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Re: [OM] ETTR, was: MooseRant on Low Light Shoot-Out

Subject: Re: [OM] ETTR, was: MooseRant on Low Light Shoot-Out
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Wed, 29 Jan 2014 14:44:39 -0500
I've been busy so thanks for providing my answer before I got here. 
Once I've used the camera for a while I can pretty well predict where 
the histogram might lead me astray on ETTR but I'm far from always 
perfect.  That's where at least some of the value of shooting raw comes 
from.  Yes, I do (sometimes more than I like) have to recover 
highlights.  I sometimes (horror) even have some blown highlights I 
can't recover.  Ah, well, I'm not perfect (but I'm trying).  I'll even 
(quietly) admit so sometimes just using the meter and not shooting ETTR. 
  I did it today whilst visiting some "war birds" in Sarasota today.  I 
was so cramped inside a B-24 and B-17 and being crushed by large numbers 
of people that it would have been inexcusable to take much time for 
photographs.  And since brightness was changing radically and calling 
for ISOs up and down the scale I even (for only the second time) threw 
the E-M5 on full auto and fired away.

But I do have to take AG to task for what I think is a totally erroneous 
statement below:
---------------------------------------------------------------
The in-camera histogram is generated off of an in-camera
JPEG and also shows only the primary (RGB) colors, not the derived
colors (CMY). You can have the yellows clip and never know it.
---------------------------------------------------------------
I think AG should certainly realize that the camera never creates 
"derived" colors.  The camera and its displays and our monitors only 
have red, green and blue pixels.  "derived" colors (like yellow) are 
only created in our brain.  When we see yellow the only thing we are 
seeing is green and blue pixels (with maybe a hint of red mixed in). 
Pixels are not additive in brightness.  It's impossible for the brain 
derived "yellow" to be blown if its component R, G and B pixels are not.

Chuck Norcutt


On 1/29/2014 12:52 AM, Moose wrote:
> On 1/28/2014 6:53 AM, Ken Norton wrote:
>> ETTR is ONLY valid if you shoot RAW, unless you are photographing a
>> subject where placement of the highlight at Zone IX is critical.
>
> On 1/28/2014 7:08 AM, Chuck Norcutt wrote:
>> ...
>>
>> Umm, no.  If I have to "recover" highlights I haven't done the ETTR
>> thing correctly.
>
> On 1/28/2014 7:24 AM, Ken Norton wrote:
>>> No, I'm not.  I make it a practice to assure that none of my colors are
>>> clipping.
>> Impossible. The in-camera histogram is generated off of an in-camera
>> JPEG and also shows only the primary (RGB) colors, not the derived
>> colors (CMY). You can have the yellows clip and never know it. The
>> only thing you can do it ETTR and then back off one stop to be safe.
>
> Is it possible you guys are arguing about definition, not substance? It's 
> seems to me you may be arguing past each other
> about different ideas about what ETTR is, rather than about real differences?
>
> Reading this thread, it sounds to me like AG is using ETTR as an absolute, 
> perhaps defined by some of those (possibly
> imaginary) unnamed web folks with whom hs is always arguing. He is arguing 
> with a dogma, dogETTR. He assumes it must
> involve highlight recovery, else why would he harp so much on the perils of 
> highlight recovery, and why would ETTR be
> invalid for JPEGs?
>
> OTOH, Chuck seems to be attempting to practically shoot as high up the 
> histogram as possible without clipping
> highlights. No dogma, just pragmatic experience, pettr.
>
> I'm closer to Chuck's idea. I'd like to have a Raw histogram that just barely 
> falls short of touching the top on any
> channel. In practice, this is very difficult to achieve outside a controlled 
> environment. So I try to pay reasonable
> attention to doing that. Highlight recovery is then a fallback when I miss.
>
> This is, or should be, about practical technique to optimize digital exposure 
> to minimize highlight clipping while
> retaining the best shadow possible, not absolute definitions.
>
> It's also far less of a problem with contemporary cameras with wider DR. One 
> need worry less about nailing just that
> one, highest pixel to the very top of the flagpole.
>
>    --- Side note ---
>
> Some JPEG engines do quite a good job of compressing highlights, rather than 
> clipping them. It often looks like clipping
> when viewed as a web image. But if one selects highlights and looks at the 
> histogram, little or nothing is clipped.
> Knowing this is one of the side effects of messing with a lot of other 
> peoples' images, as I shoot Raw.
>
> When it's the case, it's generally possible to 'recover', make visible, 
> highlight detail that was there, but not
> visible. I've posted quite a number of examples over the years.
>
> Definitional Moose
>
-- 
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