70-200f/4L softfocus??

[AXENA]

Had a weird experience today.... for the first time in over 1000+ frames, I started to get a soft-focus.... the lens either front or rear focused and I had to manually override the AF. Subject was baseball pitcher, which I have done hundreds of times before, and never had an issue.

I thought it was just my eyes playing tricks on me so then I focused on a still object about the same distance away (a tree) and the same thing happened. I did this repeatedly and got the same results. Conditions were late daylight sun (5:30OPM) so it wasn't even close to being dark. This was especially noticeable at the 70mm range. It seemed to be focusing near in this situation (the grass surrounding the pitcher's mound).

The only other variable I can think of is that I took the camera and lens from a 72-degree air-conditioned room out to the field and started shooting a few minutes later. The relative humidity was about 90%. Can weather actually have an effect on the AF of an L-lens or the 20D?

I have not had any issues at all with this lens in daylight conditions. In fact, it has been tack-sharp all through the range up until today (first day with slightly higher humidity).

Any thoughts would be great. I really don't want to get into the whole "send the lens and camera back to get recalibrated" thing. Not that I even know what that is since I never had this issue.

Thanks all....
-GSL

[AXENA]

as a side note, I shot another baseball game at night under the lights, and the 70-200f/4L focused without an issue each and every time. Not one bad shot in the lot. So it strikes me as odd that in bright daylight there would be an issue.... I expected it last night, not today.
-GSL

[AXENA]

anyone, anyone?

[JusSmith]

Perhaps I should try mine at night, cos all my day shots seem to be back-focused. Take a look at http://www.pbase.com/jussmith/test and the pictures whole.jpg (original, taken with centre focus point only) and two crops centre.jpg and right.jpg!


It's been back to Canon who just sent it back and said there's nothing wrong with it! Hardly!!!

[pcasciola]

Well, since there are no replies I guess I'll throw this crazy theory/question out there because I had a similar problem and I'm not far from you. Could it have been the extreme heat and humidity? I also had a pretty bad batch of baseball pics from the other day with my 300/4L when it was in the low 90s and very humid. I know these lenses are white to cut down on the internal heat, so I wonder if it's possibly related to that.

[AXENA]

Well, since there are no replies I guess I'll throw this crazy theory/question out there because I had a similar problem and I'm not far from you. Could it have been the extreme heat and humidity? I also had a pretty bad batch of baseball pics from the other day with my 300/4L when it was in the low 90s and very humid. I know these lenses are white to cut down on the internal heat, so I wonder if it's possibly related to that.


That was in my original question.... I am wondering if these zooms are prone to humidity issues. I did 500 shots last weekend when it was blazing hot but no humidity.... all shots were CRISP! Then the other day with higher humidity and heat I need to override the AF! WTF???? I really hope this isn't the issue, because as anyone in NJ knows, we don't get DRY HEAT! We get that nasty wet-humid-hair-frizz-sea-breeze-salt-air heat, especially by the shore. This is really going to cause some serious issues for me.... does this mean I am going to need to exchange this lens and spet yet another $1500 for a weather sealed f/2.8L????? God.... my bank account is getting thin! Thank god the jobs keep coming in and I can work well with manual focus... but really this is a pain.
-GSL

[pcasciola]

That was in my original question.... I am wondering if these zooms are prone to humidity issues. Sorry about that. I read your original post, but somehow skipped over the part about the humidity that you metioned. I'm going to give it another go today in the hot humid weather, but the game is at 5:45PM when it will already be starting to cool down a bit.

[AXENA]

I gotta call Canon. The lens is fine between 135-200mm.... focus is fine. However, between 70-135mm the lens wants to focus about 15 feet in front of target. I am using center focus only. Sounds like a fault in the lens.... it is happening consistently at these ranges. I suppose I could "fix" this by stopping down the lens to f/11 or higher, but this really shouldn't be happening, should it? Or is there something in the elusive writing famous to Canon's manuals that I missed about 70-135 front focusing?
-GSL