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s16mm to 35mm lens Conversion chart


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#1 Mark.Smith

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Posted 14 January 2010 - 06:17 AM

Hello,

Is anyone aware of a (printable) chart that shows what a s16mm lens would equate to in 35mm?

Or what the factor to multiply it by is?

Thanks

Edited by Mark.Smith, 14 January 2010 - 06:19 AM.

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#2 David Rakoczy

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Posted 14 January 2010 - 07:12 AM

An easy way is to just cut it in half. A 100mm in 35 is a 50mm in 16. A 50mm in 35 is a 25mm in 16. A 35mm in 35 is a 16mm in 16. An 18mm in 35 is a 9.5mm in 16... and so on.
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#3 Mark.Smith

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Posted 14 January 2010 - 10:48 AM

An easy way is to just cut it in half. A 100mm in 35 is a 50mm in 16. A 50mm in 35 is a 25mm in 16. A 35mm in 35 is a 16mm in 16. An 18mm in 35 is a 9.5mm in 16... and so on.



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#4 Mark.Smith

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Posted 15 January 2010 - 10:36 AM

Just to add to my question (I should have maybe posted this in student section), I downloaded pCAM, an iPhone/iPod touch tool for DP's first AC's etc does amongst many other things Focal length Conversions. So you get the exact vertical/horizontal match of focal length.

My question is when I try to convert: 8mm (on s16mm 1.78) to s35mm (3+4 perf - 1.78) it says it would be a 15.7mm, closest even focal length being a 16mm lens.

However same focal lengths but this time using the aspect ratio of 1.85 it says s16mm to s35mm would be 16.3mm lens, practically that would still mean a 16mm, but I would for technical purposes like understand what is going on here?

Can anyone explain this relationship?

Perhaps explaining vertical/horizontal match would clear things up more efficiently.

Attached is a picture of the conversion calculator.

Attached Images

  • 1.85.jpg
  • 1.78.jpg

Edited by Mark.Smith, 15 January 2010 - 10:40 AM.

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#5 David Mullen ASC

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Posted 15 January 2010 - 11:18 AM

The size of the camera aperture / gate affects the field of view of the lens in all directions.

But if you are comparing two different camera formats, you often have to deal with the fact that they aren't the same aspect ratio. If they are -- let's say 1.78 or 1.85 -- then you could just compare the horizontal view or the vertical or the diagonal, it wouldn't matter because the two formats are proportional. But if one format was 1.33, let's say, and the other was 1.85, then they aren't the same shape, the more widescreen shape has less vertical view compared to its horizontal view.

For simplicity's sake, I usually just compare horizontal view because 80% or 90% of the time, you choose a focal length for its horizontal view.

So how much of a lens' projected image a camera records is dependent of the size and shape of the camera aperture, further cropped by what framelines you use (usually the projection or extraction area planned) inside the camera aperture (the Full Aperture). You can compare the horizontal view of the Full Aperture of two cameras, or you can compare the size of the area you are actually composing for -- let's say you are composing both Super-16 and Super-35 for cropping to 1.85 for theatrical projection.

A guidebook will tell you that the horizontal width of 35mm Full Aperture is 24.84mm. 1.85 extraction area from Super-35 is 24mm wide.

A Super-16 Full Aperture is 12.52mm wide. 1.85 extraction are from Super-16 is 11.76mm wide.

So if you are composing for 1.85, and you want to match field of view horizontally, just divide 24 by 11.76. You get 2.04. That's the magnification factor between the two formats on the horizontal. So if you used a 50 lens on a Super-35 camera framed for 1.85, you'd use a 24.5mm lens on a Super-16 camera to match the same horizontal view.

So you can see that the simplest thing is to just use a 2X figure for the difference between Super-16 and Super-35. Basically the Super-16 frame is half as wide, so you need to use a lens that is half the focal length to get the same horizontal view in both formats.
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