Fun With Filters!

[Guest dpforum1968]

Ok folks thanks all those informative replies and posts!

 

Now I would like to bring up two other points.

 

1) Can't most filter effects be achieved during film to video transfer? If you're using a top of the line transfer suite it seems the Davinci colour correction system for instance can achieve any thing under the hands of a skilled colourist. Doesn't this give you more latitude since the effect of the filter is not actually on the neg, you're adding it to your liking after the fact.

 

This I have found is especially true of any gradient effects, I prefer to add them in during transfer than with the use of a filter in the field.

 

I would say from my experience the polarizer is one filter that makes indivdual stand alone shots in exterior shooting look better. And the post colour correction can improve polarized shots even more. I do a lot of stock footage shoots so matching between shots is never a concern for me in these cases as I'm simply trying to achieve the best looking stand alone shot possible.

 

2) Don't all filters degrade the image on film some what? I have heard some DPs and stills photogs say, "why put a $50.00 filter on a $50,000.00 lens?"

 

 

Thoughts?

 

DC

[David Mullen ASC]

Diffusion filters by design "degrade" the image but glass ND, colors, etc. don't unless you stack too many together.

 

Polas obviously can't be done in post. Grad filter effects can -- except that they also reduce exposure onto the negative, so therefore if you are using an ND grad to bring down a bright sky in order to record more detail in the clouds, doing the ND grad effect in post instead won't be as effective since the sky got overexposed. In that case, you'd be hoping that the latitude of the film can pull out the detail. Certainly grad filters are a lot more useful in video where they help reduce clipping in overexposed areas, something that can't just be done in post.

 

Warming filters are something that I tend to do in post.

 

When I shoot film, it's generally for print without a DI process, so obviously I have to get filter effects done in-camera except for color tints (like warming up the image) that can be done in traditional RGB color timing using printer lights.

 

There is an assumption these days that all films are posted digitally and stay digital after image capture, which is not true.

 

Diffusion filter effects are not something offered in a DaVinci or Pogle color-corrector. You'd have to book a separate Flame or Inferno session after you transferred the footage, or do it with your editing or online software.

[Phil Rhodes]

Hi,

 

You can sort of do diffusion effects with blended blur in certain colour correctors, but it's not the same thing.

 

And to the previous correspondent, no, working with the image in telecine can only ever reduce dynamic range, not increase it. If you want to make the image redder, sure - you can make it redder in postproduction, but to do that you either amplify the red channel (losing stuff off the top and increasing red noise and grain) or reduce the green and blue channels (losing stuff off the bottom). You can do it as a gamma operation but then you're compressing the range of brightness above the midpoint into a smaller number of digital luminance levels, meaning that it's recorded with less resolution (Quantised.) Now as a practical matter it is possible to very nearly accurately recreate the effects of many standard colour filters in modern colour grading but the result will be technically - and sometimes visibly - inferior to having done it in camera.

 

Optical filters have an effectively infinite dynamic range, contribute practically no noise and do not quantise digitally-sampled images. Digital adjustment has all those faults.

 

Phil

[Mitch Gross]

Phil nailed it, but let's put the issue in far simpler terms. With every step information is lost. There's the outside world, there's what passes through a lens, what is captured on film or electronic sensor, what gets transferred to video or compressed onto a video format or squeezed into a codec, what makes it to a print, etc., etc. With every single step there is information lost. So the earlier one shifts the image in the direction they are ultimately trying to acheive the more of the useful information will ultimately be retained in the final product. I try to get as much as possible done in lighting and filtering when shooting, then attenuate the effects with each continuing step.

[GWilliamPatrickB]

Phil nailed it, but let's put the issue in far simpler terms.  With every step information is lost.  There's the outside world, there's what passes through a lens, what is captured on film or electronic sensor, what gets transferred to video or compressed onto a video format or squeezed into a codec, what makes it to a print, etc., etc.  With every single step there is information lost.  So the earlier one shifts the image in the direction they are ultimately trying to acheive the more of the useful information will ultimately be retained in the final product.  I try to get as much as possible done in lighting and filtering when shooting, then attenuate the effects with each continuing step.

<{POST_SNAPBACK}>

 

Mitch and Phil are correct. One other thing to consider. Every time someone like a producer says "post" they should say "money" It is less costly to do as much in camera as you can. I just finished a 24p shoot and they are now wallowing in "no money land post". I only Operated on the movie (a two cam. shoot) and heard "we will do it in post" so many times that I knew before we finished that unless we got our pay checks before the post sessions, we were screwed for our last weeks pay. Well, I just heard that it is so expensive they may not be able to finish unless more "POST" is available. Remember, I said use the word post and money as interchangable. Thank God we all got paid right away.

 

GWPB

[David Mullen ASC]

This is one reason why it's a good idea to get the dailies to look something like the final product, even if you are going to do the color effects in post later. For example, you could forego a Coral or 812 filter and shoot neutral, then shoot a gray scale with a blue filter or gel on the light in order to get the following scene to look warmer. So the negative itself might not contain the filter effect but the dailies will have it, so the producers will get used to the look throughout post and expect it when they finish the post. However, if you don't have the look built into the dailies, they will get used to THAT look and it will be harder to convince them later to spend time or money on changing the look.

[Michael Nash]

Every time someone like a producer says "post" they should say "money" Remember, I said use the word post and money as interchangable.

 

<{POST_SNAPBACK}>

 

That's a good one.

 

Just a couple thoughts to put this in perspective:

 

In addition to the recent development of DI for feature films, you have to remember that there has been a robust commercial, music video, and episodic television industry for decades. Those DP's haven't stopped using filters just because color correction is also done in telecine and/or post.

 

It is true that some adjustment room is usually left for video-finish projects, especially commercials. But more often than not I think most DP's prefer to use color correction as a final polish to the work, and not rely on it for complete image correction. I know that's how I approach it, for the reasons previously mentioned.

 

As I mentioned before, it's not the filter but how you use it. Each step (filtering, processing, transferring) is a "tweak," used in conjunction with other "tweaks." I wouldn't rely on either filters or digital corrections exclusively.

[Tony Brown]

Hi,

 

Very long grads.

 

Tony, what size filters do you own?

 

Phil

<{POST_SNAPBACK}>

 

Hi Phil,

 

I use 6.6" and 4x4. These are the 'standard' for the UK and most countries worldwide. I have a bit of a problem in the US where 5x4 and some 138's are commonly used but usually manage to get by.