How to cure Back Focusing (or is it just me?!)

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meatcandy89

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Ok so im still very novice in the photography, and as far as my research on the topic can conclude a lot of people get called for "blaming" their kit for back of front focusing.

However, of the over 2k pics ive been processing over the past day or two, ive noticed a very re-occuring theme, a vast number of the pics that have been shot at 2.8 (its been a dark weekend for sport) have been focused on the player behind the one ive been focusing on.

Now i know my technique may be off, but when there is 90% of one player in view, and the head of another popping over the shoulder, and the focus point has been pointing at the players chest, the other players head behind seems to be a lot more in focus. (just an example im looking at.)


Picture 197 by tomcon89, on Flickr

Its not the best example but theyve all been deleted!

Is there anyway to test if this is my equipment or it is my technique as its really annoying as loads of the shots ive taken have been a little too soft from this and have been thrown out.

I use a Nikon D300 and a Sigma EX DG HSM MACRO 70-200 2.8

Thanks for any help given and sorry if i have repeated any posts.
 
Assuming that it's not user-error, and that the camera is optimally set up, you need to do an AF check. Lots of threads on this, search against my user name.

That will tell you if the camera/lens is calibrated properly, but there is another component here - a moving subject. So if everything is working correctly but the camera/lens can't keep up, you need to check that separately. Just get someone to run towards you, in servo AF at f/2.8 and fire away. You'll be able to see exactly where the focus has landed on the grass/road.
 
Your subject is moving and at 2.8 the margin for DOF focus is minimal. Hence, a few mm movement either side of focused target (even with AI Servo) and presto... you're out of luck!... Try a smaller aperture for moving stuff!
**Edit**.. Sport photography at large telephoto apertures may seem easy for you guys but, The difference between amateurs and "Pros" is: we earn our living with this, we don't blame the equipment. We learn it's limitations and work around them"!!!.... hence the term "Pro"...
 
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IGADIZ said:
Your subject is moving and at 2.8 the margin for DOF focus is minimal. Hence, a few mm movement either side of focused target (even with AI Servo) and presto... you're out of luck!... Try a smaller aperture for moving stuff!
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All true, but a decent camera and lens, such as the OP's, shouldn't have much trouble with an easy subject like that.

I've got hundreds of similar shots, taken on a 5D2 that is allegedly poor at this stuff, the vast majority bang on. I've got the same too on a 5DMk3 that are 100% sharp, and that's at 50% faster frame rate.

5D3's AF is fantastic, but that's another story :D
 
IGADIZ said:
**Edit**.. Sport photography at large telephoto apertures may seem easy for you guys but, The difference between amateurs and "Pros" is: we earn our living with this, we don't blame the equipment. We learn it's limitations and work around them"!!!.... hence the term "Pro"...
Click to expand...


If you dont want to dish out advice helping others because you maybe feel threatened then just ignore it and move along.
 
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HoppyUK said:
All true, but a decent camera and lens, such as the OP's, shouldn't have much trouble with an easy subject like that.

I've got hundreds of similar shots, taken on a 5D2 that is allegedly poor at this stuff, the vast majority bang on. I've got the same too on a 5DMk3 that are 100% sharp, and that's at 50% faster frame rate.

5D3's AF is fantastic, but that's another story :D
Click to expand...

We don't know how dark it was. Exif for the image is not available so that quantity is unknown. At high shutter speeds your statements holds true but, in low light/low shutter speed large aperture conditions conditions, it is about knowing were to focus... so that your intended target is spot on!
 
Dexy101 said:
What a great reply from a so called "pro".

If you dont want to dish out advice helping others because you maybe feel threatened then just ignore it and move along.

Im glad i caught this quote before you decided to edit it. :thumbsdown:
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As you can see, I edited my somewhat flippant reply.. wine is at play here.. mr quick!!!
As for feeling threatened.. jog on Mr.... hahahaha you could not touch me with if you tried!! hahahaha ( yet again, flippant... this time with full intention)
 
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As you may have noticed thats happened to me in the past too and appologies for that.

Ill edit my quote to save you the blushes.
 
Dexy101 said:
As you may have noticed thats happened to me in the past too and appologies for that.

Ill edit my quote to save you the blushes.
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I don't blush, but thanx all the same :thumbs:
 
The D300 is not a camera I've owned, but I've just had a quick check, and the camera is capable of micro AF adjustment. It is not hard and I recommend it. This completely transformed my pics from the D7000. Set up some focus objects at around the distance you expect to use the lens most.

I don't want to teach you to suck eggs by going into details. The process is not irreversible, and can be switched off anyway. Best check your focus point first though, just in case these other guys have a point. ViewNX2 will do that for you (also pretty good but slow processor).
 
thanks for the replies, apart from the arrogance of
**Edit**.. Sport photography at large telephoto apertures may seem easy for you guys but, The difference between amateurs and "Pros" is: we earn our living with this, we don't blame the equipment. We learn it's limitations and work around them"!!!.... hence the term "Pro"..
Click to expand...
As i stated in my first post, i am unsure if it is me! im not blaming my equipment, but i want to rule something out. So please read properly before you start bashing.

Anyway. ill do the af check and see what it turns up, thanks for the help!

T
 
Is this on;y happening with this lens or a general trait with your body? One thing I always do, despite it being a bit tedious, is do a fine AF adjust on all my lenses. I set up the camera on a tripod and set up an object with a high contrast area to focus on a couple of meters away. I'll use the lens wide open to give a narrow DOF (another reason to have the object quite close to the camera). I'll then take a shot with -20,-15,-10,-5, 0, 5, 10, 15, 20 dialled in on the AF adjustment. I'll upload these to the computer and see which 2 shots are sharpest. If that turns out to be shots 5 and 10 say, I'll then take another series of shots at 5, 6, 7, 8, 9 and 10. I upload them again and choose the sharpest one. I'll then save that value for the lens. It takes bloody ages but it can make a big difference. Worth a shot though.
 
to tell the truth gad, its really the only lens i use often enough to notice. and the only other lens ive got is 1.8 50mm and use that for a family members wedding and didnt notice anything wrong with the focus on that.

Ill have a little look tomorrow into doing the focus test, got a lot on today and wont get round to it but im rly interested to see the results!
 
Presuming it focuses correctly on static distant target (you know that, right?), could it be the case it is a slow (relatively) focusing lens and it can't keep up with the pace of the game? Does Nikon ?70-200mm if you can try one give same problems
 
meatcandy89 said:
thanks for the replies, apart from the arrogance of
As i stated in my first post, i am unsure if it is me! im not blaming my equipment, but i want to rule something out. So please read properly before you start bashing.

Anyway. ill do the af check and see what it turns up, thanks for the help!

T
Click to expand...

I had a lot to drink last night and my comments were indeed out of character, arrogant and flippant. For that, I apologize.
 
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