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Advice Requested, Light Meter Tests


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#1 Wooda McNiven

Wooda McNiven
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Posted 03 January 2010 - 03:30 PM

I shot a roll of Tri-X today, exterior, daylight.

My objective was to compare the Canon's internal light meter to incident readings obtained on the Sekonic Light Meter. A T-Stop test.

Frame rate was 24 FPS, shutter angle was 150 degrees, therefore shutter speed calculated to just about 1/60, which is what I used on the Sekonic.

Sekonic was set to Kodak daylight recommended ISO of 200. I believe the Canon just reads the Tri-X cartridge at 160 ISO.

I then selected four focal lengths to shoot at, 65mm, 30mm, 15mm, 6.5mm.

My expectation was that the longer focal lengths would produce a greater difference between the camera's meter and the external meter.

I used a human subject so at the 65mm focal length (head & shoulders close up), my gut would have been to trust the camera's reading as there was no background or foreground (either lighter or darker) to influence the camera's internal meter reading. I also expected the Sekonic's reading to be higher, perhaps as much as by a stop.

This didn't happen. The camera's readings and the light meter's readings were identical at F-11.

Any ideas why there might have been no difference?

The exterior conditions were uniform overcast skies with light snow. There was also snow on the ground but this was not in frame at 65mm.

Everything I have read about exposing Super 8 film suggests that you will see a variance between internal and external readings due to the amount of glass found in many Super 8 zoom lens (like this Canon's 10:1 zoom) plus light diverted to the viewfinder.

Has anyone performed similar tests with the Canon 1014 XLS? If so, what were the results?

I plan to repeat this test but indoors using artificial lighting.

Any feedback would be greatly appreciated.

PS: as I rolled film at the wider focal lengths, there was, of course, some variance. As the snow came into frame, the camera metered down to almost F-16. The Sekonic, as expected, read a constant F-11 as the daylight conditions did not change at all during the tests.
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