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

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Subject: [Leica] Steve Unsworth PAW - week 33
From: hoppyman at bigpond.net.au (G Hopkinson)
Date: Sun Sep 9 17:56:08 2007
References: <200709092153.ACP36822@rg4.comporium.net> <C30A2BE8.F9FB%lug@steveunsworth.co.uk>

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.
Even in my own very limited play with an M8, I was amazed how much 
information could be extracted from ostensibly blown (not quite)
highlights. I think that the camera histogram is not based on the actual DNG?

Someone give me an M8 and I promise to test carefully and report back ;-)

Cheers
Hoppy

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

Hi Tina, normally I'd agree with you, but the M8 used a non-linear 14 (or is
it 12?) to 8 bit compression algorithm when writing the DNG files that in my
understanding puts more of the 'bits' into the shadows than the highlights.
So the old adage about exposing to the right doesn't work in the same way
with the M8.

Steve


On 9/9/07 22:53, "Tina Manley" <images@comporium.net> wrote:

> At 05:35 PM 9/9/2007, you wrote:
>> The M8 has a pretty big dynamic range, especially in the shadows. Recently
>> I've started using the camera with compensation of -1/3 of a stop to 
>> control
>> any possible highlight blowing.
>> 
>> Steve
> 
> 
> Steve -  I used to do that, too, but after viewing a tutorial by Jeff
> Schewe about digital photography and color management, I'm having
> second thoughts.  He advises to be sure the histogram is balanced to
> the right.  He says that highlights contain much more recoverable
> information than shadows and that, even if the highlights look blown
> in the preview, they can be recovered in RAW files.  Overexposing
> slightly gives you much less noise in the shadows.  He says always
> bias the exposure as far as you can to the right without completely
> blowing out the highlights. The only time you shouldn't follow this
> advice is when using high ISOs because then you would just choose a
> lower ISO to get the same effect.  I haven't experimented with this
> enough to know how it works, but I'm going to try it.



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Replies: Reply from lug at steveunsworth.co.uk (Steve Unsworth) ([Leica] Steve Unsworth PAW - week 33)
In reply to: Message from images at comporium.net (Tina Manley) ([Leica] Steve Unsworth PAW - week 33)
Message from lug at steveunsworth.co.uk (Steve Unsworth) ([Leica] Steve Unsworth PAW - week 33)