focusing method for portrait..


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FireZ

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Sep 21, 2008
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#1
wondering...have this question been discussed or mentioned coz i couldn't find any thread..
so...the question begins..

there was once i heard that, if wanna shoot portrait and wanna eyes to b sharp...1 of the method is to focus the eyes first (assuming using centre AF point)..then re-compose the pics...but..won't the focus of the eyes become non-focus due to the different in angle?!..

don't shoot me ar...i really couldn't find thread or info in internet hence post here..

advance thx from noob...

thanks!
 

Snoweagle

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Jan 26, 2005
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#2
wondering...have this question been discussed or mentioned coz i couldn't find any thread..
so...the question begins..

there was once i heard that, if wanna shoot portrait and wanna eyes to b sharp...1 of the method is to focus the eyes first (assuming using centre AF point)..then re-compose the pics...but..won't the focus of the eyes become non-focus due to the different in angle?!..

don't shoot me ar...i really couldn't find thread or info in internet hence post here..

advance thx from noob...

thanks!
No. Always pick the focusing point closest to the point where u want to focus so u won't have to recompose so much. In the portrait orientation, pick the top focusing point (right-most in landscape orientation) is u want to focus on the eyes.
 

FireZ

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#4
No. Always pick the focusing point closest to the point where u want to focus so u won't have to recompose so much. In the portrait orientation, pick the top focusing point (right-most in landscape orientation) is u want to focus on the eyes.
Oh crap....so i got the wrong idea / hear wrongly ar....
argh..thx for the info!!!

OIC!!!..........recompose is possible if small apertures use for the shooting..
no wonder when i use f2.8...recompose only spoil the pics...

perhaps i gonna use like f5.6 onward if wanna focus on eyes then refocus bah...

thanks both shifu for the inputs...
cheer!;)
 

roger8

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Sep 20, 2005
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#5
wondering...have this question been discussed or mentioned coz i couldn't find any thread..
so...the question begins..

there was once i heard that, if wanna shoot portrait and wanna eyes to b sharp...1 of the method is to focus the eyes first (assuming using centre AF point)..then re-compose the pics...but..won't the focus of the eyes become non-focus due to the different in angle?!..

don't shoot me ar...i really couldn't find thread or info in internet hence post here..

advance thx from noob...

thanks!

Sounds like your problem is depth of field due to the use of f2.8 aperture. I have attached a website where you can sort out your OOF problems. As a rule of thumb, for sharp portraits try no larger than f5.6 depending on:

1. focal length of the lens,
2. distance of the subject from the camera,
3. crop factor of the sensor,
4. where your focussing point is and
5. contrast of the focussed point.

http://www.dofmaster.com/dofjs.html

You can use f2.8 or f4 for bokeh effect but you have to master the DOF issue for each lens that you use. :)
 

Snoweagle

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Jan 26, 2005
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#6
Sounds like your problem is depth of field due to the use of f2.8 aperture. I have attached a website where you can sort out your OOF problems. As a rule of thumb, for sharp portraits try no larger than f5.6 depending on:

1. focal length of the lens,
2. distance of the subject from the camera,
3. crop factor of the sensor,
4. where your focussing point is and
5. contrast of the focussed point.

http://www.dofmaster.com/dofjs.html

You can use f2.8 or f4 for bokeh effect but you have to master the DOF issue for each lens that you use. :)
I've even shot at f/2.0 from a distance, no problems with OOF. So f/2.8 is not a problem.
 

roger8

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Sep 20, 2005
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#7
I've even shot at f/2.0 from a distance, no problems with OOF. So f/2.8 is not a problem.
Agreed but as I mentioned what was your crop factor, focal length, subject distance, etc...
 

roger8

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Sep 20, 2005
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#10
I'm using FF so no crop factor, 50mm and subject distance at least 3 to 5m.
In your case let's look at the DoF:
At 3m, DoF is 430mm;
At 5m, DoF is 1210mm.

Hence, no problems with portraits but which crop factor, focal length and subject distance was our TS using when he was using f2.8 aperture?
 

windwaver

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May 19, 2007
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#11
In your case let's look at the DoF:
At 3m, DoF is 430mm;
At 5m, DoF is 1210mm.

Hence, no problems with portraits but which crop factor, focal length and subject distance was our TS using when he was using f2.8 aperture?
TS probably had a DoF that was too shallow when he recomposed (that's why it became blur). The best bet is of course have tons of focusing points and hope 1 of them work without having to recompose ;)
 

roger8

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Sep 20, 2005
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#12
TS probably had a DoF that was too shallow when he recomposed (that's why it became blur). The best bet is of course have tons of focusing points and hope 1 of them work without having to recompose ;)

Most of the time, the AF sensor locks on to the wrong point especially for close focus where the DoF is very shallow when using large apertures e.g. the eyes on a face placed on at an angle.

The AF sensor has an area larger than the square indicated and if the contrast is higher somewhere outside the square, the AF will lock on to the outside point causing the OOF problem. Hence you need to ensure that the focus point or equivalent point in the same plane as the focus point is of high contrast. A low contrast point e.g. skin will also cause the AF to lock on to the wrong point.

The focus point is one and only one plane, anything else is 'acceptably in focus' depending on the size of the print and viewing distance. So the current multi-focus points technology is made mainly for the servo modes where the subject is moving and you hope for the best!
 

FireZ

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Sep 21, 2008
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#13
wow...
some how this issue is something really to learn..thz.... i haf learn something...

btw..i'm using 450D....i shoot it pretty near... perhaps...2 or 3 metres?!...

cheers!
 

windwaver

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May 19, 2007
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#14
Most of the time, the AF sensor locks on to the wrong point especially for close focus where the DoF is very shallow when using large apertures e.g. the eyes on a face placed on at an angle.

The AF sensor has an area larger than the square indicated and if the contrast is higher somewhere outside the square, the AF will lock on to the outside point causing the OOF problem. Hence you need to ensure that the focus point or equivalent point in the same plane as the focus point is of high contrast. A low contrast point e.g. skin will also cause the AF to lock on to the wrong point.

The focus point is one and only one plane, anything else is 'acceptably in focus' depending on the size of the print and viewing distance. So the current multi-focus points technology is made mainly for the servo modes where the subject is moving and you hope for the best!
Of course the main use for multiple focusing points is more for fast moving shots but I'm just pointing out that those can be used in such a situation as well.
 

Snoweagle

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Jan 26, 2005
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#16
In your case let's look at the DoF:
At 3m, DoF is 430mm;
At 5m, DoF is 1210mm.

Hence, no problems with portraits but which crop factor, focal length and subject distance was our TS using when he was using f2.8 aperture?
Y not u ask him?
 

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