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I have a lot of experience doing travel, landscape, product, ... in short, things that don't move much. Models? Not so much. I have a beautiful 85mm portrait lens for my Canon 1Ds Mk III DSLR, and at f/6.3, I have a fairly high miss rate with auto-focus. By "miss" I mean the focus point was not the eyes, which I prefer to have in focus.

Models, as we know, don't stand still, so what is a typical reject rate because of focus? Should I feel bad if 20% of my images are focused on the nose? 30%? How do you deal with this?

Clarification: 80% in focus 20% focused on the wrong place.

Steve Ross
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    Would you be willing to post some examples of acceptable and non-acceptable images? I'm an amateur, and I'm curious as to what exactly counts as "non-acceptable" images. In my mind I'm thinking "is it really that much difference between the nose and the eyes? Would people even notice when printed in a magazine or blown-up on a billboard?" Thanks – rabbid May 23 '11 at 01:38
  • Sure. Here's a Dropbox gallery: http://www.dropbox.com/gallery/2316249/1/Stack?h=b2c17b. The left eye image is sharp. The right eye one, focus is on the hair. Yes, it's that much difference, especially when you consider that the pattern of the iris is a big part of what makes eyes so interesting. – Steve Ross May 23 '11 at 19:55

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No, that's not a good in-focus rate, but would be a good keeper rate (IMHO). Some things to check:

  • Make sure you are telling your camera which exact focus point to use. You want to select a focus point on their eyes, and not let the camera choose out of many focus points. Keep that point on the model's eyes and continuously focus as you shoot.
    • Typically, a camera will pick the closest near center object to focus on if you don't tell it which one to use.
    • Focus and recompose will change the plane of focus as you rotate. This can be noticeable at close distances and narrow depths of field.
  • Check for front or back focusing with your lens + body combination and lighting conditions. See this question.
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eruditass
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  • Checked my 24-105 and it's focusing properly. Checked my 85mm prime and it appears to be correct as well. Maybe my model is standing more still today than a couple of weeks ago. – Steve Ross May 22 '11 at 18:36
  • Make sure you aren't moving either :) http://photo.stackexchange.com/questions/7986/should-auto-focus-need-adjusting/8009#8009 – AngerClown May 22 '11 at 19:35
  • Great point, AngerClown. After I posted this, I set up lights and shot a couple of dozen images of a model (well, actually I badgered my wife to model). I do focus/recompose and the 85mm f/1.2 is a tricky lens to use. Of the test images, none were out of focus. Perhaps I'm just more aware of it now so I'm on guard. This model was very well behaved, but typically, models are all over the place on set. I can handle it with a 24-70 or 24-105 but I was losing perfect focus on about 5% more shots than normal, which prompted the original post. – Steve Ross May 23 '11 at 00:15
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    If you are trying to focus/recompose at f1.2 you're probably running into a depth of field issue. You're only going to have a razor thin focus plane and recomposing is only going to stay focused on what you actually want by luck. – Rob McCready May 23 '11 at 03:50
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Depends on the camera, technique, and situation.

If the situation is badly lit, the keeper rate is less, but with a camera that can focus better in low light, keep rate would increase.

For models who cant stand still, you need a camera with a more reliable and faster AF. Sometimes Focus and Recompose technique often employed for center focus point will not do on a moving model. You cannot rely on center focus point for reliable focus all the time.

Polishing your technique, which comes with countless hours of practice, would help you achieve your desired goals. Maybe learning from Sports Shooters would help you.

ben
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