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Archive 2011 · 7D AF (long 4 pix)
  
 
OntheRez
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p.1 #1 · 7D AF (long 4 pix)


First, Iím fairly certain that any irregularity in focus that Iím experience is operator idiocy though, Iím not certain. Second, Iíve only had this 7D since October and though Iíve shot around 8k frames thru it, I admit to still learning this camera. Finally, my standard for AF performance is the 1DIIn which I still use but wonít work in the low light action shots I am required to make. (I am the sports reporter/photographer for a small town newspaper.)

I shoot RAW, manual, never below ISO 1600 and generally at either 3200 (When using an 85mm f/1.8 or the 135mm f/2.0L) or 6400 when using a 70-200 f/2.8L or a 24-70 f/2.8L. Iím using spot metering, and AIServo. The field house I work in has truly abysmal lighting. Oh, I always have my thumb on the AF-ON button.

The cameras CFnIII settings are as follows: (1) AI servo speed - fast; (2) AI first/second - 0, AF priority; (3) AI servo AF tracking - 1, continuous AF; (4) Lens drive AF impossible - 0, focus search; (5) AF micro adjust - 2, by lens though I have done no micro-adjustment; (6) Select AF area selc mode - all are enabled; (10) Focus display in AI servo - 0, enable; (11) Af assist beam - 1, disable.

Four pictures follow with comments/questions here. (Sorry donít have external linking.)

#1 I had the AF point on the man with the rebound as he was in position and the leading rebounder. To my eye the only thing in focus here is the reflection of the field house lighting on the glass. (Nice stuff, huh?) (24-70 at f/2.8)

#2 Hard foul on #12, I was following him down court as he had stolen the ball and was on a break. To me the only thing in focus is the basket rim. (70-200, f/2.8)

#3 Fighting in the paint. I donít think anything is in focus and the action was not moving that fast towards me. (85mm at f/1.8.)

#4 Driving the lane. Itís harder to see in this JPEG, but in the original raw #11 is in clear focus, while #50 (with the ball) is slightly fuzzed. Again, I know I was focused on the man with the ball. (24-70 f/2.8)

As to why everything is shot wide open, it is the only way I can get a shutter speed fast enough stop action in this low light.

So, lack of practice/skill on my part? Inevitable result of always shooting wide open? Wrong settings on CFn III? Moron lose with too much camera? I canít do direct comparisons in this situation with my 1DIIn because of its ISO limitations but my memory is that I got better results. I do get quite a few good shots (the editor is very pleased with my work), but it seems like some of the best stuff is getting away.

Your thoughts greatly appreciate.



© OntheRez 2011

  Canon EOS 7D    60mm    f/2.8    1/1000s    6400 ISO    0.0 EV  




Dec 15, 2011 at 07:29 PM
OntheRez
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p.1 #2 · 7D AF (long 4 pix)


#2 Hard foul on #12, I was following him down court as he had stolen the ball and was on a break. To me the only thing in focus is the basket rim. (70-200, f/2.8)








Dec 15, 2011 at 07:29 PM
OntheRez
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p.1 #3 · 7D AF (long 4 pix)


#3 Fighting in the paint. I donít think anything is in focus and the action was not moving that fast towards me. (85mm at f/1.8.)








Dec 15, 2011 at 07:30 PM
OntheRez
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p.1 #4 · 7D AF (long 4 pix)


#4 Driving the lane. Itís harder to see in this JPEG, but in the original raw #11 is in clear focus, while #50 (with the ball) is slightly fuzzed. Again, I know I was focused on the man with the ball. (24-70 f/2.8)







Dec 15, 2011 at 07:30 PM
snapsy
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p.1 #5 · 7D AF (long 4 pix)


Upon initial inspection all the photos appear back-focused, including #3 where you think nothing is in focus but if you look closely the defender's left foot is in focus.

Have you verified static focus in more controlled conditions?



Dec 15, 2011 at 07:37 PM
plubbry
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p.1 #6 · 7D AF (long 4 pix)


To my eye all of the shots look like your lens is backfocussing.
1 - The wall is more in focus than the players (and like you said the light is also well in focus)
2 - #1 & #22 are not to bad out of focus but the hoop is certainly more in focus.
3 - the left foot of the defender, and the floor right behind it look to be the most in focus.

I have no experience with the gear you are using but I would first do a series of controlled shots of a static subject to determine if there is any back focussing occuring. I believe the 7D has AF fine tune? Once you determine and correct any front or back focussing you can get a better sense if it was the only problem or if there is some other limitation with the lens or body or settings.

-Bryan



Dec 15, 2011 at 07:38 PM
BennyR
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p.1 #7 · 7D AF (long 4 pix)


I think that lens is rather notorious for back focusing as I recall. Do a micro adjust and use center point and I bet your keeper rate goes way up.


Dec 16, 2011 at 01:20 AM
vawill84
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p.1 #8 · 7D AF (long 4 pix)


Back focusing aside, I also think you could have also gotten away with a bit lower ISO as well, as I see some of your shots are upwards of 1/1000 sec, which is a bit overkill in terms of freezing action. I know its tough inside cave lit gyms though.


Dec 16, 2011 at 05:26 AM
TrojanHorse
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p.1 #9 · 7D AF (long 4 pix)


They're all underexposed too, except #3.

Have you tried testing the focus of your lens on a tripod taking a shot of a fixed target?

Why is your AF servo speed set to fast? That just means if you slip off your target, you will rapidly focus on the background. That CF doesn't affect tracking speed or ability.

Are you using all focus points? Is that what I read? Open up the images in DPP and see where the focus point is, that might help clarify things. And pick a single focus point (with helper points turned on if you like), don't let the camera decide.



Dec 16, 2011 at 07:01 AM
OntheRez
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p.1 #10 · 7D AF (long 4 pix)


Okay, thanks for all who have responded.
Snappsy and Plubbry, As I look again at the posted pix I see the pattern you are calling "back focusing."
Benyr, did you mean camera or lens? The pictures were all taken with the 7D but with 3 different lenses.
TrojanHorse and vawil84 if I understand correctly you seem to be making opposite observations. If the" ISO is too high" does that result in "underexposed"?

One of the "features" of this gym is the light is not constant. Depending on where I stand and in what direction I shoot I get different light readings. Expressed in stops, it can vary by 1.5 -2 from one end of the gym to the other. The middle - oddly enough - has good lighting. Both baskets are much darker though the west one is worse than the east. Oh, just so you know, flash is banned in this league. I'm fairly quick at adjusting shutter speed, but on a fast break, there is no way I can shoot and adjust.

Trojan and vawill again, I'm using spot focus and in looking at the results can often see the red square in the middle of my intended "victim". Still can get the unfocused look I'm complaining about. I worked again last night and tried some lower ISO with my fast lenses. (as far down as ISO 1600). I was able to take the 85mm to about 2.2 even 2.8 (anything for some depth of field) and the 135 to 2.2-2.4. Haven't downloaded and examined the results yet, though chimping was encouraging. Some are under exposed and I hate the effect that PP has in fixing this.

Okay so it back focuses. I've done some quick searching on the topic and there are a number of hits with seemingly contradictory instructions. Canon's site simply repeated what is in the manual.

It seems I need to set up a completely controlled shoot on a static object and do manual focus, then AF, and compare the results? Is this where I need the proverbial brick wall? Rare around here as most everything is adobe/stucco. Can some one suggest a link that gives a step by step approach? Oh, Benny, I've studied the manual on microfocus and it seems to be a similar process. Am I correct?

Finally, if the camera really does back focus, is it time for a trip to Canon? I get a 2.5 week break after Tuesday, so I have time to be without the gear.

Thanks all,

Robert



Dec 16, 2011 at 03:38 PM
 

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RobertLynn
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p.1 #11 · 7D AF (long 4 pix)


He's using different lenses...I'm doubting they all back focus.


Dec 16, 2011 at 05:20 PM
Imagemaster
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p.1 #12 · 7D AF (long 4 pix)


the cameras CFnIII settings are as follows: (1) AI servo speed - fast;

Try changing that to SLOW.



Dec 16, 2011 at 06:53 PM
JohnBrose
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p.1 #13 · 7D AF (long 4 pix)


The lenses could easily all be back focusing. Also, the focus system is very quick to focus on something of higher contrast, so if you are trying to focus on a player's jersey that might not have anything of contrast that the spot focusing point is on and then for an instant the spot point finds something of higher contrast, then the lens will instantly snap to that other focusing range. I would suggest to switch to spot focusing with the helper points-this will give you a bit bigger focusing spot. Also test each of your lenses at approx the distance you do most of your shots to see if they are back or front focusing. It's a quick process-just take like 5-7 shots of a subject with good contrast at like -15,-10,-5,0,+5,+10,+15 of micro focus and then look at them on your computer monitor to see which is the sharpest. If it's between a couple, redo it closer to what looked best. Lighting also affects focusing a bit it seems so if possibe, try doing it in the gym. You can also make changes to 1st shot/focusing priority to customize the body also.


Dec 16, 2011 at 07:14 PM
RobertLynn
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p.1 #14 · 7D AF (long 4 pix)


Yeah all of his lenses have the SamE focus issues...
It's more likely that the camera is to blame or technique is, rather than multiple lenses.




Dec 16, 2011 at 07:43 PM
galenapass
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p.1 #15 · 7D AF (long 4 pix)


Imagemaster wrote:
Try changing that to SLOW.


+1 I'd do that before looking at anything else.



Dec 16, 2011 at 07:54 PM
Imagemaster
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p.1 #16 · 7D AF (long 4 pix)


JohnBrose wrote:
I would suggest to switch to spot focusing with the helper points-this will give you a bit bigger focusing spot.


Not sure if that is correct, but someone can correct me if I am wrong.

Spot-focus point does not have any helper points, nor can it be set to have any.

Center-focus point can be used alone or with helper points.



Dec 16, 2011 at 08:18 PM
Jase1125
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p.1 #17 · 7D AF (long 4 pix)


Single af with expanded will work on any af point in the camera. Spot focus reduces the size of the af point for greater precision. I would not use spot for sports.

I agree the first thing you should do is set servo sensitivity to slow or medium slow. Many 7D shooters have been fouled up because that was set to fast.



Dec 18, 2011 at 02:47 AM
BrianO
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p.1 #18 · 7D AF (long 4 pix)


OntheRez wrote:
...TrojanHorse and vawil84 if I understand correctly you seem to be making opposite observations. If the" ISO is too high" does that result in "underexposed"?


It would depend on your shutter speed and aperture. If you set a lower ISO you'll need to set a slower shutter and/or wider aperture to compensate, plus additional exposure to compensate for the ones that are underexposed (although they aren't bad as is, IMO).

The main advantage to a lower ISO setting is less noise and greater dynamic range, saturation, and contrast. More "pop" to use the vernacular. The main advantage of higher ISO setting is faster shutter speeds to better freeze motion, and/or smaller apertures for greater deapth of field, both of which can help to get sharper images. You have to pick which one is more important to you.

As far as the main topic, I agree with those who have said you seem to have a consistant back focusing issue. Since all three lenses used show this, it indicates the issue is on the camera body. Using Custom Function III-5 Option 1 will allow you to set the same amount of correction regardless of which lens is used. Option 2 will set each lens seperately for even more accuracy (but takes more time to test). Remember that AF is based an the camera/lens combination, so a camera error may be compounded or lessened by any given lens.

As far as how to do a AF adjustment, that's a topic of much discussion, debate, and even downright arguing. Here's one method to use as a starting point:

http://www.focustestchart.com/focus21.pdf

Note that the article deals with a Nikon body, so the specific settings to use have different names than with Canons, but the principles still apply, and the test target provided will work.

HTH.



Dec 18, 2011 at 03:29 AM
TeamSpeed
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p.1 #19 · 7D AF (long 4 pix)


Imagemaster wrote:
Not sure if that is correct, but someone can correct me if I am wrong.

Spot-focus point does not have any helper points, nor can it be set to have any.

Center-focus point can be used alone or with helper points.


Correct, however you DO NOT want to use spot focus for sports, even Canon's white papers call out that this is a specialty mode that you would use in slower shooting conditions.

Also, on a couple of these shooting at 1/640th while players are on the move without a flash is a recipe for nothing being in focus. I go to Tv and lock in 1/800th or 1/1000th every time I shoot basketball, just to make sure I stop the motion.

Regarding the AI Servo setting, you want it to the far left or one notch to the left at most.

Finally remember that the little AF box is an indicator of the general area of that AF point, and it extends beyond the box boundaries. This means if that sensor sees light reflecting off glass, that will most likely give you the most contrast and the AF will lock to that over a player.

I like the AF with expansion, this way priority is given to the main AF point, but the points around it can help out if needed.



Dec 18, 2011 at 12:33 PM





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