Diffusion?

[Harry Clark]

Has anyone done a test with different kinds of diffusion filters? I feel like TIFFs that people have posted show that 4K's worth of resolution is not always kind to an actor's complexion.
I know that we can do it in post, but sometimes as a DP you want to lock in some of your look in camera.
Classic Soft? Soft FX? Pro-Mist? Maybe Mitchells will make a comeback... :)
Cheers,
Harry

[Blair S. Paulsen]

With the RedOne system I am a big proponent of doing diffusion in post but there are situations where on camera might yield better results - fast falloff lighting, tight close ups, etc. In most cases, IMHO, the rationale for using diffusion during the shoot is less about the best technical choice and more about the real world human element. Maybe monitoring at 720P instead of 1080 isn't such a bad idea after all... :holloween:

[David Mullen ASC]

I think which filter you choose is a matter of taste, regardless of whether you use the RED camera or a 35mm camera. The only difference may be the filter strength you choose.

You could probably test these filters on a DSLR to get an idea, but ultimately, which filter you choose has to also be based on the degree of enlargement of the final image. If I'm shooting for cinema release, then I need to see my filter tests on the big screen to make a choice.

You'll notice when you get filter examples online like at:
http://www.camerafilters.co.uk/

That you can only see the effect on the heavier grades of filters. It's very hard to see any effect from the lightest grade of ProMist or something, unless it is a shot of a candle flame or other point source -- and then that would tell you about halation but not so much about whether it is too much or too little for a face. So you need to see the tests on the typical size of screen that your project will be shown on. If this is for HDTV broadcast, then you'd want to see the test on a decent-sized HD monitor, for example.

[Harry Clark]

Blair, have you used any diffusion yet on any jobs with #19?
David, just out of curiosity, do you have a current favorite filter for faces? I'm partial to the Soft FX/ Classic Soft approach (lenslets, rather than "stuff" on the glass) because I think it's a little less obvious, and it lets the picture stay relatively sharp. Thanks for the link, BTW.
Incidentally, I think that the grainless 4K image offers the extra apparent resolution to use diffusion without too much apprehension. I do agree that your target screen size and delivery medium dictates the strength and type of filter.
Hey offhollywood or ibloom, do you think the Du Art film out test you did added a bit of softness versus digital projection?
Cheers,
Harry

[David Mullen ASC]

My favorite lately has been the lightest (#1) grade of Tiffen GlimmerGlass, which is a mist-type diffusion. When I don't want that foggy effect, I've been using the lightest (#1/2) Tiffen Black Diffusion-FX, though on my last show, which I shot clean, I did shoot one close-up with the #1/8 Classic Soft.

I've been curious about testing the Classic Black, which combines a #1/8 Black Frost with Classic Softs in your grade of choice.

I like Soft-FX as well. My only problem with that filter has been that the jumps between the #1/2, #1, and #2 are too extreme. I wish they were closer together in strength. That's one thing I like about the GlimmerGlass, that the jump in strength from #1 to #2 is not too much.

[liquidigital]

Hey offhollywood or ibloom, do you think the Du Art film out test you did added a bit of softness versus digital projection?
Cheers,
Harry

Hey Harry, I saw the Du Art film out and in my opinion it did add softness (I saw the on-line version as well). Personally, I thought this added softness was subtle and looked great, so I'll definitely be looking for ways to emulate that for DVD.

[Blair S. Paulsen]

On camera diffusion can do beautiful things, no argument from me. That said, I like the control of dialing in the amount of impact on the image while viewing it in a controlled environment. If I had David's experience and skill I might be more willing to "bake in" diffusion with an on camera filter. With the rapid development of image enhancement and grading toolsets in the post suite I am more comfortable doing more manipulation there.

IMHO talent, good pre-pro, a good eye, time and budget for testing, skilled lighting, etc are all more critical to fine tuning the look of the finished product than where and how diffusion is added. Just add the right amount with the right feel to advance the story and keep the lead actress from hunting you down :help:

[David Mullen ASC]

With film, the problem with post digital diffusion has been that it tends to degrain the image, causing some mismatching if you are adjusting the diffusion strength shot to shot in a sequence, hence why I prefer a camera filter in general. Unless the problem is very localized, like a pimple that I can't get rid of with lighting (and make-up isn't helping), in which case it would probably be better to save it to post and paint it out.

Now with noise-free digital photography, playing around with post diffusion isn't so much of a problem because you won't be causing visible noise to go in and out of focus as you change the level of digital diffusion, but if there is a noise level to the image, it can be a problem unless you have sophisticated color-correction tools to match noise levels after digital diffusion.

The other issue is, again, degree of enlargement to judge the effect. If you are on a budget and color-correct on a 50" studio monitor or smaller for a digital project that will be transferred to 35mm for projection, or projected in 2K/4K on a big screen, you may not pick the right level of diffusion (or conversely sharpening) if grading with a smaller monitor as a reference. I once digitally sharpened a soft shot in HD post and realized that I overdid the effect once I saw it on the big screen later.

This is why testing in prep is so important.

If I sound picky, it's because, unless you've shot stuff for a theatrical screen, you might have no idea how tiny artifacts and mistakes (like with focus) can be magnified on the big screen.

[Blair S. Paulsen]

Unfortunately, I have seen my errors magnified on big screens, ugh. If I had the magnitude of experience that David has I might be more comfortable making filtration decisions on camera. Shooting SD video I pulled out the Black Pro Mist regularly when shooting interviews with all but the young and smooth of complexion. Shooting with the RedOne I have eschewed filtration, especially at this point in learning the camera's personality.

BTW I fully agree with David's point about scale dramatically influencing the impact of diffusion. Many thanks to David for contributing to the RedUser community, his perspective brings welcome light into the discussion.

[David Mullen ASC]

Philosophically, there are two types of diffusion, what I can visible and invisible diffusion. Visible diffusion is when you want a diffused look, like for a romance or period movie. Filters with noticable artifacts like halation tend to be used.

Then there is invisible diffusion, when you want to soften fine detail but otherwise make the picture look unfiltered so it can be intercut with clean footage. In that case, you want a diffusion filter that is pretty boring but does a good job of softening without any telltale artifacts.

In the second scenario, I find that the Tiffen Black Diffusion-FX is the best filter. You can shoot a scene sharp and then add the lightest grade of Black Diffusion-FX (the #1/2) on a close-up and no one is going to know you used a filter. Of course, it's so subtle that it also doesn't do much softening either, but it still helps get rid of some lines in a face. On a tight close-up, you could easily go to a #1 Black Diffusion-FX.

The lightest grade Classic Soft (the #1/8) is also pretty subtle though it does create a slight fringing effect around hot edges, a sort of blurred double-edge. The lightest grad of Soft-FX also works; it has a faint misty-blur around edges.

It's not all that scary to use diffusion if you are using the lightest grades -- these are pretty subtle filters.

The other scenario is to use the same filter on the whole movie, more or less, for a visible diffusion look. It can still be a light grade though, like a #1/8 ProMist for example. You'll get that little bit of halation but otherwise it's not too heavy by any means.

Contrast and sharp edges in the frame increase the feeling of sharpness in the shot, so you can counteract the softening of a diffusion filter by using more contrast in the lighting or creating a strong edge. This is one reason why a crisp backlight works well on a diffused close-up -- the lit-up hair with its bright edge creates a feeling of sharpness despite the diffusion effect.

[Blair S. Paulsen]

Excellent info David. I have also used the Black Pro Mist with a stronger edge light. It gives the rim some halation and seems to "wrap" some level onto the darker side of the face in a way that allows me to maintain a more dramatic feel while still getting the "glam" look I so often need.

Your point about "invisible" filtration with lighter grades is a good example of of what I consider smart usage of on camera filtration to accomplish something best done on camera. I even feel like it can make gradients across surfaces read more smoothly, especially when a strong light source is raking accross. Moreover, because the effect is subtle, it doesn't "bake in" a look that then proves too extreme in a particular finish/deliverable.

Fun discussion, I hope our paths cross some day, it would be an privilege to work with you and a great learning experience for me.

[Emmanuel Cambier]

Thank you guys…so much.:love:

Emmanuel

[JD Holloway]

Great Op-Ed David.

Its so rare to see things discussed (in print no less) outside the camera truck. I love how involved you are in this usergroup!

J.

[David Mullen ASC]

This description is a bit simplistic, but I have a general fifty-fifty rule when shooting -- i.e. get half the effect in-camera and finish the effect in post. So if I want a cold or warm look, I do some of it on the set with gels or filters, but I add the rest of the coldness or warmth in post. If I want a diffused look, I use a lighter grade filter than I really want because I can alway add a little more in post.

This way, some of the intended look is in the original photography, to point the way as to how it should be finished, plus the final color-correction doesn't involve extreme shifts. You are just enhancing what is already there rather than fighting the look of the original or trying to create a look from scratch.

I don't always follow this fifty-fifty rule, but you get the idea.

[Harry Clark]

Hey David...
Would you say that you apply the 50-50 rule more in a feature situation where presumably you will supervise the color correct/ film out (I'm guessing this goes into your deal memo) versus a commercial where it often seems like NO ONE is supervising anything, except for the agency and client? :(
In other words, do you think it's worth it to lock in the look more solidly with a commercial or music video versus a movie, just based on schedules etc.?
I also wonder if, as Redcine matures and we can offer clients footage with a nondestructive look applied, how can we make it easy to port the metadata along in a way that lets us keep the look intact. Maybe that's a different thread over in the Redcine forum...
Cheers,
Harry

[David Mullen ASC]

Yes, my approach is feature film based where I know I will be doing the final color-correction. For commercials where I might be delivering the footage but not get to color-correct it later, I would probably attempt, at least with a digital camera, to deliver something closer to the final look up front, unless I was told not to for some reason (like for efx work.)

Since the RED camera, with its RAW recording, is a little more like shooting color negative film, there are limits to how much you can pre-color-correct in-camera compared to a broadcast HD camera, so your tools are more like the traditional film shooters -- unless you get to do the REDCINE/REDALERT conversions yourself and some initial color-correction to the footage before you deliver it.

[Harry Clark]

That's precisely what I'm wondering; in the commercial arena, we rarely get to the "supervised transfer" on a film job, and thus usually err a bit stronger on the look.
Red's "RAW" approach and the Redcine nondestructive correction offers an interesting double-edged sword. We can put our "look" on the footage, but it's subject to a different interpretation later. At the same time, if the workflow is refined enough, we can (with a certain amount of confidence) be sure that our initial correction and look is passed through all stages to final delivery (whether the client respects it and keeps it in the end is a different matter) I'm sure Stuart or someone else at Red has thought this through.
It seems to me there is an opportunity for colorists here; to be Red-savvy and help DPs achieve the look we want for a particular project, even if we're not there personally in the end.
Cheers,
Harry