get it to "work" say it is a bad lens and give it bad reviews.
Click to expand...
Click to expand...
"like a Christian "?

What does that mean?
 
anixi said:
Reilly Diefenbach said:
Eliot Kramer said:
I am not an expert in lens design but...

1. Size, it will probably be large already, so adding motor, etc would make even larger and uncomfortable to use, especially on a really small camera like that.

2. It's DoF is going to be VERY thin and so by necessity many pics will be very unfocused or "near focused". If regular people using AF saw this, they would think it is not working and a "bad" lens and would return it and give Nikon a bad review and ruin that lens' reputation.
Click to expand...
Bingo. The tweakers would be all over alleged front and back focusing issues.
anixi said:
People that use Manual Focus usually would know what is going on and work with that. So to avoid that possibility best not to mess around with it at all.
Click to expand...
Or shoot at f2.8 like a Christian :^)
anixi said:
The situation is analogous to Nikon 58mm lens that the Noct would be take over from. People that know how to use it use it with care to produce something special. People that can't get it to "work" say it is a bad lens and give it bad reviews.
Click to expand...
Click to expand...
"like a Christian "?

What does that mean?
Click to expand...
It's just a turn of phrase. It put a smile on my face. My dad used to use the same expression in his native language. Basically it means like a civilized person. Some may get offended in these overly sensitive times, but I think Reilly used it with a sense of sarcasm fitting to the phrase.

As far as auto-focusing goes, there aren't even any f/1.2 lenses noted for especially snappy AF, just ask the Canon folks... Canon basically gave up on f/1 AF, and seems to backing off f/1.2 AF designs as well. Note the recent 85mm update.
 
ZurichPhoto said:
I thought one of the virtues of the new Z Mount was that it would provide a platform for produce more exotics like the Noct 58MM 0.95. I read/heard today that it's a manual focus. This surprised me. Is there a technical reason why a 58MM 0.95 can't be an autofocus lens?

It would likely be slow to focus -- I get it. But is there a technical reason this can't be done?
Click to expand...
Lenses with AF are designed with a relatively lightweight focus group. If you've looked at the design of this lens, all of the elements are massive, and it may even be a unit-focus lens (i.e., the entire optical assembly moves to focus).

Also f/0.95 is at least 5 stops away from the aperture used by AF (which must be compatible with f/5.6 to f/8 lenses), so the degree of focus shift is probably not manageable.

Finally, f/1 or f/0.95 lenses are going to exhibit spherical aberration which means there isn't even a precisely-defined focus plane. There is a small range of focus settings which will give different artistic effects and the photographer needs to be in control to achieve the effect they are targeting. This isn't a snapshot or sports lens.
 
I am a bit disappointed by the lack of AF, but the fact that it is MF is probably for the best for me... ;-) If it was AF the little devil on my shoulder would have a stronger argument for me getting a Z7 which I absolutely don't need.
 
Marianne Oelund said:
Also f/0.95 is at least 5 stops away from the aperture used by AF (which must be compatible with f/5.6 to f/8 lenses), so the degree of focus shift is probably not manageable.
Click to expand...
Marianne, I am def not questioning your expertise, but I would imagine that the Z series cameras would be able to work around that limitation (even if it resorts to a contrast detect only state). I believe when stating AF performance for one of the new cameras they quoted it as being sensitive down to -3 EV at F2 (I can try digging up the quote if you believe it relevant). I am hoping you can fill in some of the blanks, and help improve my understanding.

Cheers,

Diallo
 
YRUNVS said:
Marianne Oelund said:
Also f/0.95 is at least 5 stops away from the aperture used by AF (which must be compatible with f/5.6 to f/8 lenses), so the degree of focus shift is probably not manageable.
Click to expand...
Marianne, I am def not questioning your expertise, but I would imagine that the Z series cameras would be able to work around that limitation (even if it resorts to a contrast detect only state). I believe when stating AF performance for one of the new cameras they quoted it as being sensitive down to -3 EV at F2 (I can try digging up the quote if you believe it relevant). I am hoping you can fill in some of the blanks, and help improve my understanding.
Click to expand...
As is often the case, things are not as straightforward as they might seem, and CDAF isn't a universal solution. In the presence of SA and variable detail/line sizes, it can get rather confused.

There are still many unknowns, for example I don't know what the beam patterns are for the on-sensor PDAF yet.
 
anixi said:
Reilly Diefenbach said:
Eliot Kramer said:
I am not an expert in lens design but...

1. Size, it will probably be large already, so adding motor, etc would make even larger and uncomfortable to use, especially on a really small camera like that.

2. It's DoF is going to be VERY thin and so by necessity many pics will be very unfocused or "near focused". If regular people using AF saw this, they would think it is not working and a "bad" lens and would return it and give Nikon a bad review and ruin that lens' reputation.
Click to expand...
Bingo. The tweakers would be all over alleged front and back focusing issues.
anixi said:
People that use Manual Focus usually would know what is going on and work with that. So to avoid that possibility best not to mess around with it at all.
Click to expand...
Or shoot at f2.8 like a Christian :^)
anixi said:
The situation is analogous to Nikon 58mm lens that the Noct would be take over from. People that know how to use it use it with care to produce something special. People that can't get it to "work" say it is a bad lens and give it bad reviews.
Click to expand...
Click to expand...
"like a Christian "?

What does that mean?
Click to expand...
Patrick O'Brian reference :^)
 
ZurichPhoto said:
I thought one of the virtues of the new Z Mount was that it would provide a platform for produce more exotics like the Noct 58MM 0.95. I read/heard today that it's a manual focus. This surprised me. Is there a technical reason why a 58MM 0.95 can't be an autofocus lens?

It would likely be slow to focus -- I get it. But is there a technical reason this can't be done?
Click to expand...
Normal for a high $$ lens to not have A/F. I point to the Zeiss Otus series, no A/F on those (or the cheaper Milvus line). Besides, the camera will have focus peaking and other assists.
 
Last edited:
Marianne Oelund said:
Also f/0.95 is at least 5 stops away from the aperture used by AF (which must be compatible with f/5.6 to f/8 lenses), so the degree of focus shift is probably not manageable.
Click to expand...
This reminded me of something I've been wondering, and perhaps you can help me learn.

I recently shot some longish images from tripod on a D850 in a very dark, abandoned church. I was experimenting with using Live view, and touchscreen focus, which is very nice from a convenience standpoint, but I noticed that it often couldn't get focus. I had to get out my smart phone, and light up the focus subject a bit. At the same time, I noticed that the camera is focusing at the set aperture, rather than wide open, as it does in TTL shooting.

Also, it appears that the Z bodies also focus at the set aperture, rather than wide open?

Focus shift aside, why wouldn't all cameras focus wide open?
 
historianx said:
ZurichPhoto said:
I thought one of the virtues of the new Z Mount was that it would provide a platform for produce more exotics like the Noct 58MM 0.95. I read/heard today that it's a manual focus. This surprised me. Is there a technical reason why a 58MM 0.95 can't be an autofocus lens?

It would likely be slow to focus -- I get it. But is there a technical reason this can't be done?
Click to expand...
Normal for a high $$ lens to not have A/F. I point to the Zeiss Otus series, no A/F on those (or the cheaper Milvus line). Besides, the camera will have focus peaking and other assists.
Click to expand...
It's going to be extremely interesting to see how focus peaking and focus assist behave with an f/0,95 lens. I'm sure we'll quickly gain some detailed insights into why the lens doesn't have AF.
 
Marianne Oelund said:
ZurichPhoto said:
I thought one of the virtues of the new Z Mount was that it would provide a platform for produce more exotics like the Noct 58MM 0.95. I read/heard today that it's a manual focus. This surprised me. Is there a technical reason why a 58MM 0.95 can't be an autofocus lens?

It would likely be slow to focus -- I get it. But is there a technical reason this can't be done?
Click to expand...
Lenses with AF are designed with a relatively lightweight focus group. If you've looked at the design of this lens, all of the elements are massive, and it may even be a unit-focus lens (i.e., the entire optical assembly moves to focus).

Also f/0.95 is at least 5 stops away from the aperture used by AF (which must be compatible with f/5.6 to f/8 lenses), so the degree of focus shift is probably not manageable.

Finally, f/1 or f/0.95 lenses are going to exhibit spherical aberration which means there isn't even a precisely-defined focus plane. There is a small range of focus settings which will give different artistic effects and the photographer needs to be in control to achieve the effect they are targeting. This isn't a snapshot or sports lens.
Click to expand...
I think that the live view phase detective is not limited to 5.6 or 8. If this measurement is done with the pixels of the recording sensor, then probably the light from the full lens opening will also be used for the PDAF. If this is indeed the case, focus shift also has no influence when the PDAF takes place through closed aperture.
 
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