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11-01-2011, 10:18 AM   #1
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Low light metering problem

The K-5 manual says that the meter is sensitive down to EV0. The equivalent exposure is 1 sec at f1.0 at ISO100. This equates to an exposure of 8 secs at f4.0 at ISO200. On my K-5 in Live View the meter can display a reading down to 6 secs at f4.0 at ISO200 with the display flashing (speed, aperture, ISO) at 8 secs so this seems about right. My problem is that using the optical viewfinder under exactly the same conditions (including covering the viewfinder) the reading only goes down to 0.8 sec and the display flashes at 1 sec. There seems to be a difference of 3 stops between live view and optical view metering. Presumably less light is reaching the meter after being bounced off the mirror. Should it be like this or do I have a fault? I would like to know as I have 2 months of my warrantee to go so need to get it repaired if it is a fault.

11-01-2011, 10:41 AM   #2
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does your camera meter correctly for normal scenes.

I would not worry too much about extreme low light, and also note that the live view is taking metering data off the sensor, not the metering system.

edit notes

the manual defines EV0 as ISO 100 and F1.4 not F1 to begin with, and also note that regardless of metering range, many times I find the camera is limited to a maximum shutter time, in certain modes, where it won't set the shutter even if lighting suggests it should.

Not sure where the K5 is on that respect

Last edited by Lowell Goudge; 11-01-2011 at 10:50 AM.
11-01-2011, 11:30 AM   #3
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My guess is that by saying sensitive down to EV0 it means it can meter to that level at certain setting combinations (e.g. ISO100, F1.4, 2 sec.) but not all available combinations that give the same EV.

I first noticed this on my LX. But since I don't own K-5, I could be wrong.
11-01-2011, 12:05 PM   #4
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Will it get worse

In all situations the exposure is fine. I want to make sure that this is not a problem that could get worse - probably the day after the warrantee expires!

11-02-2011, 01:18 AM   #5
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While I don't know what they mean with their specification, it seems clear to me it must be about the amount of light reaching the meter. If your lens is in fact slower than whatever they define it with, less light will reach the meter under the same conditions, and so it will stop working "sooner".
11-02-2011, 03:53 PM   #6
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QuoteOriginally posted by drougge Quote
While I don't know what they mean with their specification, it seems clear to me it must be about the amount of light reaching the meter. If your lens is in fact slower than whatever they define it with, less light will reach the meter under the same conditions, and so it will stop working "sooner".
Yes, although an EV 0 can be some combination of ISO, shutter speed and aperture only aperture is important (more like T-stop) as this is the only thing that determining what the metering is seeing. The slowest (wide open) setting is how low the metering can read as this is how sensitive the meter is to low light accurately. If the lens is slow then you will not get good meter readings in as low a light as a faster lens.


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