Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Canon Lenses

Reply
 
Thread Tools Search this Thread
Old Feb 26, 2007, 5:54 PM   #1
Senior Member
 
Join Date: Nov 2004
Posts: 185
Default

Hi Everyone,

I just got a Sigma 70-200 F/2.8 EX APO HSM second hand.The lens is fine and of good quality and seems to have had very little use.I'm generally happy with the lens so far, but out of curiosity i did a few tests and found a few back focus issues.

I placed the camera on a tripod, and a tape measure about 2m away at around 45 degrees angle.

I'm focusing the lens on a point between 28 and 29 inches. its marked red and its 2-5. I've done this with manual focus and also single shot focus using the center point.

I used a usb cable and a remote capture software to eliminate any movement/ errors on my part.I ran the tests at F/2.8 F/4 and F/5.6.

Camera settings are :

Image6 - 1/60s F/2.8 ISO-400

Image7 - 1/30s F/4 ISO-400

Image8 - 1/15s F/5.6 ISO-400

Should i be sending the lens to Sigma for alignment or the Camera?


Attached Images
 
gaida is offline   Reply With Quote
Sponsored Links
Old Feb 26, 2007, 5:55 PM   #2
Senior Member
 
Join Date: Nov 2004
Posts: 185
Default

Image7 1/30s F/4 ISO-400
Attached Images
 
gaida is offline   Reply With Quote
Old Feb 26, 2007, 5:55 PM   #3
Senior Member
 
Join Date: Nov 2004
Posts: 185
Default

Image8 1/15s F/5.6 ISO-400
Attached Images
 
gaida is offline   Reply With Quote
Old Feb 26, 2007, 6:01 PM   #4
Senior Member
 
Join Date: Nov 2004
Posts: 185
Default

I also tested my Sigma 70-300 F4-5.6 APO at 214mm at F/5.6 1/15s ISO-400 using the same setup.
That also seems to have a little bit of a back focus, maybe its the camera?Its a Canon EOS 300D


Focus is on 2-6 this time
Attached Images
 
gaida is offline   Reply With Quote
Old Feb 26, 2007, 6:25 PM   #5
Senior Member
 
Join Date: Nov 2004
Posts: 185
Default

I'm begining to think that its my camera doing the backfocus, i've just tested the Canon EOS 50mm F/1.8 at 1.8 , 2,8 , 4 and 5.6 with similar results.

Focus is on the red 2-5 between 28 and 29


Attached Images
 
gaida is offline   Reply With Quote
Old Feb 26, 2007, 10:53 PM   #6
NHL
Senior Member
 
NHL's Avatar
 
Join Date: Jun 2002
Location: 39.18776, -77.311353333333
Posts: 11,547
Default

There's no adjustment on the lens!
-> It's usually the camera (especially with 3 lenses) and there's a screw in the 'film' chamber to realign the rear mirror down to the AF points underneath: http://www.stevesforums.com/forums/v...mp;forum_id=65

Some camera like my MrkII has two screws to also adjust the 'manual' focus up to the viewfinder :idea:
NHL is offline   Reply With Quote
Old Feb 27, 2007, 3:15 AM   #7
Senior Member
 
Join Date: Nov 2004
Posts: 185
Default

Thanks NHL,

I did read that post some time ago, i don't know why i forgot about it.
gaida is offline   Reply With Quote
Old Feb 27, 2007, 12:01 PM   #8
Senior Member
 
pagerboy's Avatar
 
Join Date: Feb 2005
Location: Canada
Posts: 483
Default

I would ask the store how much to align the focus. If not I've seen alot of sites that explain how to do it, not too easy but not that hard.



http://photo.net/learn/focustest/

http://www.bord-studio.com/article_01eng.php



Took me awhile to find those. I know there are more but that should help.

pagerboy is offline   Reply With Quote
Old Feb 28, 2007, 7:00 PM   #9
Senior Member
 
Join Date: Nov 2004
Posts: 185
Default

Pagerboy thanks a lot for the links.I've ordered a set of Hex keys and will be adjusting the focus on saturday.
Will post the results



Nick
gaida is offline   Reply With Quote
Old Mar 10, 2007, 12:16 AM   #10
Senior Member
 
Join Date: Nov 2004
Posts: 185
Default

well i've solved my problem by getting a 30D

I'm also getting the Sigma 10-20.The question on my mind is do i get the Sigma 18-50 F/2.8 or do i get the Sigma 17-70 F/2.8-F/4.

I've found a little software that looks at your photos and shows you what focal lenghts you use for yours shots. I had the 18-55 70-300 and most of my shots were either at 18 (covered by the 10-20) or at 55. There were quite a few taken at 70mm too, but thats because i coudn't be bothered to put he 18-55 on.

I believe the 18-50 is a better lens, anyone have an opinion on that matter?



Nick
gaida is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 3:15 PM.