Quercus
Quercus
which is why understanding then lenses we use is so important - if focus is critical on a rangefinder super wide open you can never just rely on the rangefinder - even with a newly serviced rangefinder can not be 100% certain that it is in focus - focus shift and slight discrepancies in focus on each individual lens can lead to slight focus error - but obviously this is totally outweighed by the ease an convenience of a rangefinder focusing system
Roger Hicks
Veteran
Re-read what I said, and what you queried. I agreed that focus shift is exactly what he said, IF you focus through the lens, but that you don't focus through the lens with a rangefinder.Huck Finn said:
Cheers,
R.
larmarv916
Well-known
Lets also add in one more factor that is hiding in the background and is often overlooked. When you have a modern SLR you also have a very good "Diopter" attached and you dial in any correction needed. I only bring this up as often many people never consider the fact that they are not actually getting a exact focal point they may think they see.
I recently sold my R8 as I just do not use it enough to keep it around. That camera had a wonder diopter and I wear glasses. My perscription is such that my left eye is very accutate but not spot on perfect. With the diopter lenses....if you can even get them. They are still not as accutate as the built in adjustable dipoter.
When I noticed that my eyes were starting to shift. I also found out that many times one eye goes toward far sightedness and the other will go toward near sightedness. Not always but this happens in about half of the people in general.
Ok...stick with me, many friends I know have dropped dealing with this problem all together. This is also why "auto focus" has been all the rage from many years.
If your eye is just slightly shifted in either direction you get a more pronounced occurance of shifting in your images.
So this also compounds the issue of lens shifting as.....you may not be actually focusing on the target. So now your in most cases actually focusing past the object !!
Why you ask. As your finder is matching up to make that perfect alingment. you are actually shifting the focal point farther away. So if you happen to just have a breath of over alignment now your appearence is even greater. In my case I have done exposure focus distance testing. I find this to be true.
So after taping off the exact distance to match the marked measurement on the lens barrel ....I then shot two images one based on the defined target distance and one on what appeared to be "correctly" focused to my left eye. I almost every case the I shot at F4 to limit the depth of field.
My visual distance was off by some margin...optical user error.!! This was true up to a distance of about 50 to 75 ft. After that point the error differnce seemed to all but vanish. So now I tend to focus on the near side of the target object and I get what I was looking for. In the phoio above in my previous post I showed a small marble head and this is my best personal example of a method to avoid most of the shifting. I now see and find much less focus shifting.
That is what works best for me and what I have been able to documment. You amy or may not want to go to that much trouble but is was surprising to me to see the evidence. My left eye is not to the pont that it technically requires a diopter of .5 but it is enough to create a focal shift error.
I recently sold my R8 as I just do not use it enough to keep it around. That camera had a wonder diopter and I wear glasses. My perscription is such that my left eye is very accutate but not spot on perfect. With the diopter lenses....if you can even get them. They are still not as accutate as the built in adjustable dipoter.
When I noticed that my eyes were starting to shift. I also found out that many times one eye goes toward far sightedness and the other will go toward near sightedness. Not always but this happens in about half of the people in general.
Ok...stick with me, many friends I know have dropped dealing with this problem all together. This is also why "auto focus" has been all the rage from many years.
If your eye is just slightly shifted in either direction you get a more pronounced occurance of shifting in your images.
So this also compounds the issue of lens shifting as.....you may not be actually focusing on the target. So now your in most cases actually focusing past the object !!
Why you ask. As your finder is matching up to make that perfect alingment. you are actually shifting the focal point farther away. So if you happen to just have a breath of over alignment now your appearence is even greater. In my case I have done exposure focus distance testing. I find this to be true.
So after taping off the exact distance to match the marked measurement on the lens barrel ....I then shot two images one based on the defined target distance and one on what appeared to be "correctly" focused to my left eye. I almost every case the I shot at F4 to limit the depth of field.
My visual distance was off by some margin...optical user error.!! This was true up to a distance of about 50 to 75 ft. After that point the error differnce seemed to all but vanish. So now I tend to focus on the near side of the target object and I get what I was looking for. In the phoio above in my previous post I showed a small marble head and this is my best personal example of a method to avoid most of the shifting. I now see and find much less focus shifting.
That is what works best for me and what I have been able to documment. You amy or may not want to go to that much trouble but is was surprising to me to see the evidence. My left eye is not to the pont that it technically requires a diopter of .5 but it is enough to create a focal shift error.
peterleyenaar
Member
peterleyenaar
Member
Egyptian Museum, Cairo
Egyptian Museum, Cairo
Forgot to mention, hand held ,through glass, low side light, obviously, this lens has sharp focus at f2.
Egyptian Museum, Cairo
Forgot to mention, hand held ,through glass, low side light, obviously, this lens has sharp focus at f2.
Quercus
Quercus
All lenses have sharp focus at every f-stop it is just that at every f stop the point of focus shifts compared to every other f-stop of the same lens. This occurs to greater or lesser extent with all lenses and again with all lenses is more pronounced at close focus and wider apertures (focus is an exponential function)
AKA get to know your lenses real well
AKA get to know your lenses real well
peterleyenaar
Member
Quercus said:
Yes , I will try to get to know my lenses REALLY well.
Huck Finn
Well-known
Roger Hicks said:
If you change the aperture & some rays are blocked as a result, the point of best focus can shift independent of whether you're focusing through the lens or through an RF viewing window.
Quercus
Quercus
I think what you you are missing from what RH is explaining is that in both cases SLR or RF it is the lens that has focus shift but you do not focus a RF using the lens image you focus it using a view finder and rangefinder. So you do not actually see if the lens is actually creating a point of focus on the film plane. In an SLR as long as the focus screen and mirror system is accurate representation of the lens to film lane difference (not all are as accurate as you would think) then you can see the acctual point of focus. therefore if you were to stop down as long as focus screen illumination is still good enough (which at small apertures it isnt going to be) then you could compensate for focus shift.
Zeiss have clearly stated that zm lenses have been designed to minimise focus shift , but - and very importantly, certain lens designs are more prone to pronounced FS than others. Sonnars were designed for a specific reason to be light, simple and have a wide aperture. This results in more aberrations than say a planar, but due to the fewer glass to air surfaces much higher contrast and less flare -
The Sonnar is a beautiful lens that works and works very very well, but if you anyone is really that concerned about focus shift then get the planar.
Cant wait for the discussions if Zeiss decide to start making Tessars again
I think that what RH said in his review was very fair and accurate, but the focus shift issue in this thread seems to have spiraled out of proportion. As RH rightly points out you buy a sonnar because it is a sonnar and you use it in low light wide open and quite close up and you benefit from unobtrusive size . So for what it was designed for it is brilliant.
If you want a fairly wide normal for most day to day use then get a Planar if if you want Zeiss or Summicron if you want a red dot
Zeiss have clearly stated that zm lenses have been designed to minimise focus shift , but - and very importantly, certain lens designs are more prone to pronounced FS than others. Sonnars were designed for a specific reason to be light, simple and have a wide aperture. This results in more aberrations than say a planar, but due to the fewer glass to air surfaces much higher contrast and less flare -
The Sonnar is a beautiful lens that works and works very very well, but if you anyone is really that concerned about focus shift then get the planar.
Cant wait for the discussions if Zeiss decide to start making Tessars again
I think that what RH said in his review was very fair and accurate, but the focus shift issue in this thread seems to have spiraled out of proportion. As RH rightly points out you buy a sonnar because it is a sonnar and you use it in low light wide open and quite close up and you benefit from unobtrusive size . So for what it was designed for it is brilliant.
If you want a fairly wide normal for most day to day use then get a Planar if if you want Zeiss or Summicron if you want a red dot
Huck Finn
Well-known
Quercus said:
I loved Roger's review & greatly appreciate his insights into the C-Sonnar. He made many good points that are extremely useful. It was extraordinary for him to share this work for free.
SLR focusing screens use various methods to focus (contrast, split image, etc.) but all focus only at a single aperture. Unless you have & use a DOF preview, you're not going to see the focus shift created by a change of aperture.
Regardless, the question wasn't about how you focus a lens with focus shift, it was about what consitutes focus shift & that doesn't change based on the type of focusing system you use.
Quercus
Quercus
technically there are more than one type of focus shift .... chromatic aberration is in reality focus shift this is especial true if you want to capture IR . Focus shift in the Sonnar is caused by spherical aberration the focus point in such lenses is not a "true" focus point but where the cross sectional area of the spread of lightrays (gives rise to circles of confusions) originating from the changing refractive index across the lens and their individual points of focus at slightly differening points either side of the film plane is at its smallest. As the lens is stopped down then the varying Refractive Index of the lens surface changes ( the active lens physically has a smaller diameter) and hence this theoretical "best" point moves.
I agree FS doesnt change dependent upon the camera but the ability to see it does. You can never compensate for it in a RF by eye because you do not see what the lens sees but you can in a SLR with DoF preview whilst illumination of the focusing screen is good enough.
This only works though if the focusing screen is exactly equi-distant to the film, the plane, any discrepancy and the focus shift can not be tracked in this way accurately.
It is actually surprising how many SLR focusing screens are not in this optimum position but very slightly off.
I agree FS doesnt change dependent upon the camera but the ability to see it does. You can never compensate for it in a RF by eye because you do not see what the lens sees but you can in a SLR with DoF preview whilst illumination of the focusing screen is good enough.
This only works though if the focusing screen is exactly equi-distant to the film, the plane, any discrepancy and the focus shift can not be tracked in this way accurately.
It is actually surprising how many SLR focusing screens are not in this optimum position but very slightly off.
Roger Hicks
Veteran
Yes, except that with the SLR or direct ground glass you can choose your aperture for focusing. With an RF, you can't: you are stuck with what the RF designer has chosen as the 'focusing aperture'.Huck Finn said:
Cheers,
R.
Huck Finn
Well-known
Roger Hicks said:
Yes, IF you have DOF preview & even if you do, stopping down can make focusing a less than satisfying experience.
But again, how soes any of this change the basic physics of focus shift?
Roger Hicks
Veteran
It doesn't, but on my reading, that wasn't the way he phrased his question. Maybe I misread it; maybe you did; either way it hardly seems worth going back over it. As we are in complete agreement on this, perhaps we can leave it.Huck Finn said:
Cheers,
R.
CK Dexter Haven
Well-known
How could we know?
How could we know?
I think this is an unfair assertion. There is simply no way for us to know if/how this "focus shift" may have affected any of the photographers you named.
• These guys photographed certain subjects for days/weeks/months on end, generating hundreds of rolls of film. I think it's naive to expect that all of those exposures were technically 'perfect' and that they didn't choose to print only frames that may have satisfied their technical standards, while dismissing those that didn't. Focus surely would be one of those standards.
• One of the reasons why i don't particularly care for HCB (apologies in advance) is that in too many of the reproductions in my books, the images are soft. Unacceptably soft, if they were my pictures.
• What possible difference could it make even if those photographers didn't consider this to be an issue? They worked in a different era, with different standards. Nostalgia and Legend allow us to now appreciate things in a different way. But, some of those guys printed and displayed images that would not pass muster across a contemporary art director's desk.
• I'm not even sure the issue we're discussing is even relevant to those photographers. I used to own a 1950s 50mm/1.5 Zeiss Sonnar in Leica-M mount. I tested it upon receipt, and then, and later in use, never saw anything remotely like this "focus shift."
• I can name quite a few photographers who would decidedly NOT accept this. Irving Penn comes to mind.
• If things CAN be better in this era, why shouldn't they be? Does anyone remember how soda/beer cans used to have removable pop tabs? Those little pieces of tin would litter parking lots and the sides of roads.... And, in the 70s, someone decided to invent the integrated tab. Cool. Believe me, i like to romanticize the past, but sometimes progress is a good thing.
How could we know?
ferider said:
I think this is an unfair assertion. There is simply no way for us to know if/how this "focus shift" may have affected any of the photographers you named.
• These guys photographed certain subjects for days/weeks/months on end, generating hundreds of rolls of film. I think it's naive to expect that all of those exposures were technically 'perfect' and that they didn't choose to print only frames that may have satisfied their technical standards, while dismissing those that didn't. Focus surely would be one of those standards.
• One of the reasons why i don't particularly care for HCB (apologies in advance) is that in too many of the reproductions in my books, the images are soft. Unacceptably soft, if they were my pictures.
• What possible difference could it make even if those photographers didn't consider this to be an issue? They worked in a different era, with different standards. Nostalgia and Legend allow us to now appreciate things in a different way. But, some of those guys printed and displayed images that would not pass muster across a contemporary art director's desk.
• I'm not even sure the issue we're discussing is even relevant to those photographers. I used to own a 1950s 50mm/1.5 Zeiss Sonnar in Leica-M mount. I tested it upon receipt, and then, and later in use, never saw anything remotely like this "focus shift."
• I can name quite a few photographers who would decidedly NOT accept this. Irving Penn comes to mind.
• If things CAN be better in this era, why shouldn't they be? Does anyone remember how soda/beer cans used to have removable pop tabs? Those little pieces of tin would litter parking lots and the sides of roads.... And, in the 70s, someone decided to invent the integrated tab. Cool. Believe me, i like to romanticize the past, but sometimes progress is a good thing.
larmarv916
Well-known
I agree with a great many points that "CK Dexter Haven" has just posted.
But then you have Guys like, Doisneau, Brassai, Kertesz, and Eisenstaedt and many others who worked with dramaticly "stoneage" lenses in 35mm and Medium formatt cameras and.......got extremely shrap images of the "subject".
I doubt that ever heard any of these guys whining about...Oh its just not as sharp as I wanted. Most of these guys were picking an F stop that assured the "zone" of focus we covering the required subject or action. Also most used much slower film as that was all that was on the market.
I still think we need to cast a critical eye at the fact that many shooters are often trying to use an F-stop that is politically fashionable but is so demanding that they can not correctly focus. Or a better way is to say they are not actually seeing the focus "moment" as it "is".
Sure if something can be made better do it......but user error is always the unseen and uncredited demon to botching something.
Personally I found a focus shift on my ASPH Summicron 35 F2 My Cron was not spot on until it was F 2.8....accurate. but past F5.6 it was not on target. It took 2 rolls of 36 to be sure what I thought was actually real. Did I lose sleep over it ? NO.....I did not even use the lens beyond F5.6 more than a couple of times.
I still believe that some people can never get it right and others never miss. Also Try to never shoot wide open...Hand held unless it is double the focal length. So a 50mm lens for me is a big risk at anything below 1/125
Also do not forget that when you shooting wide open my Noctilux is so narrow that the slighest "waver" is enough to destory that perfect focal effect. SO..I even shot it at 1/250 just to make sure not be vicitim of that problem.
Also shooting wide open at a focal distoance of infinity in most cases is nonproductive. There is a element of the creative photography world that is hung up with the ultra shallow depth of field as the only valid artistic statement. And is as bad a school of photography as the old F 64 Boys.
I just do not get the idea of fnding some "nit" and then blaming it for a lack of final quality. This is an artfrom and it is the end result that determines if your hitting the ball out of the park. Not an Art Director.....that is why Photoshop was created !
But then you have Guys like, Doisneau, Brassai, Kertesz, and Eisenstaedt and many others who worked with dramaticly "stoneage" lenses in 35mm and Medium formatt cameras and.......got extremely shrap images of the "subject".
I doubt that ever heard any of these guys whining about...Oh its just not as sharp as I wanted. Most of these guys were picking an F stop that assured the "zone" of focus we covering the required subject or action. Also most used much slower film as that was all that was on the market.
I still think we need to cast a critical eye at the fact that many shooters are often trying to use an F-stop that is politically fashionable but is so demanding that they can not correctly focus. Or a better way is to say they are not actually seeing the focus "moment" as it "is".
Sure if something can be made better do it......but user error is always the unseen and uncredited demon to botching something.
Personally I found a focus shift on my ASPH Summicron 35 F2 My Cron was not spot on until it was F 2.8....accurate. but past F5.6 it was not on target. It took 2 rolls of 36 to be sure what I thought was actually real. Did I lose sleep over it ? NO.....I did not even use the lens beyond F5.6 more than a couple of times.
I still believe that some people can never get it right and others never miss. Also Try to never shoot wide open...Hand held unless it is double the focal length. So a 50mm lens for me is a big risk at anything below 1/125
Also do not forget that when you shooting wide open my Noctilux is so narrow that the slighest "waver" is enough to destory that perfect focal effect. SO..I even shot it at 1/250 just to make sure not be vicitim of that problem.
Also shooting wide open at a focal distoance of infinity in most cases is nonproductive. There is a element of the creative photography world that is hung up with the ultra shallow depth of field as the only valid artistic statement. And is as bad a school of photography as the old F 64 Boys.
I just do not get the idea of fnding some "nit" and then blaming it for a lack of final quality. This is an artfrom and it is the end result that determines if your hitting the ball out of the park. Not an Art Director.....that is why Photoshop was created !
summaron
Established
Cartier-Bresson had a hard time of focusing because he was busy inventing a new genre. Under the influence of the surrealists and dadaists, his photographs from 1933 & 1934, especially in Mexico and Spain, are the best.
Irving Penn shot with a 6 x 6 Rollei in a studio, but I bet he would have liked to be Cartier Bresson once in a while.
Here is a 1946 H C-B photograph (Magnum.com), a little soft, most likely done with a 1.5 Sonnar, of Albert Camus. We should all fall short of the mark so badly.
http://www.magnumphotos.com/Archive...earch&IID=2S5RYDWHP8FM&SAKL=T&SGBT=T&DT=Image
Irving Penn shot with a 6 x 6 Rollei in a studio, but I bet he would have liked to be Cartier Bresson once in a while.
Here is a 1946 H C-B photograph (Magnum.com), a little soft, most likely done with a 1.5 Sonnar, of Albert Camus. We should all fall short of the mark so badly.
http://www.magnumphotos.com/Archive...earch&IID=2S5RYDWHP8FM&SAKL=T&SGBT=T&DT=Image
larmarv916
Well-known
summaron said:
I agree with"Summaron's" theme that again none of these "iconic" photographers were complaining about...."is or isn't my lens sharp at what F-stop" I mean really, most often they had little time to compose and many times "zone focusing" was the best bet to grab a shot. With no time for a second frame. Also Penn, HCB, Eisenstaedt, Walker Evans, Doisneau and so many others who invented the Street Photogrpahy, only wanted a camera that would focus with certainty.
Most people forget that the cost of these cameras was on par with a new car ! So the normal lens that it came with was more than most ever needed. Or could afford. Also as film was not cheap many photographers would take a long time to shoot a whole roll of film. Many times days went by between exposure of a single frame of film.
I remember when meeting Ansel Adams as a student, what impressed me was his question about how long does it take to shoot a whole roll of film? I answered, Iam not sure I go days without seeing anything worth shooting. His reply was, " that 's very wise.....you treat each frame like a 4x5 sheet of film, you will find in the end you see greater results in the darkroom. He asked how many lenses do you have for your 35 ? Only a normal sir......Adams" many people never had anything else" I tried to take that advice to heart.
When it comes to normals I have several, and each I kept has a quality that I like. This modern Zeiss Sonnar C is going to be hard to out do. My photo still do not know or care what the calabration is.