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Author Topic: 5D MKIII Auto Focus Question  (Read 2585 times)

yuxinhong

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5D MKIII Auto Focus Question
« on: March 31, 2012, 03:02:17 PM »
My 5D MkIII can not archive focus on subject that has solid color with light distributed evenly on the surface. example the walls, i tried this on all my walls with different colors, green, coffee, white, the test i did was during the day, with enough light.
my pink cabinet, powered off monitor screen, etc.

I must move the focus point to some place that have color difference like edges in order to achieve focus.

my 60D is more successfully achieving focus on these situations on the monitor screen and pink cabinet.

is it the same with your camera?
« Last Edit: March 31, 2012, 03:06:44 PM by yuxinhong »

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5D MKIII Auto Focus Question
« on: March 31, 2012, 03:02:17 PM »

swampler

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Re: 5D MKIII Auto Focus Question
« Reply #1 on: March 31, 2012, 10:12:12 PM »
Not sure why the 60D would be better, but otherwise it sounds correct. The camera needs some contrasting area to be able to focus.

neuroanatomist

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Re: 5D MKIII Auto Focus Question
« Reply #2 on: March 31, 2012, 10:27:46 PM »
A feature with contrast, and in the proper orientation relative to the AF sensor, is required.  You may not realize that the actual AF point is larger than the little box in the VF representing the point, and the differential is bigger on the 60D.  Most likely, when you get a lock it's because even though the little box isn't over an edge, it's near one, and the larger AF point is picking up that edge.
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yuxinhong

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Re: 5D MKIII Auto Focus Question
« Reply #3 on: March 31, 2012, 11:12:49 PM »
hank you for your reply, yes, when its close enough to see the details on the wall, both camera can achieve focus easily.

tested again, my 60D is can achieve focus on some subjects like my powered off monitor screen, 5D can't,
but the picture on 60D is blurry, so the focus is incorrect even thou it successfully focused.

so i guess the 60D's focus's allowance is higher than 5D to achieve more successes.

Drizzt321

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Re: 5D MKIII Auto Focus Question
« Reply #4 on: April 01, 2012, 03:47:32 AM »
hank you for your reply, yes, when its close enough to see the details on the wall, both camera can achieve focus easily.

tested again, my 60D is can achieve focus on some subjects like my powered off monitor screen, 5D can't,
but the picture on 60D is blurry, so the focus is incorrect even thou it successfully focused.

so i guess the 60D's focus's allowance is higher than 5D to achieve more successes.

Are you sure it actual does correctly focus lock? Or is it just that it stops trying to focus and gives up?
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darash

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Re: 5D MKIII Auto Focus Question
« Reply #5 on: April 01, 2012, 04:39:02 AM »
I tried focusing on a 3mm white flower today at a botanical garden and failed miserably.  To be fair, I was just using the kit lens.
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Re: 5D MKIII Auto Focus Question
« Reply #6 on: April 01, 2012, 06:46:11 AM »
One review of the MkIII commented that the MkII would often indicate focus lock in low light/contrast situations incorrectly, I would imagine it's the same with the 60D, whereas the MkIII would only indicate focus lock when it was actually achieved. I think that not locking focus is better than focusing incorrectly.
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Re: 5D MKIII Auto Focus Question
« Reply #6 on: April 01, 2012, 06:46:11 AM »

Drizzt321

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Re: 5D MKIII Auto Focus Question
« Reply #7 on: April 01, 2012, 01:47:38 PM »
I tried focusing on a 3mm white flower today at a botanical garden and failed miserably.  To be fair, I was just using the kit lens.

The 24-105L? That's a good lens. Were you in spot? Maybe try using point or expansion or surround next time. Give it more points to use, but still keep it as a small grouping.
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se7en

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Re: 5D MKIII Auto Focus Question
« Reply #8 on: April 01, 2012, 05:07:58 PM »
so the focus is incorrect even thou it successfully focused.

uhhhhh? cannot compute this sentence.

DavidRiesenberg

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Re: 5D MKIII Auto Focus Question
« Reply #9 on: April 01, 2012, 06:25:46 PM »
Hmm, maybe I wasn't paying attention or never really tried to focus on something that I know the camera can't focus on but I don't think I ever encountered a situation where a camera reports a lock when it hasn't actually really focused.

Sean Nel

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Re: 5D MKIII Auto Focus Question
« Reply #10 on: April 02, 2012, 06:24:53 AM »
Many cameras will stop focus so that the lenses doesn't hunt if it can't achieve focus lock. It's actually something you can set on something like the 5DmkIII or 7D... might that have kicked in?




darash

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Re: 5D MKIII Auto Focus Question
« Reply #11 on: April 02, 2012, 07:00:39 AM »
I tried focusing on a 3mm white flower today at a botanical garden and failed miserably.  To be fair, I was just using the kit lens.

The 24-105L? That's a good lens. Were you in spot? Maybe try using point or expansion or surround next time. Give it more points to use, but still keep it as a small grouping.

I do agree that it's a good lens. I was using spot at that time. I'll try using expansion or surround next time. Thanks for the advice.
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Re: 5D MKIII Auto Focus Question
« Reply #11 on: April 02, 2012, 07:00:39 AM »