Filters can be considered as the extension of your lenses. They affect the light coming through your lenses and hitting the sensor. They help you shape the light exactly the way you want it. But how do you know what filter to use to achieve any particular result? There are so many various filters, different types, shapes, sizes, etc. In this post I will try to describe just a few of them that I use the most.
There are 2 main group of filters that are used in filmmaking and photography – circular screw-in filters and rectangular ones that have to be mounted in special filter holders (photography) or matte boxes (film). Circular ones are more popular in the photography world and there a few reasons why they are not so popular in the film industry.
Matte box with rectangular filters
Pros
- No need to unscrew or remove filters when changing lenses
- Ability to stack multiple filters in various order quickly (without unscrewing)
- Universal for different lens diameters
Cons
- Added size and weight
Mattebox from The Cinecity
Circular filters
Pros
- No need for additional gear (matte box, baseplate with rods, etc)
- Compact size and weight
Cons
- The diameter of the filter has to match the diameter of the lens. Requirement of the step up rings for different lenses.
- Stacking multiple filters might cause vignetting
Why I use circular filters
In my current setup with the Blackmagic Pocket Cinema Camera I use circular filters mostly because I want to keep the rig small and lightweight as well as I want to use all my lenses and filters on my DJI Ronin M gimbal.
Keep in mind that the results presented below will be the same for the rectangular filters used with the Matte Box. It's just different form factor, but the physics and light manipulation is the same.
What filter diameter to pick
When you buy filters the first question should be – what size do I need?
It depends on the lenses you use and it makes sense to buy a filter that will match the biggest lens you own or plan to own at some point.
In my case almost all my lenses have the diameter of 77mm, and a few are smaller (72mm or 67mm) so I decided to stick to filters of size 77mm and get step-up adapters for the smaller lenses (that I keep on these lenses all the time – this way I can attach filters easily and I can use lens caps of the same size for all my lenses).
If you use Blackmagic Pocket Cinema Camera with the Metabones Speedbooster then the most common lenses you might end up with are:
- Sigma 18-35 f/1.8 – 72mm
- Tokina 11-16 f/2.8 – 77mm
- Samyang (Rokinon) 24mm T1.5 – 77mm
- Samyang (Rokinon) 35mm T1.5 – 77mm
- Samyang (Rokinon) 85mm T1.5 – 72mm
- Canon 70-200 f/2.8 VR IS II – 77mm
As you can see, in such case it makes sense to go ahead with 77mm filter size.
Neutral Density (ND) Filters
The main purpose of the ND filter is to lower the exposure. In other words, the only purpose of the filter is to limit the amount of the light that is hitting the sensor.
These are the most used filters in the film industry and they are almost unavoidable when shooting outside.
For example, to be able to shoot at 24fps with 180-degree shutter at ASA 100 during a bright sunny day we would need to shoot at around f/22. To be able to open the lens to f/2.8 we would need to apply a 6-stop ND filter (also marked as 1.8 or ND64).
Here's a table explaining the ratings of the NDs:
My ND filters kit
I own 3 regular ND filters in my kit, all from the company B+W. The first one reduces the exposure by 3 stops, the second one reduces it by 6 stops and the last one takes 10 stops of light.
B+W 77mm 103M Multi Coated +3 Stop (ND8, 0.9):
[ 82mm ] [ 77mm ] [ 72mm ] [ 67mm ] [ 62mm ] [ 58mm ] [ 52mm ]
B+W 77mm 106M Multi Coated +6 Stop (ND64, 1.8):
[ 82mm ] [ 77mm ] [ 72mm ] [ 62mm ] [ 58mm ]
The below filter in my kit is used mostly for the long exposure photography and shouldn’t be needed for video, but I am listing it here for the comparison to see how it affects the image:
B+W 77mm 110M Multi Coated +10 Stop (ND1024, 3.0):
Comparison – the color cast
Have a look at the comparison:
The stronger the filter, the stronger color cast it introduces. It looks quite drastic but changing the white balance neutralizes it completely.
Variable ND (Fader)
The main feature of the variable ND filter is to eliminate the necessity to use multiple ND filters. You can adjust the strength of the filter simply by rotating it (similarly to polarizer – in fact, variable ND consists of 2 polarizers).
There are Various brands, various strength ranges and various qualities. There are also some downsides when we compare them to the regular ND filters:
Variable ND Filter Cons
- Possible color casts
- X marks at maximum values with wide lenses
- Polarizer effect (faders consist of 2 rotating polarizers)
- Potentially decreased sharpness when using lower quality filters
At the moment I use Tiffen Variable ND filter. The quality is very nice for the price. I only used Light Craft Rapid ND and in comparison I like Tiffen more.
Here are some samples showing the image with various fader settings:
Notice that there is almost no color cast introduced by the filter (compared to the B+W ND filters). The fader also cuts the IR very nicely, there is almost no difference when the IR Cut filter is applied on top of the fader.
The only downside can be seen when using the fader at the maximum values with the wide angle lens – dark corners start to appear and sharpness around the edges is slightly reduced.
Here are the links to Amazon for the various diameter sizes:
[ 82mm ] [ 77mm ] [ 72mm ] [ 67mm ] [ 62mm ] [ 58mm ] [ 52mm ]
Circular Polarizer
Polarizer is probably the most used filter in photography, especially in landscape photography. How many times did you see these saturated vistas and deep blue, almost navy skies? It's the most visible effect of the polarizer filter.
Another benefit of using the filter is the removal of the reflections. It can make the water transparent and eliminate the reflections when shooting through the glass.
Here's what happens when the filter is being rotated:
Notice how the sky changes the intensity and color as well as the water reflections are reduced.
While using the polarizer might give wonderful results there are a few remarks that you should know about this particular filter.
- When using wide lenses be careful with blue skies – they will not be of consistent color. Polarizer tends to create stripes of darker and lighter colors (check the photo above).
- Polarizer affects the skin tones (in a bad way in my opinion)
Again, I think the best filter when looking at the quality and price ratio is Tiffen Circular Polarizer, that I currently use.
Here are the links to Amazon for the various diameter sizes:
[ 82mm ] [ 77mm ] [ 72mm ] [ 67mm ] [ 62mm ] [ 58mm ] [ 52mm ]
Hoya UV / IR Infrared Cut Multi Coated
The IR Cut filter is a must have when shooting with Blackmagic Pocket Cinema Camera as there is no internal IR blocking filter which results in red color casts in the image when shooting outside (hard or even impossible to remove in post production).
Here are some samples shot with Blackmagic Pocket Cinema Camera with various ND filters with and without IR Cut filter. Notice the red cast which is nicely removed when the IR Cut is applied:
ND 0.9 (3 stops)
ND 1.8 (6 stops)
ND 3.0 (10 stops)
You will find the Hoya IR Cut filters in various diameter sizes here:
[ 82mm ] [ 77mm ] [ 72mm ] [ 67mm ] [ 62mm ] [ 58mm ] [ 52mm ]
Check also the excellent write-up on IR pollution by Shane Hurlbut: What is IR Pollution and How Do You Combat it?
Tiffen Black Pro-Mist 1/4 Filter
The Pro-Mist filter can be put into the "Effects" category. What the filter does is it softens the image, lowers the contrasts and adds some sort of "halo" to the highlights. I really like the results produced by this filter.
Here's a video shot entirely with this filter on the Pocket Camera:
Check the video that the above frame comes from: There, I Seek by Thomas Simon
One of the nice things is that when there are blown out highlights in the frame the filter applies some sort of the highlight roll-off and it just looks nicer in my opinion. It also has some softening effect on the skin.
There are also stronger options (1, 1/2) but for me personally 1/4 is enough and don't feel the need to go further.
Here are the links to Amazon for the various diameter sizes:
[ 82mm ] [ 77mm ] [ 72mm ] [ 67mm ] [ 62mm ] [ 58mm ] [ 52mm ]
Xume Adapters
This adapter is a life saver when you use circular filters. The kit contains a set of lenses adapters and filter adapters. When you screw the elements on both sides you can attach filters to your lenses just by snapping them – there are some magnetic elements that hold the filter to the lens nicely. Really awesome product.
I use a bundle for 77mm diameter filters for my most used lenses. Check the official website for more options.
Summary
Filters are an essential part of your filmmaking kit. As a filmmaker, you will use ND filters the most. Some of the results achieved by using filters can be replicated in post-production (color filters, mist filters, etc) but some are possible only in front of your lens (polarizer, IR Cut).
