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Author Topic: 5DMKIII Autofocus help required  (Read 4807 times)

bjd

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5DMKIII Autofocus help required
« on: June 16, 2012, 05:39:32 AM »
Hi,
I finally got my new 5D, moved up from a 400D, and I am "ashamed" to say I have been doing a lot
of reading in the camera manual  :o
I've been playing with the autofocus settings while trying to take shots of some of the birds in our garden.
Attached an example that is causing me problems. The display will show me the "fields" being used for AF,
and they will all be lined up on the bird feeder. I havent been able to find a way to persuade the camera
to focus on the bird in such a situation. This is in automatic mode. If I go to spot with the 4 adjacent fields
then it seems to work better. But I want the automatic mode so I can use a tripod and set the camera up
as close as possible to the birds. Using AI Focus mode usually.
I am using the 70-200 F4 IS lens, at 200mm and pretty close to the subjects. Do I maybe want to move
further back so that I have more DOF therefore making the exact focus less important.
Generally I haven't been so happy with the results yet, but thats probably more me than the equiment.
Cheers BRian

 

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5DMKIII Autofocus help required
« on: June 16, 2012, 05:39:32 AM »

neuroanatomist

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Re: 5DMKIII Autofocus help required
« Reply #1 on: June 16, 2012, 07:42:04 AM »
Automatic AF point selection?  :o  That will always pick the closest subject.  Some options would be to stop down for deeper DoF, or switch out the round feeder for a directional one (only only perch) and manually focus on that spot.
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bjd

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Re: 5DMKIII Autofocus help required
« Reply #2 on: June 16, 2012, 08:06:46 AM »
Hi,
thanks for the reply.
Obviously I can do a lot with the situation in our garden, and will get to that but I was more concentrating
on getting it right with the camera first. I guessI was thinking more along the lines that AF was concentrating
more on the horizontal and vertical lines and not the fact that the front edge of that feeder will in a lot of
cases be closer to me than the subject.

Cheers Brian

bdunbar79

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Re: 5DMKIII Autofocus help required
« Reply #3 on: June 16, 2012, 09:14:01 AM »
I use AF on my 5D Mark III.  In the manual you'll see that you can choose ONE of any of the 61-AF points if you like.  I still use only one point, but I move it around the viewfinder.  Sometimes I'll use 4 point expansion (top, left, right, bottom) but mainly I move the AF point around where I know or want my subject to be in the frame.  I actually haven't had a photo yet where I missed focus.  Like the poster above said too, watch your DOF.  If you need to use higher ISO with a narrower aperture, do it!  The camera will handle it nicely.
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bjd

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Re: 5DMKIII Autofocus help required
« Reply #4 on: June 17, 2012, 12:18:26 PM »
I use AF on my 5D Mark III.  In the manual you'll see that you can choose ONE of any of the 61-AF points if you like.  I still use only one point, but I move it around the viewfinder.  Sometimes I'll use 4 point expansion (top, left, right, bottom) but mainly I move the AF point around where I know or want my subject to be in the frame.  I actually haven't had a photo yet where I missed focus.  Like the poster above said too, watch your DOF.  If you need to use higher ISO with a narrower aperture, do it!  The camera will handle it nicely.
Thanks. OK I saw that and had tried it, allows me to frame the subject where I want it.
Here's another example. Taken F14 1/160th 200mm 1.2meters from the subject. The face of the bird is pretty
sharp now I guess. Is that about the correct quality that I should get from this combination?

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bdunbar79

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Re: 5DMKIII Autofocus help required
« Reply #5 on: June 17, 2012, 01:35:42 PM »
That's pretty good quality.  I think you're doing well.  The other thing I did was practice different metering and see how it affects the exposure.  For instance, you could do spot metering on the bright side of the bird, take the reading, and adjust the shutter speed accordingly for proper exposure.  Usually, when I do something like that, I'll take 3-5 photos with AEB, -2/3, -1/3, proper, +1/3, +2/3, and then do two metering sites.  You have 10 photos then, and one will certainly be the way you personally want it.  That's just what I do.  I know it can add a lot of RAW pictures that you're not going to use and have to sift through, but in this case it might be worth trying once or twice and seeing what your options look like.  And it's fun!  :)  However, in this case you may not have had time to do that, as the bird probably took off within seconds, maybe.  I think the 5D Mark III can do spot metering everywhere (all 61 points) in single shot mode can't it?  I can't remember.  AI Servo is different.
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briansquibb

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Re: 5DMKIII Autofocus help required
« Reply #6 on: June 17, 2012, 04:47:22 PM »
The DOF seems to be very shallow for F14?

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Re: 5DMKIII Autofocus help required
« Reply #6 on: June 17, 2012, 04:47:22 PM »

bdunbar79

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Re: 5DMKIII Autofocus help required
« Reply #7 on: June 17, 2012, 04:55:56 PM »
The DOF seems to be very shallow for F14?

I was thinking 1.4 personally.  In that case, I'd shoot f/8 if I were conerned at all about DOF and in focus subjects with 5D Mk III.  If the background interferes too much, practice maybe at f/5.6, then f/4.  That's what I usually do.
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briansquibb

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Re: 5DMKIII Autofocus help required
« Reply #8 on: June 17, 2012, 05:16:57 PM »
The DOF seems to be very shallow for F14?

I was thinking 1.4 personally.  In that case, I'd shoot f/8 if I were conerned at all about DOF and in focus subjects with 5D Mk III.  If the background interferes too much, practice maybe at f/5.6, then f/4.  That's what I usually do.

I am guessing a big crop judging from the bg.

Look at the bg on this pic - ff, f/3.2, hardly cropped, much smoother bg

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bjd

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Re: 5DMKIII Autofocus help required
« Reply #9 on: June 18, 2012, 12:40:36 PM »
Hi,
F14, 1/160th, ISO 2000, 200mm at 1.2 Meter distance (according to EXIF). Which according to a DOF calculator gives me a DOF of around 2-3cm. Is it maybe because I am right at the closest possible focusing distance for this lens and therefore have
no DOF to the front of the focus plane like I should have?

Maybe I do really just need to keep away from the "Near" limit of the lens anyway.

Thanks for all the comments. I dont mind sifting through the .RAW files, as long as I do find something
worth keeping in there.


Here's the full picture, not that much of a crop.

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Re: 5DMKIII Autofocus help required
« Reply #10 on: June 18, 2012, 01:02:29 PM »
F/14 is going to reduce sharpness somewhat due to diffraction, you might actually get a sharper image by moving back a little, using f/5.6 to f/8 and cropping more or using a TC.  And, of course, lighting is everything.  Sometimes, if the sun is not right, or the subject is in a shadow, a flash is needed.
 
 

bdunbar79

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Re: 5DMKIII Autofocus help required
« Reply #11 on: June 18, 2012, 01:06:56 PM »
My personal feelings are the same as the poster above.  I would have chosen f/8 as my aperture because that would probably have been sharper than f/14, the background isn't as busy, and I also would have backed up a tad and cropped if need be later.  I know, this is really nitpicking and there really isn't anything wrong with your shot, but that's how I read the shot.  I may have metered on the bright spot of the bird with spot metering but I can't really answer that question since I can't see the whole scene and can't see the sky.  Cool shot though!
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bjd

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Re: 5DMKIII Autofocus help required
« Reply #12 on: June 18, 2012, 01:19:05 PM »
No not picky, those are the things I still need to learn. Thanks.

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Re: 5DMKIII Autofocus help required
« Reply #12 on: June 18, 2012, 01:19:05 PM »

bjd

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Re: 5DMKIII Autofocus help required
« Reply #13 on: June 18, 2012, 02:54:30 PM »
  I think the 5D Mark III can do spot metering everywhere (all 61 points) in single shot mode can't it?  I can't remember.  AI Servo is different.
I was wondering about this. Sure it has the 61 point AF, and I can select any of those points, but is the one I select
also used for metering? In the book it says something about a central area about 1.5% of the total area for spot.
So who knows this for certain?
Cheers Brian

neuroanatomist

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Re: 5DMKIII Autofocus help required
« Reply #14 on: June 18, 2012, 03:00:52 PM »
  I think the 5D Mark III can do spot metering everywhere (all 61 points) in single shot mode can't it?  I can't remember.  AI Servo is different.
I was wondering about this. Sure it has the 61 point AF, and I can select any of those points, but is the one I select
also used for metering? In the book it says something about a central area about 1.5% of the total area for spot.
So who knows this for certain?
Cheers Brian

If you're using evaluative metering, weighting is given to the region around the selected AF point.  Spot metering on the 5DIII is in the center only, not linked to the AF point selected.  AF point-linked spot metering is currently a 1-series only feature.
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Re: 5DMKIII Autofocus help required
« Reply #14 on: June 18, 2012, 03:00:52 PM »