Any idea of what could be wrong?

I just did a shoot (it wasn't for her, it was for my project thank goodness) and realized that an entire section of it was oof. I had the focus point right between her eyes. But it was obvious looking at the pictures that it was focusing in a very different spot. I had like 10 pictures in the same spot, and they were all like this. I'm out of ideas of what it could be. I was using my 50D, 50mm 1.8, and 580EX flash.

Here is the original SOC

What AF mode were you using and did the focus point you have on her eyes flash red when you pressed the shutter release?

Did you focus and recompose the shots?

That photo was taken at f1.8 (wide open) with a rather cheap lens that has a reputation for average to fair auto focus abilities. It appears to be focusing behind the point in which you tried to focus on, which is called "back focusing".

Alright it was my first time using a flash, so I'm not sure exactly how to answer the questions. I'm fairly new to this. But I've never ever had focus issues. I was in M mode, and had the focus point right in between her nose. I didn't move the camera or anything. Could it be something I did wrong, or was it the lens? I'm trying to learn.

That's why we're asking the questions; so we can get the info to (hopefully) help you.

Do you have AF set to use a single AF point? Or for the camera to choose from all available points?

Were you using One Shot AF mode or AI Servo? Also, did you get the litte, red focus confirmation flash of the AF point when you pressed the shutter button half-way down?

Maybe there wasn't enough contrast on her nose for the outer point. I've had that issue on my 5D, though I'd expect a 50D to do better since it has cross-type outer points...

You should be focusing on the closest eye, btw, not in between.

HappySnapper90 wrote in post #10123197
That photo was taken at f1.8 (wide open) with a rather cheap lens that has a reputation for average to fair auto focus abilities. It appears to be focusing behind the point in which you tried to focus on, which is called "back focusing".

The 50/1.8 has perfectly fine focusing abilities in good light. The only thing people dispute is its ability to focus in poor light.

Snydremark wrote in post #10123363
That's why we're asking the questions; so we can get the info to (hopefully) help you.

Do you have AF set to use a single AF point? Or for the camera to choose from all available points?

Were you using One Shot AF mode or AI Servo? Also, did you get the litte, red focus confirmation flash of the AF point when you pressed the shutter button half-way down?

Alrighty, thanks!

I had it set to the single AF point. I had it on AI Focus, just what it was default set to.

And yes, I did get the confirmation flash when i pressed it half way down. I shoot constantly, actually shot that morning with the same equipment and settings, and had no focus problems. I'm looking through the set right now, and all but like 5 had a complete missed focus. Some I can't find any spots where it is focused at all. And I was only at f/1.8 for the few pictures like the one I showed you here.

I hope that answered correctly what you were asking.

Nope, you answered exactly what I was looking for; thanks

So, I see two possible things. One could be that AI Focus tends to be a pretty inconsistent AF mode; if your stance/grip wasn't totally steady, the system could have switched over to Servo, inadvertently, as you were taking the shot and re-focused "for" you. This would account for the inconsistent results you're seeing there.

I would suggest changing that to Single Shot or AI Servo if you're shooting a mobile subject.

Aside from that, I'd have to third the other posters that mentioned front focusing issues; but, I'm still a little leery of that since it isn't an issue in ALL of the shots you took with the lens.

Alright thanks for your help!! I'll try the other modes and see if it helps. I'll look into getting the lens fixed if that doesn't help and the settings persist.

One other previously mentioned possibility could be that there wasn't enough contrast at the point of focus; this SHOULDN'T have allowed the focus confirmation beep/flash if that were the case, but that doesn't mean it isn't possible

Definitely work on the potential user issues before spending time/money on getting a fix.

The Nifty is a great little lens, especially for its cost. Good luck in resolving this

+1 on not using AI focus for portraits. In fact only use AI focus if you arent bothered about focussing at all. It has a reputation for inconsistency in results due to selecting the wrong mode for a particular image.

Pick your focus mode dependant on what you are shooting. Movement = AI Servo, Stills= One Shot. AI Focus= nothing.

Have you set focus confirmation off? It has focused but a mile from where you say you had selected. Did you move after focussing?

Other than that, try a different lens to see if the problem is replicated. If it is, then its not the lens.

kalahmarie wrote in post #10123438
I had it set to the single AF point. I had it on AI Focus, just what it was default set to.

I didn't think ai-focus mode allowed you to use just one focus point. I thought ai-focus always used all AF points and it will continually adjust focus. Get out of ai-focus mode. It essentially is the AF mode for full-auto mode.

Use single-shot and use only the center AF point. You'll do even better if you separate the shutter button from auto focusing. Use the custom functions to assign focusing to the * button so that you don't have to hold down the shutter button halfway after it focuses.