Like I said, I think this is / will be a very fine lens from Canon. When it hits the focus right, it is VERY VERY good IMO. Trouble is, I have not had a consistent focusing copy yet. Some people apparenty have copies that work correctly. And like I said...I'm going to wait this one out for a while and see what happens. I anticipate owning another one of these at some point.
I looked forward to the new 50L lens from Canon, and sold my original 50L f/1s in anticipation. I wanted the new lens to work for me, but I am returning this second lens, for a different set of issues.
So for me, I am out of the 50L business. I will try another one maybe in 6 months or sooner, hopefully after the issues settle. Thanks to everyone for listening to and responding to my posts through this thread!
Good show Gary, even without having the lens, I largely share your sentiments on it based on all that I have read and seen so far.
I wish you'd test every new lens from Canon in the future so that I do not have to go thru the aggravation myself.
Your knowledgeable assessment of the lens and sharing of data is much appreciated.
Edited by Peter Reesor on Jan 15, 2007 at 06:57 PM GMT
Sorry to hear you've thrown in the towel for the time being, Gary. I've been aggressively putting my 50L through the paces trying to find evidence of this back-focusing issue, but it's just not there. I tried it under 10 - 15 ft and beyond, and at various apertures starting at 1.2 down. Wherever I put the focus point it appears to have absolutely no trouble locking on its intended target. My date code is close to yours, so I started to get a little concerned. Perhaps there may be a few quirks with some of the early copies, but I think it's still a relatively small percentage of owners experiencing this. Maybe there are others having issues that aren't being reported and maybe there isn't. Maybe they just haven't discovered there is a problem yet. Who knows? My copy appears to be good, so until otherwise, it has a permenant place in my stable.
lord_malone wrote:
My copy appears to be good, so until otherwise, it has a permenant place in my stable.
Oh, I believe you 100%! And I don't blame you for hanging on to the lens. I wanted to badly myself! But, this stuff is a hobby for me and I don't have to have a 50L for now. I'll get a good one eventually.
ghuff wrote:
This lens focuses fine at f/1.2, but progressively begins to backfocus at f/1.4 and up until about f/3.5 to f/4 where the DOF begins to be large enough to encompass the focus error. This ONLY happens at distances of under 10-15 feet or so. At further distances, it does fine....and stopped down, as I have shown...it is a very sharp lens.
It does this same thing on both my 1Ds2 and Rebel XT350.
This oddly is the same thing that pcho in Australia reported and I think Madmaxx200 reported also.
Gary, thanks for all the effort you've put into this exploration.
I'm a little mystified by this phenomenon of accurate focus at f/1.2, with backfocus creeping in as it's stopped down. (I haven't observed this in mine, by the way, though I have found backfocusing at very close distances, ca 2 feet and less.) I would think the AF, which of course is always done wide open, would not be affected by stopping down. There are some very poor lenses that exhibit focus shift with stopping down, generally as a result of astigmatism (in other words, not a mechanical problem), but that shouldn't be the case here. Hmm...
I looked forward to the new 50L lens from Canon, and sold my original 50L f/1s in anticipation. I wanted the new lens to work for me, but I am returning this second lens, for a different set of issues.
This lens focuses fine at f/1.2, but progressively begins to backfocus at f/1.4 and up until about f/3.5 to f/4 where the DOF begins to be large enough to encompass the focus error. This ONLY happens at distances of under 10-15 feet or so. At further distances, it does fine....and stopped down, as I have shown...it is a very sharp lens.
It does this same thing on both my 1Ds2 and Rebel XT350.
This oddly is the same thing that pcho in Australia reported and I think Madmaxx200 reported also.
My dealer has agreed to take this second lens back.
While I am reasonably certain that there are lenses out there that work correctly, and I think this will be a very good lens for Canon....I also think that there are bugs for now in this design that Canon needs to work through.
My second lens was a UU1100, 694XXX serial number.
So for me, I am out of the 50L business. I will try another one maybe in 6 months or sooner, hopefully after the issues settle.
Thanks to everyone for listening to and responding to my posts through this thread!
Thanks for the PM and I did further test with my 50L. What I find is when focus at f1.2, I originally thought it was focusing properly but when I looked closely, it was actually back focusing. Just that it was not pin sharp but raher just sharp enough to make me think it is in focus as the background's creamy/bokeh look gives me the impression that it is not in focus. When I contrast down the file in PS, I was able to take away the creamy (foggy) bokeh look in the background and it actually shows backfocusing. So it originally gave me the impression the focus was alright at f1.2 and in reality the back focusing appears when I stop down.
There are some very poor lenses that exhibit focus shift with stopping down, generally as a result of astigmatism (in other words, not a mechanical problem), but that shouldn't be the case here. Hmm...
Good point on the focus wide open. Maybe astigmatism was why Canon decided that optical alignment was necessary as well as focus adjustment on my first lens....that always puzzled me.
But I will say this...Canon ROYALLY messed my first lens up so that it was never as sharp as it was when it was new. So...Hmmm, you may be on to something there. But I guess time will tell, if Canon actually admits a problem or if the amount of lenses with issues decreases...
ghuff wrote: Yeah, that's if there's a quality control issue at all. I've only seen these issues reported on this particular forum. Doesn't seem to be a universal problem like the 24-105L had at its introduction. But then again, I only lurk on a select few photo forums, so I could be wrong.
i bought a 50L today and will hopefully have some time to play with it tomorrow. so far the focus ring seems stiff compared to my other lenses but that could be beneficial while adjusting such a shallow DOF. i use MF more than i do AF on wide lenses so this is something i always notice right away. other than that, i really like this lens. it beats the pants off of my 50/1.8 mkII in build quality.
ed, i'll follow up later this week with some examples.
i'm quickly discovering that at its minimum focus distance of 45cm (17-3/4") it's easy to blow focus. DOF is only about 3~4mm (1/8"). using this lens at close range and f/1.2 isn't easy. but, i didn't buy it to use as a macro or a portrait lens. this is where real-world use will play a much more important role in my decision to keep or return it.
flatdraft wrote:
but, i didn't buy it to use as a macro or a portrait lens. this is where real-world use will play a much more important role in my decision to keep or return it.
mbailey wrote:
Erik,
What are you going to shoot with it?
heck if i know... you can click the 'www' link at the bottom of my signature to see the random stuff i shoot. about 8 out of 24 shots are in the 50mm range so it should be an interesting few weeks of playing "find the shot" with this lens.
i bought it because build quality, weather resistance, relatively small size, smooth focus ring, and bokeh quality were all at the top of my list of requirements. f/1.2 isn't all that important to me except for providing a bright viewfinder. i'm considering selling my 24-105L (mainly because i think it's making me lazy) so the 50L seems like a great alternative -- except for its inability to shoot at 24, 28, 35, 70, and 105mm, or utilize IS. heh
So, I got mine back from Canon and am now seeing a very strange behavior. Wide-open, the lens focuses absolutely rock solid - perfect focus every time. However, as you stop down the "center" of the focal plane clearly backfocused by about 2cm. Frankly I'm not sure if this is something that would be noticeable in real world shooting - this test was done at about 2ft, which needless to say is not a realistic representation of how most people would use the lens.
I'm going to use it through the weekend for a couple of events and see how it works out. I will be buying a 50/1.4 as a back up and will run the same focus test to make sure its not some oddity with the body.
From the properties exhibited by my last 50L f/1.2 and the description from Sam Bennett and the insightful comments of Photon, I did some searches on "focus shift". From what I can find, this is a visible phenomenon that is the result of some spherical aberrations in certain lens designs. What happens is the focus point appears to shift dramatically as the lens is stopped down, and it is not that uncommon for lenses to have it. I found some references that indicate modern AF systems and designs with electronic interfaces are able to compensate for this phenomenon mostly.
My completely speculative and uneducated guess is that "focus shift" is what some of us have seen. And, either the lens elements are not properly adjusted, and / or maybe this lens design is not properly electronically compensated (program bug)?
I never knew this effect existed, but it certainly sounds like what is happening in some reported cases...and definitely fits what I saw with my last lens.
It will be interesting to follow this and see what happens.
ghuff wrote:
My completely speculative and uneducated guess is that "focus shift" is what some of us have seen. And, either the lens elements are not properly adjusted, and / or maybe this lens design is not properly electronically compensated (program bug)?
Yeah, it seems like maybe the lenses "firmware" might get updated at some point?
I'm pretty disappointed right now. After doing my "objective" tests, I had kind of convinced myself that the issue wasn't that big of a deal. Then I shot random stuff around the office with both the 50L and the 35L. All of the 50L photos were noticeably OOF, the 35L photos were all dead on. I'm grabbing a 50/1.4 this afternoon - if the 50/1.4 focus more accurately, I'll be demanding a new 50/1.2L from Canon.
FWIW, the letter I got back from Canon said that if the problem appears to not be fixed to send the body in as well, but if the body is fine with the rest of my lenses, is there a point?
Edited by Sam Bennett on Jan 18, 2007 at 10:26 AM GMT
Ah, I see now... sorry. So, in a nutshell - leaving the focus point identical, the f/2.8 shot will in fact backfocus. It would be up to the lens electronics or camera to compensate for this.
Will be interesting to see if the 50/1.4 exhibits the same issue.
