Archived posting to the Leica Users Group, 2007/09/10

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Subject: [Leica] Steve Unsworth PAW - week 33
From: hoppyman at bigpond.net.au (G Hopkinson)
Date: Mon Sep 10 14:21:47 2007
References: <004a01c7f345$5fa1f110$6401a8c0@asus930> <C30B4F63.FA7C%lug@steveunsworth.co.uk>

Hi Steve. My information was from an LFI article as I've only shot about 30 
frames with an M8. LFI does say that the camera does
better at discriminating darker tones. Purportedly this agrees with human 
vision characteristics.
The nature of the A/D converter is that half of the tonal values are used to 
delineate the first, brightest bit, then half the
remainder for the next, etc etc, down to very few obviously for the last 
(darkest) bit. So I was trying to say that you want to use
the complete possible tonal range of the brightest bit or you are starting 
with a lot less tonal values than the possible maximum.
Naturally there is a great deal of manipulation of the recorded values in 
further processing and purpose, so it may be less
important. The files that I have are extremely robust and tonally smooth.

Whatever you're doing is making good images anyway. I can see that -.3EV 
will make clipping less likely. The M8 that I borrowed was
setup that way too. Practical performance is what counts, I just am very 
interested in the mechanics as well. It is inevitable that
there is a digital M in my future.

Cheers
Hoppy

-----Original Message-----
Subject: Re: [Leica] Steve Unsworth PAW - week 33


Hi Hoppy

It's my understanding that the compression algorithm isn't linear, and more
of the values are allocated to the shadows than the highlights, so the usual
'expose to the right' advice isn't as relevant.

Steve

On 10/9/07 01:56, "G Hopkinson" <hoppyman@bigpond.net.au> wrote:

> According to Leica, yes 14 bit, with 2 of 16 having been discarded due to
> noise contamination.
> Yes also on the non-linear, and the magic of storing as 8 bit but being 
> able
> to recover the high bit information even though the
> file is smaller.
> Half of the tonal values are used to resolve the first (brightest) stop.
> So you don't want to clip but you do want all of that right side 
> information.
> I think Tina has the right of it in her explanation.



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In reply to: Message from hoppyman at bigpond.net.au (G Hopkinson) ([Leica] Steve Unsworth PAW - week 33)
Message from lug at steveunsworth.co.uk (Steve Unsworth) ([Leica] Steve Unsworth PAW - week 33)