Soft/Mist filters - optical vs post

[Shawn Nelson]

After David Mullen gave a great post in his thread http://www.reduser.net/forum/showpost.php?p=425687&postcount=1942 it got me thinking about the whole "shoot clean, filter in post" vs physical filter in regards specifically to the effect of Classic Soft or Black Pro Mist.

Given what these filters are doing, optically altering certain areas of the image but not others, it doesn't seem a post filter could accurately give the same effect. Thoughts? To be fair, I've not experimented in post in this area and thus this post. What software are people using to emulate the look of a classic soft, black pro mist, rear stockings or front stockings? Does it really work the same?

 

[David Mullen ASC]

I don't think digital diffusion is ever exactly the same as optical diffusion, but the basic principal is the same -- you are overlaying a blurred image over a sharp image. With a glass filter, this is done with a pattern of lenslets or other surface "defect" that throws the focus off, surrounded by clear areas where the image passes through sharply. With digital diffusion, you are putting a blurred layer over a sharp layer. But you can play with the nature of that blurred layer to create different effects, and you can play with what areas in the frame it most interacts with. For example, you can just blur a luminence key so that shadows are not diffused at all.

But Tiffen does sell a cheap software package where they simulate their different filters. Again, I don't think it's a perfect replication of the optical effect, but for most viewers, it would be the same.

But the thing with optical filters is that they actually change the image being recorded, for better or worse -- for example, the misty filters that lower contrast may also be lifting the shadow detail up slightly, giving it more exposure level. But the filter pattern can also create a texture to the image that seems a bit like noise/grain, which you may or may not like.

Check this out:
http://provideocoalition.com/index.php/aadams/story/tiffen_dfx_2_digital_filters/