I DID THIS IN EXCEL A WHILE BACK.
I THINK ITS CORRECT:
1/2 stops 1/2 stops 1/3 stop calc 1/3 stops
rounded
calc rounded stops
stops
1 f 1 0 1 f
1 0
1.189166052 f 1.19 0.5 1.122462047 f
1.12 0.33
1.4 f 1.4 1 1.259921047 f
1.26 0.66
1.664832473 f 1.66 1.5 1.4 f
1.4 1
2 f 2 2 1.571446866 f
1.57 1.33
2.378332105 f 2.38 2.5 1.763889466 f
1.76 1.66
2.8 f 2.8 3 2 f
2 2
3.329664947 f 3.33 3.5 2.244924094 f
2.24 2.33
4 f 4 4 2.519842094 f
2.51 2.66
4.756664209 f 4.76 4.5 2.8 f
2.8 3
5.6 f 5.6 5 3.142893732 f
3.14 3.33
6.659329893 f 6.66 5.5 3.527778932 f
3.52 3.66
8 f 8 6 4 f
4 4
9.513328419 f 9.51 6.5 4.489848188 f
4.49 4.33
11 f 11 7 5.039684188 f
5.04 4.66
13.08082658 f 13.08 7.5 5.6 f
5.6 5
16 f 16 8 6.285787463 f
6.29 5.33
19.02665684 f 19.03 8.5 7.055557863 f
7.06 5.66
22 f 22 9 8 f
8 6
26.16165315 f 26.16 9.5 8.979696376 f
8.98 6.33
32 f 32 10 10.07936838 f
10.08 6.66
38.05331367 f 38.05 10.5 11 f
11 7
45 f 45 11 12.34708252 f
12.34 7.33
13.85913152 f
13.85 7.66
16 f
16 8
17.95939275 f
17.96 8.33
20.15873675 f
20.16 8.66
22 f
22 9
24.69416503 f
24.69 9.33
27.71826303 f
27.71 9.66
32 f
32 10
35.9187855 f
35.92 10.33
40.3174735 f
40.32 10.66
45 f
45 11
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of Scott J. Fine
> Sent: Wednesday, August 14, 2002 3:04 PM
> To: [EMAIL PROTECTED]
> Subject: Re: stops and scales
>
>
> You write:
> >Scott J. Fine" <[EMAIL PROTECTED]> wrote:
> >
> >"I am under the impression that f-stops are measured in a scale that is
> >either based on 1 or 1.4, as in:
> >
> >1, 1.4, 2, 2.8, 4.0, 5.6, 8, 11, 16, 22, 32..."
> >
> >It's actually based on the square root of 2 (1.414) and has to
> do with how
> >the area of the aperture is calculated. The f stop is the ratio of the
> >aperture diameter to the focal length. An f stop of 1.0
> (theoretical) with a
> >50mm lens at infinity would mean an aperture diameter of 50mm.
> If you wanted
> >to halve the area of the aperture (to reduce the amount of light reaching
> >the film by half), you wouldn't halve the diameter because the area of a
> >circle is:
> > pi x r**2. Halving the radius would result in an aperture one
> fourth the
> >area (or 2 stops). Therefore, to halve the aperture area you divide the
> >diameter (and therefore the radius) by the square root of 2. The
> new f stop
> >becomes f/1.414 (f/1.4) as the diameter is 1/1.414 of the focal length.
> >Divide by the square root of 2 again and you get an f stop of f/2 as the
> >diameter is now 1/2 the focal length. Keep dividing by the
> square root of 2
> >and you get the rest of the scale.
>
> Please tell me if this is correct - I subtracted one stop from the next
> largest, divided that number by 2 and added the result to the larger
> aperture. I cam up with the following 1/2 stop scale.
>
> 1.414 (1.4)
> 1.706 (1.7)
> 1.999 (2)
> 2.413 (2.5)
> 2.827 (2.8)
> 3.412 (3.5)
> 3.997 (4)
> 4.824 (4.5)
> 5.652 (5.6)
> 6.822 (6.7)
> 7.992 (8)
> 9.646 (9.5)
> 11.301 (11)
> 13.640 (13.5)
> 15.980 (16)
> 19.288 (19)
> 22.596 (22)
> 30.273 (?)
> 31.951 (32)
>
> And if I take the difference between apertures, multiply by .333 and add
> that result to the larger aperture, I get 1/3 stops? As in f/9 being 1/3
> of a stop smaller than f/8? ((11.301 - 7.992)(.333)) + 7.992 =
> 9.093 [f/9]
>
> And thank you all for your answers, even the ones with links to
> information
> that I have no hope of understanding :)
>
> s/
>
> http://www.eyecafe.net
> -
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