cinematography Polarizer side by side comparisons

[knightly]

Taken with my T3i on a super sunny day at the park... no corrections in post... no differences in camera settings except for the water image, which I used the polarizer to allow me to increase the levels of the shadows to be closer to the highlights.

The polarizer stops scattered light rom entering the lens, leaving only directly reflected light:
colors are richer, Color Correcting this image will make those background colors pop:

especially in greenery, which reflects a lot of light from all over, especially from the sky (not just the sun)

reflections can be dialed away as they're comprised of a lot of scattered / off-axis light. Here the reflection is the bridge off camera to the right.

Which allows us to get ride of the reflective sun on water allowing us to balance our images of water better to get more contrast out of them as the reflections are removed from the main calmer parts of the water


And what they do to cloudy skies is amazing!

 

[Zensteve]

I was just looking at ND filters on Ebay, and there seem to be a lot of so-called variable ND filters that change in strength as it gets rotated. Are these the same thing as adjustable polarisers, or is there a difference?

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[ItDonnedOnMe]

The specifics are beyond my understanding, but polarizing filters work by filtering out light based on the orientation of the light wave (or something like that). It only allows rays that are oriented along a specific axis through.

An adjustable polarizer just lets you rotate the polarizing element until it filters out the specific things you want to block, like reflections off of glass or scattered light from the atmosphere.

A variable ND has two of these polarizing elements instead of just one. The front one rotates so that you can filter out light waves of more than one orientation. When the two are oriented at 90 degrees to one another they effectively block out all light, at in-between angles they let partial light in - hence the variability.

A true ND filter doesn't change the light coming through, it just reduces it. Because the variable NDs use polarizing elements they actually do both - they reduce the intensity and reduce scattered light rays, so they can cut down reflections like a standard adjustable polarizer. The problem is you can't control both independently, so the reduction in reflections is just a bonus if it happens to work at the angles you need for reduced intensity. A standard polarizer also reduces intensity - usually about two stops, but you can't change that like you can with the variable ND.

So they're similar but different, I personally have both and use them for different purposes.

 

[Jeff Troiano]

I have a 77mm Genus Variable ND filter. While its not perfect, it works. I've also purchased some regular ND filters, in varying degrees of reduction. I've read the non variable ones seem to be a bit sharper.

Now I've recently started reading about IR ND filters, I'm still clueless about these. I've preordered a BMD pocket camera, and was,reading an article from a guy, suggesting getting an IRND, because its needed, so i started researching. Came across this article. Could be of interest to some.

http://nofilmschool.com/2012/12/choosing-neutral-density-filters-infrared/



https://www.youtube.com/watch?v=_T9u-1Ib6vo

 

[jax_rox]

I've found vari-NDs kill some sharpness, and some of them have really ugly colour shifts. That said, the majority of my work is not based in DSLR, so I can't give you a definite answer based on high amounts of usage.

Now I've recently started reading about IR ND filters, I'm still clueless about these. I've preordered a BMD pocket camera, and was,reading an article from a guy, suggesting getting an IRND, because its needed, so i started researching. Came across this article. Could be of interest to some.

I'd disagree with what's said at the end of the article in as much as whether or not you need an IRND. In many cases, yes, you definitely do, whether you're shooting raw or otherwise.
It greatly depends on the camera you are using as to which filter you should use. Hot Mirrors and IRNDs work slightly differently, the Schneider's and the Tiffen's work slightly differently (as you can see in those filters), but that's more about specifically what they're filtering out in relation to what the sensor's seeing, which is why some brands and some filters are better on some cameras vs others. That's why the Tiffen doesn't look 'so green' on the BMCC, and also why Hot Mirrors are recommended for the Epic, whereas the Tiffen T1 or IRNDs are more recommended for the Alexa.

Also important to note that you only really start encountering IR or Far Red pollution once you start getting to heavy densities of ND - I find it starts ~ND1.2. So, if you're looking to shoot in the middle of a bright day at 1.4, then you're going to get IR or Far Red pollution, but if you're looking to shoot an overcast day at, say, 5.6, you might be okay without them, but it all depends on what you're shooting, your locations and your lighting (whether it be artificial or the sun).

 

[knightly]

Here's the skies I was talking about (both sides, identical settings, just the polarizer turned 90 degrees):