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[OM] Re: HDR attempt

Subject: [OM] Re: HDR attempt
From: Dan Mitchell <danmitchell@xxxxxxxx>
Date: Wed, 30 Jan 2008 21:09:43 -0700
Moose wrote:
> C'mon Dan, you know we are talking here about range to contain the 
> combined DR of several 12-14 bit, bracketed shots. I mean it can hold 
> all that without losing any of the tonal detail of the originals.

  That's certainly fair -- it's sacrificing a strictly accurate 
representation of the original image by reducing the actual dynamic 
range of the file -- which gives you something which has an 
approximation to the same visual effect, or at least, which pulls all 
the different levels of brightness into the range that can be 
represented on a monitor.

> And yet, I object to the characterization of HDR, "an "HDR" image 
> actually has a lower dynamic range than the original scene did"
> based on the limited output DR, without reference to the much greater 
> range in the file.

  Ah, now I think we're talking about different things.

  The HDR images on Flickr aren't HDR in the sense you're using here -- 
they're just standard 8-bit jpegs displayed on a normal monitor, with 
the same dynamic range as any other jpeg.

  Now, the intermediate files created halfway through the process 
certainly _are_ HDR images -- but that's not what we download, and even 
if we did, there's no useful way to display those with current display 
technology, so they have to be squashed down to a dynamic range that can 
be displayed.

> You say "just". I think it rather wonderful to have the full range to 
> work with in making my own compression and clipping decisions. I can do 
> more than I could with a more limited original file. Even the greater 
> range of a 5D RAW file has much shadow/highlight detail to work with 
> than slide film.

  That's certainly fair -- even 16-bit versions of Photoshop give you a 
lot more room to play in (or, I guess, less loss while you do your 
playing around).

  -- dan

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