need help from experienced 24-70mm users

That one doesn't look too bad. I wouldn't use multipoint AF though, i'd use center point and double check it with live view if you're on a tripod.

dipps wrote in post #8810555
here's one of the group shots i took. again, tripod shot, multipoint AF. aperture at f/5.6, 1/125sec, ISO 400, 34mm.

2000x1333 image below
http://img169.imagesha​ck.us/img169/4364/img5​269i.jpg

Again, the group is backlit and the front surfaces of the people do not have significant contrast for focusing on.

What focusing mode do you have set up in the camera?

dipps wrote in post #8810567
by this are you saying that the appropriate action (if indeed it is a bad copy issue rather than a user error issue) would be to send the lens back to canon rather than take it back to the dealer who sold me the lens?

If there is a problem with the lens you can return it to the store (if within the return period) or you can send it to canon and they should calibrate it for you (for free if under warranty). I'd take some more shots that aren't so severely backlit as SkipD is suggesting and investigate further though.

I have to chime in and say that this looks like a technique problem, not a lens
problem. Auto-focusing on a very dark, very low contrast area is sure to cause
missed focus - why didn't you focus on the woman's face? The old adage "Always
focus on the eyes" still hold true, possibly even more so today.
I hope that controlled tests will reveal the lenses true potential to you.
Good luck!

mikekelley wrote in post #8810584
That one doesn't look too bad. I wouldn't use multipoint AF though, i'd use center point and double check it with live view if you're on a tripod.

normally i do use centerpoint focus, but for a large group i thought it would be best to use multipoint (as previously mentioned, i'm more of a "single person" portraits kind of guy.... i was volunteered for this ). multipoint AF just seemed to make sense to me for a group of 20+ people.

for that particular occasion, i was using single shot AF mode with multipoint/automatic AF point.

dipps wrote in post #8809057
ok, i've been waffling back and forth between the 24-70mm, 24-105mm, and 17-55mm for the past month. i shoot a rebel xsi (crop, and yes, i know most would recommend the 17-55mm for my xsi, but after much consideration, i chose the 24-70mm.... it just fits what i do better).

i hadn't planned to buy any of the lenses for a while yet (still biding my time, choosing my next lens carefully), but my wife went and volunteered me to do a group photoshoot for both our families (thanks, wifey). i was the last to know. my lenses are as shown below (the 24-70mm 2.8 isn't yet in the list). my best "20 person group portrait" lens prior to the 24-70mm was the 18-55mm IS (or maybe the 50mm 1.8). i went and tried a few practice shots with my kit 18-55mm, and wasn't real happy with them. with 20 people depending on me to get a good family pic, i wanted to do a good job (and no, i wasn't charging anything to take this pic, or the numerous other "single family" pics i took before and after the group pic). i figured with this family shoot, my own family shoot, and my best bud and his wife wanting me to do a family pic of them, it was the best time to break down and bite the bullet on my next lens. i chose the 24-70mm 2.8, despite knowing it's history of "bad copies"/people going through 3 or 4 copies before getting a good one. i hoped that wouldn't happen to me.

i don't think i was one of the lucky ones.

long story short, most pics came out ok (as far as the family was concerned), but after studying this lens and sample images from sharp copies of it for the past 2 months, i KNOW this lens is capable of more. and i'm not a pro photog, i just do this for fun (for now.... maybe someday when i really learn all that i need to know), so spending $1300+ on new lens is a major purchase!

i bought the lens at mike crivello's nearby (milwaukee, wi) and in speaking with the folks there, i asked what they knew about this lens and "bad copies". they told me they knew nothing of such things..... told me that they didn't think there was such a thing as bad copies for this lens, and that pro wedding photogs bought that lens from them all the time, and none have ever been returned. i said, "that's great, but what if i do get a bad copy, and i want to return it for a good copy?" originally they were talking at me about 15% restocking fee, and i got a little angry at that point. i made it clear i had no intention of spending that kind of coin on a new lens from them if i was going to have to pay them $160 some dollars to return a "bad copy". eventually they said they'd take care of me were i to wind up with one, so i bought the lens.

so long story short, i did the shoot, and even on my 3" LCD i was getting the suspicion that the images weren't really all that "sharp". i even got the "err99" message once while trying to shoot first time i had ever gotten that message. i powered off the camera, powered it back up, and it shot fine from there on out (no more error messages).

but looking thru the pics, i don't see anywhere near the level of sharpness that i should be seeing from this expensive lens. heck, some of the pics (many) look like they were taken with a point and shoot, as far as sharpness goes.

the details:
i was shooting with a good, sturdy tripod, and a remote trigger, so handshake was not the issue.

for the image below, i was shooting with the following settings (which SHOULD have been right in the sweet spot for this lens, according to all i've read):
- f/5.6
- 1/125 sec
- ISO 400
- 40mm (right around the middle of the focal range)
- spot metering
- image was taken from a distance of maybe 15-20 feet away

the image is a 100% crop taken from the full image (6.6mb in size), only showing the heads. pretty sure you can see the softness that i'm talking about by looking at this pic (especially looking at the lady's face/hair). if you're interested in helping me out and want to see the full size pic, shoot me a pm and i can host it on my website to view.

i have 10 days to take the new lens back if indeed it is a "bad copy".

thanks for looking, and thanks in advance if you can help me out, verifying or negating that i do indeed have a soft copy.

if all your results look like this and you are getting better results with other lenses you have a bad brick.

ed rader

My 20D is always set for the "partial" focusing mode - as close to the more modern "spot" mode as it can be. If I decide to use autofocus, I usually deliberately aim the camera at a contrasty portion of the scene that is at the same distance from the camera as the primary subject's most important features and then recompose for the shot. Otherwise, I'll use manual focus to tweak the focus to my desired point.

My 24-70 f/2.8L is the lens that rides on my 20D far more than either of the others I have (16-35L and 70-200 f/2.8L IS). It's a great lens, and so are the others.

ed rader wrote in post #8810657
if all your results look like this and you are getting better results with other lenses you have a bad brick.

ed rader

that's what i'm trying to figure out within 10 days. i appreciate all the feedback, and certainly won't rule out user error, but i've taken plenty of shots prior to this (even high contrast shots) without running into such issues, including this one with my fitty 1.8........

http://img6.imageshack​.us/img6/1008/img2003j​.jpg

turned out just fine and incredibly sharp.

maybe this will help.... a pic i took with the built-in flash.

http://img403.imagesha​ck.us/img403/1771/img5​343c.jpg

f/5.6, 1/160sec, ISO 400, 42mm

still very soft......

I'd take some more test shots the next few days and if you can't get good results I would exchange the lens. BTW, I like the Tombstone quote.

Jeff81 wrote in post #8810752
BTW, I like the Tombstone quote.

"You're no daisy! You're no daisy at all. Poor soul, you were just too high strung."

When I got mine, focus was hit or miss. Some were sharp, others were like the photo you posted here.

Finally called Canon and they asked me to send the lens in for evaluation. They found a defective chassis, a loose connection and recalibrated it. Thing is tack sharp.

Shipped to Canon Irvine on a Monday and received the lens back on that Friday. Best decision I made.

sounds very familiar.

i'm still not sure what caused the "err 99" message that i got on the camera when i was shooting with that lens. that was the first time i had ever gotten that message, in over a year of owning my xsi. definitely was not the way i wanted to start the working relationship with my new lens. prior to that error message, i had obtained this particular pic.... still not "perfect", but pretty darn good, and seemingly much better than many of the other later shots. and again, it was a "high contrast background" situation, but the pic came out fine (i was using automatic AF selection here also).

http://img66.imageshac​k.us/img66/962/img5206​.jpg

Jmantyger wrote in post #8810871
Finally called Canon and they asked me to send the lens in for evaluation. They found a defective chassis, a loose connection and recalibrated it. Thing is tack sharp.

Shipped to Canon Irvine on a Monday and received the lens back on that Friday. Best decision I made.

btw, how long ago was that? have you seen any "calibration deterioration" since then?

dipps wrote in post #8810909
prior to that error message, i had obtained this particular pic.... still not "perfect", but pretty darn good, and seemingly much better than many of the other later shots. and again, it was a "high contrast background" situation, but the pic came out fine (i was using automatic AF selection here also).

http://img66.imageshac​k.us/img66/962/img5206​.jpg

Is the AF actually doing anything? Can you hear it doing its thing and see the focus point moving? Also ensure it's not switched to MF of course (just covering all bases). A quick test on a tripod with both MF and AF, along a surface that covers from near to far (i.e. along a brick wall or a fence) would be a good idea.

That shot with the flash indoors looks like it could be front-focused going off the bottom-left of the picture.

phreeky wrote in post #8810999
Is the AF actually doing anything? Can you hear it doing its thing and see the focus point moving? Also ensure it's not switched to MF of course (just covering all bases). A quick test on a tripod with both MF and AF, along a surface that covers from near to far (i.e. along a brick wall or a fence) would be a good idea.

yep, i could see the image adjust as i half-pressed, and would hear the "beep" when it was "focused" and ready (and yes, the switch was in AF mode, not manual focus ).