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35mm equivalent for Micro 4/3


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#1 Dominic Disla

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Posted 11 September 2015 - 03:34 PM

I just got a Panasonic Gh3 and I want to buy a wide angle lens that has the same field of view of a 18mm on a 35mm film camera using the 1.37 or 1.85 ratio.

1.37= 22mm x 16mm
1.85= 21.95mm x 18.6mm
Gh3 sensor= 17.3mm x 13mm

22/17.3=1.27
18/1.27=14.17mm?

Are these figures right? What focal length should I be looking for?
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#2 David Mullen ASC

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Posted 11 September 2015 - 04:57 PM

Seems right, a 14mm or 15mm -- there are some 14mm MFT lenses on the market.
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#3 Dominic Disla

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Posted 11 September 2015 - 05:00 PM

Does height need to be taken into account or only width?
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#4 David Mullen ASC

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Posted 11 September 2015 - 05:03 PM

If the final aspect ratio is the same then it doesn't matter whether you calculate to match width or height, the crop factor will be the same so you'd get the same results.
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#5 David Mullen ASC

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Posted 11 September 2015 - 05:07 PM

If the GH4 sensor really is 17.3 x 13mm, that's a 1.33 : 1 aspect ratio so probably it crops vertically to get 1.77 (16x9) but you may want to look into the dimensions that actually get recorded in video mode to be sure.
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#6 Dominic Disla

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Posted 11 September 2015 - 05:08 PM

Ok. Thanks David.
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#7 David Mullen ASC

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Posted 11 September 2015 - 05:13 PM

At least in stills mode the GH3 camera uses the full width for 4:3 stills and 16:9 stills so I'm guessing you can use the 17.3mm measurement to calculate the crop factor.
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#8 Dominic Disla

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Posted 12 September 2015 - 01:20 AM

Would I get a better resolution by shooting in 4:3 and then scaling to 16:9 in post or should I just shoot in native 16:9?
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#9 David Mullen ASC

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Posted 12 September 2015 - 09:26 AM

4:3 is a different aspect ratio than 16:9, you could only scale it to a smaller or larger 4:3 size.  I mean, you could scale it to 16:9 by only rescaling one dimension, horizontal or vertical, but then you'd have a stretched image.

 

The only case in which it would make sense would be if you used a 1.3X anamorphic lens to squeeze a 16x9 image to fill a 4:3 sensor.  

 

Also, if you used a 2X anamorphic lens, then you could use more of the 4:3 sensor to get a 2.40 : 1 image.

 

But I think this is all moot since I don't believe the GH3 does 4:3 for video, unless it does it for standard def.  HD is always a 16:9 format.  

 

The 4K GH4 does now have a function to record more of the height of the sensor (3828 x 2496, which is 4:3), mainly for people who want to shoot anamorphic photography:

http://nofilmschool....-anamorphic-4-3

http://www.eduardoan...-panasonic-gh4/


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