April 19, 2014, 04:19:31 AM

Author Topic: choosing the right ND filter value  (Read 2256 times)

canonuser78

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choosing the right ND filter value
« on: May 08, 2013, 03:57:14 PM »
Hello there,
I am about to search and buy one or two screw on ND filters and I plan to use it specially in video mode. I have some difficulties in choosing the right ND filter values in order to be able to shoot in daylight with wide open aperture (f2.8-4), ISO 100-160, shutter speed 1/50 at 24fps.

According to this chart considering 1/4000 shutter speed in daylingt at ISO 100-160, f2.8-4, 24fps, I wonder which one between these filters ND 1.8(1/60) and ND 2.1(1/30) will fit my needs better (?)
I just need a confirmation .
thanks,

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choosing the right ND filter value
« on: May 08, 2013, 03:57:14 PM »

luciolepri

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Re: choosing the right ND filter value
« Reply #1 on: May 29, 2013, 09:48:02 AM »
I sugggest you to buy at least 3 filters to used them individually or together, according to the light conditions.
I have the 0.3 (ND2) 0.6 (ND4) and 0.9 (ND8) which reduce the light of 1-2-3 stops. I think that using at least 3 filters is the only way to achieve the right ND value in different situations, I can't see how it would be possible with just 1 or 2 filters. Obviously, to use more filters at once, you'll need a matte box (even a little cheap screw-in one) or an adapter, like the Cokin P. The Matte Box is better because it works also as a lens hood, that with the Cokin P adapter you won't be able to mount.
Trouble is, to use 2-3 filters together you have to buy really good filters, otherwise you'll end up with strong color shift (usually towards magenta) and sharpness reduction. A cheap alternative to HQ glass filters are the resin filters, some of them are quite good, but you definitely can't get a good 6 stops reduction with them, not even using a single filter. That's just my experience.
I once tried a 250 $ "slim fader", an ND filter that works, I guess, something like a polarizer and produces from 1 to 9 stops reduction, very easy to find on eBay. It was really bad, when you reached a 2-3 stops reduction you could clearly se a sort of dark cross which splitted the frame in four areas. Nice special effect, but...
On ebay you can also find complete ND and gradual ND filters set (6 filters + 1 filter holder (like Cokin P) + 8 screw lens adapter from 49 to 82 diameter) for less than 50 $. I never used them because the filters are too small for a MatteBox, but I'd be really curious to try.
To know which ND value would be good for you, just do the math: if you're shooting at 1/125 f/8 and you wanna shoot at 1/50 f/4-2,8 you need a 3-4 stops reduction. So, in my case, I'd use an ND8 or an ND8 + an ND2. That's all.

alexanderferdinand

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Re: choosing the right ND filter value
« Reply #2 on: June 15, 2013, 12:41:04 PM »
Just bought me a ND4- filter.
I am very good at mathematics, and I dont like the different misleading names, better, numbers.
It should be the number of f- stops, or the logarithmic scale (its scientific, but you have to think a second).
I absoluty don't like the 16x or 64x. Then its necessary to calculate, how much this is in f- stops.

One of the fotografic currencies is the f- stops.
And this for some good reasons.

My 2 cents.


RGF

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Re: choosing the right ND filter value
« Reply #4 on: June 17, 2013, 02:17:08 AM »
Hello there,
I am about to search and buy one or two screw on ND filters and I plan to use it specially in video mode. I have some difficulties in choosing the right ND filter values in order to be able to shoot in daylight with wide open aperture (f2.8-4), ISO 100-160, shutter speed 1/50 at 24fps.

According to this chart considering 1/4000 shutter speed in daylingt at ISO 100-160, f2.8-4, 24fps, I wonder which one between these filters ND 1.8(1/60) and ND 2.1(1/30) will fit my needs better (?)
I just need a confirmation .
thanks,


You want to go from 1/4000 to 1/50 second.

Let's see - 1/4000 -> 1/2000 1 stop
                  1/4000 -> 1/1000 2 stops
                  1/4000 -> 1/500   3 stops
                  1/4000 -> 1/250   4 stops
                  1/4000 -> 1/125   5 stops
                  1/4000 -> 1/60     6 stops

so you need a 6 stop ND filter

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Re: choosing the right ND filter value
« Reply #4 on: June 17, 2013, 02:17:08 AM »