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20D AF--getting the most out of it...

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Vance Zachary

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I use the 20D and the 5D (Canon) for photographing weddings. I am often surprised to hear about signifcant focusing problems with the 20D

Some photographers have asked me if I thought that the 5D AF was better than the 20D, The 5D is affectionately tabbed by my wedding assistants as the "gas guzzler" because of the way it chews up my 1 gig cards. With 20D, I get about 109 RAW shots per 1 gig card. With the "gas guzzler", I get 77 RAW shots per card. I get about 400-500 shots per battery charge with the "gas guzzler" compared to 800 to 1000 with the 20D.

I can't answer whether the 5D focuses better than the 20D other than to say that I think so. That is because my 20D does so well for me. I am getting about 1-3 OOF images (as determined by viewing at 100% and peeping like crazy) per 100 shots regardless of the lighting situation (I do a lot of available life photography).

The following is what I do to achieve this:

1) the most sensitive AF point is the central cross hair sensor even in cameras with 45 AF points; so I activate this sensor and use it 99% of the time; the other AF points work but are not as sensitive;

2) I try to buy lenses that are f2.8 or faster to increase the central cross hair sensor's sensitiviy

3) I use one shot focus lock mode most of the time rather than AI Servo; again, AI Servo works but is not as unfailingly accurate as focus lock; there is a time and place for AI Servo but you may have to put up with a few more focusing errors

4) I aim for an area of high contrast; often that is the face; the camera cannot read your mind but it can detet contrast and light that is in or out of phase

5) I make sure that all of the lenses that I use have been calibrated to my particular camera; lens and camera AF range tolerances can vary and lead to incompatibility and focusing errors

Good luck to you all. The "gas guzzler" has become my primary portrait camera whereas the 20D is my primary candid camera.

Keep shooting!

--
Vance Zachary
http://www.pbase.com/photoworkszach
http://www.photoworksbyzachary.com
 
Vance,

I own a 1DMkII and 20D and I use the 20D for weddings along with my 17-40 and 24-70 lenses. I have found the 17-40 to adequately serve my needs but the issue I have like many have experienced even when shooting with the more accurate Centre AF point, I get high percentage of back-focused photos perhaps failing to satisfy the "high contrasty" requirement.

I have never had the body and lens sent in for calibration and was wondering if you can realistically have one body accurately calibrated for two lenses? The only other lens I use is the 70-200 2.8 IS.

--
Jan Shim
Pro Events Photography
http://www.janshim.com
Vance Zachary said:
I use the 20D and the 5D (Canon) for photographing weddings. I am
often surprised to hear about signifcant focusing problems with the
20D

Some photographers have asked me if I thought that the 5D AF was
better than the 20D, The 5D is affectionately tabbed by my wedding
assistants as the "gas guzzler" because of the way it chews up my 1
gig cards. With 20D, I get about 109 RAW shots per 1 gig card. With
the "gas guzzler", I get 77 RAW shots per card. I get about 400-500
shots per battery charge with the "gas guzzler" compared to 800 to
1000 with the 20D.

I can't answer whether the 5D focuses better than the 20D other
than to say that I think so. That is because my 20D does so well
for me. I am getting about 1-3 OOF images (as determined by viewing
at 100% and peeping like crazy) per 100 shots regardless of the
lighting situation (I do a lot of available life photography).

The following is what I do to achieve this:

1) the most sensitive AF point is the central cross hair sensor
even in cameras with 45 AF points; so I activate this sensor and
use it 99% of the time; the other AF points work but are not as
sensitive;

2) I try to buy lenses that are f2.8 or faster to increase the
central cross hair sensor's sensitiviy

3) I use one shot focus lock mode most of the time rather than AI
Servo; again, AI Servo works but is not as unfailingly accurate as
focus lock; there is a time and place for AI Servo but you may have
to put up with a few more focusing errors

4) I aim for an area of high contrast; often that is the face; the
camera cannot read your mind but it can detet contrast and light
that is in or out of phase

5) I make sure that all of the lenses that I use have been
calibrated to my particular camera; lens and camera AF range
tolerances can vary and lead to incompatibility and focusing errors

Good luck to you all. The "gas guzzler" has become my primary
portrait camera whereas the 20D is my primary candid camera.

Keep shooting!

--
Vance Zachary
http://www.pbase.com/photoworkszach
http://www.photoworksbyzachary.com
Click to expand...
 
Vance,

According to your post, you use the central autofocus sensor and then often focus on the face. This obviously requires you to recompose after locking focus as I assume you seldom want a face dead center of the photo.

My understanding is that the area of constrant depth of field at a given distance from a lens is a plane perpendicular to the lens. This means that as you recompose, you end up focusing behind your intended target. With a shallow enough depth of field, your bride's face goes would go out of focus.

How do you deal with this situation? Do you shoot stopped down enough so this isn't a problem? With my own shooting, I select the top sensor (which of course various depending on the camera's orientation) as that allows me to minimize the amount of recomposing.

--
Blake
 
Vance Zachary said:
I use the 20D and the 5D (Canon) for photographing weddings. I am
often surprised to hear about signifcant focusing problems with the
20D
Click to expand...
but then see your #5
Vance Zachary said:
5) I make sure that all of the lenses that I use have been
calibrated to my particular camera; lens and camera AF range
tolerances can vary and lead to incompatibility and focusing errors
Click to expand...
if you need to do #5 then you are in with the lot who complain about AF.
 
Jan_Shim said:
I have never had the body and lens sent in for calibration and was
wondering if you can realistically have one body accurately
calibrated for two lenses? The only other lens I use is the 70-200
2.8 IS.
Click to expand...
I must admit, I have never had to send a Canon lens or Tamron 28-75 in for calibratiion. I must be lucky. But I do not get a high per centage of out of focus images with the 20D and hence have never felt compelled to buy a 1D II like you have.

I cannot afford to have many OOF images in my business and would not tolerate the 20D if I couldn't feel I could trust its AF.
Jan_Shim said:
--
Jan Shim
Pro Events Photography
http://www.janshim.com
Vance Zachary said:
I use the 20D and the 5D (Canon) for photographing weddings. I am
often surprised to hear about signifcant focusing problems with the
20D

Some photographers have asked me if I thought that the 5D AF was
better than the 20D, The 5D is affectionately tabbed by my wedding
assistants as the "gas guzzler" because of the way it chews up my 1
gig cards. With 20D, I get about 109 RAW shots per 1 gig card. With
the "gas guzzler", I get 77 RAW shots per card. I get about 400-500
shots per battery charge with the "gas guzzler" compared to 800 to
1000 with the 20D.

I can't answer whether the 5D focuses better than the 20D other
than to say that I think so. That is because my 20D does so well
for me. I am getting about 1-3 OOF images (as determined by viewing
at 100% and peeping like crazy) per 100 shots regardless of the
lighting situation (I do a lot of available life photography).

The following is what I do to achieve this:

1) the most sensitive AF point is the central cross hair sensor
even in cameras with 45 AF points; so I activate this sensor and
use it 99% of the time; the other AF points work but are not as
sensitive;

2) I try to buy lenses that are f2.8 or faster to increase the
central cross hair sensor's sensitiviy

3) I use one shot focus lock mode most of the time rather than AI
Servo; again, AI Servo works but is not as unfailingly accurate as
focus lock; there is a time and place for AI Servo but you may have
to put up with a few more focusing errors

4) I aim for an area of high contrast; often that is the face; the
camera cannot read your mind but it can detet contrast and light
that is in or out of phase

5) I make sure that all of the lenses that I use have been
calibrated to my particular camera; lens and camera AF range
tolerances can vary and lead to incompatibility and focusing errors

Good luck to you all. The "gas guzzler" has become my primary
portrait camera whereas the 20D is my primary candid camera.

Keep shooting!

--
Vance Zachary
http://www.pbase.com/photoworkszach
http://www.photoworksbyzachary.com
Click to expand...
Click to expand...
--
Vance Zachary
http://www.pbase.com/photoworkszach
http://www.photoworksbyzachary.com
 
Blake said:
My understanding is that the area of constrant depth of field at a
given distance from a lens is a plane perpendicular to the lens.
This means that as you recompose, you end up focusing behind your
intended target. With a shallow enough depth of field, your
bride's face goes would go out of focus.

How do you deal with this situation? Do you shoot stopped down
enough so this isn't a problem? With my own shooting, I select the
top sensor (which of course various depending on the camera's
orientation) as that allows me to minimize the amount of
recomposing.
Click to expand...
Conventional wisdom will tell you that the focus and recompose method leads to AF miscues. I have found this to be true if the distance to the subject is close and depth of focus is narrow. If this is the case, I use something else to focus on or I use one of the peripheral AF points or I manually focus (difficult on the 20D).

The focus and recompose method can work in certain situations but it has limitations and one has to know when one can get away with good results and when one can't.

--
Vance Zachary
http://www.pbase.com/photoworkszach
http://www.photoworksbyzachary.com
 
bronxbombers said:
Vance Zachary said:
I use the 20D and the 5D (Canon) for photographing weddings. I am
often surprised to hear about signifcant focusing problems with the
20D
Click to expand...
but then see your #5
bronxbombers said:
5) I make sure that all of the lenses that I use have been
calibrated to my particular camera; lens and camera AF range
tolerances can vary and lead to incompatibility and focusing errors
Click to expand...
if you need to do #5 then you are in with the lot who complain
about AF.
Click to expand...
The conclusion you state does not logically follow your premise.

With any camera, be it 20D or 1DS II, there is the chance that the combination of lens and camera can lead to focusing errors. Of course, with 1 series cameras, you would expect that specs would call for narrower tolerances but there is still that possibilty there will be a camera lens focusing tolerance mismatch. Hence the need to check each lens that you buy for focusing errors and, if you are having consistent focusing problems (which I do not have) to coonsider calibration as a possible problem regardless of what camera you use and regardless of how it behaved with your other lenses.

Where is the inconsistency in that?

--
Vance Zachary
http://www.pbase.com/photoworkszach
http://www.photoworksbyzachary.com
 
Interesting.

I guess I am fortunate. I find the focus of my 20D to be very accurate. I have a split ring focusing screen and the AF matches almost every time.

--
jerryk.smugmug.com
 
"I do a lot of available life photography"

Typo, isn't it?

Anyway, thanks for the information, it largely fits with my experience on the 20D.

Michael
 
Vance Zachary said:
bronxbombers said:
Vance Zachary said:
I use the 20D and the 5D (Canon) for photographing weddings. I am
often surprised to hear about signifcant focusing problems with the
20D
Click to expand...
but then see your #5
Vance Zachary said:
5) I make sure that all of the lenses that I use have been
calibrated to my particular camera; lens and camera AF range
tolerances can vary and lead to incompatibility and focusing errors
Click to expand...
if you need to do #5 then you are in with the lot who complain
about AF.
Click to expand...
The conclusion you state does not logically follow your premise.

With any camera, be it 20D or 1DS II, there is the chance that the
combination of lens and camera can lead to focusing errors. Of
course, with 1 series cameras, you would expect that specs would
call for narrower tolerances but there is still that possibilty
there will be a camera lens focusing tolerance mismatch. Hence the
need to check each lens that you buy for focusing errors and, if
you are having consistent focusing problems (which I do not have)
to coonsider calibration as a possible problem regardless of what
camera you use and regardless of how it behaved with your other
lenses.

Where is the inconsistency in that?

--
Vance Zachary
Click to expand...
oh, I thouht you meant you mde sure to send in every lens to get it exactly calibrated (out of apparent need). but I see waht you meant now. nevermind.
 
I've never had any issues with my 20D AF either. Whenever I can i'd AF on the same point a couple-o times until i'm sure but it's not really necessary. Just a habit I picked up when my 10D let me down so many times.

Hey Jan, surprised to find you in these parts. Not in the computer business anymore I see. How's the wife? Still with BSP? Never knew you had an interest in photography. Sold your big hulking Mitsubishi sedan already? Well anyway nice to have caught up with you. Been 10 years.

Cheers!
 
bimmerman said:
Hey Jan, surprised to find you in these parts. Not in the computer
business anymore I see. How's the wife? Still with BSP? Never knew
you had an interest in photography. Sold your big hulking
Mitsubishi sedan already? Well anyway nice to have caught up with
you. Been 10 years.

Cheers!
Click to expand...
bimmerman, please drop me an email, 10 years is a long time. It would help if you at least signed off with a first or last name.

--
Jan Shim
Pro Events Photography
http://www.janshim.com
 
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