I just figured that my last report saying that the "replacement" lens for mine suffers the same issue might have resulted in at least one response. Maybe more of us are convince that there's a fundamental lens design problem than I thought.
OK - can someone then sum up for me exactly what the issue is with this lens. I was wandering around with it for much of the day yesterday and it nailed focus every time....
Sam, you are experiencing the same thing Gary has, as well as myself. Gary went through two copies and I am on copy two right now. While copy two of mine does do it as well, it's a lot less pronounced and only does it at a few apertures and not all the time. My second copy is much better, but still not what I want.
Truth be told, I don't think its a fundamental design problem. My local photo club had the pleasure of having a Canon rep speak at our monthly meeting last Thursday. Part of the reps presentation was showing off some of the newer Canon gear, including the 50/1.2. I asked if I could shoot with it for a little bit and probably shot for 10-15 minutes with it and they obliged.
It was flawless from what I could find and after trying to get it backfocus, I just couldn't. When I opened up the files at home on my computer, I was stunned. I have a glimmer of hope for this too as well, and the sharpness on the reps copy was astounding. Ask Gary, I immediately sent him the files to look at.
So, we were both surpised at that. And from what the rep told me, she doesn't get any special treatment with the gear that is issued. Luck of the draw just like us.
Radiohead wrote:
OK - can someone then sum up for me exactly what the issue is with this lens. I was wandering around with it for much of the day yesterday and it nailed focus every time....
Where were you focusing in that first shot you posted? If it was the eyes, it's exhibiting the problem we're talking about. The easiest way to do this is to do a 3/4 view shot of someone (close enough so only their head and part of shoulders is in the frame). Focus on the eye that is closest to you, and shoot at f/2.8. If your lens is exhibiting the problem, the eye furthest from you will be in focus (indicating a backfocusing condition).
Radiohead wrote:
OK - can someone then sum up for me exactly what the issue is with this lens. I was wandering around with it for much of the day yesterday and it nailed focus every time....
In short, some copies of this lens tend to backfocus progressively at short distances when stopping down. Each lens has a varied degree of backfocusing, which leads me to believe it's not a design problem.
Canon IS aware of the potential issue and I've been in communication with several Canon people on it.
BTW, did it give you focus confirmation or is it really IN focus? Focus confirmation is not the problem.
Right - I'll give that a go later. The first shot above was at f1.2 and the cat wasn't totally head-on to me so I'd expect one of the eyes to be slightly OOF. I know I focussed on the cat's right eye (to her) but again this was 1/30s handheld and I wasn't crouching so can't say any movement with that shallow a DOF wasn't me.
eeprete wrote:
In short, some copies of this lens tend to backfocus progressively at short distances when stopping down. Each lens has a varied degree of backfocusing, which leads me to believe it's not a design problem.
Canon IS aware of the potential issue and I've been in communication with several Canon people on it.
BTW, did it give you focus confirmation or is it really IN focus? Focus confirmation is not the problem.
I also sat the lens on an outdoor table and focussed on a very small area of cloth on an umbrella - and then allowed it to AF at f1.2, 1.6, 2, 2.8, 4 and 5.6 and again, it nailed the focus both in confirmation and viewing at 100% on screen afterwards, every time.
btw, the distance it backfocuses at tends to be between MFD and about 4-5 feet.
On my first copy, I shot boxes of Arm and Hammer, without problem at varied distances and F-stops, but in real world shooting it backfocused regularly.
Thanks chaps - I'll give this a go later. Most of the shots I took yesterday were wandering around and just AFing on random targets at between a couple of feet and 10-15 feet, and viewing the shots afterwards I didn't spot anythting obviously remiss.
I had some spare time this am so I tried to duplicate this problem, this was a quick test handheld. I started at 1.2 and worked my way down to 2.8 and yes I see the progression of the backfocusing. it really comes apparent around 1.6. I guess I havent really noticed this before,, I even took some eye shots of my wife like Sams and didnt notice then. I still really like this lens and plan on keeping it, maybe if canon has a recall I will send it in, but for now I will enjoy it. View the originals to see it best backfocusing test
Allowing the camera to AF on the front battery, then focussing on something away from the scene, and then back on the front battery at a different aperture:
Your shots look focused correctly in these tests. Perhaps you got one of the lenses that has no apparent backfocus issue. From other users in this thread, there are those that continue to claim that they have no issue, and they very well may not have issues.....I'm not arguing.
I expect Canon had SOME basis for expecting this lens to be fully functional and working correctly before they released it for sale to the public. So it may be safe to assume that some lenses work correctly....
Maybe more of us are convince that there's a fundamental lens design problem than I thought.
