It seems that there is often a lot of unnecessary confusion when members have concerns about the performance of a camera or lens. This can lead to long threads with often (but by no means always) inappropriate questions about possible user error.
In another thread I thought it would be helpful to have a relatively simple set of steps for members to follow when this arises to allow faster troubleshooting of their problem and to avoid either making simple mistakes or being improperly accused of making them. CyberDyneSystems asked me to write a draft sticky..so here it goesPlease consider this a draft initially and we can hopefully make it a sticky once it has been finalized. Comments and suggestions are welcomed. I don’t consider myself a focus expert by any means but do know something about taking a logical and scientific approach to diagnosing problems.
This thread and it's suggestions were written primarily about focus issues, however please note that most of the suggestions regarding how to go about framing your questions, and what information to include when posting sample images will pertain to any issues you may be having.
If you suspect a focus problem
1. Please post some sample shots that show the problem, with Exif information intact or included. Linking to full sized images is useful
a. This post has useful information on how to do so. This site http://www.mediafire.com/ and others will allow free image hosting for samples.
b. You can use Zoombrowser to show the active focus points for a shot, then take a screencapture and upload that image to show others where the focus points were. You can use various tools for this including free Screenhunter to do so.
2. Verify the camera/lens can in fact focus under good conditions first.
a. Take test shots in good light, outdoor shots at decent minimum distance preferred, for most lenses it is a good idea to conduct focus testing at 50x the focal length or more. At the very least, people should try to focus test lenses at ranges that they plan to use the lens at. One of the biggest problems with the 8x10 piece of paper focus test chart is that it encourages people to do focus testing near the MFD for most lenses. Bad idea.
b. Verify adequate shutter speed – suggest a minimum of 1/(2 times focal length) for troubleshooting, to keep it simple use 1/1000 or faster, or use a tripod/stationary camera with remote release or self timer
c. Use a reasonable depth of field (online DOF calculator http://www.dofmaster.com/dofjs.html ). Really large apertures with tiny depth of field can easily lead to misfocus even with a perfect camera, though avoid testing with really small apertures as depth of field can be large enough to hide focus errors.
d. Verify the lens switch is set to AF not MF, IS is off if shooting on tripode. For testing use center point focus with a central object, avoid recomposing. Use One Shot focus mode at least initially to verify camera can focus and to reveal focus point selection red square.
f. If AF seems to be causing problems try manual focus, Live View is easiest for this if your camera has it. Verify you can focus sharply in manual.
g. If it's the camera that is in question verify the problem with a second lens if possible, if the lens is the question try a different camera if you can.
h. If with the above there seems to be consistent problems there may be front or back focusing, testing for this is well described here, member Teamspeed has a free lens adjustment tool to aid focus adjustment, described and available here
3. If the issue is with focus on moving targets
a. It’s helpful to link to a series of shots and to list the custom function settings for the camera. This can be seen in EXIF with Zoombrowser by right-clicking on image (Windows) and selecting “properties”
b. There’s very good information on the Canon Learning site herewith specific information for many models , the videos on the 7D focus system are very good (here) as are those at BH - click http://www.video.bhphotovideo.com/ and search for 7D.
c. Try to describe the problem in a way that others with the same gear can test for themselves to help.
d. Consider shooting some semi-reproducible motion targets e.g. oncoming cars, a friend or family member on a bicycle, etc. if tracking is the issue.
e. For more specific problems limited to certain scenarios it is often helpful to ask in the forum relevant to that topic e.g. Bird Talk, Macro Talk, Motorsports Talk etc.
f. As always searching the forum to see if others have had or solved similar problems can be very helpful.
I hope this is useful.Please add comments or suggestions and we can maybe have this made into a sticky.
Suggestions for replying to focus threads:
- Please be courteous in responses and respect the rules of the forum. Direct users to this sticky.
- Take a moment before assuming user error and be careful with your language even if you do suspect it. Have a look at the poster's other posts, website or gallery if applicable to get a sense of their expertise before making judgmental statements or asking questions that may be seen to be insulting. While anyone can be wrong it is clearly different to ask some things of a novice versus people who obviously have proven photographic skills.
- Helpful to state if you have similar equipment and to post your settings and/or your examples with EXIF if you believe it will help.
- Although threads may get long please make an effort to read through the prior answers so issues already answered don't need to be rehashed.