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light meter question


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#1 freddie bonfanti

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Posted 21 July 2006 - 02:11 AM

hi all

im testing my new 814xl´s internal meter with a sekonic 558. i noticed a few stops of difference and i was wondering why...i think that the problem is that i set my meter at 64 when probably the camera´s one is preset to a different ISO number. but then i dont understand why the camera suggests to shoot at 5.6 and the sekonic incidental reading at 2.0, i mean i doubt the camera is preset at a higher ISO number...

is the meter faulty?
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#2 Daniel Stigler

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Posted 21 July 2006 - 02:41 AM

To compare a reading taken with an incident lightmeter to a reading taken through the camera (spot) the camera needs to be pointed at a greycard. Did you do this?
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#3 freddie bonfanti

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Posted 21 July 2006 - 02:43 AM

yes, and i also forgot to say that the sekonic is working fine as it was tested not long ago.
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#4 Guy Bennett

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Posted 21 July 2006 - 10:05 AM

The readings from your camera and light meter are going to differ, independant of whatever techniques you might use to take a light reading, because of the light absorbed by the lens elements and the viewfinder, and the longer the focal length, the more light absorbed.

My camera (a Nizo 801m) shows anywhere from 1/2 stop to 3-3 1/2 stops difference at shortest and longest focal lengths, when compared to readings in the same light from my light meter (a Gossen Lunapro Digital). The difference between them is described as the difference between f-stops and t-stops.
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#5 freddie bonfanti

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Posted 21 July 2006 - 07:33 PM

[quote name='Guy Bennett' date='Jul 21 2006, 03:05 PM' post='116255']
The readings from your camera and light meter are going to differ, independant of whatever techniques you might use to take a light reading, because of the light absorbed by the lens elements and the viewfinder, and the longer the focal length, the more light absorbed.


therefore what should i trust? should be the incidental lightmeter, right?
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#6 Daniel Sheehy

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Posted 22 July 2006 - 01:08 AM

Are you sure comparing using an 18% grey will work?
Wouldn't it be better to meter an average scene...?(no strong back light etc)

just curious.

Edited by dsheehy, 22 July 2006 - 01:12 AM.

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#7 freddie bonfanti

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Posted 22 July 2006 - 06:15 AM

hi,

metering a grey card was my safest option, the sekonic l 558 has a spotmeter function so i made measurements with both spotmeters. the camera´s one was 2 stops over. the i took an incidental reading in a room and i took another reading with the camera and still, 2 stops over.

id rather rely on the sekonic as i always use it
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