Optical Filtration vs. Digital Filtration

[Nick Morrison]

If you read American Cinematographer, you'll find many of the world's best DP's use diffusion at some point. As many have pointed out, some "looks" like Glimmerglass and certain mists are hard to replicate in post; or are very expensive todo so. If you are working in TV, lower budget, or with quick turn arounds I think in camera filtration makes total sense. On a quick job, a 1/4 Classic Soft could look great. Sometimes Ultracon looks amazing. Or glimmerglass. Think of Don Burgess's inspired use of WARM mists in 42 ...Bronze Glimmerglass, etc. That movie looked amazing, and was shot on RED. Or you can use White Frost for a period "feel". Or Black Promist for a slightly more filmic look. Or blend CS and BPM and go Hollywood Black Magic. Or go oldschool Kubrick and use a Lowcon.

Why does there have to be a right or wrong answer? Some projects look good clean. Some warrant optical diffusion. And some are best affected in post. I think trying to be categorical leads to stifled creativity.

Options are good. Absolutes are not.

 

[Mark K.]

I've recently become a huge fan of Black Promist, the lower densities give you a beautiful and modest halation in the highlights without sacrificing any real resolution. It filters out just that little bit of reality, and it really makes all the difference to otherwise ultra-clean digital images IMO.

 

[Mike Nagel]

there is the argument that since you're dealing with "digital data" you can pretty much "do anything" in post, but that is not necessarily true b/c with a camera like RED - as an example of a digital camera - u're dealing with a compressed digital RAW file captured by a sensor that has certain characteristics... that in itself presents limitations (in some cases).

example: if you shoot Tungsten and you try to re-create in post the optical effect a CTB would have on the sensor under Tungsten, you'll end up with some problems - b/c when you push the starved blue channel in post u'll introduce noise etc. - so u can never get a true match b/c the capture was "compromised" - same goes for the UW example Bjoern and Rudi described

--> obviously these particular cases should be categorized as optical filtration needed to counteract or help a specific characteristic of the camera sensor (or the environment), rather than to apply a certain aesthetic look, but they demonstrate limitations of the digital RAW capture

so, which effects are easier to re-create in post than others ? Diffusion ? Is a clean and not "compromised" capture necessary to be able to push the RAW data in post w/o penalty to create realistic, digital filtration effects ?

Has anybody succeeded to *truly* re-create effects in post like Classic Soft, White Promist, Black Promist, Glimmerglass, Haze, Fog, Double Fog, Low Contrast (exact match of the halation of the highlights), Ultra Contrast, Streak, Warming Mists etc. ?

It would be great to see some example pictures posted - one with the optical filtration and one with a clean capture and then digital filtration applied to achieve the exact same effect.

if you can share: what is your workflow in post to create the effects ? software, specific plugins ? what do you feel are technical limitations of post ?

Thanks everybody, great discussion !!!

- M

 

[Mike P.]

Actually Nagel, that's a very interesting point/test (which I haven't done).

Has anyone tried to use a "digital CTB" to footage shot under Tungsten? I know After Effects has the "photo filter" with an Type 80 present; if you used a .r3d at 5000k and applied a filter to a (16bit) adjustment layer, would it be *cleaner* than setting the colour temp to 2800-3200K in RCX? Theoretically, it should be cleaner since you're actually adding a layer of additional blue rather than just stretching the (starved) blue-channel by changing the colour temp.

To be perfectly honest, I've had insanely impressive results with baked footage at the cost of render time... I'd say I could change even crappy 8bit footage within 20% (33% if it's a 422 codec) of the original and it still looks "real." And 20% difference is quite dramatic when you're shooting for that look to begin with (which you have to do when it's baked).

 

[David Mullen ASC]

David, thank you for your detailed response !



Can you elaborate on this ? do these patterns (in CS and HBM) introduce a slightly more uniform and therefore maybe more inorganic look ?

No, that's not what I am saying. True diffusion (forget side-effects like halation or contrast-lowering) is designed to throw some parts of the image out of focus while clear areas of the filter allow a sharp image to pass through. It's the combination of sharp and blurred that create diffusion as opposed to merely throwing a picture out of focus. A poorly-designed diffusion filter doe not allow a sharp image to also pass through -- an example would be shooting through Cling-Wrap cellophane or spraying some hairspray onto a piece of glass (which can work if you manage to disperse the hairspray particles evenly with gaps between them, but most of the time, you don't get enough even spacing between the particles.)

The classic diffusion filter is a stretched piece of pantyhose, a net -- the threads of the net diffract / bend the light rays and blur the picture and the clear gaps allows a sharp image to pass through. A glass version would be something like a Schneider Classic Soft, which has a bubble-like indented pattern in the glass to blur the image, surrounded by clear areas. A Tiffen Diffusion-FX filter has sort of a kidney shaped indent pattern that is smaller and more irregularly-spaced. Same goes for the Schneider HD Classic Soft, designed with a smaller and more irregular pattern because 2/3" video cameras using Classic Softs were seeing the pattern in the glass because of too much depth of field.

Then there are mist and low-contrast filters, a sort of subset or side-alley of diffusion. They have some sort of powder or other particulate matter scattered on glass that causes bright areas to halate into dark areas. The nature of the particulates also act to some degree to blur detail like in a regular diffusion filter, so you can control how much contrast lowering you get versus halation versus softening by the nature of the particulate matter and how it is applied. This takes a lot of testing, plus you have to figure out how to manufacture it consistently and how to create degrees of strength. Older mist filters like Fog Filters (pre-1970's) probably don't have enough clear areas between the mist particles so have a tendency to slightly throw the image a bit blurry depending on how the light catches the filter. The Low-Cons (1970's) are a bit better in terms of sharpness, as well as Double Fogs (Fog + Low-Con). Tiffen UltraCons (1990's era) are even better at retaining sharpness and lowering contrast with almost no halation, same for Schneider DigiCons (2000's), which have an added dark particulate that acts like an ND on highlights to reduce some clipping up there. But with the modern UltraCons and DigiCon's, you don't get the halation that some people like, hence why some are more likely to use the older Low-Cons or a mist diffusion like ProMist or Frost.

And now there are combo filters that put diffusion patterns and mist particles together -- Schneider Hollywood Black Magic for example. Tiffen even has a new filter called Pearlescent which combines two different mist filters together (the GlimmerGlass and the ProMist I think.)

 

[Dave Blackham]

For our work we have enough DR to cope with most situations so filters offing increase in DR have less value to us. Even dark forest against bright sky only a couple of times have we used HDR. What Im much more interested in is filtration to roll off highlights or offer controllable micro halation.Im interested to see if this can be done in post or in camera.

The other issue is is that the camera is clean and neutral. To create a look needs work, which some folk don't seem to spend as much time creating as others. I wonder if the should be a library of looks available in RCX if its achievable in post, it may or may not be, to help out those with less time to get a particular look more easily.

 

[PatrickFaith]

...
(off-topic: I hope your movie is not eating all the time from your painting work away ;o) -- I sold my last hundred paintings in Europe in the past year and donated the money, I like to focus on digital purely since a while )

Hey Dr ... since I start off with a drawing and that is moved to a computer format, I don't have to worry much (plus someone else almost always owns the drawing). I'm the art director on my film, which is helping me re-use a lot of my paintings. btw, saw you at fxphd.com, I love that place.

The beauty of the RED EPIC cameras and the incredible POST flexibility and strength of the R3D files for me are invaluable, and I will almost NREVER alter the RAW in camera, but always in post, exception of the Polarization, and in absolute rare situation with a particular need with precise need for a particular look, I know I can not get in Post.

As far as Low-Con filters, I despite this type of filters and think of them to be absolute worthless and damaging to the RAW file, that if I was to see any one working for me try use one on any of my shoots, I would literally kick him in the nuts...

Most masterful example of this that I have seen are all the low contrast shots in Girl with the Dragon Tattoo, the before and after plates are amazing (the blu-ray of the film goes into this in some detail, plus their are a lot of great articles). Basically a lot of that was shoot in blue sky's, then converted to fog/overcast/rainy/dingy light look in post (their are some examples of the nuke nodes at different locations). I have even seen the locations were that was shot and I would never recognize the location if I wasn't specifically told.

...
Why does there have to be a right or wrong answer? Some projects look good clean. Some warrant optical diffusion. And some are best affected in post. I think trying to be categorical leads to stifled creativity.
Options are good. Absolutes are not.

+1 ... to me one of the unsung masterful things about red is all the options. I love the mount options, i love the resolution options, the compression options, the raw/log/linear/film/gamma options - the whole camera is designed so it's up to the cinematographer to choose what is best for the story. I do think people that lack competence don't like options, I just try and stay away from that crowd.

 

[Michael Mayda]

Thank you for your succinct contributions to this thread, David. And so many other discussions. I am taking notes...

 

[Dave Blackham]

David Mullen, thanks very much for you posts on this subject they are very helpful.

 

[Dr. Sassi]

I have followed the forum since a quite some time and learned tons from it. But also got in some points uncertain, based on too much different information -- and nearly no recourses to "double-check" the data. So, I appreciate this thread tremendously. Thanks to everyone sharing here, it is a great value to me; Especially a big thanks to David Mullen ASC! (David, any chance to have a practical filter workshop in L.A.?)

Having said that, I have read in the past here, that the consistency of filters is not given if one mixes lenses from short to long. That would be my first uncertainty using some "new" filters for a shoot. Any input on that?

...though keep in mind that designs like Classic Softs and Hollywood Black Magics have a pattern designed to soften detail as opposed to just mist particles like a ProMist or Frost filter might have. ...

Secondly, I see often in the blooming-highlights or bokeh the dark particles of some filters, like a grain pattern. (Which is again, in most movies not consistent.) Would be there a post approach not the better way, grain free ? Since images get cleaner, this (dark grain) stands out more often these days.


==================

Yes, it FXPHD is a great place. Knowing Mike since the PXC, I certainly feel very safe with their content. Well, after nearly 100 courses that I took, I think I can say that )

Hey Dr ... since I start off with a drawing and that is moved to a computer format, I don't have to worry much (plus someone else almost always owns the drawing). I'm the art director on my film, which is helping me re-use a lot of my paintings. btw, saw you at fxphd.com, I love that place.

P.S.: ... and yes, options -- the real challenge to find ones own mix and not just copying something else.

 

[Ben Scott]

Very interesting thread. As always, thanks for your insight David.

While it's clear that there's no one size fits all solution it would be great to hear some recommendations for the more essential first purchases when building a diffusion/filtration kit.

 

[Nick Morrison]

No, that's not what I am saying. True diffusion (forget side-effects like halation or contrast-lowering) is designed to throw some parts of the image out of focus while clear areas of the filter allow a sharp image to pass through. It's the combination of sharp and blurred that create diffusion as opposed to merely throwing a picture out of focus. A poorly-designed diffusion filter doe not allow a sharp image to also pass through -- an example would be shooting through Cling-Wrap cellophane or spraying some hairspray onto a piece of glass (which can work if you manage to disperse the hairspray particles evenly with gaps between them, but most of the time, you don't get enough even spacing between the particles.)

The classic diffusion filter is a stretched piece of pantyhose, a net -- the threads of the net diffract / bend the light rays and blur the picture and the clear gaps allows a sharp image to pass through. A glass version would be something like a Schneider Classic Soft, which has a bubble-like indented pattern in the glass to blur the image, surrounded by clear areas. A Tiffen Diffusion-FX filter has sort of a kidney shaped indent pattern that is smaller and more irregularly-spaced. Same goes for the Schneider HD Classic Soft, designed with a smaller and more irregular pattern because 2/3" video cameras using Classic Softs were seeing the pattern in the glass because of too much depth of field.

Then there are mist and low-contrast filters, a sort of subset or side-alley of diffusion. They have some sort of powder or other particulate matter scattered on glass that causes bright areas to halate into dark areas. The nature of the particulates also act to some degree to blur detail like in a regular diffusion filter, so you can control how much contrast lowering you get versus halation versus softening by the nature of the particulate matter and how it is applied. This takes a lot of testing, plus you have to figure out how to manufacture it consistently and how to create degrees of strength. Older mist filters like Fog Filters (pre-1970's) probably don't have enough clear areas between the mist particles so have a tendency to slightly throw the image a bit blurry depending on how the light catches the filter. The Low-Cons (1970's) are a bit better in terms of sharpness, as well as Double Fogs (Fog + Low-Con). Tiffen UltraCons (1990's era) are even better at retaining sharpness and lowering contrast with almost no halation, same for Schneider DigiCons (2000's), which have an added dark particulate that acts like an ND on highlights to reduce some clipping up there. But with the modern UltraCons and DigiCon's, you don't get the halation that some people like, hence why some are more likely to use the older Low-Cons or a mist diffusion like ProMist or Frost.

And now there are combo filters that put diffusion patterns and mist particles together -- Schneider Hollywood Black Magic for example. Tiffen even has a new filter called Pearlescent which combines two different mist filters together (the GlimmerGlass and the ProMist I think.)

Mr.Mullen thanks for this great breakdown. What would we do without you??!!

 

[Nick Morrison]

+1 ... to me one of the unsung masterful things about red is all the options. I love the mount options, i love the resolution options, the compression options, the raw/log/linear/film/gamma options - the whole camera is designed so it's up to the cinematographer to choose what is best for the story. I do think people that lack competence don't like options, I just try and stay away from that crowd.

I agre 1000% percent with you Patrick! What I love are OPTIONS! So many ways todo things! So little time to try them all!!!

 

[Timur Civan]

There is something about the optical path thats difficult to duplicate.

Filters are critical.
ND for the sake of shooting at a particular stop, Graduated ND to hold a sky, and in my opinion lowcon and diffusion filters, 80C under tungsten. (thanks Mike)


Go for the look, make a decision. Its good to have options, but use them before you shoot to craft the image.

 

[Mike Nagel]

There is something about the optical path thats difficult to duplicate.

Filters are critical.
ND for the sake of shooting at a particular stop, Graduated ND to hold a sky, and in my opinion lowcon and diffusion filters, 85C under tungsten.


Go for the look, make a decision. Its good to have options, but use them before you shoot to craft the image.

Timur,

is it not 80C under Tungsten light (to feed blue channel) and 85C on Tungsten film (to remove blue cast)... ?

- M

 

[Timur Civan]

Timur,

is it not 80C under Tungsten light (to feed blue channel) and 85C on Tungsten film (to remove blue cast)... ?

- M

Ugh youre right... Its 80C under tungsten light.... its late....

 

[Nick Morrison]

Ugh youre right... Its 80C under tungsten light.... its late....

Timur is 80C worth the stop in light for you?

 

[Timur Civan]

without question.

 

[Jon MIchael Puntervold]

the only Filter I will always use will be the Polarizer, as the it is the only one that can not truly be replicated in post

For what my experience is worth, this is not the case, neither Benckert or others with strong experience in post or cinematography seems to agree...

 

[Ketch Rossi]

For what my experience is worth, this is not the case, neither Benckert or others with strong experience in post or cinematography seems to agree...

I should have phrased differently form the start were I would no to make it sound that every one can do as I do, as each have or might have a very different need based on their client's request, this is no to my case, I am always the one in charge of what I do , never my clients, so what I mean is that in all that I use and would use in looks, the Polarizer is the absolute only filter I must have in camera.

All others I can have done in post, this is of course my opinion and my experience and likes, I can't and will not speak for all, yet I am giving my opinion as every one else, each can make their choice I have made mine since the advent of RAW... And will continue to do unless as said, absolutely necessary to bake the image in the RAW for a specific need, which will be to be used only and only for that purpose, which in my case would be very difficult, so I don't think I would ever use any baked filtration in camera, yet never is a long time, so you never really know, but in general I can say that I will always preserve th original neutral RAW files... And work in Post, as I know exactly what I would want from my files before acquisition...