1 stop in light loss = what in % at DVinfo.net

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Old March 8th, 2005, 11:05 PM   #1
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1 stop in light loss = what in %

1 stop in light loss = what in % loss from original?

if measured light equaled 100% and you stoped down the iris by 1, what is the percentage loss?

thanks for the edu.

jh
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Old March 8th, 2005, 11:25 PM   #2
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50 %
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Old March 9th, 2005, 12:41 AM   #3
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wow.
so one stop more would be half again? IE 25%of the original 100%

2 stops = 25%

jh
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Old March 9th, 2005, 01:13 AM   #4
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Yup.

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Old March 9th, 2005, 07:36 PM   #5
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also, keep in mind that your camera may not stop down incrementally in full stops. both the PD150 and DVX100 can be adjusted in half-stop increments. the full stop scale is:

1 - 1.4 - 2 - 2.8 - 4 - 5.6 - 8 - 11 - 16 - 22



hope this helps,

kris
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Old March 9th, 2005, 10:11 PM   #6
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why the jumps from 8-11-16-22?

jh
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Old March 9th, 2005, 11:37 PM   #7
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The scale starts at 1 to get every second stop:
1, 2, 4, 8, 16
and 1.4 for every other:
1.4 ,2.8 ,5.6, 11.2(rounded to 11), 22

This gives double/half the light with each full stop.

Cheers.
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Old March 10th, 2005, 01:12 AM   #8
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when I'm on a set I hear the DP's and thier "people" talking "two eight" alot, figuring they mean a 2.8 stop. is this some mean value they are looking for from setup to setup for continuity?

jh
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Old March 10th, 2005, 01:22 AM   #9
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See also this informative thread that I started:

http://www.dvinfo.net/conf/showthrea...hlight=numbers

One thing that's neat and helps you remember is that every OTHER stop is twice/half that of the one that is. . .um. . .two before it. . .er

What I mean is - 1, 1.4, 2, 2.8, etc.

2 is double 1, 2.8 is double 1.4, and it goes on like that.

halves and thirds, I don't know if there's an easy trick to them other than just rote memory.
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Old March 10th, 2005, 01:38 AM   #10
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THE PERFECT THREAD!

Opps, sorry for shouting.

that was a good read indeed. now I understand, just don't ask me to explain it yet.

jh
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Old March 10th, 2005, 02:26 AM   #11
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Old March 10th, 2005, 03:10 PM   #12
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As I said in that thread, it's just square root of 2 times an f stop is the value of the next one:

1 * 1.4 = 1.4

1.4 * 1.4 = 2

2 * 1.4 = 2.8

etc etc etc

(approx here of course)

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Old March 10th, 2005, 03:12 PM   #13
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Sorry, I forgot to mention the doubling thing to get every second stop, which was kinda the point of my post...
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