intensity of diffusion filters and focal length/Shot sizes

[DanielSydney]

Hey guys,

I read somewhere in the internet:

"A 1/4 pro mist (black or white) will be much stronger on a 85mm lens than it will be on a 25mm lens. A common formula for using Pro Mist Filters is 1/2 Promist for 18mm and wider, the 1/4 Pro Mist for 25mm - 35mm lenses, and 1/8 for 50mm and above"

I wonder what you think about that, because I would think the opposite: I would use a stronger intensity of diffusion filter for the closer shots and a lesser intensity for the wider shots.

Best,Daniel

 

 

[David Mullen ASC]

The issue here are two somewhat contradictory ideas. One is that longer focal lengths needs less diffusion to match strength. Two is that tighter shots needs more diffusion because our eyes want more clarity (information) for wide shots.

Both are correct. What confuses people is that we associate using longer focal lengths with going in tighter, and we think wider shots always use shorter focal lengths.

What this all really boils down to is that you have to pick the strength of the diffusion by what feels right to you in terms of the degree of softening.

Or you can think of the two rules, being contradictory somewhat, as cancelling each other out and you can just use the same filter most of the time. But I would still adjust the strength now and then to control the level of detail (use less or none for extreme wide shots, use more for extreme close-ups) or to compensate when the situation is already causing softening (low-contrast scenes like in a hazed set for example, or shooting into a hot sky and getting a lot of flare.)

[DanielSydney]

thanks a lot David!