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Old February 13th, 2003, 01:35 PM   #1
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Comparison Table For Focal Lengths?

Is there a comparison table for focal length differences between
DV and Film lenses somewhere on the web?Why do these differences exist because I thought one lens set was as good as another in terms of focal length,but,perhaps I'm missing something about the media differences as well?

Also,seeing how most DV isn't exactly forthcoming about proper lens barrel markings,could someone tell me what each "x(power)" translates to in the "reel" world of mm.For instance if my cam has a 10x zoom lens,what would that be,in mm, if I was shooting on an Arri 16?

Thanks!

A.
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Old February 14th, 2003, 11:10 AM   #2
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There has been lots of discussion already on this topic - here's another short summary view:

Field Of View is the quantity you are interested in when comparing 35 mm to DV. Field Of View has a relatively simple relationship to focal length, and except for extreme wide angle, the relationship is nearly a straight line. What's important is the diagonal length of your media vs. focal length. For 35 mm film, this length is around 43 mm - hence a lens in the 40-55 mm f.l. range appears "normal". Now, a 1/4" CCD has a diagonal of only 6.4 mm (and 1/3" CCD is 8.5 mm). If you couple a 45 mm f.l. lens to a 1/4" CCD, one is already in telephoto range. To get a "normal" FOV on a 1/4" CCD you need an f.l. of 6.4 mm.

To find magnification (approximately), just divide f.l. by the f.l. for a "normal" FOV. For Canon GL1/2 (1/4" CCD), min f.l. is 4.2 mm for an FOV of 4.2/6.4 = 0.7x normal; max f.l. is 84 mm for an FOV of 88/6.4 = 14x. (Actual values are 0.72x and 12.27x).

Ron Johnson
Portland, OR
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Old February 14th, 2003, 07:33 PM   #3
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Table of Equivalent Focal lengths
35mm Neg AOV DIAg. Video 1/3" CCD
20 mm 90 3 mm
25 mm 77.3 4 mm
30 mm 67.4 4.5 mm
35 mm 59.5 5 mm
40 mm 53.1 6 mm
45 mm 47.9 7 mm
50 mm 43.6 7.5 mm
55 mm 40 8 mm
60 mm 36.9 9 mm
65 mm 34.2 10 mm
70 mm 31.9 10.5 mm
75 mm 29.9 11 mm
80 mm 28.1 12 mm
85 mm 26.5 13 mm
90 mm 25.1 13 mm
95 mm 23.8 14 mm
100 mm 22.6 15 mm
105 mm 21.6 16 mm
110 mm 20.6 16.5 mm
115 mm 19.7 17 mm
120 mm 18.9 18 mm
125 mm 18.2 19 mm
130 mm 17.5 19.5 mm
135 mm 16.9 20 mm
140 mm 16.3 21 mm
145 mm 15.7 22 mm
150 mm 15.2 22.5 mm
155 mm 14.7 23 mm
160 mm 14.3 24 mm
165 mm 13.8 25 mm
170 mm 13.4 25.5 mm
175 mm 13 26 mm
180 mm 12.7 27 mm
185 mm 12.3 28 mm
190 mm 12 28.5 mm
195 mm 11.7 29 mm
200 mm 11.4 30 mm


The software limations wont't allow for charts so I hope this makes sense. If you have questions, please post back.
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