From: Paul Furman on
DRS wrote:
> "Floyd L. Davidson" <floyd(a)apaflo.com> wrote in message
> news:87eipfql83.fld(a)apaflo.com
>
> [...]
>
>> The point is still the same, contrast settings do *not*
>> affect the exposure.
>
> Since nobody has said it does why don't you slow down and pay attention to
> what is being said?
>
> What is being said is that where manufacturers draw the histogram settings
> from the compressed JPEG instead of the Raw image, lowering the contrast
> setting will render the histogram more accurately (closer to the Raw). The
> claim is that this more accurate histogram *subsequently* enables the
> photographer to make more accurate adjustments to the exposure.
>
> Check out the images under the heading "Contrast adjustment" on this page:
> http://www.dpreview.com/reviews/CanonEOS30D/page13.asp. The luminosity
> histogram expands left and right as you increase the contrast. If you were
> to judge by the +4 histogram you would think the image was clipping both
> highlights and shadows but this is not the case.
>
> If the histogram at -4 is in fact more accurate than the histogram at 0 (the
> Canon default) then the photographer in fact has greater room for exposure
> compensation to the right than the histogram at contrast setting 0
> indicates. For those wishing to compensate to the right this is useful
> information. What the photographer *subsequently* chooses to do to the
> exposure is another discussion entirely.

What about saturation? Reducing saturation seems to give more detail to
the edges also.

--
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam
From: Clues on
On Wed, 07 Oct 2009 17:19:12 -0500, John Sheehy <JPS(a)no.komm> wrote:

>Exposure to the right is usually given as advice for RAW shooting. The
>RAW data usually clips well above the level where a JPEG would clip it,

Very true, for all those cameras that intentionally do a poor job at the
RAW to JPG conversion. This is why RAW became so popular. DSLRs are
inherently poor at this process. In fact it's the very reason that having
access to the RAW data became so popular. Far too many DSLR owners wanted
to repair in their resulting images what the DSLR's firmware programmers
failed to do correctly in the first place. Companies then realized that
they could turn this into an asset. Not only sell a camera that didn't work
quite right, bundled with a kit-lens that wouldn't provide images any
better than a Barbie-Cam, conning them into buying a $5,000-$10,000 lens to
make their $500 DSLR functional, but now also sell them expensive editing
software to fix what their cameras weren't doing properly to provide a
useful image right out of the box.

A popular business model for the last couple of decades. Not unlike how
microsoft popularized this practice. They released Win95 in alpha phase (I
was a pre-beta-tester and read the in-house memos back then). M$ was
worried that they'd get sued worldwide for false-advertising if it wasn't
released on the promised date. In fact they were already behind several
deadlines and lawyers were starting to circle, ready to get their piece of
the M$ castle. M$ decided to go ahead and ship the alpha-phase Win95
anyway. What buyer would ever know. They then also charged (on a per-call
basis) their customers who bought this unfinished software for the
tech-support needed to get it running somewhat. A very effective means to
increase the profitability of an incomplete or improperly functioning
product. (This is why you should never buy any windows platform until after
the second or third service-pack is released. Let all the others happily
and foolishly pay for the privilege to be microsoft's beta-tester grunts.
When the reverse should be true. M$ should pay everyone to try out the
first few issues of their latest versions. If they're lucky, and they pay
all their beta-testers enough for all the time and work involved, we might
even tell M$ what is wrong.)

Sell them a DSLR that should work well and produce a useful image, but
doesn't. Then provide a $5,000-$10,000 lens and $200 software that they'll
need to get it working right. It's just the M$ marketing strategy applied
to cameras, nothing more. Your valuable time that you spend in editing all
your RAW images for this privilege is merely a courtesy feature and should
go unmentioned, lest people become even more angry over how they've been
cunningly turned into more CEOs' saps.

There are many cameras now on the market where you will find little need
for RAW. Take the RAW data and try to get it to look better than the JPG
from the camera and you'll be hard pressed to better it. They manage to do
the process right the first time with no need for time-consuming RAW
editing intervention, other than setting white-balance and exposure
properly while shooting, as any decent photographer will and should.

Yes, they could easily provide the JPG images in the 16-bit HD-Photo format
(nearly all good editors fully support it) with compression ratio saving
options (as all editors do), for those of you that understand the need for
the extra data when trying to recover from your snapshooters' mistakes and
accidents. But then how could they sell the required RAW editing software
to you too? Not going to happen if they can find a simple way to make you
pay more of your money and waste even more of your valuable time.

Enjoy your crippled cameras. You got exactly what you were willing to pay
for.

From: DRS on
"Paul Furman" <paul-@-edgehill.net> wrote in message
news:hajt19$8gj$1(a)news.eternal-september.org
> DRS wrote:

[...]

>> If the histogram at -4 is in fact more accurate than the histogram
>> at 0 (the Canon default) then the photographer in fact has greater
>> room for exposure compensation to the right than the histogram at
>> contrast setting 0 indicates. For those wishing to compensate to
>> the right this is useful information. What the photographer
>> *subsequently* chooses to do to the exposure is another discussion
>> entirely.
>
> What about saturation? Reducing saturation seems to give more detail
> to the edges also.

That is possible but not something for which I have evidence. My concern
here was to short-circuit this increasingly hysterical subthread by
demonstrating that Floyd has been tilting at windmills. Everything Doug
McDonald has said about the effect on the histogram of changing the contrast
setting on the 30D is borne out by the images on the page to which I linked.
Since all the major DSLR manufacturers, to the best of my knowledge, derive
histograms from the JPEGs then what he has described would be universally
applicable.



From: Floyd L. Davidson on
"DRS" <drs(a)removethis.ihug.com.au> wrote:
>"Paul Furman" <paul-@-edgehill.net> wrote in message
>news:hajt19$8gj$1(a)news.eternal-september.org
>> DRS wrote:
>
>[...]
>
>>> If the histogram at -4 is in fact more accurate than the histogram
>>> at 0 (the Canon default) then the photographer in fact has greater
>>> room for exposure compensation to the right than the histogram at
>>> contrast setting 0 indicates. For those wishing to compensate to
>>> the right this is useful information. What the photographer
>>> *subsequently* chooses to do to the exposure is another discussion
>>> entirely.
>>
>> What about saturation? Reducing saturation seems to give more detail
>> to the edges also.
>
>That is possible but not something for which I have evidence. My concern
>here was to short-circuit this increasingly hysterical subthread by
>demonstrating that Floyd has been tilting at windmills. Everything Doug
>McDonald has said about the effect on the histogram of changing the contrast
>setting on the 30D is borne out by the images on the page to which I linked.
>Since all the major DSLR manufacturers, to the best of my knowledge, derive
>histograms from the JPEGs then what he has described would be universally
>applicable.

The web page you cited has absolutely *nothing* on it
that supports what you or McDonald have said. It talks
only about the effect of changing contrast settings on
the resulting JPEG image, not on the exposure or how it
affects camera raw data.

The histogram images show that *no* change in exposure
is demonstrated, and that *logically* it is not possible
to improve the accuracy of the histogram. (Indeed, the
histograms shown are apparently purposely styled, with a
white foreground against a *grey* background and with a
grey scale at the bottom so that the lower right corner
has a white border against the white foreground. They
have made it impossible to see where the right edge of
the data is!)

What it does show is that the peaks in the graph get
moved around, and if you *mistakenly* believe that where
the peak is at is related to exposure, you will
mistakenly think that contrast has somehow helped.

The problem with saying that contrast adjustments make
it more obvious where the right edge of the graph is at
is that different setting help or hinder with different
types of scenes. For one scene you might well be right
that it is easier to see with low contrast, but just the
same for the next scene you shoot it could be high
contrast that would help. It is *not* inherently better
for all purposes when set to low contrast!

Showing that it helps to see the edge in one condition
without being aware that the condition is a special
case, leads to a logically invalid conclusion.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd(a)apaflo.com
From: DRS on
"Floyd L. Davidson" <floyd(a)apaflo.com> wrote in message
news:87zl82qsmh.fld(a)apaflo.com
> "DRS" <drs(a)removethis.ihug.com.au> wrote:

[...]

>> That is possible but not something for which I have evidence. My
>> concern here was to short-circuit this increasingly hysterical
>> subthread by demonstrating that Floyd has been tilting at windmills.
>> Everything Doug McDonald has said about the effect on the histogram
>> of changing the contrast setting on the 30D is borne out by the
>> images on the page to which I linked. Since all the major DSLR
>> manufacturers, to the best of my knowledge, derive histograms from
>> the JPEGs then what he has described would be universally applicable.
>
> The web page you cited has absolutely *nothing* on it
> that supports what you or McDonald have said. It talks
> only about the effect of changing contrast settings on
> the resulting JPEG image, not on the exposure or how it
> affects camera raw data.

That is because they are two different things which nobody has conflated but
you. The images on that site show exactly what Doug McDonald claimed and
nothing more. Of course they show nothing on the effect on exposure or on
Raw data but that was never the claim except in your mind. You have created
a straw man.

> The histogram images show that *no* change in exposure
> is demonstrated, and that *logically* it is not possible
> to improve the accuracy of the histogram.

It is possible to improve the accuracy of the histogram relative to the Raw
data and the fact that you cannot see it when it is right before your eyes
is your problem, not ours. Those images show 5 different histograms where
the only variable is the contrast setting. Since the exposure has not
changed then only one of the histograms can be the most accurate relative to
the Raw image. It happens to be the -4 setting.

[...]

> What it does show is that the peaks in the graph get
> moved around, and if you *mistakenly* believe that where
> the peak is at is related to exposure, you will
> mistakenly think that contrast has somehow helped.

Straw man. All five histograms have different right-edges, indicating
different possibilities for exposure compensation before clipping occurs.
One of the 5 most accurately indicates the true feasible extent of ETTR, and
that one is the -4 histogram. That is all that has been claimed.

> The problem with saying that contrast adjustments make
> it more obvious where the right edge of the graph is at
> is that different setting help or hinder with different
> types of scenes. For one scene you might well be right
> that it is easier to see with low contrast, but just the
> same for the next scene you shoot it could be high
> contrast that would help. It is *not* inherently better
> for all purposes when set to low contrast!

The question of when ETTR is suitable is a different question again., and is
not something I addressed.

> Showing that it helps to see the edge in one condition
> without being aware that the condition is a special
> case, leads to a logically invalid conclusion.

You are really not in any position to lecture on logic.