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Author Topic: ND Filter for video - how to use?  (Read 6108 times)

schemula

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Re: ND Filter for video - how to use?
« Reply #15 on: February 26, 2012, 07:45:23 AM »
Actually, all cfl's do flicker or strobe. You can really see it on the cheaper lights and if your power source isn't good or your batteries are low. It also depends on the ballast they use.

These test pics are just my desklamp. I'm not using CFLs otherwise.

For the video I'm using one 650w and two 300w ARRI tungstens.

I'm going to exchange the ND filter for a less powerful one and try to avoid it by using the scrims and a softbox or maybe a 300w fill and scrimmed 300w key or something.

Last shoot was kinda rushed. Trying to plan out how to handle the next one.

I think all these 10 stop one have some sort of cast. The one I got is a nice B+W one, but, it's too much I think.

Avoiding it sound like a nice plan. I don't need to stay at f2.8, but do want some DoF effect.

Thanks, I got some good ideas/knowledge from this thread.

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Re: ND Filter for video - how to use?
« Reply #15 on: February 26, 2012, 07:45:23 AM »

neuroanatomist

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Re: ND Filter for video - how to use?
« Reply #16 on: February 26, 2012, 07:51:37 AM »
Your white balance is off because the 10-stop ND filter has a warming effect (my B+W 77mm and Schneider 82mm 10-stoppers do).

That doesn't sound very "neutral" at all! Do all 10-stoppers have that problem? And if so, why?

I think so. 

Lee doesn't seem to publish transmission curves, but for the Big Stopper they warn, "Use of the Big Stopper may result in a slight colour cast.

B+W does publish transmission curves (one reason I like them - you know, up front, what you're getting), and it's clear that with the 110 (10-stop) and to a lesser degree with the 106 (6-stop) filter, there's increased transmission in the red area of the spectrum.  B+W calls this out in their description of the 106 stating, "Because of its higher transmission in the red beyond 660 nm, this filter brings a slight warm tone to color photographs.  If this effect is undesirable, a B+W UV-/IR-Blocking Filter 486 in front of the neutral density filter (not behind it!) remedies that situation."  For the 10-stop filter, they indicate that the warm tone is slightly stronger than with the ND 106.

You can see the warmer tone below, top shot is no filter, bottom is the 82mm 10-stop ND from Schneider Optics (parent company of B+W and the only 82mm screw-in 10-stop filter available, AFAIK).  As you can see, I use the 10-stop to blur out the people walking through the shot, cars going by, etc.
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Axilrod

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Re: ND Filter for video - how to use?
« Reply #17 on: February 27, 2012, 05:43:01 PM »
you should leave your shutter on  1/60th

1/60th if he's shooting 30fps, but 1/50 for 24fps.
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Positron

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Re: ND Filter for video - how to use?
« Reply #18 on: February 27, 2012, 07:14:15 PM »
Your white balance is off because the 10-stop ND filter has a warming effect (my B+W 77mm and Schneider 82mm 10-stoppers do).

That doesn't sound very "neutral" at all! Do all 10-stoppers have that problem? And if so, why?

I think so. 

Lee doesn't seem to publish transmission curves, but for the Big Stopper they warn, "Use of the Big Stopper may result in a slight colour cast.

B+W does publish transmission curves (one reason I like them - you know, up front, what you're getting), and it's clear that with the 110 (10-stop) and to a lesser degree with the 106 (6-stop) filter, there's increased transmission in the red area of the spectrum.  B+W calls this out in their description of the 106 stating, "Because of its higher transmission in the red beyond 660 nm, this filter brings a slight warm tone to color photographs.  If this effect is undesirable, a B+W UV-/IR-Blocking Filter 486 in front of the neutral density filter (not behind it!) remedies that situation."  For the 10-stop filter, they indicate that the warm tone is slightly stronger than with the ND 106.

You can see the warmer tone below, top shot is no filter, bottom is the 82mm 10-stop ND from Schneider Optics (parent company of B+W and the only 82mm screw-in 10-stop filter available, AFAIK).  As you can see, I use the 10-stop to blur out the people walking through the shot, cars going by, etc.

That's actually pretty dramatic, but since it's very even across the frame I'd assume it can be pretty much completely corrected with a white balance adjustment. Personally, I actually like the colors on the bottom image more, but that's not the point. Did you use manual WB for those? I feel like auto would have picked up on such a large color shift.

neuroanatomist

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Re: ND Filter for video - how to use?
« Reply #19 on: February 27, 2012, 09:09:09 PM »
That's actually pretty dramatic, but since it's very even across the frame I'd assume it can be pretty much completely corrected with a white balance adjustment. Personally, I actually like the colors on the bottom image more, but that's not the point. Did you use manual WB for those? I feel like auto would have picked up on such a large color shift.

Actually, it was Auto WB (which I typically shoot because I always shoot RAW).  But the difference in the camera-selected WB is minor - the no-filter shot was 5034 K and 0 tint, and the 10-stop ND shot was 4996 K and +4 tint.  Setting them alike doesn't change the differential, although you are correct in that it could be corrected with a WB adustment.  But in this case, I completely agree...I prefer the warmer tone anyway!
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cinema-dslr

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Re: ND Filter for video - how to use?
« Reply #20 on: February 28, 2012, 06:52:41 AM »
you should leave your shutter on  1/60th

1/60th if he's shooting 30fps, but 1/50 for 24fps.

As i see it the problem of the original poster was about the strobing effect due to higher shutter settings.
This has al to do with the freq. of the powergrid and nothing to do with the prefered shuttersetting for motionblur.
All light sourches directly connected to the powergrid will resonate at 60hz(50hz in europe) that is why if i'm shooting in the usa i would have to use 1/60th even when i'm shooting 25p.
Maybe that is the reason some people experience light flicker in the US when shooting 24p at 1/50th
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Re: ND Filter for video - how to use?
« Reply #21 on: February 28, 2012, 07:23:15 AM »
...it was nice and bright, and for some brain fart of a reason, turned the shutter speed up, and it was strobe and stutter looking.
you should leave your shutter on  1/60th

1/60th if he's shooting 30fps, but 1/50 for 24fps.

As i see it the problem of the original poster was about the strobing effect due to higher shutter settings.
This has al to do with the freq. of the powergrid and nothing to do with the prefered shuttersetting for motionblur.
All light sourches directly connected to the powergrid will resonate at 60hz(50hz in europe) that is why if i'm shooting in the usa i would have to use 1/60th even when i'm shooting 25p.
Maybe that is the reason some people experience light flicker in the US when shooting 24p at 1/50th


Maybe the OP can clear it up, but I'm pretty sure in this case he was talking about the stutter you can get from using very high shutter speed, not related to the grid.  You'd even get this shooting outside.  I shoot a lot at 1/50th (or 1/48th with magic lantern) and 24p and don't have trouble at all with tungsten or other constant light sources.

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Re: ND Filter for video - how to use?
« Reply #21 on: February 28, 2012, 07:23:15 AM »

schemula

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Re: ND Filter for video - how to use?
« Reply #22 on: March 02, 2012, 10:44:15 PM »
Maybe the OP can clear it up, but I'm pretty sure in this case he was talking about the stutter you can get from using very high shutter speed, not related to the grid.  You'd even get this shooting outside.  I shoot a lot at 1/50th (or 1/48th with magic lantern) and 24p and don't have trouble at all with tungsten or other constant light sources.

Yes my problem was specifically related to the faster than 1/60 shutter speed and not the lights. I upped the shutter speed to deal with the fact that my scene was a little too bright. I forget what I used, but it was in the 1/200 range and as long as the subject was still, it was ok, but any side to side movement, and oh man, awful.

The light kit I rent is an ARRI tungsten constant light source.

I've decided to buy the light kit and solve this from the light side. I was not happy with the ND filter color cast and while I may get a less drastic ND filter, I'm going to move to a softbox and scrims and maybe a dimmer or two to get control over the lights.

I'd like to stay under ISO 400 with a 1/60 shutter speed (or 1/50 for 24p) and in the 2.8 to 4 aperture range. But I think attacking this from the light side is going to be the way to go.

Thanks.
« Last Edit: March 02, 2012, 10:46:45 PM by schemula »

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Re: ND Filter for video - how to use?
« Reply #23 on: March 03, 2012, 11:05:54 PM »
Maybe the OP can clear it up, but I'm pretty sure in this case he was talking about the stutter you can get from using very high shutter speed, not related to the grid.  You'd even get this shooting outside.  I shoot a lot at 1/50th (or 1/48th with magic lantern) and 24p and don't have trouble at all with tungsten or other constant light sources.

Yes my problem was specifically related to the faster than 1/60 shutter speed and not the lights. I upped the shutter speed to deal with the fact that my scene was a little too bright. I forget what I used, but it was in the 1/200 range and as long as the subject was still, it was ok, but any side to side movement, and oh man, awful.

The light kit I rent is an ARRI tungsten constant light source.

I've decided to buy the light kit and solve this from the light side. I was not happy with the ND filter color cast and while I may get a less drastic ND filter, I'm going to move to a softbox and scrims and maybe a dimmer or two to get control over the lights.

I'd like to stay under ISO 400 with a 1/60 shutter speed (or 1/50 for 24p) and in the 2.8 to 4 aperture range. But I think attacking this from the light side is going to be the way to go.

Thanks.

Good decision, I think.  And I think if you use a softbox that should cut enough light to not need ND inside.  I find dimmers are helpful for adjusting back light--just keep in mind that when you dim tungsten it gets a warmer color temp so you may need to get a new white balance if you dim drastically.  If you do any outside shooting at all though, you'll eventually want to get a variable ND so you can get those wide apertures in bright light.

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Re: ND Filter for video - how to use?
« Reply #23 on: March 03, 2012, 11:05:54 PM »