Once again, most recent tips are at the bottom.
(From Jodi Jacobson – answering a question from Parker Deen) ND 8 Filter Is a Neutral density with a darkness factor of 8. I’m not technical but it looks like a really dark filter that evens out the lighting in the shadows and highlights and stops down the camera so you can have a longer exposure for motion blur.
(from Camrocker) A ND8 filter reduces the light by 3 stops. 8 is the attenuation factor.
It goes like this.
ND2= 1 stop reduction
ND4= 2 stops
ND8= 3 stops
Also, a ND filter does nothing but block light, it doesn’t even out shadows and highlights that would be a miracle.
A ND filter has two basic uses. It reduces the amount of light coming through the lens witch allows you to decrease depth of field, or get motion blur.
(From Ron Bailey) Don’t think in terms of “turns of the dial”. Think in terms of time. Each full f-stop that you close the aperature cuts the light allowed in by half. Notice I said “full f-stop”, most camera dials adjust in 1/2 or 1/3 f-stop incremement. So, if you change the apperture from 4 to 5.6 you’ve cut the amount of light in half. If a propper exposure at f4 was 100th of a second, then the propper exposure at f5.6 would be a 50th of a second (if you half the amount of light coming in you have to double the amount of time you gather light). So, if a propper exposure, without the nd filter was 1/80th of a second at f9, then the propper exposure with the nd filter at f9 would be 1/80 doubled 10 times…
1/80 * 2 = 1/40
1/40 * 2 = 1/20
1/20 * 2 = 1/10
1/10 * 2 = 1/5
1/5 *2 = 1/2.5
1/2.5 * 2 = 1/1.25 (this is pretty much 1/1 which equals 1)
1 * 2 = 2
2 * 2 = 4
4 * 2 = 8
8 * 2 = 16
So, the propper exposure should have been around 16 seconds.
If you’re better at doing complicated math in your head, you can think of it as 1/80 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2. Since the 2s never change you can multiply them (2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 * 2 = 1024) so your equation becomes 1/80 * 1024. If you plug that in to a calculator, the answer is appx 13 (the difference between this an the 16 I came up with originally, is the rounding error where I said 1/1.25 = 1).
So, here’s what I do. Without the filter I do an in-camera metering with the f-stop I want. Then, if I dont have a calculator, I take the shutter speed and double it 10 times (since I have 10 fingers, I can run through them to do it the right number of times). If I have a calculator (my cell-phone has one), I take my shutter speed and mutiply it by 1024.