ND questions

[boulder]

I've found some articles on the web about NDs but these are usually dealing with stills for blurring waterfalls, street scenes etc. Are there any good references for using ND's with 24p video? Or any quick rule of thumbs about when to use them etc? Also would it be advisable to go with a fader ND or a set of normal ones?

From a camera dummy.

[Barry_Green]

ND filters are "sunglasses" for your camera. You use them whenever the light is too bright.

[boulder]

So what is the difference between that and just stopping down?

[Barry_Green]

You can only stop down so much. What do you do when you're at f/16 and it's still too bright? Or, more importantly, what do you do when you want your aperture to be nice and open for a shallow depth of field look, but it's still too bright?

You don't want to change the shutter speed when shooting video, so the other option is to use neutral density filters to cut the amount of light entering the lens.

[boulder]

understood thanks

[jjwvu]

I'm new to dslr video (just got my GH1). Do those of you who have been working with DSLRs keep several ND filters on hand, and if so, which ones. Do they roughly correspond with the built in filters on prosumer video cameras - say the 1/4, 1/16, 1/64?

[mhood]

Did you see this?

http://www.dvxuser.com/V6/showthread.php?t=189689

[Barry_Green]

ND filters are typically labeled with decimal numbers, so 0.3, 0.6, 1.2, etc.

The video cameras are talking about how much light reaches the sensor when each ND is in place, so 1/4 as much light, or 1/16, or 1/64.

ND filter numbering is based on 1/3-stop increments, so a 0.3 ND filter cuts the light by 1 stop, or in half. So an ND 0.3 = 1/2. ND 0.6 = 1/4. ND 0.9 = 1/8. ND 1.2 = 1/16, ND 1.8 = 1/64.

And the hot ticket for DSLR usage is something like a Fader ND or Singh-Ray VariND, which is a variable neutral density filter. That way you don't have to be attaching and removing a bunch of individual filters (and trying to keep them clean, and avoid fingerprints, and all that); you just rotate the filter to increase or decrease the amount of ND it applies.

[muntus]

So, say you have a matte box like the Redrock. Can you use the two filter stages to turn it into a ND Fader? I'm assuming the answer is yes, but I'm still learning all these things.

[jjwvu]

Thanks for the info. I Think I'll give the FaderND a try.

[Barry_Green]

Read about do-it-yourself faders; the short answer is that yes, you could make a homemade version by using two linear polarizers (or is it one circular and one linear? I forget).

[Kholi]

I haven't tried the Fader yet but I dunno how I feel about it still. Especially in conjunction with a Polarizer... I'm considering purchasing one for my next job (which means two =( ) but I've had no issue using Multi Coated 2 4 and 8's.

[ydgmdlu]

Read about do-it-yourself faders; the short answer is that yes, you could make a homemade version by using two linear polarizers (or is it one circular and one linear? I forget).
It's either two linear polarizers or one linear polarizer on top of a circular polarizer.

If you get good quality polarizers, then the image quality should be the same as the Singh-Ray.