Focus help for shallowDOF portraits of kids

I'm trying to improve my shooting. I have been using outdoor, cloudy/indirect lighting, center (or selected) point AI/Servo autofocus; shooting at f/2.8-f/4. Shooting fast moving kids I can't imagine being able to properly manually focus.

My problem is that despite my carefully making sure the focus point is exactly on the eyes, the camera only seems to properly focus on the eyes about 1/3 of the time, the rest of the time it seems to catch their hair/shoulders/somethi​ng else and their eyes/face is softer & OOF.

I am using the XTi/400D and Tamron17-50 lens. I had the same problem when I used my kit 18-55 lens as well. For older kids I can perhaps freeze them long enough to manually focus, but what can I do to help toddler shots? Do you think it is user error, or more likely a body or lens issue?

Servo focus on the 5D and XXD cameras is worse than on the 1D, and the Rebels are a step down from the XXDs. I found that my old Rebel XT was not reliable in shallow DOF situations (like closer than 15 feet and faster than f/2.8 ) with some lenses.

I'd also point out that the Tamron lens has a pretty slow AF too. Not in the same league as anything with a ring USM motor.

Try posting some examples, but the kicker is usually if the AF is dead on for static targets but misses on moving that it is simply not keeping up. That usually results in just slightly OOF subjects.

You shooting in AI Servo mode? That might help if you aren't.

Thanks for explaining that, Jeffrey. As much as I hate to think about needing to upgrade, if it made me get even 1/3 better keepers I think it would be worth it ten times over. If Servo mode isn't up to par on the rebel series, should I choose another mode or they would be equally inefficient?

I am really considering getting the 40D-I have a relative who may want to buy my XTi so it would lessen the cost. Do you think that should make a noticeable difference in focus ability? I don't think I'm going to be able to afford the Canon17-55mm for awhile, I need to prioritize a good telephoto zoom for sports first.

You may be onto something about it just not keeping up-but I noticed a few shots where they really weren't moving, and it focused on the hat/forehead instead. Let me see if I can dig one up to show you what I am experiencing.

c71clark wrote in post #5590700
You shooting in AI Servo mode? That might help if you aren't.

I almost always shoot in Servo. I tried switching to the others to see if that would help-it didn't-so I switched back. Thanks for the suggestion though.

I'm going to go out on a limb and say that from my own experience, I'd have to place blame on the Tamron 17-50 way before I'd place it on the XTi. I can say this because I do own one as my primary everyday lens.

When I still had my XTi, I rented the Canon 17-55 f2.8IS and had a much better keeper rate than with my 40D and Tamron 17-50. In this case I think it's just the consequence of shaving $500 off the price of the lens. The Tamron 17-50 just can't do what the Canon 17-55 can do.

When I switch to my Canon 50mm 1.4, I get a keeper rate that is much closer to the Canon 17-55, but I don't use it as my primary because I really miss the wide end. It's a trade off. I've been working more on adding a bit of fill flash -- it really helps get the eyes sharper.

I am not sure how much longer I'll hold out with the Tamron, which is really a very excellent lens for the money. It just has some limitations that are understandable given the price. It does a great job with my 5 year old because he's willing to pause even briefly, but not for the 2 year old... at all.

Sorry, I ended up crashing last night. I hope it really isn't all the lens, b/c I just wasted some $ I should have saved for the upgrade if that is the case. Here are two examples. In both, somehow it seemed to focus on his clothing, but I had the eye exactly centered in the AF point, taking up the entire AF point in my viewfinder, and I know it wasn't because he was moving b/c the pictures immediately before and after had him in the same spot.

It isn't horribly obvious, but his face/eyes/eyelashes are just soft. Ick.

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Oh, no sharpness or PP done to these. I think I may have adjusted the exposure .17 of a stop in DPP, and resized and converted to jpeg, if it makes any difference. In the full size version, you can see the detail in the clothing threads nicely sharp, but the face (where focus should have been) without crisp detail.

The xti is suppose to have the same focus system as the 20/30d cameras. I would definately be looking at the lens in your situation. If you are considering a 40d why not look at a 450d?
Lets be honest, SLR cameras and cheaper lenses don't mix as well as one would like. This is a fact that those of us who are on a budget have to live with.

If I were you I would consider a Canon 50mm 1.8 to see how things works out? I would suggest a 17-70 but not sure of it's performance compared to the tAmron and besides I have a 350d which is worse than the XTi!

Before you spend money on a new lens or camera I would suggest eliminating some other possibilities.

Your symptoms sound very similar to a friend of mine. He has a 400D with an expensive L lens and was having similar issues. It was only after a year of blaming himself for poor technique that he read about back focusing. He found that some cameras suffer from back focus problems where they focus slightly behind (or in front of) the target. He tried a focus test - see http://photo.net/learn​/focustest/ for an example and discovered that his camera / lens combination was focusing about an inch behind the target at the closest focusing distance which was enough to make the eye soft and fur or feathers further back on the head sharp with his bird and wildlife photography. He sent his camera and lens to canon for a simple recalibration and it is amazing what a difference it has made. All his images are now fantastically sharp exactly where he wants them to be. We did a lot of research on the subject of back-focusing at the time so if you want more information just shout.

ashleynaugust wrote in post #5594443
Oh, no sharpness or PP done to these. I think I may have adjusted the exposure .17 of a stop in DPP, and resized and converted to jpeg, if it makes any difference. In the full size version, you can see the detail in the clothing threads nicely sharp, but the face (where focus should have been) without crisp detail.

If you're shooting raw and not sharpening at all you will get soft results. The raw file is soft because the AA filter deliberately blurs the image. Try setting sharpening to 3 in DPP and you should see a substantial improvement. 3 is my default sharpening amount in DPP. It is very rare that I use less than 3. If a photo is OOF I may need to bump things up to maybe 5-6. If I feel the need to go beyond 6 I figure the photo is junk.

That first image looks like back focusing to me, especially if the FP was on his eye. I don't know if it's just me but the wood behind the boys head look sharper.

If it was me, I would print off copies of this and send the lot to Canon for calibration.

Perhaps a silly question - what focal points are you using?

[SIZE=2]I have photographed kids allot for a couple of my clients that have services directly related to children. These shots wind up in annual reports, brochures and other type print and wed media supporting their services. Shooting with shallow DoF is kinda my style. I live in the world between 1.2-4 and I have an 851.2mkI. The slow focuser .

OK OK I'll get to my point. When I photograph these kids its usually as they are in their world in fast moving situations and I shoot with three lenses, all prime, all fast, 24L, 35L and 85L.

If theres not a problem with body focus on your camera or a lens issue my advice is get comfortable with your gear. Most of the problems with focus are usually a problem of not knowing how to get the best out of your stuff that you have . You need to spend allot of time shooting wide open or near it to get good at it. Theres no book or easy way to get you there. Good glass is only part of the answer.

So to rap it all up I can get good consistent shallow DoF from fast moving kids without allot of FPS and a so called slow focusing lens because I've spent allot of time with my gear and I know how to use it to get the images I need. My advice is spend hours a day with you equipment and if your not having an equipment problem you will learn to get the kind of shots you desire. You will learn where to be because you've done it so much it becomes second nature Focus and exposure will also be second nature.

adamlc wrote in post #5597750
That first image looks like back focusing to me, especially if the FP was on his eye. I don't know if it's just me but the wood behind the boys head look sharper.

If it was me, I would print off copies of this and send the lot to Canon for calibration.

I suspect you would get a more helpful response by sending the lot to Tamron?