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Thread started 25 Jul 2010 (Sunday) 12:45
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7D focus - Please advise on these examples.

 
rider997
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Jul 26, 2010 10:40 as a reply to  @ post 10603773 |  #16

I'm finding this thread interesting. I recently acquired a 7d and have become quite frustrated with some focus behaviors that appear essentially random.

I'm mostly concerned with critical focus on the eye of a subject with a narrow DOF (large aperture). I have literally thousands of these shots in my portfolio shot with a 30d (and prior Canon DSLRs) and a number of lenses (primarily 50mm, 17-50mm, 70-200mm, but others as well at times) at very large apertures, and the behavior of the 30d has always been predictable.

The eye of a typical subject will always have high contrast areas, whether it be the pupil/iris, the eyelid/sclera, the eyelashes/eyelid, etc. On the 30d, it was certainly important to know where to place the focus point (generally the center double precision point) and to accept that some small percentage of shots may have the corner of the eye in critical focus, so great care should be given to subject positioning and focus methodology.

I will generally shoot in one-shot focus, but as conditions dictate, I may shoot in AI-servo. Similar results are expected and experienced with both modes, as long as they're used judiciously.

On the 7d, I've experienced (as stated above) what appears to be essentially random focus behavior. I've used several lenses and especially in low-EV situations (EV 6 or less), I will see back focus OR front focus (without any evident pattern) by no less than 1x - 2x DOF. This means that if my DOF is only 2", the shot will be back focused or front focused by 2" - 4" -- which means that the focus target (the eye) is completely out of focus. No part of the subject which is in focus is even remotely near the active AF point that was used for the shot. No focus and recompose is being used in my testing.

I have run dozens of test shots in both AI-Servo (to try to rule out any for or aft subject or camera movement, although certainly nothing has actually changed by simply picking up a different camera body) as well as One-Shot focus mode, and I'm seeing absolutely no consistency whatsoever. I've used both manual point selection as well as spot manual point selection, and have used the high precision center point as well as peripheral cross-point AF points.

I've even gone so far as to shoot test charts and static subjects (on a tripod, of course, with MLU and a remote release), tried to MA the lens, and used other methods to try to definitively attribute the behavior to a controllable variable- but yet I'm still seeing arbitrary focus come and go. I might get a number of shots sequentially with perfect focus, and then see random front and back focus -- while the camera is on a tripod shooting a static subject in One Shot AF mode, with spot manual AF point selection, and focusing on a subject with high contrast in the focusing area. Of course, in One Shot AF mode, the camera is happily blinking active AF point and beeping to indicate that it's acquired focus.

I'm certainly aware of the behavior, positioning, precision, and size of the AF points on Canon cameras (having owned and used more than half a dozen models since the D30, which is sitting on my desk as I type, was released in 2000) and at this point I'm confounded by the AF behavior of my 7d.

It is absolutely capable of amazingly sharp, detailed photos, has great autofocus, and is overall a stunning camera, but where the focus really matters (low DOF, wide aperture, low light), it's simply not consistent.

The more I mull over this, the more I see parallels with the 1dMk III, where the sub-mirror was actually returning to a slightly different resting position after each shot, causing a physical difference in light-path distance to the AF-sensor, and a corresponding "random" focus behavior. I know this was primarily experienced in AI-Servo mode, but I still recall people complaining about random One-Shot AF performance as well. I'm not saying that this, or anything like it is the cause of the problems that some very small number of 7d owners are experiencing, but merely noting that "random", arbitrary, or unpredictable behaviors do exist and sometimes have origins in hardware as well as software (firmware).




  
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jwcdds
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Jul 26, 2010 10:42 |  #17

Shooting at f/1.2 is challenging. :lol: I say I get about 25%-50% keeper rate for the time being. But much of it is my fault/doing since I should simply slap on my flash instead. My son's not terribly compliant at 6months old in holding steady for me.

I'm curious to see your results. Let's see if you just have a screwy 7D, or whether it's the 24L.


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snyderman
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Jul 26, 2010 12:24 |  #18

I've posted this before because there have been instances of 7D bodies with inconsistent or random focus issues. This is a good way to identify if your body is experiencing random focus issues:

Take a magazine cover with really sharp test or graphics. I used a Golf Digest cover. Tape it to a wall at around 4' height. Light it well but make sure no glare is present.

Mount camera on tripod. Move tripod to a reasonable distance from target for lens focal length. For my test I used an 85mm f/1.8 lens at about 10' from the target. Set camera to 2 second timer. Set camera to ONE-SHOT mode and single centerpoint focus. Use something around these settings: ISO 400, f/8; 1/200 on shutter. Somewhere around there should give a decent exposure.

Take a series of 5-10 shots manually defocusing the lens each time and using auto focus to refocus the target. Upload your 5-10 shots and see how many produced razor sharp focus.

If your results remain random or inconsistent, send the body to Canon like I did. Mine came back with zero focus issues. Before, I was lucky to get 1 in 5 shots in sharp focus.

Good luck and keep us posted.

dave


Canon 5D2 > 35L-85L-135L

  
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Ross_Curtis
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Jul 26, 2010 13:49 |  #19

Mine seems to be accurate in high contrast well lit situations, the test snyderman suggested doesn't show up my issues. I've done this using a VFG lens chart and at f8 in a well lit situation it's perfect.

However, rider997 is experiencing the exact same issues I have, totally inconsistent random focus shifts in lower lighting situations.

I can shot a series of shots which will be almost perfect, then suddently the next 10 are completely out.
I have done some tests this evening (I need to sort through them), but from inital checks it does seem the 40D is VERY consistent where as the 7D is all over the place. At times it's almost spot on, then other times completely out. There almost seems no explaination for why this is happening as nothing in the pictures has changed.

I hope to post these later on this evening.


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Ross_Curtis
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Jul 26, 2010 17:04 as a reply to  @ Ross_Curtis's post |  #20

I didn't use a tripod as it is a PITA to keep swapping cameras (allen key type), instead I layed the camera on the table/floor and used a remote
release. All the images are taken of a white box with black writing and in all cases I used the centre of the barcode as my centre point.

Each shot has 4 images, the bottom right being the control shot using live view zoomed into 10x, the others are all auto focus, single shot, centre
(spot in the 7D case) with the ISO at 400 in order to keep a high shutter. Between each shot I cranked the focus to either infinity or minimum focus.

The first 4 images are taken with the door behind me IE light falling onto the surface of the box and then turned round so the box was in shadow.

There are two images with each camera. All with the 24L II set at F/1.4.

40D

http://i267.photobucke​t.com …urtis/7D%20test​s/40D1.jpg (external link)
http://i267.photobucke​t.com …urtis/7D%20test​s/40D2.jpg (external link)

7D

http://i267.photobucke​t.com …Curtis/7D%20tes​ts/7D1.jpg (external link)
http://i267.photobucke​t.com …Curtis/7D%20tes​ts/7D2.jpg (external link)

As you can see the 40D handled this with ease.

Next up I swapped the 24L for the 135L, all shot at F/2

40D

http://i267.photobucke​t.com …is/7D%20tests/4​0D1351.jpg (external link)
http://i267.photobucke​t.com …is/7D%20tests/4​0D1352.jpg (external link)

7D
There is a slight variation, but on the whole pretty good:

http://i267.photobucke​t.com …20tests/7D1351a​llgood.jpg (external link)

Straight after this set came these:

http://i267.photobucke​t.com …D135straightaft​ergood.jpg (external link)

Then:

http://i267.photobucke​t.com …tis/7D%20tests/​7D1352.jpg (external link)

I've not handpicked certain images to show the 7D in a bad light. In some of the 40D shots there was some variations; however, they are negligable.
These shots are typical of the results I have been getting since day one.

There does seem a coralation between OOF images and lower contrast scenes, if both cameras were struggling in these circumstances I'd accept this as, 'just the way it is', but when the 7D performs so badly and inconsistently compared to a stella 40D it raises questions.

As ryder997 said, the focus behavior appear essentially random.

Thanks
Ross


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Jul 26, 2010 17:28 |  #21

IMO, time to contact Canon and send them the photos and see what they have to say as an explanation.


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Brett
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Jul 26, 2010 17:41 |  #22

Remember that you are looking at a significantly smaller portion of the total image when viewing a 7D image than when viewing a 40D image, when both are viewed at 100%.

I made a graphic awhile back comparing the 100% view of a 5D image vs. 5DII. The image is pixel-accurate. Note how much smaller of an area of the image is shown on my old 1440x900 monitor:


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Jul 26, 2010 17:47 |  #23

snyderman wrote in post #10605695 (external link)
If your results remain random or inconsistent, send the body to Canon like I did. Mine came back with zero focus issues. Before, I was lucky to get 1 in 5 shots in sharp focus.

Ditto: my shots were inconsistent with probably even fewer than 1 in 5 in focus, I sent the camera to Canon, I got it back with zero focus issues.


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rider997
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Jul 26, 2010 17:51 |  #24

jgrussell wrote in post #10607380 (external link)
Ditto: my shots were inconsistent with probably even fewer than 1 in 5 in focus, I sent the camera to Canon, I got it back with zero focus issues.

I don't suppose your repair bill had any useful information regarding the diagnosis and fix, did it? I know Canon tends to print meaningless boilerplate like "Autofocus not to spec, brought autofocus to spec, camera focuses as designed".




  
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Ross_Curtis
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Jul 27, 2010 04:20 |  #25

Luckily I live close to Canon so I will be hand delivering it tonight.

I didn't mention this but I took the lens and camera into Canon last week. It was returned simply saying calibrated auto focus.

Tonight I will be armed with my test shots. I'll let you know the outcome later in the week.

Thanks for all your comments and advice.

Ross


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peber
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Jul 30, 2010 11:45 |  #26

Just a thought... do you have filters on your lenses? When I got my 7d my first pictures seemed quite soft compared to my old 30d. Then I removed my filters and now if it misses focus it is - probably - just "user error", if I have chosen the right focus point and pointed it at the right place my pictures are sharp. I have not done a "scientific" test but this solved my problems...

/Per


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Aug 07, 2010 16:59 as a reply to  @ peber's post |  #27

Any updates after taking your 7d to canon the second time?


Jason

  
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rider997
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Sep 12, 2010 21:52 |  #28

jase1125 wrote in post #10679304 (external link)
Any updates after taking your 7d to canon the second time?

For the record: Canon replaced the main PCB assembly in my EF 50mm f/1.4 lens and did another electronic adjustment on the AF assembly on the camera.

It's now focusing absolutely brilliantly. I'm getting used to some slight differences in how it focuses or what it will focus on compared to past xxD bodies, but overall the focus speed and accuracy are absolutely amazing.




  
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JPayne
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Sep 13, 2010 07:43 as a reply to  @ rider997's post |  #29

So, if you are going to send the camera to Canon for a fix, do you have to provide examples? I have similar problems.

I've noticed it on every shoot I have done but never thought too much about it. I never had issues like this with my 400D.

Yesterday I did a family shoot. Most shots where at F8 and on a tripod, it was dim in certain conditions but only about 60% of the shots are in focus. The rest can clean up ok but nothing like they should be. It's highly annoying as when I shoot weddings I get some shots that are critical or would have been tremendous if focus was correctly achieved but for some reason some are just out. I have less of a problem at short focal lengths but the 70-200 on a tripod has very inconsistent results in conditions without high contrast.

What to do?


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paddleout
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Sep 13, 2010 11:22 |  #30

j28 wrote in post #10898934 (external link)
So, if you are going to send the camera to Canon for a fix, do you have to provide examples? I have similar problems.

What to do?

In the same boat with you... this is my first Canon product I have questioned but about to seriously give up on all the fixes I keep trying and send the body back.


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7D focus - Please advise on these examples.
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