Bob T
Established
Concerning the focus moving to the cans behind the focus point, I've heard that as depth of field increases the area of focus is roughly split 1/3 in front of the focus point and 2/3 behind the focus point. That may explain why the cans behind the focus point seem to become sharper than the cans in front of the focus point. Please correct me if I'm wrong.
john_s
Well-known
At close distances, it's more like half in front, half behind. As subject distance increases, the DoF is distributed something like the 1/3 and 2/3 you described. For larger distances, it approaches infinity behind and (obviously) a lot less than infinity in front.
john_s
Well-known
What the carefully done tests show is that, if you are facing a brick wall and photographing it, there is no problem at any aperture. If, however, you are relying on DoF to keep a 3-dimensional subject in good focus, you just need to be aware that all or most of the DoF is behind the focus point at certain apertures. And when you change lenses, remember that the next lens is probably different.
kbg32
neo-romanticist
Hmmm, if I drank that many cans of Hoegarden, my focus would shift too!
Marek, interesting test, thanks. Focus shift is not uncommon in fast lenses, and seems manageable in this new Ultron.
Since the Summicron's hood has been mentioned, note that the smaller hood from the 35 Summilux ASPH fits. Certainly a good change for M8 users, and maybe for film as well.
Since the Summicron's hood has been mentioned, note that the smaller hood from the 35 Summilux ASPH fits. Certainly a good change for M8 users, and maybe for film as well.
HenningW
Well-known
Yes, the hood from the 35 Summilux works fine, and doesn't vignette with film either. For the M8 you can also use a 46mm filter ring (filter without glass) as a very short 'hood' which will keep dirt and fingers at a little distance, and is very compact.
Regarding the focus shift; I too did a test for focus shift after I noticed it on some M8 shots. The CV 28/2, and even more so the 35/1.4 definitely show focus shift on digital, and it is large enough to be a problem. The 28/2 unfortunately also has soft corners, and in general I prefer the older 28/1.9. The newer lens is built better and a bit smaller, I think, and has less flare, but in other regards I like the older one better. The Summicron is better overall than either, but whether the difference is worth the price difference is of course an individual decision.
On film I also found the focus shift of the 28/2 to be rather insignificant, but not that of the 35/1.4. I still have the latter, and use it regularly, but I usually use it wide open or at 5.6 and higher.
To the poster that said that someone always criticizes the CV lenses as soon as they come out and must be in the pay of someone else; that is utter nonesense. All lenses get examined, tested and criticized when they come out. It's just that CV lenses, even though they are very much cheaper than Leica lenses inevitably get compared to them, and strangely enough CV doesn't go to the same lengths in design and manufacturing as Leica. Who knew??? CV lenses are great value compared with Leica, and are often truly outstanding lenses compared with Canon, Nikon, Sony and other brands in their price range, but their faults will be exposed, and in the end all lenses have faults.
Testing lets you know about the faults, and lets you use your lenses to best advantage. If you know a fault, you can work around it, ignore it or use it to your benefit, depending on the occasion. All are valid, but it's good to know what you are dealing with.
Henning
Regarding the focus shift; I too did a test for focus shift after I noticed it on some M8 shots. The CV 28/2, and even more so the 35/1.4 definitely show focus shift on digital, and it is large enough to be a problem. The 28/2 unfortunately also has soft corners, and in general I prefer the older 28/1.9. The newer lens is built better and a bit smaller, I think, and has less flare, but in other regards I like the older one better. The Summicron is better overall than either, but whether the difference is worth the price difference is of course an individual decision.
On film I also found the focus shift of the 28/2 to be rather insignificant, but not that of the 35/1.4. I still have the latter, and use it regularly, but I usually use it wide open or at 5.6 and higher.
To the poster that said that someone always criticizes the CV lenses as soon as they come out and must be in the pay of someone else; that is utter nonesense. All lenses get examined, tested and criticized when they come out. It's just that CV lenses, even though they are very much cheaper than Leica lenses inevitably get compared to them, and strangely enough CV doesn't go to the same lengths in design and manufacturing as Leica. Who knew??? CV lenses are great value compared with Leica, and are often truly outstanding lenses compared with Canon, Nikon, Sony and other brands in their price range, but their faults will be exposed, and in the end all lenses have faults.
Testing lets you know about the faults, and lets you use your lenses to best advantage. If you know a fault, you can work around it, ignore it or use it to your benefit, depending on the occasion. All are valid, but it's good to know what you are dealing with.
Henning
ampguy
Veteran
The Summicron 28/2 is one of the finest 28's, but the 28/2.8 M-Hexanon is both sharper, and smaller (no/less VF blockage) according to photodo and Puts.
Freakscene
Obscure member
I can't remember seeing any reports from film users where the focus shift was of any concern on the film bodies.
The Noctilux, 75 Summilux and this lens, among others, show a decrease in contrast and if you shoot at targets, resolution, with focus shift. It's measureable and easily perceived. But it makes a lot less difference than on a digital sensor where the point of focus with the rf is just out of focus in the file.
Concerning the focus moving to the cans behind the focus point, I've heard that as depth of field increases the area of focus is roughly split 1/3 in front of the focus point and 2/3 behind the focus point. That may explain why the cans behind the focus point seem to become sharper than the cans in front of the focus point. Please correct me if I'm wrong.
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.
Marty
The Noctilux, 75 Summilux and this lens, among others, show a decrease in contrast and if you shoot at targets, resolution, with focus shift. It's measureable and easily perceived. But it makes a lot less difference than on a digital sensor where the point of focus with the rf is just out of focus in the file.
Concerning the focus moving to the cans behind the focus point, I've heard that as depth of field increases the area of focus is roughly split 1/3 in front of the focus point and 2/3 behind the focus point. That may explain why the cans behind the focus point seem to become sharper than the cans in front of the focus point. Please correct me if I'm wrong.
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.
Marty
filmfan
Well-known
Haha. Does anyone even know what focus shift is? There never seems to be a consensus.
MaxElmar
Well-known
Good test. (This is one reason live view can be really cool for static subjects. Punch up 7x and focus, no worries about focus shift, shimming, mirrors/screens out of alignment on SLRs or RFs that aren't quite spot-on.)
I should add - too bad very few things worth photographing are truly static!
I should add - too bad very few things worth photographing are truly static!
gavinlg
Veteran
Ahh yes, the dreaded ultron focus shift which makes the lens unusable. Thanks for showing us how 'unusable' it is. 
(this is why I never trust internet reports about 'focus shift' - my 50mm 1.2L was exactly the same - dreaded on the internet, but perfect in real life)
(this is why I never trust internet reports about 'focus shift' - my 50mm 1.2L was exactly the same - dreaded on the internet, but perfect in real life)
