Author Topic: Spot metering on a non central focus point.  (Read 3530 times)

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Offline Hidrieus

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Spot metering on a non central focus point.
« on: December 19, 2013, 06:38:24 PM »
Hello,

 I usually use an other than the central focus point to track a person with AF - Continue because I want her partner to be visible but out of focus. I want spot metering also on her face because she moves around lights on a theatre scene, difficult situation. What can I do? The manual says to meter with the central point, lock exposure and then recompose. But I do not have time to do this because my subject is constantly moving.

A700, A550, A580

Offline chappo1

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Re: Spot metering on a non central focus point.
« Reply #1 on: December 19, 2013, 08:23:05 PM »
There are a number of questions here.
Is she moving much front to back or just side to side?
If it is mostly side to side then flick to manual focus and shoot.  I am guessing that you are struggling for light as well.  What F stop are you operating at and what is the DOF for that F stop over the distance to subject?  You can use DOFmaster to calculate this.
Even if she is moving front to back you can hopefully find and F stop ISO combo that will accommodate this.  The blurring of the partner a little can be done in photoshop if needed.

For exposure- similar deal?  Are you shooting raw?  You can get two stops either way in the convertor after the fact. Flick to manual exposure.  You can then control the magic pudding F-top/shutter speed and ISO to give a reasonable compromise knowing you have some exposure com in the convertor....john
“Time is a great teacher, but unfortunately it kills all its pupils."

Hector Berlioz

Offline Hidrieus

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Re: Spot metering on a non central focus point.
« Reply #2 on: December 21, 2013, 10:19:55 PM »
Thank you for considering and replying to my question. To be more specific, the actress is moving around the theatre scene talking and arguing with her partner. I focus on her eyes using either the upper left or the upper right  focus point holding the A700 or the A550 vertically, depending on which side her partner stands at the moment. I always use the optical view finder even with the A550/A580, that is the way I like to work, so live view and face detection are not useful for me. The theatrical scene has no even lighting. It is lighted by powerful spots from the ceiling. So as the actress moves around she gets under extreme light if she stands under the incandescent theatrical spot to near dark in between the incandescent theatrical spots. I need spot exposure metering on the focus point which I keep on her eyes as I follow her using AF-C. I can do it with my Nikons easily, as the Nikons feature spot metering on the active focus point. But I prefer to use my Sonys because I want in body Image Stabilization with my prime 50mm f/1.4. With any prime lens onNikon, stabilization is out of the question.

Any other suggestions?

Offline chappo1

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Re: Spot metering on a non central focus point.
« Reply #3 on: December 22, 2013, 03:50:01 AM »
The A99 with face recognition is an option if you can stretch to the money.  You register a face with the camera and it focusses on that face...john
“Time is a great teacher, but unfortunately it kills all its pupils."

Hector Berlioz

Offline REX (aka TG)

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Re: Spot metering on a non central focus point.
« Reply #4 on: December 22, 2013, 07:26:17 AM »
What John said is right if you own one camera that has face recognition then you have solved the problem the canera will keep the face  of the selected person with the right exposure where ever it goes
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Offline Hidrieus

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Spot metering on a non central focus point.
« Reply #5 on: January 05, 2014, 03:01:39 PM »
I have the answer to my problem from an old post in 'dyxum' forums: the Sony Alpha cameras, unlike the Nikon cameras, when in multi segment (forty segment on my A700, A550, A580) do the exposure metering taking much consideration for optimum exposure under the focus point currently selected. Even in manual focus mode, the currently selected focus point is properly exposed. So  I will just have to chase my actresses face to be under my current focus point with AF-C mode and not worry about exposure, I will leave the camera in multi segment metering and the Alpha will take care of it. I have experimented on this method using in the same plane opposite focus points, one in dark the other in light, and I confirm that this is the way multi segment metering works. With standard ISO and aperture it chooses different speeds to compensate. I wonder why I have not see it through reading the Alpha manuals.

Offline CHOLLY

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Re: Spot metering on a non central focus point.
« Reply #6 on: January 05, 2014, 06:28:06 PM »
Reading the Alpha manuals?!?

HA!!! :(

There are people who actually think LENS stabilization is better than sensor shifting!

Offline REX (aka TG)

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Re: Spot metering on a non central focus point.
« Reply #7 on: January 06, 2014, 07:05:19 AM »
I have the answer to my problem from an old post in 'dyxum' forums: the Sony Alpha cameras, unlike the Nikon cameras, when in multi segment (forty segment on my A700, A550, A580) do the exposure metering taking much consideration for optimum exposure under the focus point currently selected. Even in manual focus mode, the currently selected focus point is properly exposed. So  I will just have to chase my actresses face to be under my current focus point with AF-C mode and not worry about exposure, I will leave the camera in multi segment metering and the Alpha will take care of it. I have experimented on this method using in the same plane opposite focus points, one in dark the other in light, and I confirm that this is the way multi segment metering works. With standard ISO and aperture it chooses different speeds to compensate. I wonder why I have not see it through reading the Alpha manuals.


What you said is not Sony innovation it exist since Minolta time back when thy introduce the honeycomb metering but today Sony made it more acurate with the face detection.
« Last Edit: January 06, 2014, 07:08:12 AM by REX (aka TG) »
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Offline sum_of_all_parts

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Re: Spot metering on a non central focus point.
« Reply #8 on: February 23, 2014, 04:48:44 PM »
I like the suggestion on using face detection for solving the problem of keeping the moving theater actress in focus.

I'd like to explore this idea further--and hopefully, I can improve my skills when using this feature. First, I use an a77 with which has this feature, but I found that with my camera and kit lens, I frequently lose this capability. It seems that if the person turns their face so that I get a profile view, the identification fails. Also if they are wearing glasses, this also seems to cause problems. In my hands, this feature works best with persons who are standing relatively still rather than moving about. Is this something others have observed? Or is this problem unique to my operating style and hardware? What can be done to get maximum use out of this feature?

Brian Matsumoto

Offline chappo1

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Re: Spot metering on a non central focus point.
« Reply #9 on: February 24, 2014, 04:20:11 AM »
Brian,
I turn face recognition on but do not "register"a particular face so it looks for faces.  Usually I am chasing the two grandkids.  I have not looked how it decides which one but it is better than spot focussing and composing....john
“Time is a great teacher, but unfortunately it kills all its pupils."

Hector Berlioz