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Author Topic: focus-- 5diii  (Read 3119 times)

dbm

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focus-- 5diii
« on: September 19, 2013, 02:32:12 PM »
I know i should know the answer to this but  . . . .
when focusing on a face with a 5diii, using all the sensors and allowing the camera to choose, does it focus on the nose (the nearest part) or the eyes
i have typically used a single point , in AI focus mode, focused on the eyes and then recomposed
i have noticed when i use an aperture that had a narrow DOF, especially when recomposing, that some of my portraits are subtley off, with focus on the wrong part of the face.
not sure if the focus is off from the start, if it is the recompsing that is throwing it off, or if it just is a matter of the subject (kid) moving just a bit in the context of narrow DOF
i am wondering if i should be using a larger group of focus sensors or all the sensors and if tha might help it lock and track a bit better
thoughts?

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focus-- 5diii
« on: September 19, 2013, 02:32:12 PM »

neuroanatomist

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Re: focus-- 5diii
« Reply #1 on: September 19, 2013, 03:06:23 PM »
Are you looking through the viewfinder?  If so, the 5DIII does not have face recognition with its phase detect AF (the 1D X does).  Face detect is available in live view only, and I would assume it tries to focus on the eyes (but I really have no idea, as I have never used it).

Your best bet is to select an AF point manually, and make sure that point is on the subject's eye.  Be aware that when you are looking through the viewfinder, the actual AF point is larger than the little box that represents it in the viewfinder.  Therefore, if there something of substantially higher contrast than the eye just outside the box (such as a dark hairline), the AF system will likely lock onto that instead.
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dbm

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Re: focus-- 5diii
« Reply #2 on: September 19, 2013, 06:15:20 PM »
thanks
i am looking through the vf
i have no experience with live view, i find it a bit harder to stabilize the camera
i usually do use a single center point on the eye, and then recompose
do you think recomposing can be the problem with a narrow DOF situation (i especially notice it now that i have gone from crop to full frame, with closer subjects, with the 24-70 lens as opposed to the 70-200)

Drizzt321

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Re: focus-- 5diii
« Reply #3 on: September 19, 2013, 07:37:54 PM »
thanks
i am looking through the vf
i have no experience with live view, i find it a bit harder to stabilize the camera
i usually do use a single center point on the eye, and then recompose
do you think recomposing can be the problem with a narrow DOF situation (i especially notice it now that i have gone from crop to full frame, with closer subjects, with the 24-70 lens as opposed to the 70-200)

Yes, with a very narrow DoF with focus & recompose you might move the part you focused on out of the acceptable plane of focus. Instead, if there is time, move the AF point towards the top/side. You can actually set the 5d3 to only use the cross-type AF points if you want, or leave it using all 61-points and you can choose the exact one.
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dbm

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Re: focus-- 5diii
« Reply #4 on: September 19, 2013, 09:08:33 PM »
thanks, i will try that
till now i have found it useful to use only the center point because it seemed to give me control of the situation but i think the tolerances are a bit more stringent with my current setup

what is the advantage of limiting to only the cross type?

(i understand that i am one of those people whose equipment exceeds their skills and understanding but it certainly is fun to learn)

scottkinfw

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Re: focus-- 5diii
« Reply #5 on: September 19, 2013, 09:55:40 PM »
I am not an expert on explaining this but will try.

When you recompose, especially with a very narrow DOF, the focus may be slightly off because the length from plane of the sensor to the point of focus has shifted when you recompose.

You may want to try to compose, and pick a focus point on the camera to hit right on the eye. You might also try One shot (if the subject is still, faster shutter speed) as well which may help.  A tripod is also helpful.  When you use more sensors, the camera will try to focus on the closest point, which is usually the nose on the face.

The 5DIII is a lot to master.

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dbm

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Re: focus-- 5diii
« Reply #6 on: September 20, 2013, 06:27:37 AM »
thanks sek
btw what is your profile picture of?

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Re: focus-- 5diii
« Reply #6 on: September 20, 2013, 06:27:37 AM »

rpt

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Re: focus-- 5diii
« Reply #7 on: September 20, 2013, 06:58:47 AM »
thanks sek
btw what is your profile picture of?
It is probably a billy goat... The snout looks like my dog's though.

Drizzt321

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Re: focus-- 5diii
« Reply #8 on: September 20, 2013, 01:11:01 PM »
thanks, i will try that
till now i have found it useful to use only the center point because it seemed to give me control of the situation but i think the tolerances are a bit more stringent with my current setup

what is the advantage of limiting to only the cross type?

(i understand that i am one of those people whose equipment exceeds their skills and understanding but it certainly is fun to learn)

Well, the edge points are horizontal only, which means if you have primarily horizontal lines it will struggle, whereas the cross-type have both horizontal and vertical which means (in theory) that it will be more capable of focusing on both horizontal and/or vertical lines on the AF point. However, in practice, I haven't noticed much of a difference either way.

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Scott_McPhee

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Re: focus-- 5diii
« Reply #9 on: September 24, 2013, 05:08:33 PM »
I have a 5D3 and I select an AF point closest to where I want to focus, back-button AF to lock and move to recompose then shoot.
This minimises the chance that re-composing would change the AF plane of focus.

Works well for me.

Also, I try and shoot portraits in the studio at f8 or f11 - nice sharp aperture for my lens and decent depth of field to work with too.

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Re: focus-- 5diii
« Reply #9 on: September 24, 2013, 05:08:33 PM »