I've been trying to properly get my head around the usage of incident vs spot readings for past couple of weeks (lots and lots of reading of this very forum) and while I think I understand it for the most part, I still find second guessing myself from time to time when it comes to using the light meter and interpreting the readings the right way. So I've come to hopefully clarify some things once and for all
To sum it up:
if incident measurement gives me, say, f4.0, it means that the light at the spot of the lumisphere combined with aperture of f4.0 will give me perfect exposure of mid-gray - therefore everything in frame that is brighter than mid-gray (eg caucasian skin) will look as it should and everything that's darker than mid-gray (eg skin in shadow) will also look as it should.
Is my understanding of this correct?
Now, if I take a spot measurement of a shadow on the wall and it says f4.0, it means that IF the shadow was mid-gray, it would be perfectly exposed. However I do not want to have the shadows to be at level of a mid-gray, so I should shoot at, say, f8.0 to get them the proper exposure (according to the Zone System, if I wanted to place them in Zone 3). I would have to, of course, light the rest of the shot accordingly for everything to fall in the right place (for example, skin should be 3 stops brighter than my aforementioned shadows to have it in the right zone 6).
Is this correct?
If both statements are correct, then that leads to my main question:
Can I use an incident light meter instead of spot meter (if I don't have one) to measure the contrast of the scene.
For example, if I am shooting a midshot of a person sitting in a chair in a living room at night and there is a bookshelf in background, and I want to make sure I retain some subtle detail in the bookshelf, can I take an incident reading of the key+fill on the face and then take an incident reading of the light spilling on the bookshelf to get the contrast between them? If, say, the incident reading on the face says f4.0 and on the bookshelf it says f2.0 is it safe to assume that the contrast between the face and the bookshelf is a little more than 2 stops (I know I have to account for the reflective properties of the objects/subjects that incident measurement ignores)? Is my logic valid or am I completely misunderstanding something?
And one more thing - is the reflective and spot metering the same thing except spot has a very narrow field of view while reflective is wide or are there any other differences?
metering light and contrast
1 reply to this topic
Posted 07 November 2011 - 01:33 AM
I think the more accurate way to say what you are suggesting is that you will be measuring the contrast of the lighting not the scene. For many Cinematographers, this is all they need, except for more difficult situations where it might be impossible or difficult to get an incident reading. An example of this might be photographing a sunset, or a snowstorm, etc. You don't have to expose skin at zone 6 unless you really want to. Everyones skin is different colors, and naturally falls at different zones. Under or overexposing skin will yield different results, and could be useful for what you are shooting. For example I've noticed that underexposing a person who has shiny skin can make them look sick. The news media got in trouble a while back for darkening the faces of african american criminals, because it tended to make them look "more guilty/ criminal". Anything else can be exposed at whatever level you want it to as well. You can either decide these things with or without a spot meter.