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D21´s real Log C Sensibility


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#1 Lucas Mormandi

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Posted 06 October 2008 - 06:51 AM

A had only two oportunitys to test it, and not so deep. And I still have this question. Wich is the ASA to shoot with LOG C curve? Wich is the real ASA of the D 21?

Thanks for your help!

Lucas Mormandi
Cameraman - DIT
Argentina
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#2 Rob van Gelder

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Posted 07 October 2008 - 03:07 AM

As I have seen from the menu and heard from the explanation from the Arri technician, it is 200 ASA using the Log curve, when using the HD mode you will have several "electronic" sensitivities, from 100 to 800 ISO/ASA. This will also change the contrast and the noise (similar as with film). It is like the gain setting on normal video cameras: -3 dB, 0, +3 dB, + 6 dB.


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#3 Lucas Mormandi

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Posted 07 October 2008 - 06:38 AM

As I have seen from the menu and heard from the explanation from the Arri technician, it is 200 ASA using the Log curve, when using the HD mode you will have several "electronic" sensitivities, from 100 to 800 ISO/ASA. This will also change the contrast and the noise (similar as with film). It is like the gain setting on normal video cameras: -3 dB, 0, +3 dB, + 6 dB.


Rob van Gelder
Bangkok


So. You say that if I work whith Log C curve, I tell the DOP to use the photometer in ASA 200? Remember this is an ARRI D 21.
Fortunetly, I work tomorrow in linear mode.

Thank´s Rob!!!
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#4 Keith Mottram

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Posted 07 October 2008 - 01:52 PM

So. You say that if I work whith Log C curve, I tell the DOP to use the photometer in ASA 200? Remember this is an ARRI D 21.
Fortunetly, I work tomorrow in linear mode.

Thank´s Rob!!!


I do not know why you would want to work linear, get your tests into a decent grading suite and you'll quickly see the benefits to shooting log...
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#5 Rob van Gelder

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Posted 07 October 2008 - 09:19 PM

Just need to be careful with the highlights. HD and video is like positive (slide) film, so when you reach the top , the end in the highlights you are about to loose detail.
Over-exposure is difficult to correct and most likely degrades the image, while underexposure can be lifted to a certain degree.

In one test we did with the Sony F35 we found that for instance skin-tones ( similar to 18% grayscale, approx.) overexposed for 4 stops are recoverable, but that cannot be said for the background which usually has lighter parts to begin with.

Rob van Gelder,Bangkok
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