Luminance or Illuminance ?

Started Mar 28, 2013 | Discussions thread
GeorgianBay1939
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Re: Luminance or Illuminance ?
In reply to Tom Axford, Mar 28, 2013

Tom Axford wrote:

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).

Thank you for your very generous comments and explanations.  It really helps me put things in context.

I tend to narrow in on techniques that will work MY camera (and me!) to their limits in producing quality imagery.  That sometimes obscures a broader view of photography.

I have to be careful around some of my very experienced (and competent) photog friends who were expert with their cameras and darkrooms many years ago.  They still talk zones, sunny f/16s, grey cards, exposure triangles, etc and sometimes get their sekonics out.  I sometimes try to cut though that historical information to the physical optics and image processing of what is going on and they often clam up, or say that they don't need to know that stuff.     Some folk have all that good stuff as background AND also really understand the technicalities of modern digital imaging, including thereasons behind ETTR etc.   Some of them have moved from FF cameras to MFT and are realizing that EVF's aren't really evil,  but even have some advantages compared to OVFs.  Those are the folks who generally understand why and how to load their sensors in critical situations.

In the meantime I am thoroughly enjoying my GH2 (AND LR4 and PhotomatixPro) and hope to have it well explored before long.

Outgrowing it seems to be the only acceptable reason for considering getting another camera with more capability.

Thanks again for your help.

t

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