RED and B&W filters

[Medavoym]

Hi!

When going for Black & White on the RED camera, is it a good idea to use B&W filters, just like when shooting film? For example, Yellow 8, Orange 16, Red 25 or Green 11 - depending on the degree of contrast you want in the final result.

Or is it better to shoot normally, and then do it all in post?

However, the above filters really do improve contrast and - when shooting film - it's always a good idea to use them on camera, compared to trying to increase contrast in post. At the same time, this approach is very depending on the nature of the film emulsion... the RED sensor can have other qualities, so I'm not sure using B&W filters (which block certain wavelengths) is a good idea.

Any advice?

Thanks!

 

[Nir Shelter]

Good question would really like to know the answer to this one...

 

[Brent J. Craig]

I would recommend always shooting full color, then you can choose which colors give you which black and white tones in post. You can produce the exact same effect as any black and white filter simply by adjusting the colors in post.

Play around with Photoshop's (CS3E) excellent black and white features to get a feel for what's possible. It has black and white options within the RAW import box, and also under Image / Adjustments.

Example:

BEFORE

AFTER

ALTERNATE INFRARED LOOK

 

[George A.]

You can produce the exact same effect as any black and white filter simply by adjusting the colors in post.

That's the main question.

 

[David Mullen ASC]

You don't get the same advantages with the b&w filters as you do on panchromatic b&w emulsion, where the b&w filter is basically rendering certain colors darker or lighter than others.

In a color image, you have a lot more flexibility in post working with a full color image to then do a digital version of what the b&w filter does to b&w emulsion -- you can take the blue channel and make it darker than the reds and greens, etc. But if you had used an orange camera filter to make the blue sky darker, then you don't have as much flexibility to adjust the blue channel separately in post because it has been muddied in saturation to look closer to the red and green channels.

 

[Shane Betts]

One of the key advantages of digital acquisition (as stills photogs have realised) is the flexibility in post. Secret is not to commit when you shoot (by using filters for instance) but just record as much information as possible and do it in the grade. You can do more and have greater control that way and what's more, you can change your mind.

 

[David Mullen ASC]

But one of the keys to being an artist is to make bold choices and live with the consequences, not taking the most middle-of-the-road approach that allows you to constantly change your mind...

Besides, I don't think digital is actually all that flexible -- there are limits in pushing an image around in post before you get artifacts (particularly noise) so there is some advantage for post color-correction from shooting an image that is close to being correct for the final look, so post color-correction decisions are not extreme, but minor adjustments. Especially in a movie where you want some consistency in noise level shot-to-shot.

And film is not dead.

 

[Nir Shelter]

One of the key advantages of digital acquisition (as stills photogs have realised) is the flexibility in post.

No need to state the obvious.

Secret is not to commit when you shoot (by using filters for instance) but just record as much information as possible and do it in the grade. You can do more and have greater control that way and what's more, you can change your mind.

Absolutely disagree with you.

My theory is shoot to a look basically what David said on his second post. True we must try and limit our selves as least possible, but always have intention in lighting, filter use and look in general. If the use of filters brings our footage closer than post to what we need use them.

Has any body tried using B&W filters on the RED?

 

[GlennChan]

There are some interesting black and white tricks that you can do in post if you had shot color.

You can use channel blending to emulate the effect of optical filters (granted, channel blending could be a PITA in your finishing system/editor of choice). But once you do that, you can do unintuitive stuff like use channel blending / color filters to REDUCE contrast, and then use curves to add contrast back in. This can give a lot more texture/detail to your images. See pictures here:
Black and white conversions

2- From a practical standpoint, you can shoot slightly faster without color filters. No loss of light, no time spent changing filters, and you don't have to rent filters.

 

[Alexis Vanier]

I know shooting without filters will give the most flexibility in post, but I believe shooting 'baked in' with filters still has something to offer : uncompromised dynamic range. Altering in post will always dig into your dynamic range and managing that margin is definitely today's digital game. But if one was experienced enough and knew exactly what he was going for... wouldn't you benefit from 'NOT doing anything in post', safeguarding your dynamic range for a nice compressed sky effect or prevent highlights blowing out in some high contrast scene?

Filters also have the advantage of instant preview : kill the saturation on the monitor, put the filter in and off you go, panchromatic black and white preview.

Now, I couldn't say if those characteristics could prove a 'significant' advantage or if they're worth the trouble.

I personally think the hard way forces you to stretch you brain an go on set prepared (and can make for great pub talk afterwards). But then, once you've had it hard (in your own private time tinkering with fruits and film in your backyard) you don't need the rest of the production you're working on to have it hard for you...

 

[Dan Hudgins]

HDR through filters

HDR through filters

but I believe shooting 'baked in' with filters still has something to offer : uncompromised dynamic range.

Aside from issues with the Bayer filter, if you shoot 4K and down res the right way to 2K in post, shooting through a color filter can extend the tonal range.

When you sum the Red, Green, and Blue images in post you can mix the curves from the three colors that are exposed at different ranges.

The Blue cut in the Bayer (and over lens) filter will pass some IR also, so the blue Bayer filter does not give you the same bad skin tones as it would on film with just blue and UV exposure, perhaps, depending on what IR filters you use.

Likewise the Green Bayer filter may pass some far red and IR to give some more detail in far red.

So since all three sensors are far red and IR sensitive, you can use a Wratten 25 or 29 filter plus IR cutoffs to get Black and White, the exposure will be different in all three seperation images, so you can mix them to get HDR.

Depending on the filters you use you can get +10 stops in the RED and -10 stops in the BLUE and +/- 0 stops in the GREEN. This would extend the sensor latitude to +/- 20 stops over its normal 11 or so stops, giving you maybe 9 stops extra tonal range, depending on how you mix the tones.

In my CC you can mix the colors in the Matrix to any percent and generate a neutral gray tone image.

You can also use color filters on color film to extend the tonal HDR range when you scan color film for conversion to monochrome in CC my software, it works well to pick up both ends of the scale.

You might want to reduce the 4K images to 2K by mixing four pixel groups to avoid some of the Bayer filter artifacts, you can then up res the images back to 4K if needed. At any rate, you can get a longer tonal range if you use the right filters over the camera when you know that you are shooting for monochrome conversion.

Note that the lens witness mark will be off for far red and IR focus, so you should focus on the monitor and stop down when you can.

You can go the other way as well, using a heavy blue filter, and then using the red, green, and blue Bayer filters, this lets you reduce the exposure to the red bayer filter to hold the sky on that sensor, rather than having the blue bayer filter be the under exposed one like when you use a red filter over the lens.