5d & 50 mm 1.8 auto focus problems

bethany138 · Jun 13, 2006

Hi,

Just wanted to check with you guys about the 50 mm 1.8 used on a 5d. I have problems getting it to autofocus. Is this common? I find that there is a "sweet spot" when it comes to distance from the subject where it will actually focus. OR.. I will get the focus I want..then the camera won't take the shot.

If I switch to manual focus I have no problems, but I just wanted to make sure that there is nothing wrong with the lens.

Thanks!

b

Big Mike · Jun 13, 2006

Is there anything flashing when you can't take the photo? In some modes, the camera might not fire the shutter if it can't get the settings it wants.

The AF should work well with that combination. The 50 1.8 is not especially fast but the wide aperture should allow the 5D to find focus well. Sometimes you need to have the focus sensor over something that is contrasty.

Your "sweet spot" is not the minimum focus distance, is it? The lens won't focus on anything that is closer than that....but I think that lens is fairly close (less than a foot)...so I doubt that is your problem.

bethany138 · Jun 13, 2006

Big Mike said:
Is there anything flashing when you can't take the photo? In some modes, the camera might not fire the shutter if it can't get the settings it wants.

The AF should work well with that combination. The 50 1.8 is not especially fast but the wide aperture should allow the 5D to find focus well. Sometimes you need to have the focus sensor over something that is contrasty.

Your "sweet spot" is not the minimum focus distance, is it? The lens won't focus on anything that is closer than that....but I think that lens is fairly close (less than a foot)...so I doubt that is your problem.

Umm... I don't have the manual on me.. and i'm learning the terminology for Canon - but inside the viewfinder... the focus light (i think..green light on right) is flashing. I figured that was why it wasn't fireing..but it was set to manual... The "sweet spot" is probably at least 3 feet from the subject...any closer and it won't fire. How do I know where the focus sensor is?

Thanks!

b

Big Mike · Jun 13, 2006

By focus sensor...I mean the area in the view finder where the little [ ] boxes are. If your sensor areas are on a flat featureless subject (blank wall) then the focus will hunt.

Three feet seems a little far (but maybe this lens is different than my 50mm F1.8 mk I). It might just be that this lens won't focus any closer than three feet.

Digital Matt · Jun 13, 2006

The close focusing distance for that lens is 1.5 feet. It's not terribly close. If you are in manual mode, there shouldn't be any reason why it won't take a picture, unless your lens contacts are dirty, and you are getting an Error 99.

Maybe you weren't in manual mode, and you were trying to focus closer than you could.

bethany138 · Jun 13, 2006

Oh...those focus points.. yeah I know what that is...lol. I thought you meant something else. Maybe I was just too close. I don't think I was within 2 feet though. I will work with it some more to see if i can find a common problem. If I was in manual mode (almost always...so probably was).. would that override the camera so that it would shoot when I wanted it to (whether it was focused or not)?

b