meandihagee
Well-known
i keep reading about this problem with rangefinder M mount lenses. a few things aren't really clear for me so *who you gonna call?*, *range-finder-forum!* 
i want to buy a r2a+35mm nokton (or skopar, or zm) and upgrade from there. if i want to avoid focus shift, can i first stop down the lens and after that focus?
is the focus shift REALLY a problem? i mean, will your subject by out-of-focus and the shot completely ruined? i need prints as big as i can get them with a 35mm...
it seems silly to me to spend 1000$ or more on a lens that's not 100% accurate and somehow compensate and focus forward. i need a clean and fast focus, without wasting time and thinking how to override that expensive lens...
so, is focus shift internet paranoia or am i going to get just f2 lenses if i want to be on the safe side with the M mount?
thanks for your time
i want to buy a r2a+35mm nokton (or skopar, or zm) and upgrade from there. if i want to avoid focus shift, can i first stop down the lens and after that focus?
is the focus shift REALLY a problem? i mean, will your subject by out-of-focus and the shot completely ruined? i need prints as big as i can get them with a 35mm...
it seems silly to me to spend 1000$ or more on a lens that's not 100% accurate and somehow compensate and focus forward. i need a clean and fast focus, without wasting time and thinking how to override that expensive lens...
so, is focus shift internet paranoia or am i going to get just f2 lenses if i want to be on the safe side with the M mount?
thanks for your time
Larry H-L
Well-known
Some fast lenses focus shift, that is the point of focus changes slightly if the aperture is changed. It is most noticed at close focus distances.
If you stop down a couple of stops, or shoot at moderate distances, you are unlikely to see it, because depth of field overtakes the slight shift.
Some lenses are known to shift more than others, the Sonnar 50mm f1.5 is probably singled out most often.
If you stop down a couple of stops, or shoot at moderate distances, you are unlikely to see it, because depth of field overtakes the slight shift.
Some lenses are known to shift more than others, the Sonnar 50mm f1.5 is probably singled out most often.
Sparrow
Veteran
Using a fast lens close up focus-shift is just one of many ways to screwup a shot, I've never noticed it in real life
Jamie123
Veteran
It's not the lens that's not accurate it's the rangefinder. If you want to avoid focus shift completely just use an SLR.
sevo
Fokutorendaburando
Not quite - that would be "misaligned rangefinder". "Focus shift" usually means "aperture dependent focus shift" (zooms may also have focal length dependent focus shifts, and lenses with moving elements may have higher order shifts beyond that).
It is fairly inevitable in most asymmetric lens designs, but usually it is well compensated and invisibly small in modern lenses. Unless you shoot with quite antique lenses or do closeups with stopped down ultra fast lenses, you probably will never encounter it in real life - worrying about it it is mostly a preoccupation of bokeh loving toy figurine shooting freaks.
By the way, SLRs have the same issue, as the focus shifts between focusing and exposure, when the camera stops down. But some AF systems have compensation factors stored in the lens chip, so it will only strike there when focusing manually.
le vrai rdu
Well-known
Sparrow
Veteran
The focus on an SLR doesn't shift if it's at maximum aperture
It's all operator error
It's all operator error
ferider
Veteran
If you shoot film, consider it mostly internet paranoia caused by pixel-peeping M8 and M9 users
The only lens where it has bothered me (on film) is the ZM 50/1.5 since I used it for close-up portraits, mostly.
For all others typically mentioned lenses (for example Nokton 35/1.4) I find it a non-issue.
Roland.
The only lens where it has bothered me (on film) is the ZM 50/1.5 since I used it for close-up portraits, mostly.
For all others typically mentioned lenses (for example Nokton 35/1.4) I find it a non-issue.
Roland.
ampguy
Veteran
new fangled stuff?
new fangled stuff?
If you use older non auto gear like a Nikon F3 with 43-86 non AI zoom, you see very clearly (depending on which of the ~15 or so screens you are using) the focus shift as you meter with different apertures.
Not all SLR's have wide open metering and viewing, just like not all RFs have meters, or not all cameras are digital ...
new fangled stuff?
If you use older non auto gear like a Nikon F3 with 43-86 non AI zoom, you see very clearly (depending on which of the ~15 or so screens you are using) the focus shift as you meter with different apertures.
Not all SLR's have wide open metering and viewing, just like not all RFs have meters, or not all cameras are digital ...
The focus on an SLR doesn't shift if it's at maximum aperture
It's all operator error
Sparrow
Veteran
I use an F3 with an f2.5 105 and I can assure you, sir, I am more than capable of miss-focusing that whichever screen I fit, however the fact remains at full aperture that clearly cannot be focus-shift it's all down to me
ampguy
Veteran
right
right
I agree with you if you focus and shoot at 2.5.
But what I'm trying to explain to the OP is that whatever he focuses on with an SLR, he will likely get some shift, possibly noticeable, if he focuses wide open, then without refocusing stopped down, stops down to take the photo.
Get it?
right
I agree with you if you focus and shoot at 2.5.
But what I'm trying to explain to the OP is that whatever he focuses on with an SLR, he will likely get some shift, possibly noticeable, if he focuses wide open, then without refocusing stopped down, stops down to take the photo.
Get it?
Sparrow
Veteran
ampguy
Veteran
well
well
If you don't re-check your focus after stopping down, for example with the 43-86 Nikkor zoom after focusing at 3.5 (wide open), then your subject won't be in sharpest focus if you simply stop down without re-focusing.
well
If you don't re-check your focus after stopping down, for example with the 43-86 Nikkor zoom after focusing at 3.5 (wide open), then your subject won't be in sharpest focus if you simply stop down without re-focusing.
Em, yep ... but why would one worry about focus-shift when stopped down?
back alley
IMAGES
'worrying about it it is mostly a preoccupation of bokeh loving toy figurine shooting freaks.'
oh jeez, i fell off my chair reading this.
it may just be the quote of the yaer.
oh jeez, i fell off my chair reading this.
it may just be the quote of the yaer.
Sparrow
Veteran
If the DOF didn't cover it I’d suspect it to be faulty; but you may very well be correct, thankfully, I wasted my youth gazing into more attractive navels
Freakscene
Obscure member
It is wrong to state that focus shift is only theoretical or that it is irrelevant. You can see it in photos from the CV 35/1.4 under certain circumstances if you look closely enough, particularly if you print very large.
No, this won't work to fix the issue.
If you need to get big prints and retain sharpness, carefully using slow film and a good tripod will make a vastly greater difference than anything else. And nothing will make as great a difference when making big prints as going to a larger format.
No lens or other piece of equipment is perfect. Somewhere or another, there are always compromises. Even in a $10K Leica lens, you can be sure it would be better if it was designed with a retail cost of $20K in mind.
Think of depth of field as a theoretical band of acceptable sharpness in space that varies in width and with distance from the film or sensor plane as you stop down. This shifts in all lenses, but shifts more in lenses that display certain kinds of spherical aberration. With the CV 35/1.4 you should get sharp photos at f1.4, although designers typically make compromises about this kind of thing too. At close range and wide open the focus point of fast RF lenses is often ever-so-slightly in front or behind the point at which you focus - if the lens is poorly adjusted and this is too great, this can result in softness, but this is 'out of specification collimation', not 'focus shift'. As you stop down the focus point shifts away or towards the film or sensor plane (depending on the lens' design). You run into problems when this shift is greater than the increase in depth-of-field.
The distribution of the field of acceptable sharpness depends on the focal length of the lens. Shorter focal length lenses always have less depth of field in front of the subject than longer focal length lenses, but they have more depth of field behind the subject than longer focal length lenses. So shorter lenses have more and more asymmetric depth of field. If you spend some time with an SLR with DOF preview you can see this.
It is not internet paranoia; focus shift is a fact of life in optical systems. The focus shift in the 35/1.4 CV lens shifts the plane of greatest sharpness in the film plane about the same amount as the thickness (120 microns or so) of the very thinnest (and usually sharpest) film emulsions. What we can't tell you is if this is of relevance to the way you shoot, or what you own acceptable limit for sharpness is.
If you want a 35 mm lens with a focus shift less than the thickness of a thin film emulsion, buy a Leica 35 Summicron ASPH. If you really want to make huge prints, buy a medium or large format camera. If you try the R2/CV 35-1.4, however, you might really like it. No-one here can tell you.
Marty
No, this won't work to fix the issue.
If you need to get big prints and retain sharpness, carefully using slow film and a good tripod will make a vastly greater difference than anything else. And nothing will make as great a difference when making big prints as going to a larger format.
No lens or other piece of equipment is perfect. Somewhere or another, there are always compromises. Even in a $10K Leica lens, you can be sure it would be better if it was designed with a retail cost of $20K in mind.
Think of depth of field as a theoretical band of acceptable sharpness in space that varies in width and with distance from the film or sensor plane as you stop down. This shifts in all lenses, but shifts more in lenses that display certain kinds of spherical aberration. With the CV 35/1.4 you should get sharp photos at f1.4, although designers typically make compromises about this kind of thing too. At close range and wide open the focus point of fast RF lenses is often ever-so-slightly in front or behind the point at which you focus - if the lens is poorly adjusted and this is too great, this can result in softness, but this is 'out of specification collimation', not 'focus shift'. As you stop down the focus point shifts away or towards the film or sensor plane (depending on the lens' design). You run into problems when this shift is greater than the increase in depth-of-field.
The distribution of the field of acceptable sharpness depends on the focal length of the lens. Shorter focal length lenses always have less depth of field in front of the subject than longer focal length lenses, but they have more depth of field behind the subject than longer focal length lenses. So shorter lenses have more and more asymmetric depth of field. If you spend some time with an SLR with DOF preview you can see this.
It is not internet paranoia; focus shift is a fact of life in optical systems. The focus shift in the 35/1.4 CV lens shifts the plane of greatest sharpness in the film plane about the same amount as the thickness (120 microns or so) of the very thinnest (and usually sharpest) film emulsions. What we can't tell you is if this is of relevance to the way you shoot, or what you own acceptable limit for sharpness is.
If you want a 35 mm lens with a focus shift less than the thickness of a thin film emulsion, buy a Leica 35 Summicron ASPH. If you really want to make huge prints, buy a medium or large format camera. If you try the R2/CV 35-1.4, however, you might really like it. No-one here can tell you.
Marty
meandihagee
Well-known
thanks everybody
Focus shift is related to spherical aberration. I need to check the shift on the Ultron 35/1.7 aspherical on the M8.
Leigh Youdale
Well-known
Now I'm getting REALLY worried by the deep technical information coming to light in this thread. I've just realised that my Nikkormat SLR has, for the last 40+ years been focus shifting each time it stops down from full aperture metering to take the shot. And to think I never even noticed it! All those shots wasted because of this terrible thing called focus shift!
What is also of immense concern now is all the eminent photographers who used Nikon F's and other focus-shifting SLR's through the 50's, 60's and 70's whose work is widely revered --- they too have been victims of this equipment deficiency. It's enough to stop me buying any more books on famous photographers or even go to exhibitions.
I mean, who can you trust if the iconic examples held up before us are so technically flawed?
What is also of immense concern now is all the eminent photographers who used Nikon F's and other focus-shifting SLR's through the 50's, 60's and 70's whose work is widely revered --- they too have been victims of this equipment deficiency. It's enough to stop me buying any more books on famous photographers or even go to exhibitions.
I mean, who can you trust if the iconic examples held up before us are so technically flawed?
Sparrow
Veteran
I'm detecting a hint of sarcasm creeping in there sir