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-   -   How/where does a DSLR sense light for metering? (http://www.velocityreviews.com/forums/t869407-how-where-does-a-dslr-sense-light-for-metering.html)

Peabody 03-15-2012 12:23 AM

How/where does a DSLR sense light for metering?
 
Does it just measure the light intensity via the focus points, or
is there some other mechanism involved? This would be in normal
viewfinder mode, not liveview, so the sensor can't be involved.


nospam 03-15-2012 01:26 AM

Re: How/where does a DSLR sense light for metering?
 
In article <20120315-002305.812.0@news.astraweb.com>, Peabody
<waybackNO784SPAM44@yahoo.com> wrote:

> Does it just measure the light intensity via the focus points, or
> is there some other mechanism involved? This would be in normal
> viewfinder mode, not liveview, so the sensor can't be involved.


it reads it off the focusing screen. different cameras have different
numbers of metering zones and may weigh them differently (spot,
center-weighted, matrix, etc.)

Ray Fischer 03-15-2012 03:34 AM

Re: How/where does a DSLR sense light for metering?
 
Peabody <waybackNO784SPAM44@yahoo.com> wrote:
>Does it just measure the light intensity via the focus points, or
>is there some other mechanism involved? This would be in normal
>viewfinder mode, not liveview, so the sensor can't be involved.


If you can peer into the front of a DSLR you might see a 2nd mirror
behind the main one. The main mirror lets some light through where it
reflects off of the 2nd mirror down to the focusing and exposure
sensors.

--
Ray Fischer | None are more hopelessly enslaved than those who falsely believe they are free.
rfischer@sonic.net | Goethe


nospam 03-15-2012 05:47 AM

Re: How/where does a DSLR sense light for metering?
 
In article <4f61635b$0$12018$742ec2ed@news.sonic.net>, Ray Fischer
<rfischer@sonic.net> wrote:

> >Does it just measure the light intensity via the focus points, or
> >is there some other mechanism involved? This would be in normal
> >viewfinder mode, not liveview, so the sensor can't be involved.

>
> If you can peer into the front of a DSLR you might see a 2nd mirror
> behind the main one. The main mirror lets some light through where it
> reflects off of the 2nd mirror down to the focusing and exposure
> sensors.


focus sensors are in the mirror chamber via the secondary mirror. the
metering sensors are normally in the prism.

<http://www.mir.com.my/rb/photography...ikonF5/meterin
g/Sensorlocation.jpg>


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