Anyone know the math for contrast?

M

morisato

Active member
Hi everyone,

I'm wondering if anyone knows the math to this. This is not a real situation, but a hypothetical one. Let's say you want to light a wall that has a divider in it. On one side you want it to be one step away from completely black and on the other side you want it to be one step away from being blown out. Does anyone know the ratio of light between the two as far as how much light needs to be blasting the white side? Does it differ depending on the camera even though all cameras run from 7.5-110 IRE? If they do differ, do you know what the ratio is for the HVX? Assuming the distance to the camera is exactly the same, and the angle of light to the wall to the camera is also the same, type of light is the same, quality of light is the same, and all other variables the same except for pure light intensity, how much light would you need on the white side in comparision to the black side.

So say I was shining a 100w light on the black side, adjusted the camera's iris and shutter so that that side read 7.5 IRE, how much light would I need to shine on the white side to read ACTUAL 110 and not 200 that was squashed to 110 because 200 IRE doesnt exist.
 
Learn the Zone System designed by Ansel Adams, with this you will be able to more clearly understand levels of exposure, against total black, medium grey, pure white, and everywhere in between to achieve the effect you are looking for.
 
It does depend on the camera, though. Each one has a unique dynamic range. If you were shooting this on film, you'd have to add quite a bit of light on the light side to get it close to blowing out. On an HVX, I don't know the dynamic range of the camera (probably somewhere around 7 stops), but it's much less than film, and will require less light on the light side to get it close to blowing out.
 
Joshua Provost said:
It does depend on the camera, though. Each one has a unique dynamic range. If you were shooting this on film, you'd have to add quite a bit of light on the light side to get it close to blowing out. On an HVX, I don't know the dynamic range of the camera (probably somewhere around 7 stops), but it's much less than film, and will require less light on the light side to get it close to blowing out.
Click to expand...


I peg the HVX at around maybe 5 1/2 stops for capture, and about 4 after you color correct....

Dynamic range is a bit tricky, I always tell people that you have two ranges, an input range, and a output range. Really nice clean images have a much more narrow range than the originally captured image does. I always light based on my output range. I shoot with an Andromeda, which has a range of about 9.5 stops max when capturing, however, the biggest scene contrast I allow for is 5 stops. This lets me expose more of the image brighter before blow out, and a nice bright image means clean data. In post I darken and add a little bit of contrast to finish.
 
You must log in or register to reply here.
Back
Top