Roy Pertchik wrote:
Where is the 50 1.2L focus shift thread? Search hasn't helped me. Anyone remember?
Maybe in the archives by now? I don't recall any posts more recent than a month ago.
Do you have some new info to share? It might be worthwhile starting a new thread (which I guess you've just done) if there's a chance we could renew the interest of the Canon designers. I continue to use mine, always remembering that I have to be wary of one kind of situation that's pretty common. For tight head shots, I would often want to shoot right around f/2.8-4, and that''s exactly where I have to go to the trouble of shifting the focus a bit in front of the near eye at those apertures. (Focusing on the eyebrow usually does it.)
I would love it if Canon could come up with a firmware fix that shifted the focus with aperture change. From 1.2 to 1.8, the lens is a dream, and that's why I have it, but it's really ridiculous to get focus shift at 2.8.
I'm glad you are able to use your lens, with a work around. I've been getting into low light/prime shooting, and I would love to upgrade my 50/1.4, but I'm waiting for word about a fix. I have no new info, just thought I'd check in and see if there is any update. I did learn from a Canon exec that letters to canon customer service would probably help.
He recommended:
.... contact our Customer Support Center directly if you wish to pursue the matter:
* Telephone: Call Canon’s Customer Support Center toll-free at 1-800-828-4040. Kindly provide the service representative with your contact information, your EF 50mm f/1.2L USM serial number, and details about the focusing issues you are experiencing.
Sounds like it would be productive to remind Canon that there are Canon users who would like to hear a statement.
Edited by Roy Pertchik on Aug 31, 2007 at 09:59 PM GMT
I have that lens too and at very close range (less than 1m focus distance) get shift even at f2, which is amazingly annoying. Sent it to Canon and they of course found no problems. My workaround is to simply aim more forward, but as has been said, it's a pain and it would be nice if they did something about it.
stanj wrote:
I have that lens too and at very close range (less than 1m focus distance) get shift even at f2, which is amazingly annoying...
Just to clarify, the focus shift doesn't suddenly disappear at f/2 (or any other aperture), it just gradually becomes insignificant as depth of field increases. At 5.6 I've never had the slightest problem (and it is sharp), and for most really close work I'd want to be stopped down that much or more. I suppose I've gotten a few examples where even f/2 disappointed me because I was close enough that the shift made the far eye sharper than the near eye in a portrait. Yup, amazingly annoying. It just happens that for the way I use it, 2.8 is the aperture that annoys most, and the contrast and resolution at that aperture can blow you away when you do what's needed to get the focus dead on.
Roy, thanks for the link to the feedback/support site.
I just got off the phone with a Canon service tech and I told him of the issues people have been reporting for the last nine or so months.
He said that this was the first he had heard of it, which sort of amazed me. Then he said he had a 50 1.2L there with him and he proceeded to try it on a 5D, then a 30D. For some silly reason, the lens back focused on both bodies, he said. I stayed on the phone with him while he did these tests, on his lunch box, from 1.2 to 8.0 and it back focused at all aperatures, he said.
He seemed to think that it was a simple back focusing issue, that could be fixed with calibration. I mentioned that some people had tried that and the problem persisted. Anyway, he said he would file a complaint. He also said that Canon took customer complaints very seriously and that if more people would file complaints that Canon would probably do something.
cactusclay wrote:
I just got off the phone with a Canon service tech and I told him of the issues people have been reporting for the last nine or so months.
He said that this was the first he had heard of it, which sort of amazed me. Then he said he had a 50 1.2L there with him and he proceeded to try it on a 5D, then a 30D. For some silly reason, the lens back focused on both bodies, he said. I stayed on the phone with him while he did these tests, on his lunch box, from 1.2 to 8.0 and it back focused at all aperatures, he said.
He seemed to think that it was a simple back focusing issue, that could be fixed with calibration. I mentioned that some people had tried that and the problem persisted. Anyway, he said he would file a complaint. He also said that Canon took customer complaints very seriously and that if more people would file complaints that Canon would probably do something. ...Show more →
Great!
How could it be a simple back focusing issue when for many of us the focus is dead on the money at 1.2-1.6?! Too bad his copy was back focusing.
p.1 #10 · Where is the 50 1.2L focus shift thread?
Thanks! I was just about to start the exact same thread. Its now been three months since Chuck Westfall ([email protected]) emailed the following response to me and several others inquiring about the focus shift issue:
"Canon Inc. is definitely aware of the claims concerning the AF accuracy of the EF50/1.2L USM. They've been investigating for the past couple of months, and I am told that there will be some kind of public announcement forthcoming in the near future. Stay tuned, and thanks for using Canon equipment! "
I'm wondering if this is still the case or if Canon is going to stay silent. I find it very hard to believe that a service tech hasn't heard of the problem after all this time. I think that is their standard answer to these types of inquiries.
Has anyone with this focus shift problem verified that this isn't a systemic problem with the lens? I've seen a lot of reports from folks claiming that their lens doesn't have the problem but have never seen conclusive proof. If a number of lenses could be shown to not have the problem then I think this would give some weight to us in trying to get Canon resolve the issue. I've got a couple of months left on my warranty so I hope this gets resolved soon.
Here is a 100% crop of the focus shift at 3 feet and f/2.8. The vertical line at the bottom center of the crop is in the focus plane (flat target at top of crop). You can see from the angled section at the bottom of the crop that the DOF is shifted backward about 2cm and that the intended focus plane is at the extreme front (or beyond) the front of the DOF. Yes this lens is sharp at f/2.8 as many reviewers have noted. Problem its just not sharp where you want it to be. As mentioned this is very frustrating when the intended focus point is an eye in a close in portrait shot. For that you need f/2.8 to get sufficient DOF.
By the way, using the outer AF points helps a lot with the focus shift issue. I've posted a few test shots on this also. I've had some good success using that technique. Still it would be nice not to have to accomodate the lens.
p.1 #11 · Where is the 50 1.2L focus shift thread?
Photon wrote:
How could it be a simple back focusing issue when for many of us the focus is dead on the money at 1.2-1.6?! Too bad his copy was back focusing.
Assuming that the tests were done correctly, which you would assume given this is a Canon tech, then I think this is a separate quality control problem with the lens. I've seen many reports of backfocus wide open. It's a bit confusing in various discussions because many then think this is the same as the focus shift issue when in reality it is just a simple back focus problem.
p.1 #12 · Where is the 50 1.2L focus shift thread?
I sent Canon this e-mail yesterday:
Dear Sirs;
Many users of the new 50 1.2 L have demonstrated a flaw wherein the lens focuses badly at 3 to 6 feet, between f2.8 and 5.6, or so. A Canon exec has said, off the record, that Canon is working on this. Is there any new development, and when can I expect to be able to buy this lens with confidence that it will focus properly at all distances and all apertures?
Thanks,
Roy Pertchik
I got this reply:
Dear Mr. Pertchik:
Thank you for contacting Canon product support. We value you as a Canon customer and appreciate the opportunity to assist you.
We haven't found any focus issues with the EF 50mm f/ 1.2L USM lens.
We hope this information is helpful to you. Please write to us again if you have any questions or concerns.
Thank you for choosing Canon.
Sincerely,
Erik
Technical Support Representative
Special Note: Certain issues are very difficult to resolve via email.
If your question remains unanswered after you have received this email,
you may call our special toll-free number for email customers with
unresolved issues and speak to a technician by dialing 1-866-261-9362,
Monday - Friday 8:00 a.m. - 12:00 midnight ET, and Saturday 10:00 a.m. - 8:00 p.m. ET (excluding holidays).
If you prefer to continue to communicate via email, reply to this
message and we will respond as quickly as possible.
I don't think the whole support staff or the technicians at the service centers have been clued in at all!
p.1 #13 · Where is the 50 1.2L focus shift thread?
Oh, I think the service center personnel have been clued in all right.....to the fact that Canon pays their salary and they cannot say anything UNLESS Canon tells them to.
I had one of the first 50L lenses on this forum....and I can PROMISE you that Canons entire tech support org in California heard me after I had sent my 50L back the third time....and then got another lens that did the same thing...
And I can also tell you that Canon's org in Jamesburg also heard the issues from Sam Bennett on this forum and several others. Then Mr. Westfall spoke with several members on the forum about this same issue...
SO Canon IS clued in.... but my guess is they just have their mouths shut in fear of losing their paycheck....and I don't blame them.
I have lost lots of respect for Canon over this issue and their silence.
p.1 #14 · Where is the 50 1.2L focus shift thread?
Roy Pertchik wrote:
I got this reply:
Dear Mr. Pertchik:
Thank you for contacting Canon product support. We value you as a Canon customer and appreciate the opportunity to assist you.
We haven't found any focus issues with the EF 50mm f/ 1.2L USM lens.
We hope this information is helpful to you. Please write to us again if you have any questions or concerns.
.......
I got a similar reply:
"Thank you for contacting Canon product support. We value you as a Canon
customer and appreciate the opportunity to assist you. I am sorry to
hear that your EF 50mm f/ 1.2L USM lens backfocuses.
We haven't found any issues with the lens. Since your lens does not
focus properly, we recommend that it be examined by the service center.
For factory service, please forward your lens to one of the Factory
Service Centers shown below. When shipping your lens, you are not ...."
Has anyone tried to get Canon to replace or take the lens back as defective? I still hear reports from folks that their lens doesn't exhibit the focus shift. If this is true, then Canon should be replacing the defective lenses.
I'm guessing however that it is a systemic issue and the folks reporting no problems are probably front focusing a bit which offsets the focus shift. I've calculated for my lens that about a 1.5 cm forward shift is probably the best trade-off I can make to have ok AF between f/1.2 and f/4. I really need about a 3cm shift at the higher apertures but that is too much at f/1.2 which for my lens is just slightly backfocused at 0.5cm.
"Unlike focusing by eye, your autofocus camera racks the lens until the contrast in the critical points of the image are at a peak level, then it stops. According to where your lens was focused before the shot, you’ll either have focus at the front or back of your subject—rarely in the center. "
Perhaps with the 5D's 6 "invisible" auto-focus points, the auto-focus has indeed maximized contrast that happens to result in a back focus (since the farther the distance, the deeper the depth of field)? Is there anyway to disable the 6 auto-focus points, and just use the center thereby narrowing the area of contrast measurement?
p.1 #16 · Where is the 50 1.2L focus shift thread?
Jeff Chou wrote:
I am no means an expert at shallow depth of field photography, but I owned a 50 1.2 (with 5D) and also experienced back-focus from about f2.0 - 4.0
However, reading this article on shooting with shallow depth of field :
"Unlike focusing by eye, your autofocus camera racks the lens until the contrast in the critical points of the image are at a peak level, then it stops. According to where your lens was focused before the shot, you’ll either have focus at the front or back of your subject—rarely in the center. "
Perhaps with the 5D's 6 "invisible" auto-focus points, the auto-focus has indeed maximized contrast that happens to result in a back focus (since the farther the distance, the deeper the depth of field)? Is there anyway to disable the 6 auto-focus points, and just use the center thereby narrowing the area of contrast measurement?
Flame away at my stupid suggestion... ...Show more →
Nothing stupid about your suggestion, but the information you found about AF is inaccurate.
DSLR AF systems use partially silvered mirrors arranged so that the sensors are measuring contrast at two distances, one in front of the true plane of focus and one behind. Rather than hunting for maximum contrast, the system tries to equalize the contrast in both sensors (which are reading the same part of the image, of course). When the contrast is equal behiind and in front of the focal plane, it is assumed that the focal plane is optimized, i.e., the image is in focus.
There is always some inconsistency in where the camera focuses, but it is generally not affected by the "direction of approach". Try it. One simple test is to carefully note the focused distance on the scale of a lens that has a detailed, fine-grained distance scale. Focus repeatedly, starting from infinity and close limit. I've found that with a good high contrast focus target, my 50L will nail the same distance each time, sometimes with very tiny differences which seem entirely random (and are as tiny as with any other lens I've tried).
To repeat, the issue with the 50/1.2 is not AF operation, but an optical property resulting in focus shift as the lens is stopped down. The hope is that camera firmware could be designed to compensate for this. It would obviously only work in AF operation, as the camera would have to make a minor focusing adjustment based on aperture set, after the original focus was achieved.
p.1 #17 · Where is the 50 1.2L focus shift thread?
Photon wrote:
Nothing stupid about your suggestion, but the information you found about AF is inaccurate.
DSLR AF systems use partially silvered mirrors arranged so that the sensors are measuring contrast at two distances, one in front of the true plane of focus and one behind. .
p.1 #18 · Where is the 50 1.2L focus shift thread?
Part of me wonders if the attempt here of Canon to let this issue die quietly is a prelude to what they will do with the 1DIII. Early comments from chuck westfall, and then silence.
Edited by Al_10D on Sep 06, 2007 at 12:40 PM GMT
I should have said split prisms. My main point is valid. In spite of all the articles claiming that AF has to rack the lens on either side of focus, that's not the case. Unless the AF system is unable to achieve focus and resorts to a search of the full focusing range (very annoying when that happens!), it is capable of driving the lens directly to a rather accurate point of focus, without backward movement.
. I stayed on the phone with him while he did these tests, on his lunch box, from 1.2 to 8.0 and it back focused at all aperatures, he said.