Archived posting to the Leica Users Group, 2000/05/06
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 10:27 PM +0200 5/6/00, Jean-Claude Berger wrote: >Joe wrote: > >> If you had a clear sun behind you during the test, I would say that the >> Nikon meter is off. > >Hello Joseph, > >IMHO, I don't think so. In his first post, Simon told that he took a measure >against a white wall. The M6 gave 1/1000 at f/11 and a half. With a 400 ISO >film, this is an impossible value: but a specular reflect, nothing needs a >EV18+ >exposure. Let's say that Simon wants to have a white textured wall. He >will have >to open 1 and a half to 2 stops depending on the density he wants to get. The >Nikon's matrix saw a large white area and opened one stop. The F5 was off, >yes, >but because it did not open enough! This is consistent with the results I get >with my F5. He compensates underexposures of very bright area but a little >less >(say half a stop) that I would like. That said, the lighmeter of the M6 is >much >more predictible as it behaves like good old time lightmeters. Let's follow this through. a) He said that he had used the F5's spot metering. No color metering. b) If it is an even white surface, no variations, the F5 meter with color info considered can't tell whether it is white grey or black in any case. Spectral response would be the same if they were true white, greys or black, and the metered value would only depend on what actual reflectance there is and how much light is on it. c) If the Nikon produced a slower shutter speed/ wider aperture, it did 'open up', but because of points a and b, it wouldn't know that it had to. d) If there was sunlight falling on a white wall, the value metered by the M6 is possibly a bit low. Joseph didn't say what type of light fell on the wall. e) The one other variable is that Nikon's matrix metering, and I believe others, don't normally allow more than 16 or 17. I don't believe that the spot metering has this restriction. The meters respond differently. It's the nature of meters. We don't know what the true spectral reflectance of the wall is, nor the light source, nor the filtering on the meter cells (they all have filters to reduce sensitivity to IR). * Henning J. Wulff /|\ Wulff Photography & Design /###\ mailto:henningw@archiphoto.com |[ ]| http://www.archiphoto.com