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Author Topic: 7D focusing question??  (Read 39238 times)

justsomedude

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Re: 7D focusing question??
« Reply #90 on: June 04, 2011, 01:10:05 AM »
Nice shot. How'd you light it?

Thanks unfocused! 

This shot was lit with two off-camera speedlights triggered by the cheapie Yongnuo RF602 radio triggers

The main light was a Canon 580exII bounced off a white umbrella.  It was located just above and behind the camera position, about 4' off the gym floor.  The umbrella was angled at an approximate 45-degree down angle and aimed directly at the kettlebell/hand area. 

The side light was a Vivitar 285HV gelled red using the old DIY credit card gel holder trick (which only works on the Vivitars).  The speedlight was 90-degrees off the camera position, about five feet to the left of the kettlebell.  It was mounted on the Yongnuo radio shoe, which was attached to a Gorilla pod.   The flash head was no more than 18" off the floor, and aimed directly at the kettlebell - or just five-to-ten degrees to its left (into the image).

Sorry, but I don't remember the power settings on the speedlights.  I need to start taking better notes of my setups.  :/ 

Here's a graphical depiction:

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Re: 7D focusing question??
« Reply #90 on: June 04, 2011, 01:10:05 AM »

justsomedude

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Re: 7D focusing question??
« Reply #91 on: June 13, 2011, 03:42:43 PM »
After experiencing various AF problems with my Tokina 11-16mm, I finally sent it in to THK Photo Products (Tokina's US servicer) in California for service/repair.  It looks like Tokina is quasi-acknowledging a compatibility issue with the 11-16mm lens and the 7D.  Here is the first response I received from the THK service representative in my email correspondence with him on June 13, 2011:

Quote from: THK Photo Products
In regards to the Tokina 11-16mm lens you sent in for repair, my technician has informed me that it was necessary to send your lens back to the factory in Japan.

We can offer you a replacement lens or arrange for a refund from the place of purchase.

After replying that I would love a replacement (as I truly love the lens), I asked the service rep if a replacement would definitely solve my problem - as I would like to avoid a repeat of the same AF issue.  Here is his response:

Quote from: THK Photo Products
Japan has found that when using this lens on the 7D, it works best when used in the Center Focus Mode. In the 19 point AF mode, the camera will automatically focus in on what ever is nearest in the frame, and this can cause soft images., However, when using the Center Focus Mode, the camera will focus in of the center of the subject without any problem.

We will replace the lens for you immediately.

However, it is not clear why my original lens would have to be sent back to Japan, unless there is some type of update required on earlier models of the 11-16mm to make it compatible with Center Focus Mode on the 7D.

Anyway, it looks like this should solve my OOF problems, and I'm looking forward to receiving the replacement lens (even if it means I can't use the other focus points).  I do love the Tokina 11-16mm, and am glad THK was prompt and responsive to my service request.

Hopefully others will find this information useful.

neuroanatomist

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Re: 7D focusing question??
« Reply #92 on: June 13, 2011, 04:47:28 PM »
Quote from: THK Photo Products
In the 19 point AF mode, the camera will automatically focus in on what ever is nearest in the frame, and this can cause soft images.

Gee, you mean Tokina has discovered the normal behavior of automatic AF point selection?   Regarding Automatic AF point selection Mode, Canon states, "When working with non-moving subjects in the One-Shot AF mode, the EOS 7D starts with all 19 AF points active. The camera will then use the point or points which “see” the nearest subject with adequate detail."  I'm not sure what Tokina thinks the problem is here...
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justsomedude

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Re: 7D focusing question??
« Reply #93 on: June 13, 2011, 05:14:42 PM »
Gee, you mean Tokina has discovered the normal behavior of automatic AF point selection?   Regarding Automatic AF point selection Mode, Canon states, "When working with non-moving subjects in the One-Shot AF mode, the EOS 7D starts with all 19 AF points active. The camera will then use the point or points which “see” the nearest subject with adequate detail."  I'm not sure what Tokina thinks the problem is here...

Neuro,

Maybe I should've been clearer in my original post, but the problem I experienced was in manual AF point selection mode.  Manually selecting any of the outside AF points would result in no-focus, and the lens would automatically focus on whatever was nearest to it.  So, even if I had selected a distant object with an outside focus point - if something was closer - the lens would focus on that.

That, to me, is a problem - but can be overcome as long as the user is aware of the limitation.

unfocused

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Re: 7D focusing question??
« Reply #94 on: June 13, 2011, 05:50:23 PM »
Okay. I was confused too. Because I was also thinking: "isn't that what autofocus does anyway?"

Glad you clarified that. I'm a big fan of the Tokina 11-16. At the risk of unleashing a firestorm of Canon lens fetishists, I have to say I think it's a better lens than the Canon 10-22. I'm going to have to try the center-point focus now. I guess usually, with a lens that wide, I haven't found focus to be as critical, so haven't really noticed the problem. Now, I'm curious.
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neuroanatomist

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Re: 7D focusing question??
« Reply #95 on: June 13, 2011, 05:57:02 PM »
...the problem I experienced was in manual AF point selection mode.  Manually selecting any of the outside AF points would result in no-focus, and the lens would automatically focus on whatever was nearest to it.  So, even if I had selected a distant object with an outside focus point - if something was closer - the lens would focus on that.

Thanks for the clarification, that makes sense and also clarifies Tokina's response.  It sounds like an issue with Tokina's reverse-engineering of the Canon AF systems not playing nicely with the 7D's AF system.  That's a risk with 3rd party lenses, especially for bodies released after the lens.  IIRC, in some cases Sigma offered to re-chip lenses in some situations, to correct problems of that nature.  Maybe Tokina can/is working something out...which would be good, because by all accounts the 11-16mm is a very nice lens.
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justsomedude

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Re: 7D focusing question??
« Reply #96 on: June 13, 2011, 05:59:00 PM »
Okay. I was confused too. Because I was also thinking: "isn't that what autofocus does anyway?"

Glad you clarified that. I'm a big fan of the Tokina 11-16. At the risk of unleashing a firestorm of Canon lens fetishists, I have to say I think it's a better lens than the Canon 10-22. I'm going to have to try the center-point focus now. I guess usually, with a lens that wide, I haven't found focus to be as critical, so haven't really noticed the problem. Now, I'm curious.

Unfocused... I totally agree, and feel the Tokina 11-16mm is far superior to the Canon 10-22mm.  I've owned both, and after comparing the CA and clarity between the two, I found that the Canon was no match for the Tokina (at least on my 40D).  I'm hoping the replacement lens brings similar performance to my 7D.

Regarding the focus issues I had, check some samples on my website.  Look for "Tokina" in the title of the problem images.

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Re: 7D focusing question??
« Reply #96 on: June 13, 2011, 05:59:00 PM »

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Re: 7D focusing question??
« Reply #97 on: July 30, 2011, 12:22:50 PM »
I have a hard time getting a sharp image with my new 7D.  None of the Sigma lenses I'd used with my old Canons work (looks like I need a major eye exam, even on auto-focus!) and I was told by my local Canon dealer that only the new Canon lenses are compatible.  I've rented some Canon lenses, and the images are good, but I wouldn't call them razor sharp.  Looks like I'm going to need new lenses.  Does anyone have recommendations?  For a start I'm looking for a wide angle zoom (12-24 range) and a general zoom (24-200 range).

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Re: 7D focusing question??
« Reply #98 on: July 30, 2011, 12:40:06 PM »
I have a hard time getting a sharp image with my new 7D.  None of the Sigma lenses I'd used with my old Canons work (looks like I need a major eye exam, even on auto-focus!) and I was told by my local Canon dealer that only the new Canon lenses are compatible.  I've rented some Canon lenses, and the images are good, but I wouldn't call them razor sharp.  Looks like I'm going to need new lenses.  Does anyone have recommendations?  For a start I'm looking for a wide angle zoom (12-24 range) and a general zoom (24-200 range).

Any Canon EF lens is compatible, they have been made for many years now.  The really old FD, and FL lenses are not compatible, and will not even mount to your camera.  Older sigma EOS compatible lenses may be incompatible electronically with Digital SLR's, so watch out with used Sigma lenses, try them if in doubt.

The high resolution of the camera body means that to get sharp images when you view them 1:1, the AF must be near perfect.  The camera has a facility called Autofocus micro adjustment, and I do it on all my lenses.  On the 7d, it makes a huge difference to just tweak the setting by 2 points.

There are lots of writeups on how to do this, here is my favorite for adjusting your body to your lens.

http://regex.info/blog/photo-tech/focus-chart

You have two options, one is to adjust the body for all lenses, the second is to adjust it for each lens.

I always adjust it for each lens.  for zooms, I use the longest focal length.  Always adjust at maximum aperture.

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The second thing is to realize that the tiny pixels in a 18 mp sensor are more susceptable to shaking motion of the camera, so if you do not have IS, or have it tripod mounted, keep the shutter speed to 1/triple the actual focal length as a mimimum.  Conventional wisdom is to use 1/equavalent focal length.

So, for a 100mm lens and no IS, use 1/320.  Conventional wisdom would say 1/160 sec, and that works well on the lower MP cameras.  You can experiment to find what works for you.

If your subject is moving, much higher shutter speeds may be required to freeze action.




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Re: 7D focusing question??
« Reply #98 on: July 30, 2011, 12:40:06 PM »