Archived posting to the Leica Users Group, 2004/09/04

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Subject: [Leica] Leica Digilux 2 @ 1600 :-)
From: DouglasMSharp at (Douglas M. Sharp)
Date: Sat Sep 4 06:40:02 2004
References: <> <> <000401c4917a$9c3fa1b0$87d86c18@ted> <> <p05100301bd5f080a6807@[]>

Thanks Henning !
Is there any equivalent to reciprocity or Schwarzschild effect when
shooting digitally ? I gather that
noise can be a problem at high ASA/ISO and have read that lenses can be
"too good" for a sensor, but nothing yet along
these lines. It appears to me that the learning curve is shallow but
does require quite a bit of new thinking.


Henning Wulff schrieb:

> At 9:08 AM +0200 9/3/04, Douglas M. Sharp wrote:
>> I was shooting in a very dim chapel of remembrance in Berlin and was
>> getting shutter speeds
>> too slow for hand holding and didn't have a tripod with me. Shooting in
>> RAW mode at 400 ASA I deliberately underexposed in manual metering mode
>> and then corrected the image
>> in Canons File viewer Facility (which allows the pre-processing of RAW
>> images) to get
>> back to the shutter speed I would have had to use according to the
>> automatic mode.
>> The shot turned out IMO better than I expected (within limits)
>> see
>> I also read in a German photo publication that the ASA/ISO setting of
>> 100 is not necessarily better than
>> at 200, though I didn't quite understand why, they even suggest avoiding
>> the lowest value.
>> In addition, shooting with higher ASA values, at least with the Canon,
>> seems to make the files larger - any ideas/explanations on this count?
>> greetings from sunny Northern Germany.
>> Douglas
> If you shoot at higher ISO values, you produce more noise, or pixels 
> with values that have little to do with the scene values. In a 
> simplified sense, JPEG works by describing a value for an area with 
> similar values, so if there is a 'noise pixel', it has to be described 
> separately, taking up more space in the file. In some cameras, 
> shooting at the highest ISO can produce files that are 50% larger than 
> the slow speed, smooth toned low ISO files of the same scene.
> The 'underexpose' technique works just like pushing film. You're using 
> just the most sensitive part of the film or sensor, and then in 
> Photoshop you're 'overdeveloping'. With film this means that you get 
> higher contrast, more grain and generally poorer tonal quality. With 
> digital it means that you are getting more noise and getting poorer 
> tones through something called 'banding', as you are expanding your 
> finite number of digital levels that are useful to the total number of 
> levels your printer can handle. With the standard JPEG files, you get 
> 256 levels for each colour, and if you then only use the bottom 50 
> (because the top 206 don't contain any useful info) and expand them 
> into the 256 level space, you might find that these are too large 
> 'steps' in some areas, resulting in a 'banded' look.
> With a DSLR, shooting in RAW and producing a 16bit file with millions 
> of values, this banding doesn't happen very easily because you might 
> wind up using 'only' the bottom 10,000 values, as 16bit has over 
> 65,000 values for each colour. When you then get the file ready for 
> printing, these 10,000 values easily get reduced to 256 that the 
> printer can deal with.

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