Canon 50mm 1.2? Are back focus issues just related to autofocus?

[joel_orbita]

<p>Hi, I have the Canon 50mm 1.2L and use it with my 5DII and now have access to my brothers 7D, where it becomes a longer 80mm (is that correct? A 1.6 x crop right?)<br /><br />I have mainly been using "liveview" with this lens, due to its ability for such shallow DOF and was wondering if this focus shift issue is solely related to autofocus? If manual focusing with either the lens or with liveview, does it become an issue at all? Sorry if this is a dumb question..<br /><br />Ok, thanks so much, look forward to your thoughts.</p>

[paddler4]

<p>I don't have that lens, but:</p>

<p>1. it will act like an 80mm would on your camera in terms of field of view, but in other respects, it is still a 50mm lens.</p>

<p>2. back- and front-focus refer to errors in autofocus. It has nothing to do with manual focusing. </p>

[Marcus Ian]

<p>The focus shift occurs when you stop it down. In other words, when the aperture blades snap shut, it affects the point of focus. This happens in most lenses, but the extent of the shift falls within the increased DOF, so you usually don't notice a problem. Focus shift is an optical/mechanical quality of the lens (and is pretty bad on the 50/1.2L), and is independent of AF/MF (or type of AF).</p>

<p>If you are using the lens WO, focus shift should be zero.</p>

 

[joel_orbita]

<p>Hmmmm, well that is not good news at all.. Was hoping I was going to get away with it by using manual focusing exclusively.. From some reports I have read, the worst seems to be between f2-f4? Any reason for this? I mainly intend to use it wide open or just down from wide open (1.2-1.8). <br>

I have been toying with the idea of getting selling this lens and getting another 50mm and with the extra cashola getting the 85mm 1.2II. Maybe the Sigma 50mm 1.4 or the Nikon 50mm 1.2 (with adaptor).</p>

<p>Any thoughts? </p>

[Marcus Ian]

<p>It would be helpful to identify for certain whether or not the problems <em>you are experiencing</em> are due to back focus, or the focus shift. I find that reading about 'common' problems are often less than helpful... Backfocus may be corrected (assuming you are using AF) w/ MFA a feature on the 5D2 and 7D. If <em>that</em> is the problem, you shouldn't be seeing it in imagery focused w/ LV. Focus shift can not be corrected for in camera (since the camera evaluates/focuses/ feeds to LV based only on WO condition), but that problem is common for many fast primes (including the Sigma 50/1.4 HSM)</p>

<p>The good news w/ focus shift is (if you have time) you can compensate for it's impact by using the DOF preview button, and refocusing while the lens is stopped down. For normal shooting this is obviously largely impractical, but if you are already using LV to manually focus, it's pretty easy. </p>

[sheldonnalos]

<p>The complaints about focus shift you read across the the internet forums about the 50 1.2 "focus shift" are mostly from people who don't understand the differences between missed focus and the very slight shift in focus that takes place when the lens stops down. It is supposed to be the worst between f/2-4 at near middle distances of 3-4 feet.</p>

<p>I've shot thousands of frames with my 50L and not noticed focus shift. Yes, I've missed focus before but I didn't blame it on focus shift.</p>

<p>If you test for it by manually focusing wide open (shooting from a tripod) then shooting a series of shots at different apertures, you can find it. Probably the easiest way to describe what you'll see is that as you stop down the areas behind the original plane of focus will sharpen up more than the areas in front of the plane of focus. The original plane of focus gets sharper too.</p>

<p>I just tried a bunch of shots up close and at f/2.8 in a real world close headshot, and there's nothing that jumps out at me as a focus problem. Eyelashes are still sharp at 100% (1Ds III files).</p>

<p>The "focus shift" issue is mostly internet hype. </p>

[looscanon]

I've had the 50L since it was first introduced. I heard about the focus shift issue a couple of months after. It's claimed by some that it's an inherent part of this type of lens and that it should have had a floating element to correct this like the 85L. However, I've tried everything to duplicate the focus shift with my 5D and I've not been able to do it. I've put it on a tripod from 3-6 feet and shot photos at all lens openings of the same object from f/1.2 to f/2.8 with the focus being spot on at all times and no deviation whatsoever. I can only tell you of my own experience with this lens. Focus shift may exist but at least one 50L doesn't have it and believe me I've tried to produce it with my camera and lens. I believe the 50L is one of the finest 50mm ever produced and the perhaps the most maligned because in a great many cases people do not understand how to use it properly because of the extremely thin depth of field involved to focus in.

[PuppyDigs]

<p>I've used the 50 1.2L for 4 years now (5D and 5D2) and have suffered no problems with AF or focus shift. And, yes, I have often used it stopped down to F 2, 4 and 5.6. I'm not saying that focus shift doesn't exist just that it is so little it hasn't changed my shooting technique or ruined any images. Of course, if you are mainly a lens cap and ruler shooter, I'm sure you'll find something wrong with every piece of gear out there. </p>

[chris_clarke3]

<p>I first used my 50L on my old 20D and it didn’t really do it for me at that crop FL, especially indoors. With FF the 50 is the classic FL . On the focus-shift, I have experienced it but it’s not as big as a problem for me as it seems to be for some posters in the forums.<br>

The 50L is a great lens and (IMHO) but it does take a bit of getting used to at the wide open end. When I first used the lens I got very frustrated at F1.2-1.8 with my hit (or lack of) rate. It just takes a bit of skill to use and once you get the hang of it the results are very rewarding. I think the 50L really upped my skill levels</p>

[philip_wilson]

Focus shift is generally only an issue at close distances. It also depends on the calibration of the lens (I.e. what the

manufacturer assumed you would be shooting at) I am not sure about this Canon lens as I do not own it. For many

lenses you can have the lens adjusted. A major example of this is the Zeiss M mount 50 F1.5.

[joel_orbita]

<p>Wow! Thanks so much for all the responses! I will keep an eye out to see if my particular lens exhibits this trait..</p>

<p>Thanks again.</p>