When to use filters, and when to not use filters? Addem, correct combinations for different circumstances...
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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.
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