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16mm crop factor? errrr......


Lewis Hart

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So either im being a total idiot, I was under the impression that 16mm film optics was around a 2x crop factor in 35 equivalent when calculating FOV? 

But ive seen some people say that its a 3.40x crop? 

Was looking at lenses and calculating them always as 2x crop, eg 15-50 would be a FOV around 30-100mm for example?

But then someone said on a post I saw that this Angenuix 17-68mm lens I was looking at was around a 48mm on 35? Which is around a 2.8x? 

Very confused here as ive thought It was 2x for a long time..

Edited by Lewis Hart
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Full frame  to S35mm is around .8x crop. 

S35mm to 15mm is around 2x crop. 

So if you're thinking full frame (still camera) to 16mm motion picture camera and you're thinking about the crop factor, it's 2.8X. 

If you're thinking S35mm (4 perf motion picture camera) to 16mm motion picture camera and you're thinking about crop factor it's 2x. 

 

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What format are you used to shooting?

Crop factors tend to use full frame still photography lenses as the benchmark, which is pretty useless for most cinematographers unless they came from photography or DSLR video. 35mm for cine is a smaller frame than 35mm stills, so if you're used to 35mm cine (or APSC stills) then yes, S16mm is roughly 2x crop factor. If you're used to a stills full frame, then it's closer to 3x. If you're shooting standard 16mm on a Bolex, then it's even more, closer to 3.4x compared to full frame.

The maths is pretty simple, you just use the diagonal of the format. So for full frame which is 36mm x 24mm, the diagonal is 43.3mm. A Super 16 frame has a diagonal of 14.6mm, so the crop factor is 43.3/14.6 = 2.97x. For standard 16mm, with a diagonal of 12.7mm, the crop factor is 43.3/12.7 = 3.41x.

It can get complicated by the different frame sizes of what people refer to as S35. The aperture of a S35 camera has a diagonal of around 31mm, but an Alexa 16:9 sensor has a diagonal of anywhere from 27.3mm for 2.8K to 33.5mm for Open Gate mode. An APSC camera is usually around 27mm diagonal, but can also vary a little by brand. So crop factors for S35 (in relation to full frame 35mm) can be listed as anything from 1.6x (which would be for a 27mm diagonal) to 1.4x for the full S35 film frame with a 31mm diagonal. 

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Thank you both for your detailed replies much clearer now and yes I was used to the full frame as I came from a dslr background until I saw the magic of film and now there’s no going back to digital haha. ?

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I prefer comparing just the horizontal view (sometimes the vertical) when calculating conversions because the diagonal will vary by the aspect ratio of the sensor, unless you are careful only to compare the diagonal of one aspect ratio for all formats rather than the whole sensor.

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