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PostPosted: Thu Sep 29, 2011 7:08 pm 
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Location: The Netherlands
Hi all,
Ive got some problems, which I now discover, with my 70-200 f/4L. From 70-135 mm it front focusses. I tried to use the Micro AF Adjustments for it, but of course, at 200mm its focus is spot on, so the use of Micro AF Adj. will ruin the focus at 200 of course.
What could I do? The focus isnt always wrong, sometimes it's fine, sometimes. It's clearly though, because when I focus, I could just zoom in to 200mm to see if the focus was correct, and many times it's just from centimeters to meters (infinity) in front of the lens.

Help!

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Ruben

Panasonic DMC-FZ18, Panasonic DMC-FZ28, Canon G5, Canon 350D, Canon 50D + BG-E2N
Tamron 17-50 2.8, Canon EF 70-200mm f/4L USM,
Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies


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PostPosted: Sun Oct 02, 2011 3:39 pm 
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Could nobody help me?

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Ruben

Panasonic DMC-FZ18, Panasonic DMC-FZ28, Canon G5, Canon 350D, Canon 50D + BG-E2N
Tamron 17-50 2.8, Canon EF 70-200mm f/4L USM,
Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies


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PostPosted: Sun Oct 02, 2011 4:07 pm 
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Joined: Tue Jan 04, 2011 7:58 pm
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Location: United Kingdom
If the lens is still under warranty or you took out an insurance policy on it, have you not considered contacting Canon or with whomever you have the lens insured, assuming that there is a warranty-covered fault with it?

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PostPosted: Sun Oct 02, 2011 4:28 pm 
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Location: The Netherlands
Well, it's a used one (not from a store), as my 50D is. So I think there's no warranty left...

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Ruben

Panasonic DMC-FZ18, Panasonic DMC-FZ28, Canon G5, Canon 350D, Canon 50D + BG-E2N
Tamron 17-50 2.8, Canon EF 70-200mm f/4L USM,
Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies


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PostPosted: Sun Oct 02, 2011 11:22 pm 
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Location: bit east of Melbourne
I thought I replied. confused now.

Is it worse in AI Servo compared to single shot mode?
My 50 1.8 does this.

You might have to get it looked at by canon

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PostPosted: Mon Oct 03, 2011 2:18 pm 
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I'll have a try! But since I only use the single shot AF, Im not too sure about it though.
But sending/ letting Canon have a look will cost me money, when I dont have any warranty anymore, right?

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Ruben

Panasonic DMC-FZ18, Panasonic DMC-FZ28, Canon G5, Canon 350D, Canon 50D + BG-E2N
Tamron 17-50 2.8, Canon EF 70-200mm f/4L USM,
Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies


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PostPosted: Fri Nov 04, 2011 8:46 pm 
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Location: The Netherlands
Guys, I really need your help. Except my 70-200 front focusses quite terribly, I also found it to be less sharp than my 18-55 II lens!

I took two pictures, one with the 18-55 II at about the sharpest point, 24mm, @ f/4.
Yes, f/4. The kit.
The other one is the 70-200 f/4L, at its sharpest point, if I have to believe lenstip.com
It's 135mm f/5,6.

What I did is just quite simply, tripod, shot the 2 pictures with the same settings and a remote control. JPEG. Cropped them at +- 100%.

Do I just have a sharp kit lens, or sucks my 70-200? Since it also frontfocusses until you reach the 135mm...

18-55:
Image
18-55 crop by RubendeRoos, on Flickr

70-200:
Image
70-200 crop by RubendeRoos, on Flickr

Could you help me out?

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Ruben

Panasonic DMC-FZ18, Panasonic DMC-FZ28, Canon G5, Canon 350D, Canon 50D + BG-E2N
Tamron 17-50 2.8, Canon EF 70-200mm f/4L USM,
Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies


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PostPosted: Fri Nov 04, 2011 11:22 pm 
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Location: bit east of Melbourne
its not a good picture for comparing front or rear focus. Focus it on a teddy bear or what ever just something that will show depth.
Try doing it in tripod and manual focus maybe.


Alternatively, I have done this before, stand at 22.5 degrees ( or whatever just a shallow angle) to a wall or fence and with AI servo, spot focus on a mark or spot on the wall/fence and take a shot with aperture at f4. Try it at 2m and then at 4-5m at different focus length.
Then just have a look at results and post a few.

If you do it at 70, 110,150 and 200 at f4 at 2 m and then same again at 4m, it may give you a better idea of what is going on.

At least it will show you if its sharp, just at a different spot to what you are focusing on and how much its out where.

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Canon Powershot S95, Canon 6D,7D, Canon 40 2.8 STM, Tamron 24-70 2.8 VC, Canon 17-40 L, Canon 15-85, Canon 85 1.8, Sigma 30 1.4, 50mm 1.8, Canon 100 2.8L Macro, Canon 70-300L +Kenko 1.4 Pro 300DGX, Canon 430EX II and RS 4 Classic


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PostPosted: Fri Nov 04, 2011 11:30 pm 
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To be honest I don't really see the issue

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PostPosted: Sat Nov 05, 2011 6:40 am 
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Google focus test chart and print out the last page in the PDF file. Read the directions and shoot at f4 70mm, 135mm and 200mm on a tripod and post the results here. Then take a picture of a flat object like a poster with some text with a tripod again at the same focal lengths. Take one set using phase detect AF and the next set using contrast detect (live view) AF. Are the results much better in live view? Do the last tests at 50 times focal length so if you are at 200mm be around 10 meters away. (this is just to get a different test from the MFD first test and doesn't have to be that far away if you don't have room.)

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PostPosted: Sat Nov 05, 2011 8:26 am 
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Oh, I think you dont really understand what I meant. Excuse me.
These pictures are taken with contrast AF in live view. That the 70-200 frontfocusses is clear, but not from this test.

What I mean is that the 18-55 looks just a bit sharper than the 70-200, but is my 18-55 really sharp or is the 70-200 that bad that it compares with th 18-55?

Ill do a simple test and post the pictures to let you see it frontfocusses.

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Ruben

Panasonic DMC-FZ18, Panasonic DMC-FZ28, Canon G5, Canon 350D, Canon 50D + BG-E2N
Tamron 17-50 2.8, Canon EF 70-200mm f/4L USM,
Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies


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PostPosted: Sat Nov 05, 2011 1:26 pm 
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I think I just have a very sharp copy of the 18-55, the front/back focus problem is solved though. Spent a few hours with the gear, tripod and some subjects, and finally I got the sharpess Im after, with the regular Phase AF.

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Ruben

Panasonic DMC-FZ18, Panasonic DMC-FZ28, Canon G5, Canon 350D, Canon 50D + BG-E2N
Tamron 17-50 2.8, Canon EF 70-200mm f/4L USM,
Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies


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PostPosted: Sat Nov 05, 2011 11:17 pm 
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come on, you cannot just tell us its solved. We want pics :D
What did you do?

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PostPosted: Sun Nov 06, 2011 7:57 am 
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Oh, Ive already deleted all the pics Id used.
Well, I did hundreds of focus tests in Live View, with different subjects inside (a miniature bike, some sheets with text) and outside (flowers, trees at infinity)...
I started at 70mm, Micro AF Adj. -10. And from -10 to -5, look if you see some sharpness differences, from -5 to +5, back to 0, and all the way to +10, +11... same story at 200mm though, and this for every subject. Evertytime I concluded +10/+11 gave the sharpest pictures.

For now, the front/backfocus issue is solved, but the fact the kitlens has the same sharpness as the 70-200... and yes, those tests were done with Contrast AF, nothing to do with front/backfocus.

I think I should just be happy I got a very sharp kitlens, for $25 :)

Cheers guys!

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Ruben

Panasonic DMC-FZ18, Panasonic DMC-FZ28, Canon G5, Canon 350D, Canon 50D + BG-E2N
Tamron 17-50 2.8, Canon EF 70-200mm f/4L USM,
Canon 18-55 II plus lots of Minolta MD/M42 lenses and bodies


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