Archived posting to the Leica Users Group, 2008/05/18

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Subject: [Leica] RE: Raw exposure for dynamic range, HDR and now WB
From: hoppyman at bigpond.net.au (Geoff Hopkinson)
Date: Sun May 18 17:34:01 2008
References: <001001c8b92d$2df7a390$6b01a8c0@dadquad> <20080518233417.QKCR14275.eastrmmtao107.cox.net@eastrmimpo02.cox.net>

Ken, I find it hard to tell with much precision what is going on, via the M8
camera histogram display anyway. Maybe other cameras are easier to
interpret. I also don't know how the jpg settings of the camera affect the
camera preview histogram.
With Raw capture, my reading suggests that the point where WB is set (during
the conversion) doesn't matter if you are only making minor exposure
correction (say .25) Beyond that, set it first, automated or sampling then
do your exposure adjustment. I'm now trying a Mini ColorChecker chart
inclusion in one frame. As used by Bruce Fraser developing the camera
profiles. The grey cards that I tried weren't ideal. The WhiBal is supposed
to be better than standard grey cards, which aren't really colour neutral,
just the right average tone.  
You can see each channel separately anyway and ACR is good at reconstructing
any clipping if not in all three channels (and sets those clipped to white,
not grey). I'll have to play with Capture One 4 that I have now too.
As for those Benedictine nuns and on-camera flash, don't you dare!

Cheers
Geoff
http://www.pbase.com/hoppyman/e
http://gallery.leica-users.org/v/gh/

-----Original Message-----
Subject: RE: [Leica] IMG: Yosemite too... and Raw exposure for dynamic range

Hi Geoff,

Here is the link to a thread on making a custom white balance:

http://luminous-landscape.com/forum/index.php?showtopic=22250&st=0

The idea is that the JPG histogram, as displayed, is now closer to the
histogram of the raw file, after conversion.  I tried it today, and watching
the green channel on the camera histogram, it was indeed further to the
right (than auto white balance), and the resulting ACR histogram was not as
compressed.  As a bonus, your camera display is now green, like night vision
gear, to impress your friends.  As far as the real WB, I always take a gray
card shot (with the WhiBal) for that.  From the thread, I noted that some
raw converters (specifically ACR) are not supposed to be able to handle this
well, but the images looked fine to me in ACR.  I will try it in Capture One
4.1, but I'm out of play time for today.

Evidently this is a technique well known to everyone but me(no surprises
there), but I will try it some more.  I don't have anything critical coming
up until late June, when I am to do a Blurb book for a big gathering of
Benedictine nuns here, something they do every 40 years or so.  If I screw
that up, my next email address will be in Belize!  BTW I have to learn
on-camera flash by then too!

Ken




Replies: Reply from kcarney1 at cox.net (Ken Carney) ([Leica] RE: Raw exposure for dynamic range, HDR and now WB)
In reply to: Message from hoppyman at bigpond.net.au (Geoff Hopkinson) ([Leica] IMG: Yosemite too... and Raw exposure for dynamic range)
Message from kcarney1 at cox.net (Ken Carney) ([Leica] IMG: Yosemite too... and Raw exposure for dynamic range)