Contrast

[Irri]

Say I have a studio with soft flat lighting at T8 (incident).

I spot a dark gray object at T4 and a white object at T16. A difference of 4 stops.

If I drop the studio lighting to T5.6, do I still get 4 stops difference between the two objects?

Same question for closing down a stop with the lens.

 

[Irri]

97 views and no one knows the answer?

 

[Pawel Achtel]

The answer is: Yes

 

[David Mullen ASC]

Say I have a studio with soft flat lighting at T8 (incident).

I spot a dark gray object at T4 and a white object at T16. A difference of 4 stops.

If I drop the studio lighting to T5.6, do I still get 4 stops difference between the two objects?

Same question for closing down a stop with the lens.

If you lower the overall light level or the overall exposure, the relative contrast between objects won't change.

However, once the light levels get low enough, it's very hard for natural ambience from other sources to not start to add to the lighting, usually filling in the shadows -- whereas at high light levels, you have more precise control over fill levels because you are providing them.

Some people say that stopping down a lens increases contrast. Truth is that it doesn't really affect contrast, it affects depth of field, and the sharper everything in the frame is, the easier it is to see the range from highlight to shadow -- whereas when something is out of focus, that range is blurred together. Just point a video camera at a high contrast scene and look at it on a waveform... and then throw the picture out of focus. What you see on the waveform then is that there are still faint peaks at 100% and 0, but the bulk of the signal has been mushed into the middle.

You'll find when lighting a room to a wide aperture, like to f/2, that with your key levels being so low and the depth of field being more shallow, the image tends to look somewhat softer in contrast because ambient bounce and light from real practicals are filling in the shadows more, and the backgrounds are soft and blurry. Whereas if you light a room to f/8, you have to be very careful about using the right amount of fill light because natural ambience is hardly going to contribute.

 

[Irri]

Thanks David

 

[Dan Hudgins]

Stopping down

Stopping down

Some people say that stopping down a lens increases contrast.

It depends on the lens and coatings. Some older un-coated fast lenses had a huge amount of flare when wide open, so the contrast for small details does go up quite a bit when stopped down because the iris blocks most of the rays that bounce around in the lens. If you are less than f/4 then the increase in contrast would be much less, but if you are open to f/1.2 or in the case of the lens I am talking about f/0.99 you can see the blacks get more black after the shutter angle is re-adjusted to compensate.

Also some older lenses had a fuzzy bloom around the small details cutting the MTF contrast for detail in the image, stopping down makes the details have better contrast.

Its not something you would see much from todays highly coated lenses, and at stops smaller than f/4.

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The "dark gray" would be very dark, almost black since 18% gray is about 2.5 stops from 90% white, to get 4stops you would need the white with a spot on it, or the gray almost black. You can cut the light on the white things, and point more light at the dark things to even out the contrast, while still having enough range in the files to expand later. If you underlight the dark things you get noise, you can subtract the fill light on the dark things in post to push them down and reduce the shadow noise.