20D Focusing or Flash Problem

[Chargers70]

I am not sure what the problem is, but I am having major issues with my 20D. I was photographing a Wedding today and I missed at least a dozen shots because my camera would hunt and not fire. It was not because of low lighting because I was in a fairly well lit area. The dot in the bottom right hand side of the viewfinder would just flash and the camera would not take a picture. If I switched it to manual focus it would take the picture though. Has anyone had this problem? Do you think it could be a flash problem? The reason I ask is my flash dropped the other day and I had to replace my hot shoe piece. It seemed to be testing fine though. The fact that the camera worked when I switched it to Manual focus though has me more concerned with the fact that it could be a problem with the camera itself. Has anyone at all had this happen to you? Your inputs are appreciated.

[PacAce]

What camera settings were you using? What lens?

Normally, if the camera can't lock focus and starts to hunt, it could mean that you are closer to the subject than the minimum focusing distance of the lens, or that the lighting is too low for focusing without a focus assist light, or that the target you were aiming at did not have enough contrast for automatic focusing.

The camera will fire whether you have focus or not if you put the lens in MF mode. And I don't think the flash will have any bearing on the focusing unless you are using it for AF assist and the led isn't emitting the AF pattern.

[scottbergerphoto]

Your camera for some reason was unable to lock focus in AF. This shouldn't be related to the flash if you were in a well lit area that didn't require the AF assist lamp of the flash. It could be the lens/camera connection. Did you try to remove and reattach the lens? Clean the contact? Have you tried a different lens? Have you tried Single Point vs. Auto Focus point selection?

[Chargers70]

It was not a focusing distance problem because I was a good 10 ft. away. I am not positive on the lens though. I know it was happening a lot with the Tamron 17-35because that is the primary lens I was using for all the pre-wedding photos. I don't remember having any problems with it during the actual ceremony and I was using my Tamron 28-75 then. Thank you I will have to check my lens and connections and see if that is it. I need to figure it out because I have another wedding coming up in two weeks and in small conversations with the mother of the bride I can already tell it will be an interesting one. The last thing I want is an equipment issue on top of it.

[scottbergerphoto]

When you start using a non Canon lens you add another possible confounding factor, camera lens incompatibility. Test your system with a Canon lens. If the Canon gear is OK, you are probably looking at a lens issue.

[robertwgross]

Also check your custom functions. Make sure that you have the autofocus assist beam enabled. That is the red pattern that comes from the flash unit.

---Bob Gross---

[Chargers70]

I double-checked and the flash assist is set. I am not sure what the deal is because I cannot get it to repeat the problem now. I even shut the light off in my room and tried focusing in there in extremely low light and it did fine. I fired a dozen straight shots and it didn't hesitate. Maybe there was something on the connection that was making the camera and lens have trouble interacting. I am going to have to set some time aside this week after work and do a lot of test shooting to make sure everything is in order before my next wedding. I am heading to San Diego next week for a Photo Seminar and to take some architecture photos for a friends business, so that will be a good test of the equipment too. I realize using none proprietary gear can add some problems but I have heard great things about these new tamron DI lens. I have gotten great results with them so far. Agreed maybe not quite "L" quality but the 28-75 is close. Making the move to Canon digital I just wasn't able to shell for the "L" glass right now. I knew I wanted the 70-200 2.8 IS, but I have to wait on the others. If I have another problem like this though there will be no waiting. I can't charge someone for a service and then have difficulties providing it.

[RJSorensen]

I find it is usually low contrast not low light. Find an edge, then recompose the shot . . . all will be well.

[scottbergerphoto]

I wasn't suggesting you buy L glass. I should have been more clear in my post. I meant to suggest that if you used the Canon lens you already have and there was no problem, then you had to look at incompatibility with that Tamron lens as a possibility.

[cc10d]

I suspect you have already found your problem but just in case, here is another thought. On some lenses, there is a switch to select what range the lens will autofocus over. It takes longer to run through the close range when shooting further away subjects and the selection allows us faster focusing when not using close range. The switch chooses full range or just the farther away range. Might check for that.

[Chargers70]

Yes the limiting switches are usually only placed on your long telephotos though. I was using wide and medium length lens. I am hopping that Scott's thought is correct and there was something inhibiting the contacts of the camera and lens and taking the lens off and messing with it has fixed the problem. I still haven't been able to make it repeat the problem so that is a good sign. I have photographed weddings, college basketball, arena football, and various other events without this problem ever happening before. Hopefully it is gone and I won't have to worry about it. Thanks for all the replies I appreciate the help. I will let you know if it holds up on my trip home next week.