Nokton 50/1.1 focus shift

[Lord Fluff]

The focus shift IS precisely repeatable

While I don't want to get in the middle here, while the shift itself may be precisely repeatable, the 'lean back' isn't, so that's not a solution I'm happy with.

 

[bidnez]

Thanks, Lord F! That goes a long way to answer my q.
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[Sonnar Brian]

Is it possible to (simply) explain why the focus shift problem (aka back focus?) is notable on, say, the M8, and not on a film camera.

With the M8, you can "pixel peep" and see details at 75LP/mm. You are resolving well past the acceptable DOF for prints.

My experience: I could not see much, if any, focus shift on pre-war 5cm F1.5 Sonnars and early J-3's until getting the M8. With the M8, I can shim the lens to optimize the focus to minimize the shift. I set the exact focus for my 1953 J-3 to sligtly front-focus at F1.5, which reduced the back-focus at F4. Could not see the difference before.

Full-Image with 1930s Sonnar, at F1.5

100% crop of 1930s Sonnar, at F1.5

At F4, sharpest focus shifts backwards.

 

[Lord Fluff]

I think I'd tolerate a shift within the increase in DOF, but to stop down and have the point on which you've focussed on get SOFTER just seems insane.

I may try another copy of the lens to check if this one is a dud.

 

[Lord Fluff]

I've seen lovely stuff from that lens it's true - I was mentioning it as its behaviour attracted a lot of negative press, something that it seems isn't the case with RF lenses.

That said, if they can make the 85L without a whiff of focus shift and the original 50/1.0 without focus shift, or their 50/1.4, I fail to see why they opted for a shifty design this time round for their 'elite' 50.

 

[jaapv]

Thanks Roger, and yes 'ridiculous hassle' does seem quite apt. It also raises the point that if 'most' fast lenses show this behaviour, then that implies that some don't, and obviously I'd like to know which these might be. I think I'd sacrifice a little in 'character' to have a lens that behaves 'correctly'.

Does anyone have experience with a fast modern 50 that shows no shift? It's evidently possible since my 1950's Summarit 1.5 has no such issues....

Yes - the Summilux 50 asph has no focus shift.

 

[ferider]

Neither does the CV 50/1.5.

LF: I'm surprised you think the original 1.0 Noctilux does not shift.

Regarding an earlier comment: the CV 28/1.9 also doesn't shift. If or not focus works on your camera is another matter.

 

[jaapv]

You are right, Ferider, it does shift. The new 0.95 seems to be free of the phenomen, but I have a feeling that it might be a bit pricey for somebody contemplating a CV lens.

 

[johannielscom]

Never noticed anything like it on my Konica M-Hexanon 50/1.2, but never went through the whole movement to thoroughly check either. Ask Krosya, he's shooting the M-Hex 50/1.2 as well, he might know.

 

[fbf]

I used it exclusively at F1.1. It works great. I never stop down. I believe the F1.1 is the only reason I bought it at first place.

 

[squirrel$$$bandit]

I used it exclusively at F1.1. It works great. I never stop down. I believe the F1.1 is the only reason I bought it at first place.

This is probably why I haven't noticed this problem, either.

 

[Lord Fluff]

Ok as further info for anyone considering this lens....

I returned my lens and exchanged it for another of the same. I can confirm that the second copy displayed exactly the same shift of focus plane that the first one did, so it seems entirely possible that this is simply a function of the design of this lens.

As others have noted, if you want a 50mm lens that is faster than f1.4 and intend never to use the aperture ring, then the results are very good indeed.

However if you're looking for a 50mm that is more than a one trick pony you'd be advised to look elsewhere. A pre-asph Summilux is proving a worthy substitute for now.

 

[Lord Fluff]

LF: I'm surprised you think the original 1.0 Noctilux does not shift.

I have very little experience of the Nocti - I was actually commenting on the Canon 50/1.0 at the time

 

[Gregoryniss]

My Lens that i got about 3 weeks ago seems to be free of focus shift, or it's so minimal that it isn't affecting my shooting. However, I usually stay under f4-5.6 so i'm not sure if it's a problem at those apertures.

 

[john_s]

AFIK all 50/f1.4 lenses have some focus shift except maybe the ASPH. You would expect that wider aperture lenses would be worse. The Noctilux 50/f1 has huge focus shift around f2.8. So much so that the growing DoF comes nowhere near keeping the focused distance sharp.

In the case of the Nokton 50/f1.1, as far as film is concerned, I found that mine focuses perfectly at f1.1. On stopping down, I have found that the DoF increase is enough to keep the focused distance sharp. The growth of DoF is all to the rear, and there is at f2 a very very slight drop in front DoF. However that is partly compensated by the higher contrast as the lens is stopped down, so IMO it's just not noticeable. I did my tests with ISO=25 film, and since I just use ISO=400 (film!) with this lens there is nothing to worry about.

For digital, I guess it's a different story.

 

[Sonnar Brian]

Too bad no one ties the aperture ring to an indexed cam.

 

[Bruin]

I'm glad to be hearing this about the Ultron as well, as that was on the shopping list as a cheap alternative to the 28 Cron, though I can't believe the shift on a 28 lens will be anywhere near as terrible.

It's not an issue on film; even controlled testing could not get any focus shift to show up. On M8 it's slight at f/2.8, most noticeable from f/4-5.6, and covered by DOF by f/8.

With the 28mm Ultrons, the biggest issue is sample variation. That will make a much bigger difference than focus shift. Both can be superb, superb lenses though!

 

[awilder]

When I owned the Limited 50/1.2 Hexanon-M it had only slight focus shift as stopped down, comparable to the 50/1.4 pre-asph. Summilux. Probably the sharpest 50/1.2 for an RF with the possible exception of the rare original 50/1.2 Noct'.

 

[ampguy]

For me, the nod back a bit, is just not worth the hassle, although I don't doubt that Roger and others can get used to it and make it repeatable.

My J8 pre-rebuild had this, and I never found it fun to use, even though I could repeat the nod back and mfd repeatedly.

Also, my Noct f1 E60 never had focus shift to f5.6. I never measured and rarely used at smaller apertures. With color, and 35mm, you get a) resolution loss and b) diffraction when used at small apertures.

 

[Lord Fluff]

My Lens that i got about 3 weeks ago seems to be free of focus shift, or it's so minimal that it isn't affecting my shooting. However, I usually stay under f4-5.6 so i'm not sure if it's a problem at those apertures.

The shift I experienced is near minimum focus distance (ie around 1m or so) and happens as you stop down from wide open to f4, with the DOF moving backwards by more than the increase in its size. For me this equated to getting ok results wide open but at 2.8 I was more likely to have someone's ears sharper than their eyes (or at least it looked like that was the point I had been aiming for).

I initially dismissed this as user error since my RF focussing is only ok, but the shift was definite and repeatable when tested with a static target.

My aim is not to put people off this lens, since wide open it is a valid alternative to the Noct. I really wanted to keep mine but couldn't see myself having one 50mm for f1.1 and another for everything else. YMMV of course