Cinematography : Filters by Bryan Bethke

Is there any filmmakers in my network who can help Bryan out?

Hey Bryan, I guess this is a bit late of a post and hope it helps. Filters are usually a call to make for the cinematographer to get he desired look of the film you’re going for. The most common filters are ND filters that cut down the amount of light entering the lens without changing your apersture. So if you want to shoot at a 2.8 but everything is blown out you can add .3 ND to cut down one stop of light. The other filters such as BPM, Pearl, etc.. are more cosmetic. They may change the dark and heighlifht areas of the image, they may create a bloom effect. Some may add imperfections to a lens that may be super sharp, because the DP wants a more softer look to them.

At the end it’s to help you get the look

If I'm allowed to, I always ND up to shoot wide open simply because I like shallow dof. However, you can achieve the same using gels on lights. I was in FotoKem years ago watching the dailys from The Matrix and was surprised that BIll Pope never used any filters at all, the entire look was done using gels with little grading.

Filters basically affect 2 things, colour or diffusion with at least one notable exception.

Colour change with filters are in 2 general categories; technical correction and let’s term it artistic correction.

Technical correction would include accurate colour changes for colour temperature, i.e. using a native 3200K sensitive material with 5600K a light source. Also included would be neutral density filters, which should be but are not always totally neutral or having no effect upon the colour. Artistic colour filters are used to add an effect to part or all of an image to enhance an emotional response to images, i.e. adding a pinkish filter to change the feel of an image.

Diffusion filters spread light from sources (some perhaps outside of the frame) to other parts of the image. In a controlled way. Perhaps you wish to have sources in the frame to have a glow around them, perhaps you wish to lessen the contrast. Both will happen. One of the common uses is to soften faces in the image in various ways.

The one exception to the above categories is polarizing filters. They lessen the impact of light reflections on surfaces. Polarizers are the only filter that will darken a blue sky more than the rest of the image. There are many uses, but caution, care, and artistry must be used because without reflections many images do not look as good, faces being one of them that can be over polarized. Because the orientation of polarizer needs to be adjusted before every shot, the need for a rotating mount goes without saying.

When using filters to affect images, the final effect will probably not only be the filter. Many things contribute to the final effect. A given diffusion filter will have a different effect upon an image shot with a wide angle lens and one shot with a long lens. Similarly colour and diffusion will interact with the lighting and the exposure. You need to know, do not just assume, what the final effects upon the image will be. Testing and experience is critical.

One final point is that there are “filters” available in post. Know when to use optical filters, post filters, lighting filters or in reality all 3 of them. Diffusion on the lens has a very very different look than anything created by an algorithm in post. If you choose in part to utilize post filtration, the DP must control which post filters are used and the degree to which they are used.

Thank you all for your feedback I've learned a lot!

FWIW, the camera's WB function is not necessarily an adequate replacement for colour correction filters. The greater the difference between the sensor and the ambient light, the more you need physical filters. Keep this in mind, especially when shooting in low light levels.

Ken, since you mentioned it, could you please explain to me the purpose of grading? thx

Bryan Bethke - you have some responses, sorry for the late replies!

How does it feel when you watch it? - When you feel it... You will know...

Huge fan of using gels myself, Ken Koh. I love bringing the scene to live on set. Tend to use filters in front of the lens, when a softer look is needed (and generally, with the incredible sharp look of today's camera's, it nearly became a necessity.

What Andrew Sobkovich said. And I will add lens filtration is one of the opportunities a DP still has to burn in at least some of look before someone else gets hold of the RAW and ruins his or her originsl intentions... which happens far too much. Intentional use of a pola, for one, cannot be duplicated in post, nor can it be removed per se. Polas NDs and nets are my usual modern choices. Once in a while I use corals. As for comments on whote balance, a discipline of presets-only goes a long way to better, way more consistant footage... of course you have to learn how to shoot digotal as though it were emulsion. Not a bad thing to learn.

Forgive me Theresa. I've been on a social media detox. With grading you can create a 'look' by adjusting and manipulating colors, contrast, gama and all that. Provided there's good exposure and enough information on the negative or digital file, you can totally change the look. Grading is an art in itself. Sorry for the ridiculous late reply.