p.2 #1 · Risk of focus shift issues in new 1.4/35?
edwardkaraa wrote:
One thing that I noticed at dpr is the tendency to mediocrity. It's like the members want to pull others down to their level instead of pushing others to improve. Good (and expensive) glass is bashed while cheap kit lenses find so many people to praise their quality. APS-C is better than FF, Canon consumer grade is better than Zeiss, SLT is better than SLR... Etc. Asking such questions as this one on dpr is like asking for a good bashing.
In general I agree, but to be fair, there are some (very) knowledgeable users on dpr too (such as Iliah Borg).
p.2 #2 · Risk of focus shift issues in new 1.4/35?
AhamB wrote:
In general I agree, but to be fair, there are some (very) knowledgeable users on dpr too (such as Iliah Borg).
Certainly, and those users are the reason why I keep on visiting despite the general unpleasant atmosphere.
Mar 11, 2011 at 11:10 AM
AmbientMike Offline • • • • • • [X]
p.2 #3 · Risk of focus shift issues in new 1.4/35?
If you focus with live view, simply focus at shooting aperture and you're in focus. Oof is oof and if you get that from focus shift, you get it from focus shift, and you will get oof images. Focus shift gets worse as you stop down. dof doesn't cover it.
Mar 11, 2011 at 11:30 AM
AmbientMike Offline • • • • • • [X]
p.2 #4 · Risk of focus shift issues in new 1.4/35?
Maybe minor focus shift but the big problem is focus shift that doesn't allow you to focus wide open and stop down, because you are then oof.
p.2 #6 · Risk of focus shift issues in new 1.4/35?
Rodluvan wrote:
As most know the 1.4/85 suffers from pretty tangible focus shift giving it an erroneous reputation of being soft.
Not exactly. The ZE/ZF 85 Planar is soft wide open, especially at closer distances because of heavy spherical aberrations (SA). Wide open it has no focus shift per definition as the reference aperture is the largest one as you focus with it. The noticeable focus shift on the 85 Planar is between f/2 and f/2.8, by which time it sharpens up as the impact of the SA is reduced.
p.2 #7 · Risk of focus shift issues in new 1.4/35?
denoir wrote:
Wide open it has no focus shift per definition as the reference aperture is the largest one as you focus with it.
That's not true. The focusing screen doesn't show the real DOF at f/1.4, but rather something like f/2.8 for screens optimized for MF and f/4-5.6 for stock screens.
AF confirm is also "working" at ~f/2.8-5.6.
If the Z* 85/1.4 is anywhere close to the 50/1.4, focus is very accurate at f/2.8. But wide open there's front focus and stopped down there is back focus.
All lenses with heavy spherical aberration will behave this way, which is the case with most very fast lenses of "traditional" design.
p.2 #8 · Risk of focus shift issues in new 1.4/35?
It doesn't matter what the focusing screen shows - what matters is at which aperture you are actually focusing - which is at f/1.4, unless you press the DOF preview button. The focusing distance markings on the lens correspond to the focus point at the widest aperture.
p.2 #10 · Risk of focus shift issues in new 1.4/35?
denoir wrote:
It doesn't matter what the focusing screen shows - what matters is at which aperture you are actually focusing - which is at f/1.4, unless you press the DOF preview button. The focusing distance markings on the lens correspond to the focus point at the widest aperture.
Yes it does; it matters a lot. The screen does NOT show the correct DOF for a lens with maximum aperture of f/1.4 or so. So, you are actually focusing at the aperture that the focusing screen shows, which normally is f/2.8-5.6.
This derives from the design of the screen, allowing to transmit light only at certain angles (corresponding to aperture opening). If you use the DOF preview button, you can clearly see that DOF is more or less the same for f/1.4, f/2 and f/2.8. The only thing that differs is the illumination of the screen.
p.2 #11 · Risk of focus shift issues in new 1.4/35?
One interesting example is the Zeiss 50/1.5 Sonnar - a rangefinder lens that suffers from very heavy focus shift (the worst I've ever seen). Now the rangefinder coupling on the lens is optimized for f/2.8, so at f/1.5 you get bad front focus while at f/2.8 it's just right.
So, you'd expect perhaps the distance scale to match the rangefinder coupling, right? No, the distance scale is for f/1.5. It can be easily verified by using one of there:
It's a laser rangefinder with an error of less than 1mm per 100 meters. It only takes a few seconds to see that the distance markers are calibrated to the largest aperture. I don't know for certain but it would surprise me very much if this was not a universal standard.
p.2 #12 · Risk of focus shift issues in new 1.4/35?
Makten wrote:
Yes it does; it matters a lot. The screen does NOT show the correct DOF for a lens with maximum aperture of f/1.4 or so. So, you are actually focusing at the aperture that the focusing screen shows, which normally is f/2.8-5.6.
And if you close your eyes, you see even less, but that has zero to do with the lens. Focus shift is a lens attribute regardless if you are using live view, a focusing screen or are legally blind.
p.2 #13 · Risk of focus shift issues in new 1.4/35?
denoir wrote:
And if you close your eyes, you see even less, but that has zero to do with the lens. Focus shift is a lens attribute regardless if you are using live view, a focusing screen or are legally blind.
Of course, but the problem is that the focusing screen does NOT show what the final image will look like. So, with an f/1.4 lens and a camera with a screen that cannot show shallower DOF than f/2.8, you will focus the lens correctly at f/2.8 regardless of what aperture the lens is set to (assuming the lens stops down when the image is captured).
p.2 #14 · Risk of focus shift issues in new 1.4/35?
No you won't - a focusing screen does not shift focus together with the lens. The center of the focus point at f/1.4 will be correct on the focusing screen but with a larger DOF.
As the camera stops down the real focus point at f/2.8 will move while you, focusing wide open, will still see it centered on the f/1.4 spot with your f/2.8 focusing screen. If the focus shift is severe enough, you'll be off focus at f/2.8 even though it looks right in the viewfinder. That's why focus shift is problematic in the first place. It's the whole point of the complaint about focus shifts - you see one thing in the viewfinder and the camera captures something else.
The problem with focus shift is, as the name implies, that the focus shifts. It won't matter what kind of device you use to focus or what DOF it has. If the focus shifts at f/2.8 more than the extension of the DOF takes care of relative the largest aperture then you have a problem. In your viewfinder it will look as if it is in focus but when the camera stops down before it takes the image the focus points moves and the focal plane does not end up where you intended it to.
p.2 #15 · Risk of focus shift issues in new 1.4/35?
denoir wrote:
No you won't - a focusing screen does not shift focus together with the lens. The center of the focus point at f/1.4 will be correct on the focusing screen but with a larger DOF.
As the camera stops down the real focus point at f/2.8 will move while you, focusing wide open, will still see it centered on the f/1.4 spot with your f/2.8 focusing screen. If the focus shift is severe enough, you'll be off focus at f/2.8 even though it looks right in the viewfinder. That's why focus shift is problematic in the first place. It's the whole point of the complaint about focus shifts - you see one thing in the viewfinder and the camera captures something else.
The problem with focus shift is, as the name implies, that the focus shifts. It won't matter what kind of device you use to focus or what DOF it has. If the focus shifts at f/2.8 more than the extension of the DOF takes care of relative the largest aperture then you have a problem. In your viewfinder it will look as if it is in focus but when the camera stops down before it takes the image the focus points moves and the focal plane does not end up where you intended it to....Show more →
We're saying the same thing. But, you will and can NOT "focus wide open" since the screen won't see what the lens sees at full aperture. What you see in the viewfinder will correspond to something like ~f/2.8 or slower, whatever lens you put on the camera. If the lens shifts focus, you do NOT see the correct focus at f/1.4 in the viewfinder. That's physically impossible with the screens available for the cameras we are talking about.
So, at f/2.8 focus will likely be correct. At f/1.4, focus will probably be a tad closer than what the viewfinder (or AF) sees as correct. At f/5.6 focus will probably be a tad farther away, and so on.
p.2 #16 · Risk of focus shift issues in new 1.4/35?
Actually, I don't think we are. What you see in the viewfinder corresponds to a DOF equivalent to f/2.8, but the focal plane, i.e the center point of the DOF "bubble" will be where it is at f/1.4 because you are focusing with the lens wide open - you have not stopped it down.
If it is a lens with a severe focus shift, then at f/2.8 it's unlikely that the focus will be anything close to correct. The exception are rangefinder lenses where the focusing coupling is independent of lens focus. With TTL cameras you see through the lens. At f/1.4 the focal plane will be where it is at f/1.4 - regardless of how deep the viewfinder DOF is. If your focusing screen shows f/2.8 DOF or f/8 DOF won't matter - the focal plane will be centered on exactly the same spot as if you had a f/1.4 focusing screen. The fact that focusing screens have a larger DOF only makes it difficult to find focus at f/1.4 - it does not mean that you'll avoid the focus shift at f/2.8.
As I said, the focal plane you see on the focusing screen will not move as the actual focal plane moves due to focus shift. Focusing a lens with focus shift wide open is not a problem - you can use live view or simply estimate where the middle of the DOF 'bubble' is on the focusing screen. The problem with a lens that has significant focus shift (where the focal plane moves outside the DOF) is that it moves and that it's something that you can't see in on the focal plane.
A simple example. Suppose you have a 50mm f/1.2 lens (like the notorious focus shifter, the Canon 50L). You focus on a spot 50 cm away. At this distance the DOF at f/1.2 is roughly in the 49.8-50.2 range. Now you change to f/2.8. Your DOF is in the 49.5 - 50.5 range.. however the focus shift is a 1 cm at f/2.8. So your actual DOF is in the 50.5-51.5 range. Your intended target, at 50 cm is not within DOF and you have a problem. On the focusing screen you see 49.5-50.5 while the end image shows 50.5 - 51.5!
With manual focus lenses on a DSLR this is typically less of a problem as you can actually force the lens to stop and to focus at the final aperture. With live view it's really a non issue - you just instruct the camera to stop down to the actual aperture when you are using live view. The real problem is with AF lenses where you don't have the option of stopping down and of course with rangefinder lenses where you have no DOF preview.
p.2 #17 · Risk of focus shift issues in new 1.4/35?
denoir wrote:
What you see in the viewfinder corresponds to a DOF equivalent to f/2.8, but the focal plane, i.e the center point of the DOF "bubble" will be where it is at f/1.4 because you are focusing with the lens wide open - you have not stopped it down.
This is where you get it wrong. Regardless of the maximum aperture of the lens, what you see on the focusing screen is what the lens gives at the aperture that the screen can show.
This is not rocket science. It's about angles of light.
I'm not sober enough to explain any further, but I'll get back tomorrow.
p.2 #18 · Risk of focus shift issues in new 1.4/35?
If that was the case, focus shift wouldn't be a problem and AF lenses would not be compatible with focusing screens.
I can probably show you a real world example with the 85/1.4 tomorrow, but I have to whine a bit about Leica repairs in the Leica thread and then I have to call it a day - I'm already very late for a dinner.
p.2 #19 · Risk of focus shift issues in new 1.4/35?
I think that Makten is probably correct: the DOF at the focusing screen is deeper because it shows less SA. The rays of the lens that normally contribute to unsharpness/SA glow are not in the original focal plane but contribute to the brighter VF image (I could be wrong here though; I haven't completely wrapped my head around the optics of this).
So the focusing screen would be effectively stopping down the lens, although it's most probably not 100% the same effect as what actuall stopping down of the aperture does.
p.2 #20 · Risk of focus shift issues in new 1.4/35?
All I like to say here, is that the I do not find the 1.4/85 soft wide open at distances beyond 5 meters (and I haven't found it soft below that either, but I can't pull an example to mind). Softness being a relative term though. Only at 100% can I find anything resembling softness if I focus correctly. It's perfectly adequate for a 1.4 lens as far as I can tell. Adding to that PP softness can not be an 'issue' with this lens.
I have not used another 1.4 85 lens though, so this opinion must be taken with that in mind. Absolutely speaking though, I would never call this a soft 1.4 lens (and of those I've tried a few).
These are PP'd 1.4/85 photo @1.4
(edit: I didn't think these photos would show up so I posted the link to huge photos, sorry)
