Frustration with 24-70L focus

t truong · Jan 23, 2004

Please help! I recently got a Canon 24-70L and have been having some frustrating experience with it.

In good light or bad, it sometimes front or back-focus when shot wide open regardless of focal length and . The results are better when stopped down to 4.0 or 5.6, though I suspect that this is secondary to increased DOF rather than AF accuracy. There also seems to be some improvement with AI Servo mode. I am using a 10D. My previous similar lens was a 24-85/3.5-4.5 with which I never had problems.

Considering how much this new lens costs, I would expect it to nail the focus at any time and every time. Am I being unfair in this judgment?

I only have a couple of days more that I can exchange it.
--
T TRUONG

William R Wood · Jan 23, 2004

t truong said:
Please help! I recently got a Canon 24-70L and have been having
some frustrating experience with it.

In good light or bad, it sometimes front or back-focus when shot
wide open regardless of focal length and . The results are better
when stopped down to 4.0 or 5.6, though I suspect that this is
secondary to increased DOF rather than AF accuracy. There also
seems to be some improvement with AI Servo mode. I am using a 10D.
My previous similar lens was a 24-85/3.5-4.5 with which I never had
problems.

Considering how much this new lens costs, I would expect it to nail
the focus at any time and every time. Am I being unfair in this
judgment?

I only have a couple of days more that I can exchange it.
--
T TRUONG

--

I have a new 24-70/2.8L too. I thought it was backfocusing until I tested it more carefully using a tripod and good light. Focus is well centered at close range using a diagonal row of 7 Coke cans or a single screw placed on a plain wooden table top, wide open of course.

I do have problems with AF with the lens wide open on more distant shots. I do not have any problem at f/5.6 or higher. At 2.8 if I am careful to give the AF a good target the images are reasonably sharp. I have one 2.8 shot that is sharper than the 5.6 shot at the same target because the AF locked perfectly. I find that I have to switch between using just the center AF point and all 7 points, sometimes one method works better than the other. Generally however the images at 2.8 are softer than at 5.6 due to the slight misfocus. This is annoying given the high price of the lens and I don't know what to think since I bought the lens primarily for the 2.8 aperture.

I am considering returning the lens and switching to primes.

Regards,

Bill Wood
Fountain Hills, AZ

t truong · Jan 23, 2004

Thanks for the reply.

I share in your frustration. Do you find that one focusing mode is better than the other? I usually use center focus only. Currently, I only take informal pictures of kids and other family members. Perhaps I don't know how to use the camera well, but I could never get the 7-point focus to lock on the subject that I want to focus on.

I have downloaded one of those focus test templates. I found that even in short distances (

I am in a quandary as whether the problem is the lenses (particularly the 24-70), the camera (10D), the operator, or all of these factors.

Terry

chuck kofahl · Jan 23, 2004

I'm on my second 24-70. I have found that the 2nd one is right on, however this is a great lens, it is very unforgiving. I have to make sure that any hand held shots @ the long end is at least 2x the focal length or my shots are soft.

Try putting on a tripod and use a remote or timed release and then see what happens.

t truong said:
Please help! I recently got a Canon 24-70L and have been having
some frustrating experience with it.

In good light or bad, it sometimes front or back-focus when shot
wide open regardless of focal length and . The results are better
when stopped down to 4.0 or 5.6, though I suspect that this is
secondary to increased DOF rather than AF accuracy. There also
seems to be some improvement with AI Servo mode. I am using a 10D.
My previous similar lens was a 24-85/3.5-4.5 with which I never had
problems.

Considering how much this new lens costs, I would expect it to nail
the focus at any time and every time. Am I being unfair in this
judgment?

I only have a couple of days more that I can exchange it.
--
T TRUONG

Michael Louis · Jan 23, 2004

as what you are describing with your 24-70L is exactly what's happening to my 100 f2. I find that the closer I get to a good contrasty subject the better the focus, and the distance when the focus starts to slip is not terribly long; something like 15'. So I think I am sending it off to Irvine tommorow. I shot over 200 'real life' shots today just to make sure and I can't excuse it's sorry behavior any more.

I had the same issue with the 70-200 4L, but Irvine has gotten that lens to focus tack sharp on almost every shot.

William R Wood said:
t truong said:

Please help! I recently got a Canon 24-70L and have been having
some frustrating experience with it.

In good light or bad, it sometimes front or back-focus when shot
wide open regardless of focal length and . The results are better
when stopped down to 4.0 or 5.6, though I suspect that this is
secondary to increased DOF rather than AF accuracy. There also
seems to be some improvement with AI Servo mode. I am using a 10D.
My previous similar lens was a 24-85/3.5-4.5 with which I never had
problems.

Considering how much this new lens costs, I would expect it to nail
the focus at any time and every time. Am I being unfair in this
judgment?

I only have a couple of days more that I can exchange it.
--
T TRUONG

Click to expand...

--
I have a new 24-70/2.8L too. I thought it was backfocusing until I
tested it more carefully using a tripod and good light. Focus is
well centered at close range using a diagonal row of 7 Coke cans or
a single screw placed on a plain wooden table top, wide open of
course.

I do have problems with AF with the lens wide open on more distant
shots. I do not have any problem at f/5.6 or higher. At 2.8 if I
am careful to give the AF a good target the images are reasonably
sharp. I have one 2.8 shot that is sharper than the 5.6 shot at
the same target because the AF locked perfectly. I find that I
have to switch between using just the center AF point and all 7
points, sometimes one method works better than the other.
Generally however the images at 2.8 are softer than at 5.6 due to
the slight misfocus. This is annoying given the high price of the
lens and I don't know what to think since I bought the lens
primarily for the 2.8 aperture.

I am considering returning the lens and switching to primes.

Regards,

Bill Wood
Fountain Hills, AZ

t truong · Jan 23, 2004

Thanks for the suggestion. I'll try it tonight. I did notice that outdoors with faster shutter speeds (> 1/500 sec.) the percentage of misfocus did decrease. Unfortunately, the subject distance, thus DOF, increased as well.

However, I do have a question. Let's say that with a tripod, the focus is quite good on the short & long end, wide open & stopped down. Now what? Am I doomed to using flash + - tripod forever if I can't get at least 1/140-180 sec. That really defeats the purpose of a fast lens doesn't it?

I don't mean to be wining. It is just frustrating.

--
T TRUONG

chuck kofahl · Jan 23, 2004

It's a general rule of thumb, that it's good to get at least twice the focal length for a hand held shot. I thought that I was fairly steady with my 50mm 1.4 lens, but the 24-70L is heavy and it's not as easy to hold steady. My 28-135 has IS and that gave a false sense of security. I did a test and took some shots of my wife out side, hand held 3 of the 8 there was a little camera shake, I then put the camera on a mono pod and took the same shots, all were focused properly, no soft shots. The 24-70 is a great lens, but very unforgiving.

t truong said:
Thanks for the suggestion. I'll try it tonight. I did notice that
outdoors with faster shutter speeds (> 1/500 sec.) the percentage
of misfocus did decrease. Unfortunately, the subject distance,
thus DOF, increased as well.

However, I do have a question. Let's say that with a tripod, the
focus is quite good on the short & long end, wide open & stopped
down. Now what? Am I doomed to using flash + - tripod forever if
I can't get at least 1/140-180 sec. That really defeats the
purpose of a fast lens doesn't it?

I don't mean to be wining. It is just frustrating.

--
T TRUONG

t truong · Jan 23, 2004

Well, I put the camera on a tripod and shot at a series of Coke cans staggered about 1 in distance, available light only (1/10 - 1/30):
1. All focal lengths
2. Wide open and stopped down (4.0, 5.6)

There were zero misfocus.

I also shot with flash (1/200 sec) and found only camera shake when I'm not careful. Misfocus occurred when I was not careful and got the focus point on the wrong can.

The same was performed with more light and higher ISO hand-held (1/125 sec - 1/250 sec. Again, the results were the same as with flash.

I guess the operator was at fault & not the camera or lens. This is terribly humbling. You are absolutely right that this is a very unforgiving lens.

Thanks for your help.

Mun Weng · Jan 24, 2004

I have to agree.. very very unforgiving...

right now my 24-70 seems weird. my first copy was an absolute disaster.. now this 2nd copy seems difficult to use. it doesn't always focus where I want it to. (using center focus). I've never had this problem with other lenses though.. I believe that this lens will work brilliantly if you have extremely contrasty point of focus. other than that, IMHO, you better hope to be lucky.

I don't know if I should return mine. but there doesn't seem like anything is wrong with it as it focusses accurately sometimes. I just don't want to take any risks when doing big assignments. right now, I can't trust it enough. I have to learn more about how this lens works.. I just wish I can get a bright and sunny day... too bad I'm getting overcast and -30 degrees celsius weather here.. yeah yeah.. and I live in northpole.

t truong said:
Well, I put the camera on a tripod and shot at a series of Coke
cans staggered about 1 in distance, available light only (1/10 -
1/30):
1. All focal lengths
2. Wide open and stopped down (4.0, 5.6)

There were zero misfocus.

I also shot with flash (1/200 sec) and found only camera shake when
I'm not careful. Misfocus occurred when I was not careful and got
the focus point on the wrong can.

The same was performed with more light and higher ISO hand-held
(1/125 sec - 1/250 sec. Again, the results were the same as with
flash.

I guess the operator was at fault & not the camera or lens. This
is terribly humbling. You are absolutely right that this is a very
unforgiving lens.

Thanks for your help.

--

Cheers,
kevin aka mun weng

My idea of a perfect weekend:
shooting football from the end zone with a 600mm F4 L IS.

My photo website:
http://www.cs.wisc.edu/~mun-weng/

Photosig:
http://www.photosig.com/go/users/userphotos?id=106220

Konrad Hoelzl · Jan 24, 2004

Just take a look at the thread i started right now. there you can see my focusing problems with my 24-70L and my D60.

focusing at 70mm i get the exif info of the distance with 11.9 meters which could be quite right. focusing at 24 mm i get a focusing distance information of 655 meters which is definitly wrong.

http://forums.dpreview.com/forums/read.asp?forum=1029&message=7385354

Konrad

t truong said:
Please help! I recently got a Canon 24-70L and have been having
some frustrating experience with it.

In good light or bad, it sometimes front or back-focus when shot
wide open regardless of focal length and . The results are better
when stopped down to 4.0 or 5.6, though I suspect that this is
secondary to increased DOF rather than AF accuracy. There also
seems to be some improvement with AI Servo mode. I am using a 10D.
My previous similar lens was a 24-85/3.5-4.5 with which I never had
problems.

Considering how much this new lens costs, I would expect it to nail
the focus at any time and every time. Am I being unfair in this
judgment?

I only have a couple of days more that I can exchange it.
--
T TRUONG

GPB · Jan 24, 2004

Mine would close focus, but not focus at infininity. That's what you also should test because they're are seemingly calibrated separately. Here is my composite photo that you've undoubtedly seen before if you've been researching this lens. I now have eight lenses that all focus correctly (still testing the 35 f/2). I tried to 24-70's with no luck with either sample. I sent both back and decided to look into primes. I added an 85 f/1.8, 35 f/2 and Sigma 15 f/2.8 fish...with money to spare. Granted, there are trade-offs between the two options. If you get a good 24-70...you should be happy...if you don't mind the weight.

-- Greg

http://www.pbase.com/image/24418049/original

Comparison using 85 1.8 at f/2.8 (for comparison and full size)

http://www.pbase.com/image/24924943/original

t truong said:
Well, I put the camera on a tripod and shot at a series of Coke
cans staggered about 1 in distance, available light only (1/10 -
1/30):
1. All focal lengths
2. Wide open and stopped down (4.0, 5.6)

There were zero misfocus.

I also shot with flash (1/200 sec) and found only camera shake when
I'm not careful. Misfocus occurred when I was not careful and got
the focus point on the wrong can.

The same was performed with more light and higher ISO hand-held
(1/125 sec - 1/250 sec. Again, the results were the same as with
flash.

I guess the operator was at fault & not the camera or lens. This
is terribly humbling. You are absolutely right that this is a very
unforgiving lens.

Thanks for your help.

Ben Lanterman74611 · Jan 24, 2004

My experiences are entirely different, interesting. I use my 24-70L as a point and shoot lens. No thinking necessary (it's a good thing according to my wife). I find it is a very forgiving lens as long as I point the camera at what I want to take a photo of. I do try to make the camera exactly still in space when I push the shutter button. In that respect the weight of the 1D or 1Ds and 24-70 is good. The mass/inertia of the system will smooth out the shakes a lot. Also there are photographic scenes that will give the camera the hardest time. Try to find out what those are and if you find yourself with one do a manual focus setup.

--
Ben Lanterman

http://public.fotki.com/benlanterman/
http://webpages.charter.net/benlanterman/Index.html
http://www.photo.net/photodb/folder?folder_id=208093

William R Wood · Jan 24, 2004

I have 95% decided to keep my 24-70L. As mentioned in my first post my copy does not have a front/rear focus problem on a 10D, nor does it have any sharpness problem when stopped down. The lens also focuses perfectly at macro distances and at infinity. My only problem is soft images at f/2.8 and I mean soft only in comparison with the sharper images the lens produces at f/4 and higher. Images at f/2.8 are reasonably sharp (close up shots and distance shots) but I can take the same image on a tripod at f/2.8 and at f/4, or higher, and if I compare the f/2.8 and f/4 images side by side at 100% size on my computer monitor the f/4 images are definitely sharper. The difference is not huge and would probably not be apparant to a casual observer but it is easy to find if you look carefully.

I originally suspected that the softness at f/2.8 was an AF error but today I tried manual focusing at f/2.8 and after many attempts I can equal but not exceed the sharpness of the 10D's auto focus. I guess that this proves there is nothing wrong with the AF system.

I was considering returning the zoom and switching to primes not because there is anything wrong with the 24-70 but simply because I want super sharp images at f/2.8 so I can use it wide open in low light. But from reading more and looking at other folk's images I am wondering whether any fast lens is as sharp wide open as it is stopped down.

Since I like L lenses and see that the fast primes near the focal length range of the 24-70 are real pricey (24/1.4L - $1,112; 35/1.4L - $1,115 and 85/1.2L - $1,475) it looks like I had better be happy with the 24-70L zoom

)

--
Regards,

Bill Wood
Fountain Hills, AZ

William R Wood · Jan 24, 2004

Konrad Hoelzl said:
Just take a look at the thread i started right now. there you can
see my focusing problems with my 24-70L and my D60.
focusing at 70mm i get the exif info of the distance with 11.9
meters which could be quite right. focusing at 24 mm i get a
focusing distance information of 655 meters which is definitly
wrong.

Konrad,

How do you get the focus distance in your exif info. I looked at my exif data and I do not see focus distance anywhere.

Thanks for your help.

Regards,

Bill Wood
Fountain Hills, AZ

Ira Blumberg · Jan 24, 2004

as sharp wide open as stopped down.

Take a look at http://www.photodo.com and the MTF charts at Canon's site.

I had the Canon 24 f/2.8 and tested it against the 24-70 when I got it. The 24-70 was sharper at 2.8, but the difference between 2.8 and 4.0 on the zoom was very noticeable at 100% in Photoshop. This is just a fact of optical life.

The only exception to this is the 70-200 f/4 versus the 2.8. From what I have seen, the f/4 is about as sharp at f/4 as is the f/2.8 at f/4. This is amazing since the f/4 lens is so much smaller diameter and lighter than the f/2.8 (which is why I own a copy). Even for these great lenses, you still get better performance stopped down to f/5.6 or smaller.

Ira

William R Wood said:
I have 95% decided to keep my 24-70L. As mentioned in my first
post my copy does not have a front/rear focus problem on a 10D, nor
does it have any sharpness problem when stopped down. The lens
also focuses perfectly at macro distances and at infinity. My only
problem is soft images at f/2.8 and I mean soft only in comparison
with the sharper images the lens produces at f/4 and higher.
Images at f/2.8 are reasonably sharp (close up shots and distance
shots) but I can take the same image on a tripod at f/2.8 and at
f/4, or higher, and if I compare the f/2.8 and f/4 images side by
side at 100% size on my computer monitor the f/4 images are
definitely sharper. The difference is not huge and would probably
not be apparant to a casual observer but it is easy to find if you
look carefully.

I originally suspected that the softness at f/2.8 was an AF error
but today I tried manual focusing at f/2.8 and after many attempts
I can equal but not exceed the sharpness of the 10D's auto focus.
I guess that this proves there is nothing wrong with the AF system.

I was considering returning the zoom and switching to primes not
because there is anything wrong with the 24-70 but simply because I
want super sharp images at f/2.8 so I can use it wide open in low
light. But from reading more and looking at other folk's images I
am wondering whether any fast lens is as sharp wide open as it is
stopped down.

Since I like L lenses and see that the fast primes near the focal
length range of the 24-70 are real pricey (24/1.4L - $1,112;
35/1.4L - $1,115 and 85/1.2L - $1,475) it looks like I had better
be happy with the 24-70L zoom )

--
Regards,

Bill Wood
Fountain Hills, AZ

William R Wood · Jan 24, 2004

Ira Blumberg said:
as sharp wide open as stopped down.

Take a look at http://www.photodo.com and the MTF charts at Canon's site.

I had the Canon 24 f/2.8 and tested it against the 24-70 when I got
it. The 24-70 was sharper at 2.8, but the difference between 2.8
and 4.0 on the zoom was very noticeable at 100% in Photoshop. This
is just a fact of optical life.

The only exception to this is the 70-200 f/4 versus the 2.8. From
what I have seen, the f/4 is about as sharp at f/4 as is the f/2.8
at f/4. This is amazing since the f/4 lens is so much smaller
diameter and lighter than the f/2.8 (which is why I own a copy).
Even for these great lenses, you still get better performance
stopped down to f/5.6 or smaller.

Ira

Thanks Ira, this info is very helpful and appreciated.

Regards

Bill Wood

GPB · Jan 24, 2004

That's a good question. First, the lens has to support it and I used to think that was all that was needed. Then I noticed a couple times when I used the same lens and took two photos back to back, one had the distance info and the other did not. It comes from a lookup table in the lens as I understand it. Also, the data is not particularly reliable as someone else here commented (not a finely graduated scale is my guess).

-- Greg

William R Wood said:
Konrad,

How do you get the focus distance in your exif info. I looked at
my exif data and I do not see focus distance anywhere.

Thanks for your help.

Regards,

Bill Wood
Fountain Hills, AZ

EOS freak · Jan 24, 2004

Ah, the 24-70L and D60 or 10D focus problems.

My new lens was awful, although DoF did mask some problems. Canon did admit lens was out and there was an improvement, but I did find my 28-135IS sharper.

Went into independent repairer for 2nd opinion - was told problem is in D60 body and it needed electronic adjustment to AF. This does not affect other lenses.

All is now OK.

Ben Lanterman74611 said:
Ben Lanterman wrote:
My experiences are entirely different, interesting. I use my
24-70L as a point and shoot lens. No thinking necessary (it's a
good thing according to my wife). I find it is a very forgiving
lens as long as I point the camera at what I want to take a photo
of. I do try to make the camera exactly still in space when I
push the shutter button. In that respect the weight of the 1D or
1Ds and 24-70 is good. The mass/inertia of the system will smooth
out the shakes a lot. Also there are photographic scenes that will
give the camera the hardest time. Try to find out what those are
and if you find yourself with one do a manual focus setup.

--
Ben Lanterman

http://public.fotki.com/benlanterman/
http://webpages.charter.net/benlanterman/Index.html
http://www.photo.net/photodb/folder?folder_id=208093

Konrad Hoelzl · Jan 24, 2004

Maybe thats a problem of your viewing application. I cant see the distance in my ACDsee V4.0 but i see it in breezebrowser. it can be tht this info is some canon extension to the exif so the program has to be specialised to see it. And as much as i know PS cant see it either.

Konrad

William R Wood said:
Konrad Hoelzl said:

Just take a look at the thread i started right now. there you can
see my focusing problems with my 24-70L and my D60.
focusing at 70mm i get the exif info of the distance with 11.9
meters which could be quite right. focusing at 24 mm i get a
focusing distance information of 655 meters which is definitly
wrong.

Click to expand...

Konrad,

How do you get the focus distance in your exif info. I looked at
my exif data and I do not see focus distance anywhere.

Thanks for your help.

Regards,

Bill Wood
Fountain Hills, AZ

Randy Nelson · Jan 24, 2004

You are not alone in your frustrations with the 10D and good lens and I don't think going to primes will help. I recently got hold of a 50mm Mk I and was initially disapointed in sharpness of shots from f1.8 to f4. It seems like a waste of a good lens to have to stop down to get acceptable sharpness. I stumbled on this site which explained in quite detailed fashion the problems with focus on the 10D. It explains why my 70-200 f4 misses way too many shots as well.

At the risk of opening another can of worms.
Read this:
http://www.canondslr.com/articles/af-accuracy/

and this:
http://www.canondslr.com/articles/af-flaw/

I've been depressed over the whole thing until I realized that it's a chance to keep my great lens and upgrade to a new body that works after PMA.

RN

t truong said:
Please help! I recently got a Canon 24-70L and have been having
some frustrating experience with it.

In good light or bad, it sometimes front or back-focus when shot
wide open regardless of focal length and . The results are better
when stopped down to 4.0 or 5.6, though I suspect that this is
secondary to increased DOF rather than AF accuracy. There also
seems to be some improvement with AI Servo mode. I am using a 10D.
My previous similar lens was a 24-85/3.5-4.5 with which I never had
problems.

Considering how much this new lens costs, I would expect it to nail
the focus at any time and every time. Am I being unfair in this
judgment?

I only have a couple of days more that I can exchange it.
--
T TRUONG

Frustration with 24-70L focus

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