24-105 back focus

[tarwoona]

Hi everyone,

Have just lashed out on a 24-105 for my 50D and found the pictures weren't as sharp as i expected or would have liked.
So i've tried to adjust the mirco focus adjustment and find that that even at -20 i cant quite get it right.
Does anyone know if this is common for this lens as i think i've read that backfocus can be an issue.

Anyway, i should get it right. Does anyone know the proceedure for getting it checked out/calibrated by Canon. Do i need to send both the lens and camera to them or just the lens? How long does it take?

Also it is a 'true' Aussie lens from a shop, but came out of a 5D kit. Should this matter.

Thanks in advance.

Cheers,
Steve

[Tricky]

Steve

I haven't heard of the 24-105 suffering back focus issues. In any case, it shouldn't do it full stop, so definitely do something about it. Firstly, I'd take it back to the shop where you bought it. If none of your other lenses back focus, then it is likely the lens, not your body. Get the shop you bought it from to hook it up to one of their own cameras - they should be able to see the same problem. I'd be asking for a new one, as the one they sold you was defective and not 'fit for purpose' under Sale of Goods Act.

One way to show the back focus issue very clearly is to mount the camera/lens on a tripod, then use live view to focus on a stationary object. Then switch off live view and re-focus using the autofocus system. If the focus ring moves a tiny bit, then the lens is back/front focusing.

If the shop can't help, then you can take the lens to Canon for calibration. I've never done this, but I hear they like to see the body and all lenses together, so that they can ensure the calibration is correct for all (otherwise they might 'tune' the body for the 24-105, throwing it 'out' for all your other lenses).

There's a Sydney head office service centre and a branch in Victoria:

Canon - Sydney Branch OfficeAddress:
1 Thomas Holt Drive
Suburb: North Ryde
Postcode: 2000
State: NSW
Phone: 13 13 83
Fax: 02 9888 3314

Canon - Victorian Branch OfficeAddress:
Building 1, Unipark 195 Wellington Road
Suburb: CLAYTON
Postcode: 3168
State: VIC
Phone: 13 23 53
Fax: 03 8585 8444

[tarwoona]

Thanks so much Tricky

[adilucca]

I was recently worried about whether I needed to do some micro-adjustment for my L-series lenses. I did the following to confirm the lenses were fine - it was my technique that needed the adjustment (not saying you have the same issue):
1. downloaded a good test pattern from the web and printed versions with a big -15, -10, -7, -5, -2, 0, +2, +5, +7, +10 and +15 overlaid on them. This was to ensure that when I inspected the images I could tell the micro-adjust setting at the time;
2. set camera on a tripod at least 50x the focal length of the lens away from the test images;
3. set the camera to -15 micro-adjust and pointed it at the image with the -15 overlaid on it;
4. turned on mirror lockup and turned off IS on the lens;
5. connected my remote shutter release;
6. manually focussed the lens to infinity;
7. using the remote shutter release, took a photo;
8. repeated steps 6-7 twice more;
9. repeated steps 6-8 for each micro-adjustment after I changed the test pattern with the appropriate number overlaid on it;
10. did some pixel peeping at 100% to determine which setting gave the best image - that's where the test pattern helps.

If there was anything radically wrong- say over +/-10, I would have taken it to Canon for re-calibration.

Hope that helps.


Cheers
Alan

[Gollum]

If you want to do it yourself, here is a tool that will help. It will cost you about $100AUD and take 3-4weeks. There are also a number of links on this site to videos that show how others have used this tool.

http://mtapesdesign.com/

IMHO this is something that all serious camera owners will have to learn to do in the future.

Hope this helps