Filters: ND or Polarizer

[Charles Papert]

Mark:

The standard measure for ND filters is that a ND .3 equals one stop of light reduction, and thus a .6 is 2 stops and so on. This will be acurate for filters made by professional manufacturers such as Tiffen, B&W/Schneider etc. On this page is a chart (scroll down) that lists the strengths and transmission of the ND series.

[Jeff Donald]

Avoid cheap ND filters (Quantaray etc.) because they may give your video an unusual color tint (they aren’t very neutral). There are several threads here about this effect.

I use circular polarizers for my video work. They are not that much more than linear polarizers and have the added benefit of doing double duty on your 35mm SLR (almost all modern cameras require circular polarizers). The use of circular polarizers on video cameras is somewhat controversial and has been discussed here in depth. Use the Search function if you want more information on the subject.

[David Martin]

I am a little surprised at the recomendation for linear polarizers for an auto-focus system, whether still photographic or video. Linear polarizers and circular polarizers are not the same. Using a linear polarizer on an autofocus system can not only affect the autofocus system, but also the metering system.

It is a known fact to filter manufacturers, and we always tried to educate dealers on the differences. This said, you can use a linear polarizer on an autofocus system, however, there is no guarantee. The bottom line has been, if you use linear on an auto-system you run the risk of affecting the auto-focus and metering systems of your cam and while you can't necessarily predict WHEN this will happen to you, or if you are ever in a certain situation that may increase your risk, you WILL then lose your shot, and in some instances, shots are not re-creatable. This is usually why amatuers who are more concerned with cost than with quality and reliability buy linear and take the risks, pro's buy circular since they can't afford to lose an important shot due to trying to work "on the cheap".

[Vladimir Koifman]

Linear polarizer dusturbs mostly SLR TTL focusing that use microprizms or similar stuff for focusing.
Most videocams use more simple contrast-detection AF systems. I do not see how they can be affected by linear polarizer.
Did you see any videocam suffering from it? What brand?

[Bryan Beasleigh]

I think it's more of a case that people aren't sure and recomend the circular just to be safe.

[David Martin]

Linear polarizers and circular polarizers handle light differently. I haven't tested it on video cameras, however, I can tell you two things, first, as I mentioned, you CAN use linear with auto-focus systems, BUT the results are not guaranteed and in different circumstances people may get different results - in other words...your mileage may vary...and pro's can't afford to take chances. Secondly, as I also mentioned, it is not just auto-focus that can be affected, but the metering system as well.

[Charles Papert]

<<you CAN use linear with auto-focus systems, BUT the results are not guaranteed ...and pro's can't afford to take chances.>>

This may be obvious but as a rule, "pros" don't use auto-focus.

I have personally never experienced metering problems using a linear pola on a broadcast video camera.

[David Martin]

Well that's fine. Aside from the fact that every pro I ever met uses circular, and every dealer I ever dealt with agrees, as do the filter manufacturers themselves and camera manufacturers. Suffice it to say, to each his own, good luck and enjoy.

[Charles Papert]

Then I'd say you just met your first pro who doesn't use one.

All the best,

[Andre De Clercq]

David, I think you don't realise that "autofocus" (and other "metering" concepts in video) are in no way related to the systems used in some photographic camera's. If there are reasons for using circulars in video, it's for shure not the autofucus...which is involved.

[John Threat]

Pro's don't use auto-focus.