XL H1 20X Zoom Number vs 35mm Equivalent Focal Length at DVinfo.net

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Canon XL H Series HDV Camcorders
Canon XL H1S (with SDI), Canon XL H1A (without SDI). Also XL H1.


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Old December 13th, 2006, 01:22 PM   #1
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XL H1 20X Zoom Number vs 35mm Equivalent Focal Length

The relationship between Zoom Number and focal length in Canon cameras is curvilinear. Method:

- Measured the width of the field of view (FOV) every ten Z Numbers.
- Plotted the Z=0 and Z=99 FOV against the published focal lengths in an Excel chart, and let Excel calculate the linear regression for the expected FOV intermediate focal lengths.
- Used the regression to convert intermediate FOV numbers to focal lengths.
- Also converted actual camera focal lengths to 35mm equivalents (7.00 conversion factor).
- Replotted focal lengths against Z Number.

Here is the XL H1 chart.
Attached Thumbnails
XL H1 20X Zoom Number vs 35mm Equivalent Focal Length-xl-h1-20x-zoom-numbers.jpg  
Attached Files
File Type: xls Canon XL H1 20X Zoom Numbers.xls (22.5 KB, 457 views)
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Old May 27th, 2007, 06:23 AM   #2
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Using this chart, is it possible to get the Z numbers for the most commonly used prime lenses that they use in film production? Like 50mm, 85mm, 100mm, 150mm, 200mm? I am not a great performer in Excel, but if I remember well Excel can calculate those things quite easily if you know the formula.
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Old May 27th, 2007, 11:25 AM   #3
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Can you explain this better ?

Thanks,

CQ.
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Old May 27th, 2007, 12:59 PM   #4
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You can calculate the equivalent focal lengths for different formats here:

http://www.panavision.co.nz/main/kba...enseqvform.asp
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Old June 3rd, 2007, 12:24 PM   #5
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What I really would like to see is the equivalent focus value in 35mm terms for each zoom number. I have the sheet but I can't remember how to have Excel output and interpret the numbers for each given value.

If someone can help me with this it would be greatly appreciated. It has to do with interpolation I believe. But I am really not good in maths.
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Old June 4th, 2007, 10:59 AM   #6
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38.2/2.72 = 14.044 != 20. ???
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Old June 5th, 2007, 04:15 PM   #7
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The XH A1 has a 20X zoom lens, and in the specifications, it states:
"32.5mm-650mm; 35mm photo equivalent"

I don't for sure that it's the same for the XL H1 20X, but it should be close.
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Old June 5th, 2007, 07:54 PM   #8
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I took the direct approach: ask the camera. Interestingly enough the camera reports the same focal length (9.9mm) for indicator settings of 30 and 35 (I went in 5 unit steps) even though the focal length did clearly change. It also reported 18.4 mm for indications of 55 and 60 and 44.8mm for 80 and 85 though the image size does change over those ranges. There is some sort of quantization issue at work here. That aside the log of the focal length is modeled pretty well by

log(fl) = 0.75569 + 0.00425*I + 0.00008231*I*I

where I is the indicator value (0-99)
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