Nokton 50/1.1 focus shift

L

Lord Fluff

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Hi guys

I recently bought this lens new and have just started playing with it, and generally I really like it. Or at least I really like the idea of it - some reasonably scientific testing with the M8 yesterday revealed strong and consistent focus shift as you stop down. I shot our garden fence from a little over MFD (which is where I'll be shooting a lot of the time) and with each click of the aperture (stopping down) the plane of focus moves further away from the focussed point, and the worst thing is that it moves more than the increase in DOF, so the thing you were focussing on gets steadily softer!

Is this a known issue, has anyone else run into this? Steve Huff's review seemed very positive, but the emphasis seemed very much on shooting wide open. Granted that's how you'd use the lens a lot of the time, but I'd like the option to use other apertures at times!!

I suspect I'll be taking it back to the shop, but the dilemma is whether to replace or refund, and then I guess head more towards a 50 lux.

Thanks guys
 
MFD = Minimum Focus Distance?

Most fast lenses have some focus shift. You can compensate quite easily by rocking backwards as you stop down. With my C-Sonnar, at closest focus distance at f/1.5 I rock my head back an inch or so, at f/2.8, 6 inches or so. This gives more or less equal depth of field in front and behind.

This may seem like a ridiculous hassle at first, but it soon becomes almost instinctive.

Cheers,

R.
 
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....
 
Roger Hicks said:
MFD = Minimum Focus Distance?

Most fast lenses have some focus shift. You can compensate quite easily by rocking backwards as you stop down. With my C-Sonnar, at closest focus distance at f/1.5 I rock my head back an inch or so, at f/2.8, 6 inches or so. This gives more or less equal depth of field in front and behind.

This may seem like a ridiculous hassle at first, but it soon becomes almost instinctive.

Cheers,

R.
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It is a ridiculous hassle. Guesswork has no place in my work, I won't use things that do not 'just work' accurately and flawlessly everytime with no guessing or kludges. When I focus a lens, I expect my images to be in focus! Every time! No matter the aperture. Which is why I will never buy a lens that has a focus shift. We don't see these problems with fast SLR lenses, why are so many RF lenses affected by it?
 
Nicely put Chris - coming from the world of SLR shooting for many years it does seem pretty alien to me to have to think of wobbling my head around to approximate where the plane of focus might possibly be!

Canon's recent 50/1.2 is known as the 'shifty 50' as it exhibits this behaviour, and it's why I never bought it. It was roundly slammed by users and sales tanked - SLR users clearly expect better.

Maybe Leica and CV think - 'hey, they'll compromise enough to use a RF, they won't mind focus that moves around - heck they'll probably think it was their fault anyway!'
 
Chriscrawfordphoto said:
It is a ridiculous hassle. Guesswork has no place in my work, I won't use things that do not 'just work' accurately and flawlessly everytime with no guessing or kludges. When I focus a lens, I expect my images to be in focus! Every time! No matter the aperture. Which is why I will never buy a lens that has a focus shift. We don't see these problems with fast SLR lenses, why are so many RF lenses affected by it?
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Dear Chris,

Actually, it's not guesswork: it's completely repeatable.

Many fast SLR lenses do in fact exhibit focus shift, just not as much. They are of course a lot bigger and heavier, and use a degree of Retrofocus design to leave room for the mirror.

I have no problems with the focus shift on the C-Sonnar because it's a small, light lens which gives results I like. But if I didn't like it, I wouldn't use it. No point in getting quite so excited about it!

Cheers,

R.
 
Lord Fluff said:
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....
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I wonder if your Summarit shows no focus shift on the M8 or maybe just on film (full frame) Leicas?

There was a discussion recently on the same problem with the CV 28mm f2.0 Ultron and the possibility that this is only noticeable on DRFs.
 
Roger Hicks said:
Dear Chris,

Actually, it's not guesswork: it's completely repeatable.

Many fast SLR lenses do in fact exhibit focus shift, just not as much. They are of course a lot bigger and heavier, and use a degree of Retrofocus design to leave room for the mirror.

I have no problems with the focus shift on the C-Sonnar because it's a small, light lens which gives results I like. But if I didn't like it, I wouldn't use it. No point in getting quite so excited about it!

Cheers,

R.
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The only reason I shouldn't get excited about it is that I didn't waste my money on one. Sorry, but moving back and forth is not precisely repeatable, and not a technique to use when your professional reputation and paycheck DEPEND on sharp images every time, no exceptions. Even if I were just a hobbyist, I'd not tolerate that. Like I said, if it doesn't "just work" I don't want it. I have too many hassles in my life as it is.
 
And Roger, I'm not sure where 'many' comes from, but I can tell you that there's no detectable shift to be found in the Canon range, barring the aforementioned 50/1.2, and yes I do speak from experience of owning almost every Canon prime.
 
hans voralberg said:
Lawrence his is a Nokton ;) Just want to point that out. Don't think the Summarit shift if at all.
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He says that the Summarit doesn't shift but I just wanted to check whether this is the case on the M8. Sean Reid has found focus shift on the 28mm f2.0 Ultron whereas some experienced RFFers have found no such problem with this lens on film cameras.
 
I'm not sure how it could not be noticeable to be honest Lawrence - it's pretty severe. Shooting at near MFD (1m) the backwards shift by f4 (from in-focus at f1.1) is about six inches.
 
Lord Fluff said:
I'm not sure how it could not be noticeable to be honest Lawrence - it's pretty severe. Shooting at near MFD (1m) the backwards shift by f4 (from in-focus at f1.1) is about six inches.
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Very strange how recent CSV lenses appear to have this 'feature' and the older ones don't. As mentioned, Sean Reid found it in both the new 35mm f1.4 and the 28mm f2 and now it seems the 50mm f1.1 has it too. I have to say that Roger's suggestion wouldn't work for me in many situations as I'm far too tied up with shutter speeds, composition and so on to be able to remember 'Ah yes, Nokon at f5.6 (or whatever) means I have to move my head backwards a couple of inches'. Not saying this would be a problem for everyone.

Purely by the way, the 50mm that I can recommend is the current version Summicron. It's totally predictable, sharp at every aperture and, to my eyes, the bokeh is lovely. It's also very compact. I hardly ever want to use a rangefinder lens above f2 anyway due to possible focussing error and the 'Cron cost me no more than a Nokton f1.1 (s/h on eBay). So unless wide apertures are essential that might be the way to go...
 
As I'm a wedding photographer, speed is (almost) everything, which combined with the poor high-ISO performance of the M8 make the Cron a no-no (I actually own both a 40 and 50 pre-asph Cron already, great lenses but not always fast enough).

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.

I guess this puts me in the position of deciding whether to keep a pretty dear lens to use ONLY at f1.1, which I guess is what Noctiloonies do, and wide open focus is bang on. I guess that may have been the compromise involved in making an affordable f1.1 lens, but it's still a disappointment I have to say.
 
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focus shift

focus shift

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.

Some time ago I bought a CV 1,9/28mm that was close to useless on my M8. I sold it cheaply to a friend who uses it on his film M(s). No problems.

le
 
Chriscrawfordphoto said:
The only reason I shouldn't get excited about it is that I didn't waste my money on one. Sorry, but moving back and forth is not precisely repeatable, and not a technique to use when your professional reputation and paycheck DEPEND on sharp images every time, no exceptions. Even if I were just a hobbyist, I'd not tolerate that. Like I said, if it doesn't "just work" I don't want it. I have too many hassles in my life as it is.
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Dear Chris,

What, unlike mine? You're the one who's always complaining he can't earn a living. I'd like a better living, but it's OK.

Sorry, all you have to do is use the right tool for the job. If this isn't the right tool for your job, don't use it. It works for mine, so I do -- so it isn't a waste of money.

The focus shift IS precisely repeatable. The only point is that you don't normally want to use a focus slide, so you guess at 2" insead of 3": well inside tolerance.

Cheers,

R.
 
bidnez said:
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.

Some time ago I bought a CV 1,9/28mm that was close to useless on my M8. I sold it cheaply to a friend who uses it on his film M(s). No problems.

le
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Before we go any further, let's not interchange the terms. Back-focus usually refers to a consistent misfocussing, whereas focus-shift refers to a movement of area of DOF away from the original focus point as aperture changes.

Or at least that's how I use the terms!
 
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