24-70mm CA issue

Hi all,


A month ago I got my first L lens and I'm sad to say I'm a bit disapointed. I've had the 28-135mm kit lens on my 50D and was looking for some sharper images. After a long decision process between the 24-70 and 24-105 I choose the 24-70 with in the back of my mind three weddings I'm going for three friends this summer. I was quite pleased with the shallow DoF, bright viewfinder, and quick/accurate focusing, but I found that the 24-70 suffers from both red and green CA much more so than my 28-135. Anyone else with this experience? I understood that CA was well controlled with this lens so I expected the 24-70 to do much better! In particular, focussing on my B/W cat's whiskers shows the CA most severely. I'm debating exchanging the lens for another copy. Any thoughts?

I haven't seen it to any real degree with my EF24-70 F/2.8L. Do some testing off the tripod (taking out the variables of lighting, distance, focus, subject, etc) with both lenses back-to-back and post the results, it is always possible you have a bad copy, but I haven't heard many complaints about that particular lens.

Thanks for your response Dallasphotog. Below, I've posted some samples with descriptions. All photos were taken with a 1/250 shutter speed, ISO 100, WB "Flash", sharpness=1, contrast/saturation/color tone=0, Evaluative metering, on a tripod in live view mode with 2 second timer and the 580EXII (mounted on camera, directly aimed) at different intensities to compensate for varying apertures.


[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.29.23/I-24_2D00_70-f5-70m-8ft-crop.JPG[/img]





[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.29.23/I-28_2D00_135-f5-70mm-8ft-crop.JPG[/img]


Top: 24-70mm, f/5 at 70m, subject distance 8ft, 100% crop


Bottom: 28-135mm, f/5 at 70m, subject distance 8ft, 100% crop





[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.29.23/II-24_2D00_70-f3.5-28mm-8ft-crop.JPG[/img]


[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.29.23/II-28_2D00_135-f3.5-28mm-8ft-crop.JPG[/img]


Top: 24-70mm, f/3.5 at 28m, subject distance 8ft, 100% crop


Bottom: 28-135mm, f/3.5 at 28m, subject distance 8ft, 100% crop





[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.29.23/III-24_2D00_70-f5-70mm-1ft-crop.JPG[/img]


[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.29.23/III-28_2D00_135-f5-70mm-1ft-crop.JPG[/img]


Top: 24-70mm, f/5 at 70m, subject distance 1ft, 100% crop


Bottom: 28-135mm, f/5 at 70m, subject distance 1ft, 100% crop





[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.29.23/IV-24_2D00_70-f3.5-28mm-1ft-crop.JPG[/img]


[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.29.23/IV-28_2D00_135-f3.5-28mm-1ft-crop.JPG[/img]


Top: 24-70mm, f/3.5 at 28m, subject distance 1ft, 100% crop


Bottom: 28-135mm, f/3.5 at 28m, subject distance 1ft, 100% crop





I hope this gives you an idea of what I'm seeing. Even worse are the results at f/2.8 but obviously I couldn't compare those with my kit lens which starts at f/3.5. Just to illustrate, here is a sample at f/2.8:





[img]/cfs-file.ashx/__key/CommunityServer.Components.UserFiles/00.00.00.29.23/24_2D00_70-CA-problem.JPG[/img]


I would like to believe I'm doing something wrong so I won't have to return the lens, but I'm not sure what else to try!

Recently a friend of mine bougth and return it on the next day ... replace it with new lens adn THEY RECOMMEND TO CALIBRATE THE LENS.... so went to CANON Center got calibrated according to with camera bnody this lens will be use.... sofar tried it out NO ISSUES raised... GOOD LUCK

Interesting test pictures. I'll try to duplicate with the same basic set-up and see what I get.

Thanks, I'm interested to see your results! I don't think it has to do with bad calibration as CA is more of a lens flaw, but if all else fails I suppose that's another option!

Well, I returned the lens to B&H, received a new copy (compared the serials), and sure enough, still chromatic aberration. Called Canon support to see if they had any recommendations other then sending it in for service or returning it to B&H again, but to avail. The guy owned the 24-70 himself and assured me that there should be absolutely no chromatic aberration. It is encouraging to know that there exist good copies as well, I just wish I had one myself!


I'll send it back to B&H again tomorrow. Anyone else who has issue with this lens?

I just tried a copy, and found CA when it's wide open and fairly close (like your tests at 1 foot). Stopped down it's ridiculously good.


If Canon says it's not normal, I'm just going to send it in. I think it will be faster than doing the whole return thing, and at least it will get checked out, assuming they do their job, which they usually do [:P]

I know that we all want to regard the 24-70 as unreservedly awesome, but I was wondering if I could get some feedback.


I'm pending answers from Canon and Adorama, but given the copy I have, my impression would be impressed at sharpness, but pretty depressed with CA.


Here's a 100% crop on a 5D (not the highest pixel density)


http://i110.photobucket.com/albums/n...CA-NormSat.jpg


For the sake of illustration, here's the same image with the color saturation cranked up...


http://i110.photobucket.com/albums/n...CA-HighSat.jpg


Do other owners not have this problem? Think it's a bad copy, or am I just too picky?

I see these type of CA all the time with my 24-70L. I'm very sure that you're not along with this and it's not an issue of the lens. I also see the same type of CA on the Sigma 50/1.4 and my 85/1.8 lenses. I'm not sure about the theory behind it, If you see Bryan's review about the 85/1.2L II going through a focus calibration on the 1Ds III body here (go down the page until you find the section), the same type of CA occurs when the lens is not well in focus. I assume this is just an optical property, nothing serious to worry about.


As long as the CA does not appear at the point where the image is sharp on focus, I personally don't really care.

Interesting.


It may be, then, that the Chromatic Abberation issues arise moving out of focus. I noticed that in the focal plane, in the middle of the screw, there isn't any to speak of. If that's just the way it is, it is, and it's up to post-processing and stopping down to deal with it.

<span style="font-family: 'Arial','sans-serif'; color: black; font-size: 11pt;"]Areijnders,


<span style="font-family: 'Arial','sans-serif'; color: black; font-size: 11pt;"]I would photograph a bright white object outdoor that has sharp edges. Then if you have excessive CA I could compare it to similar images that I have taken. By the way, the 24-70'sCA is at is worse at 24mm and the aperture does noteffect the amount of CA on this lens.<o:p></o:p>

If it is by design, I guess the follow up question is, why? The 28-135 posted above does better in this regard, at the same apertures and focal length, both for full-frame use. I wonder how my 24-105 would compare. I'll try it when I get it back from a friend who 'forgot' to take it off his camera... Though I now have my 28-135mm back to try the same test with...

I did a comparison at 70mm between the 28-135 and the 24-70mm. The widest the 28-135 would go at 70mm was f/5, so I used it for both. Didn't see any CA in either, but the 24-70 was significantly sharper.

So, the saga continues...


At this point, the question is, "Is the 24-105 lens actually superior to the 24-70 when it comes to chromatic aberration beyond the focal plane, or did I (and a few others) just get bad copies of the 24-70?"


http://i110.photobucket.com/albums/n...mmF4_24-70.jpg


Now, I realize that this isn't an exact duplicate, as the natural lighting changed a little and I didn't hold the paperclip exactly the same, but I think the results are still valid, particularly since I tried this several times and got similar results on each...


http://i110.photobucket.com/albums/n...mF4_24-105.jpg


Both at f/4, both at 70mm focal length.


I'm wondering if Canon is going to give me an excuse, admit to the particular design shortcoming of the 24-70, or actually step up and fix the damn thing.

Quote:

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Originally Posted by Colin

For the sake of illustration, here's the same image with the color saturation cranked up...

---

Wow, really stripped that screw! Better get that fixed [H]

Yeah... If I ever need to remove that screw, it'll probably require a drill..


I can't complain about the detail...


I wonder if it's one of those design choices.. Something about allowing more chromatic aberration as you move out of focus lets you really nail what's in focus, or does something for the bokeh, or whatever....


Stupid real world. If the CA I'm seeing is just inherent to the lens, that doesn't make it a deal breaker. It's so fantastic in other ways. But, if i can NOT have the CA that I'm noticing, that'd be MUCH better. However, if it's inherent, it's one more reason to keep the 24-105 around.