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On the Alexa 65 (and large format digital cinematography in general)


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#1 Lucas Ferreira Gesser

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Posted 09 September 2015 - 10:15 PM

What exactly would be the advantages of shooting on a camera like the Alexa 65?

What does shooting on a large format actually does to the images produced?
 

If i shoot a image at 6K on a 65mm sensor will I get more "quality" than shooting the same image at 6K on a Super 35 sized sensor?


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#2 David Mullen ASC

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Posted 09 September 2015 - 10:32 PM

You don't get more resolution if both sensors are 6K, however the lens on the larger format doesn't have to be as high a MTF because you can resolve fewer lines per millimeter if that area of detail is captured with more millimeters compared to the smaller format.

 

You'd probably notice less depth of field in general because if the format is twice as large, you effectively lose 2-stops of depth of field if you match field of view, distance, and f-stop between the two formats.  So the 65mm movie shot on a 50mm at f/2.8 would look like the 35mm movie shot on a 25mm at f/1.4, more or less.  Which means in theory you could match the depth of field, particularly since many large format lenses don't go to f/1.4.

 

You'd have less noise / more sensitivity probably with the larger sensor since the photosites could be larger, if both formats were 6K.

 

You may notice the optical artifacts of the larger format lenses, they may feel different - some of those lenses are older and have a bit more barrel distortion and fall-off in the corners.


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#3 Leon Liang

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Posted 10 September 2015 - 01:34 AM

David, could you please explain what MTF is? Google isn't really helping....
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#4 Tyler Purcell

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Posted 10 September 2015 - 01:38 AM

David hit all the key points. I do think the whole point was to use those older lenses and get that more shallow depth of field look. That's one of the biggest problems with smaller imagers, the smaller they are, the harder it is to get shallow depth of field. You've gotta resort to opening the lens all the way up and using longer focal lengths.

Remember, Arri has no intentions on selling the 65, it's for rental only. It's really a specialized product so they can ditch the 765 film cameras and have an alternative, at least that's what I've been told.

It's unfortunate our distribution methods are stuck with a max resolution of 4k. I'm not even aware that finishing software like DaVinci can accept anything over 4k. So… yea, 6k shooting and finishing? Still a long way away.
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#5 Tyler Purcell

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Posted 10 September 2015 - 01:39 AM

David, could you please explain what MTF is? Google isn't really helping....


http://kenrockwell.com/tech/mtf.htm
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#6 Leon Liang

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Posted 10 September 2015 - 01:48 AM

Thanks Tyler. One day I'll learn what that means...one day...
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