40D backfocusing

<p>I was doing a wedding yesterday and my camera was driving me nuts. It all started when we moved from the outside to take pictures inside of the castle where they had their ceremony at the chapel. <br>

I couldnt take a properly focused picture. I kept on focusing on the couple - pressed half way shooter and took a picture (without moving the camera and recomposing). All pictures were back focused on the back wall, on t he camera, focused to infinity. I tried manual focusing and wasnt getting any better results. Ceremony took an hour and I dont have any good pictures. I swapped my 16-35 to 70-200, but the distance was too long.<br>

After the ceremony I was getting the same results outside. I called my friend telling him about this problem and then I reset all custom functions on the 40D. Then when I locked AF I pressed the AF-ON button on the back, recomposed and took picture.<br>

Finally, I could take properly focused pictures. But my mood was down and I was pretty disappointed. <br>

It is weird, as I used the camera last week and I havent changed any settings.<br>

Any ideas what went wrong?</p>

<p>Also, I had a back up body, that I didnt use, but I know I should have!</p>

 

<p>My 40D backfocuses pretty badly with my 70-200. It does particularly if the main subject doesn't fill a big portion of the frame. It works much better when I use it when my 300mm lens.<br>

I however don't use it for weddings, I still use my 20d and 30d because I like to color much better. </p>

<p>Could be several things.</p>

<p>I'd first check to make sure you are using One Shot focusing. If not, AI Focus will interpret any camera movement as subject motion and usually focus on whatever moves or is contrastiest in the background, and AI Servo will do the same, PLUS you don't get focus assist from your flash at all.</p>

<p>Otherwise, realize that the focus points are actually bigger than what is marked on the viewfinder screen, so keep the focus points toward the inner parts of the subjects or it could get 'snagged' on the background if you try to focus on a subject edge. Also, wider focal lengths are always harder to focus correctly.</p>

<p>Nadine, indeed, Single shot, one frame.</p>

 

Were you using a flash? Sometimes the camera cannot focus if it's too dark, it hunts for the subject without success. A flash uses infrared, I think it's infrared, it's a red beam, that zero's in on the subject. It assists the camera regarding focusing.

<p>Bob, yes I had a flash on, tried everything, with diffuser on and off, nothing worked I think my AF in custom functions was set incorrectly.<br>

Also, I should have used my other body - I used that for taking some pix when I went to see the location beforehand and I took nice pix, sharp, nice light...</p>

<p>So what AF custom function was set, then and now? And by "single shot, one frame", you mean One Shot, which is different from the Drive Mode, right?</p>

<p>The default, by the way, is that focus is performed on the half press of the shutter, but the AF button also works.</p>

MM, is the camera working correctly now that you've changed the custom setting? I'm interested in your findings, because this can happen to any of us and perhaps you can let us know exactly what happened. Needless to say it could be something to keep in the back of our brains regarding the cause and the fix.

 

I actually carry the camera and flash manuals wherever I go. Usually with my cameras, I use the 1DsMk3's, when I'm totally messed up I'll a camera reset that puts the camera back to the factory default settings.

<p> </p>

<p>Nadine, yes One shot, not continuous...<br>

Bob, I will check today on the conditions of the AF, but I think is fine now. <br>

I guess that camera got tired :) also, when you suggested flash infrared in dark places, I had an external battery pack mounted from the bottom of my body and had a cable plugged in m y flash. The cord was wrapped around the bottom of the flash and possible could be in the way of the infra assist from the flash, but Im not 100 percent positive on this) also something similar happened last week, my camera didnt focus correctly here and there. <br>

And good point, we should all learn, I guess that using an alternative body on the job site can save ur ass. Otherwise, delete custom settings, reset to factory default and start from the scratch. <br>

I packed my manual today as well, more info tomorrow. </p>

 

<p>You mosly likely changed a setting inadvertently. It sounds like that was the cause since you reset all settings and it started to work properly.</p>

<p>Sorry for your troubles, lesson learned hopefully.</p>

<p>MM--David W. has a good point. Seems like user error--either setting got changed or use of AF was faulty.</p>

<p>Re-reading your description, I am thinking it is the fact that the focus points are so large on a cropped sensor camera. When photographing a scene in which the subjects are small, surrounded by a large area of higher contrast (than the subjects), the 'snagging' problem I described above may surface, particularly if in dim light, since the camera 'gives up' too easily and wants to go for the contrastiest thing.</p>

<p>However, one question--do you use the AF button at all in your autofocusing?</p>

<p>Im sending a sample shot, just checked again, some images are ok to be given to the client, also when I noticed that the camera is actiong up I shot about 20 shots to RAW, will see what I can get out of them.<br>

I use to use teh AF button on MK2 I had before and havent been using it on my 40D. However, after the ceremony, I kept on using the AF button.. any other ideas?</p>

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<p>In that picture, what did you put the focus point on?</p>

<p>On the groom</p>

<p>Then I'd guess that maybe your focus assist wasn't working right or the focus point was trying to deal with a black, smooth surface, gave up and backfocused, which is what Canon lenses do when they can't lock on.</p>

Based on the image you presented, the photo is very much in focus. Your exposure looks dead on as well. The church doesn't look that dark, so your camera should have focused properly. Weird...

<p>Bob yes, something is in the focus, shot on F8.0, to me, the sharpest and most person is focus is that statue in the background :( </p>