Luminance or Illuminance ?

Started Mar 28, 2013 | Discussions thread
Tom Axford Veteran Member • Posts: 4,028
Re: Luminance or Illuminance ?

Beautiful images and very expertly exposed.

I must confess it is not something I have really thought about before, but I am inclined to think that the sophistication of ETTR (coupled with PP) renders incident light metering obsolete (having said that, I feel sure that someone will say that they still use it and swear by it).

Yes, I entirely agree with the method you outlined for obtaining the 'best' exposure. Some years ago, I mainly used incident light metering with medium format film cameras, but I would have to search to find my old light meter - it hasn't been used for years. With colour transparency film there was effectively no opportunity for post-processing correction after the shot had been taken, so it was more important to get the exposure exactly right beforehand.

These days, it is more important to ensure that you don't clip the highlights but otherwise use the highest exposure you can (i.e. ETTR) so that you reduce the noise to the minimum. If the result looks either too light or too dark, you simply adjust in PP. That was not a possibility with colour transparency film (at least, not in most circumstances).

Concerning the black cat/white snow, all I meant was that if you set your camera on auto exposure and photograph a black cat (filling the frame), the result will look more like a grey cat; while if you do the same thing with white snow, the result will look like grey snow (your photo of the twig in the snow shows this effect, but in this case you deliberately did it to allow the sparkling twinkles in the snow to show up - if the twinkles hadn't been there, the snow would look rather dark and you would probably have brightened it as in your second image).

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