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Author Topic: Focusing issues  (Read 3558 times)

jim t

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Focusing issues
« on: September 30, 2009, 04:05:06 pm »

Shooting a Canon 40D with a 24-70mm 2.8L lens, my photos are out of focus.  I've heard these lenses have focusing issues.  Even in manual mode it is hard for me to get a clear shot with my vision.

So my questions are, do I need to send this to Canon and have it checked out?  What can I expect if I do and what costs are involved?

By the way, I have a $90 Tiffen Filter protecting the lens.
« Last Edit: September 30, 2009, 04:16:21 pm by jim t »
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lovell

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Focusing issues
« Reply #1 on: September 30, 2009, 04:52:40 pm »

Quote from: jim t
Shooting a Canon 40D with a 24-70mm 2.8L lens, my photos are out of focus.  I've heard these lenses have focusing issues.  Even in manual mode it is hard for me to get a clear shot with my vision.

So my questions are, do I need to send this to Canon and have it checked out?  What can I expect if I do and what costs are involved?

By the way, I have a $90 Tiffen Filter protecting the lens.

What kind of shots are you taking, and what is your camera workflow/setup?  F-stops, how far from subjects, etc...first lets determine if the problem is user error, then go from there...
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kevinwilson

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Focusing issues
« Reply #2 on: October 02, 2009, 04:48:48 pm »

Quote from: jim t
I do all sorts of shooting.  From Landscape to portrait I'm having very soft and unfocused photos with this lens.  Even with a tripod, fast/slow shutter, different ISO speeds..........

I suggest you take it back to Canon and have it checked before you do anything of importance. It has often been mentioned  this lens has issues, then again it happens to have sold many units.

Kevin
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Sheldon N

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Focusing issues
« Reply #3 on: October 02, 2009, 07:26:14 pm »

Quote from: jim t
I do all sorts of shooting.  From Landscape to portrait I'm having very soft and unfocused photos with this lens.  Even with a tripod, fast/slow shutter, different ISO speeds..........

Example photos? Is this an issue with the lens focusing too closely or too far from the intended focus point (front/back focus) or is it a problem with general unsharpness?

I've had a couple 24-70's and they've never been anything but stellar.
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pcunite

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Focusing issues
« Reply #4 on: October 03, 2009, 12:46:31 am »

I went through it trying to get my 24-70 fixed... but they did get it right. It is a very good lens and sharp as a prime at f5.6.
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K.C.

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Focusing issues
« Reply #5 on: October 03, 2009, 02:17:56 am »

Quote from: Sheldon N
I've had a couple 24-70's and they've never been anything but stellar.

Same here. I've used several of them, own one now and none of them have had any issues. Great lens.
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Sheldon N

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Focusing issues
« Reply #6 on: October 03, 2009, 11:32:52 am »

Well, your first problem is that you shot it at 1/15 of a second. I'm assuming you were shooting handheld? If so, you can't expect sharp images. You should have bumped the ISO from 500 up to 1600 and gotten a more acceptable shutter speed.

Do you have any example photos shot in better lighting?
« Last Edit: October 03, 2009, 11:33:12 am by Sheldon N »
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nemophoto

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Focusing issues
« Reply #7 on: October 03, 2009, 02:12:13 pm »

I've owned the lens for about five years and find it very sharp at f4 and above. And, that includes having had Canon rebuild the lens after it crashed, tripod and all, and snapped in several pieces. Afterward, I was on a shoot last year and found I had horrible focus falloff, especially at the edges, even at 5.6. Now here's the "DUH" moment. I got rid of my UV filter, and suddenly, everything was tack sharp. I had a quality optic, trashed by a crappy filter. Since then, I've replaced all my filters with B+W filters (made by Schneider), and haven't experienced comparable problems with any of my seven lenses.

So, when you question the focus, you might do a test with the lens without any filter (if you use one). Additionally, as Sheldon pointed out, 1/15 won't guarantee you the sharpest results hand-held. If you really feel it's an issue, send the lens and body to Canon for focus calibration.

Nemo
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jjlphoto

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Focusing issues
« Reply #8 on: October 03, 2009, 03:51:26 pm »

Quote from: jim t
These two photos were shot at 1/64 of a second, ISO 400, F4, F4.5 & handheld.  Very similar setup.  Targeting the center of the flower, the first one isn't as clear as the second.  I remember manually focusing the sharper one, (photo 2).

I assume it's more difficult to get a sharper picture at F2.8.(?)

And when selecting Full Auto, shouldn't the camera come close to giving me a sharp shot?


You are asking your camera to do too much. There is no substitute for experience and talent. Also, 1/64 is still pretty slow for the macro-type floral shots you posted.
« Last Edit: October 03, 2009, 03:53:40 pm by jjlphoto »
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Sheldon N

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Focusing issues
« Reply #9 on: October 04, 2009, 11:05:35 am »

My guess is that your problem is technique, not your lens. You are seeing a combination of blur from too slow shutter speed, shallow depth of field, and not knowing exactly which focus point the camera is selecting when autofocusing.

I wouldn't send it to Canon, that won't help with any of the above issues.
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Ken Bennett

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Focusing issues
« Reply #10 on: October 04, 2009, 09:03:17 pm »

Quote from: jim t
I assume it's more difficult to get a sharper picture at F2.8.(?)

And when selecting Full Auto, shouldn't the camera come close to giving me a sharp shot?


1. The amount of the photo in focus (Depth of Field) is less at f/2.8 than at smaller apertures. So you have less room for error -- a very slight focusing error is much worse at f/2.8 than at f/8. But when properly focused, the area in focus will be very sharp even at f/2.8.

2. No, absolutely not. The camera doesn't have any idea what part of the image you want to be in sharp focus. For example, in your macro flower shot, you could want the tip of the stamens in focus (or maybe those are the pistils -- biology was a long time ago), or maybe you want the petal, or the bee hovering over the flower. On full auto mode, the camera will simply focus on whatever part of the subject has the most contrast (or is the closest to the camera, or whatever algorithm the camera uses.)

In each of your examples, the shutter speed is too slow to guarantee a sharp photo hand held. The camera moves during the exposure, and results in slightly blurry images. In those situation, you can either boost your ISO to get a higher shutter speed, use a tripod, or you can try shooting two or three images on Continuous High motor drive -- this often results in one photo being noticeably sharper than the others. (I get a lot of sharp photos using this last technique, at surprisingly slow shutter speeds.)

This is not to say that you don't have a technical problem with your camera and lens. I have a 40D and it absolutely would not focus my 24/1.4 with any precision. After testing it very carefully on a tripod, with good technique, I sent the camera, lens, and some test photos to Canon, who fixed the problem. (Newer cameras allow the user to fix this, for the most part.) But my 24-70 is a great lens on the 40D, very sharp and makes nice photos.

So your best bet is to test the camera and lens combination on a solid tripod, using autofocus (choosing the center point), in various kinds of light, and check the resulting images. I also like to manually focus using Live View, zoomed in to 10x to adjust the focus. Then I compare the two. Always defocus the lens before initiating auto focus. Give it two or three tries, and check all of them. If you are still having problems, call Canon's service department. They have fixed this issue for me under warranty when the camera and/or lens was new.

In the meantime, tighten up your shooting technique. Make sure your shutter speed is fast enough, press the shutter button slowly and carefully, brace your arms in against your torso, etc. Use a tripod when necessary. Good luck.
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