FILTRATION ON MULTI-CAM SHOOTS: ADVICE/TIPS

[Nick Morrison]

Hey guys, I'd love some input and feedback on the best way to approach filtration on narrative shoots...where you may often be shooting Multicam with 2 or 3 cameras. How do you stagger the filtration strengths across the focal lengths?

For example, with DIFFUSION (say Classic Soft) I've heard that wider focal lengths (21mm, 25mm) will generally get stronger diffusion than telephotos (85mm, 100mm). Is there a rule of thumb to go by? Or do you judge by eye? But I've also heard if you are using an 85mm or 100mm for portrait work, for a CU, then you can leave the diffusion THE SAME as on the wide, or maybe make it stronger! What do you guys think?

How about COLORED FILTERS? I've heard that you should keep all focal lengths the SAME, as this is a color shift and you'l want to keep this uniform.

How about FOG FILTERS like Smoque? If you are using Smoque 1, do you just leave it on all the focal lengths and call it a day, or are you actually adding a Smoque 2 on the wide?

And how about BLACK PRO MIST. Do you treat that like Classic Soft? Make the wides stronger, and longer focal lengths weaker? (Except again if you are on a CU then you judge by eye). Or because this affects the blacks do you treat it more like a color filter and keep all focal lengths uniform.

I need some help figuring this stuff out. I'm totally confused. Thanks.

 

[Nick Morrison]

PS any help or advice would be appreciated.
thx!!

 

[Nick Morrison]

If anyone has any thoughts, please share. I'd love some input. Thx!

 

[Nick Morrison]

This brilliant post on cinematography.com has sort of answered my own question.

But that's more about diffusion, still curious about colored filters like Coral or Antique Suede. Do all focal lengths get the same strength colored filter? (so would the 25mm and 85mm both get a 1/2 Coral, or would you bump one to a Coral 1?).

thx again, as always.

 

[ericyoung]

Hi Nick

I think filters that affect halation and sharpness are worthwhile as their effect on light sources and edge detail is difficult if not impossible to completely replicate in post.

Colour effects however are much easier to do in grading as long as your footage is well exposed with high CRI lighting, so I would leave those for post-colouring.

 

[David Mullen ASC]

You do diffusion by eye generally and when in doubt just use the same lighter filter on everything and the when you see a problem, go even lighter or pull it. Generally pick a filter that is one grade lighter than the one you like because you can always add more in post but it is harder to remove it. Diffusion filters with large patterns in the glass risk having the pattern become visible if you are stopped down too much on a wide angle lens and the out of focus halation around edges with Classic Softs can be too large on telephoto lenses, maybe over 150mm. The pattern in a Promist is finer so harder to come into focus.

Smoque is a tricky filter so use carefully, the effect disappears and reappears when an object crosses and momentarily blocks the light source in the frame creating the glow.

Technically, yes, focal length affects diffusion effect so logic tells you that wider angle lenses need more to match longer lenses. But generally the opposite is true because our eyes want more detail on wide shots (often shot on wider focal lengths) and need to see less detail in a close-up (often shot on longer focal lengths) ... Which is why you judge it by eye, by how it looks on the monitor, and the needs of the shot. But starting out you could just put a 1/4 Black Promist, for example, on everything and then pull it when necessary, but that way all the lenses start out with a base diffusion that is the same and not too heavy.

 

[Nick Morrison]

You do diffusion by eye generally and when in doubt just use the same lighter filter on everything and the when you see a problem, go even lighter or pull it. Generally pick a filter that is one grade lighter than the one you like because you can always add more in post but it is harder to remove it. Diffusion filters with large patterns in the glass risk having the pattern become visible if you are stopped down too much on a wide angle lens and the out of focus halation around edges with Classic Softs can be too large on telephoto lenses, maybe over 150mm. The pattern in a Promist is finer so harder to come into focus.

Smoque is a tricky filter so use carefully, the effect disappears and reappears when an object crosses and momentarily blocks the light source in the frame creating the glow.

Technically, yes, focal length affects diffusion effect so logic tells you that wider angle lenses need more to match longer lenses. But generally the opposite is true because our eyes want more detail on wide shots (often shot on wider focal lengths) and need to see less detail in a close-up (often shot on longer focal lengths) ... Which is why you judge it by eye, by how it looks on the monitor, and the needs of the shot. But starting out you could just put a 1/4 Black Promist, for example, on everything and then pull it when necessary, but that way all the lenses start out with a base diffusion that is the same and not too heavy.

Mr Mullen, this is very helpful. Thanks so much for taking the time to spell this out.

Question for you about Classic Soft: if 1/4 Black Promist is a common "base" to start with in BPM, what's a common starting point with Classic Soft? 1/4 as well, or 1/8 as Classic Soft is more visible?

Thanks again.

 

[PatrickFaith]

Some ASC guys were talking, and i'm not sure I was tracking the conversation, but they change the smoke/fog filters by the ratio of depth of field meters (i.e. combination of T-stop and focal length gives them the depth of field in meters - which then is used to pick the smoke value). This is primarily for outside shots with high T stop (i.e. wide depth of field, so you get more atmospherics). If your doing 1/4 scale miniatures and practicals this becomes super important.