[HDRI] Re: RAW capture

[L.Yimm]

Greg,

Thanks for the information on RAW capture....definitely worth more 
than 2 cents!  I've never been good at the math part of digital 
photography...my knowledge is purely experiential.  Many years of 
Zone system shooting, printing, and plotting film curves.


>
>The potential benefit you cite for RAW images, the bit depth, turns 
>out to be an illusion.  Although many RAW files contain 12 
>bits/channel, it's in a linear space rather than the gamma response 
>space of JPEG or 24-bit TIFF, and doesn't actually encompass a 
>greater dynamic range.  (See my page at 
><http://www.anyhere.com/gward/hdrenc/>  and scroll down to "What Is 
>a Gamma Encoding?" to more.)  Since the camera and the A/D converter 
>inside the camera are both linear devices, this is in fact why 12 
>bits is necessary for an 8-bit gamma-encoded output.  Otherwise, 
>you'd end up with horribly visible quantization errors (banding) at 
>the bottom end.

I also expect this is why CS2 is inferior in assembling HDRs to 
Photosphere.   I recently ran a test with the same set of 5 
panos...and the CS2 image was noticeably contrastier, with banding in 
the extreme ends of the exposure.   Also the .hdr file size was 4 MB 
smaller than the one generated in your app.

It's taken me many months of trial and error...but I've finally got 
an all OSX work flow that's reliable and repeatable.

I capture 5 or more exposures at each of 6 positions around, using a 
Nikon 5700 with FC-E9 full spherical fisheye.  I crop and de-warp 
images in Photoshop (using a custom plug-in), then stitch in 
Stitcher 4 (now 5), then put back the missing EXIF data and do the 
finally assembly in Photosphere.

Anyone else have experience using a non-SLR digital camera for HDR capture?

Lisa

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