Filters Take Two by Mark Peterson

We continue our look at external camera filters, focusing on what makes the most sense for outside shooting. Like the last blog, we feel strongly that today’s cameras and post abilities are so versatile, it only makes sense to use filters when time or money keep you from achieving the desired look.


UV Filters and Common Thread Size

Like frequent oil changes in your car, a UV filter on every lens that can accept one is a great investment. For under $20/lens you are adding one more layer of protection. Scratches, abrasions, dirt and “bumps” all take it out on the UV filter first before permanently damaging your expensive lenses. Buy a decent quality UV filter, one with decent threads and then forget it is even there. If your lenses have several filter sizes try step-up or step down rings (If you aren’t losing field of view) to make a common filter size for all your shooting lenses. If all the lenses end up the same size, then they can share ALL of your screw on filters. If you can’t do that, consider a Mattebox. The goal is to be able to use all the filters on all the lenses.


ND Filters

If your camera does not have internal ND filters or you often find yourself in lighting situations where it is just too bright for what you want to do, then ND filters are a must. 0.3 ND equals 1 Stop of latitude, so a 0.6ND would be 2 stops, 0.9ND would be 3 stops and so on. Fixed ND Lenses work well, but consider getting a screw-on variable ND Filter. This will allow you to “dial-in” the exact amount of ND you require. If you have had the joy of working with a de-clicked cine lens, then you know the benefit of working between the hard stops.


Graduated ND Filters

As the name implies, these filters are graduated from full ND to No ND over half of the filter, then clear on the other half). Move the filter, No ND side first, into the frame until you lower the light level sufficiently for the desired look. You can move from top to bottom, bottom of frame to top, or side to side. In a multi-tray Mattebox, graduated ND’s can be used from multiple directions. Obviously, camera (Tilts and Pans) moves at right angles to the line of ND will not work, but if you shoot 4k then you know what to do….


Graduated Colored Filters

These filters are designed to give in-camera, dramatic effects. Our take: if you don’t have to, don’t. So much can be done in post, if you have even a small amount of time the flexibility of what can be done in post far outweighs committing to a colored filter effect in the field.



Polarizer (Linear and Circular)

Linear and Circular Polarizers do the same thing. They reduce reflections on glass surfaces, increase color saturation in foliage and darken a blue sky. All polarizers have a linear polarizing element. Circular Polarizers contain a Linear Polarizer component that does the main work of polarization, as well as a second layer inside the filter called a Quarter Wave Plate, which “spins” the light after it goes through the linear layer and before it enters the camera lens. This prevents "cross polarization" with any reflective surfaces in the system.



The main problem is that a linear polarizer can cause cross polarization on other reflective surfaces in your system such as mirrors and beam splitters.

Reflective surfaces polarize light, which is why a polarizer can reduce or eliminate those reflections. If you have a mirror or other reflective surface inside your camera, a linear polarizer can cross polarize the reflected image and possibly black out the image.



If you ever shot 16mm or 35mm film with a video tap while using a linear polarizer you know the video feed would often go dark because the partially silvered mirror in the video tap would get cross-polarized. This same type of cross polarization is used to create the Variable Neutral Density Filters.  



With a circular polarizer, the quarter wave plate on the rear of the polarizer spins the light before it enters the camera lens so that it doesn't get cross-polarized on any reflective surfaces in the system, such as the partial mirror in a video tap or a DSLR mirror. If there are mirrors in your optical system, the circular polarizer solves any problems or potential problems.



Day for Night

Although it was a classic movie by FrançoisTruffau, there is not much to recommend it as a filter. Today’s cameras have such a great latitude and low light capabilities that shooting at night or low light is infinitely preferable.



Soft filters

Use these outdoors only if it makes sense for what you are shooting, specifically faces and beauty product shots. Remember this is committing to an effect that can not be removed in post, so shooter beware!



External Filters by Mark Peterson

The question:

Are physical filters for your cameras worth it in a world where almost any look can be replicated (usually) with ease in post?

The answer:

Maybe.

Joking aside, the real answer depends on what you need and when you need it. Having a filter for your lens in the field can help you greatly if you need to turn around your video quickly. Meeting deadlines are a challenge when you need to spend an extra hour in the edit room making sure you footage looks the way you want it.

If you are filtering your image in the field, can you expect to have as versatile an image to work with in post? The simple answer is no. Once you have affected that video by using a filter, the ability to remove that effect is gone. What hits the sensor is what you have to work with. You are committed to the effect created by the filter. Any attempt at a post production tweek is limited by how much the filter/s used changed the video, so user beware!

There is a time and a place for filtering, and we have concluded that the determining factor for that is time, regardless of the product you are putting out. If you can spend countless hours in the edit room, I am sure that you can replicate or even improve upon a filtered look you get out in the field. All the while maintaining image versatility, be it native camera output, LUT corrected, LOG or RAW. Filtering simply locks you into a look that is harder to correct later. But, If you need to upload a video right after shooting or feel like you will be rushed in the edit room, the right filter in the field can give you a superior look to a stock Rec 709 look off your sensor.

Shooters using DSLR rigs might prefer using screw-on lens mounted filters, rather than buying a matte box with with 4 x 4 or 4 X 5.65 inserts. Screw-on lens mounted filters are advantageous for those run and gun DSLR rigs due to their lightweight nature and ease of mounting/storing. Serious cinema type shooters will appreciate the versatility and flexibility of a Matte box.

In conclusion...

If you’re a run and gun DSLR shooter who needs to put out content fast, get yourself a few solid filters you can slap on that bad boy to achieve a higher quality or designed look.If you’re shooting video that you want to spend some time with in post, grading, coloring, tweaking, ect… maybe skip the filters. Use your in-camera ND filters and mess with the rest in post.