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"Why Raw" Article

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August 31, 2005 2:06:46 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

I have written Part I of an article titled "Why Raw". The article can
be found on my web site at:

http://ronbigelow.com/articles/raw/raw.htm


Other articles can be found on my site at:

http://ronbigelow.com/articles/articles.htm


Comments are always welcome.

More about : raw article

August 31, 2005 10:43:44 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

David,

The 255 light levels have to do with tonal range not dynamic range. The
article assumed a 5 stop dynamic range camera. That is fixed. The
camera can not exceed that. The gamma curve can make the image more
contrasty and make it appear to the eye that there is more dynamic
range. However, that will simply readjust the spread of the 255 light
levels (compressing some and spreading out others), but there will
still only be no more than 255 light levels in a JPEG file. The article
is correct.
Anonymous
August 31, 2005 3:54:43 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Very informative.
Thank you!

"ron" <ron@ronbigelow.com> wrote in message
news:1125464806.813111.116210@g47g2000cwa.googlegroups.com...
>I have written Part I of an article titled "Why Raw". The article can
> be found on my web site at:
>
> http://ronbigelow.com/articles/raw/raw.htm
>
>
> Other articles can be found on my site at:
>
> http://ronbigelow.com/articles/articles.htm
>
>
> Comments are always welcome.
>
Related resources
Anonymous
August 31, 2005 5:22:05 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

[]
> "ron" <ron@ronbigelow.com> wrote in message
> news:1125464806.813111.116210@g47g2000cwa.googlegroups.com...
>> I have written Part I of an article titled "Why Raw". The article can
>> be found on my web site at:
>>
>> http://ronbigelow.com/articles/raw/raw.htm
[]
>> Comments are always welcome.

Ron,

There is a major error in the article, section Raw Advantage #2: Bits,
making the comparison between JPEG and RAW quite incorrect. The data in
JPEG files has a gamma correction of (typically) 2.2 applied, which means
that it can accommodate a far greater dynamic range than just 255 linear
light levels. The difference between RAW and JPEG in is the accuracy of
light level representation, not in the dynamic range.

Cheers,
David
Anonymous
August 31, 2005 6:30:03 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

ron wrote:
> David,
>
> The 255 light levels have to do with tonal range not dynamic range.
> The article assumed a 5 stop dynamic range camera. That is fixed. The
> camera can not exceed that. The gamma curve can make the image more
> contrasty and make it appear to the eye that there is more dynamic
> range. However, that will simply readjust the spread of the 255 light
> levels (compressing some and spreading out others), but there will
> still only be no more than 255 light levels in a JPEG file. The
> article is correct.

The way I'm understanding it, "Figure 4: Shades vs. Stops of Light" for
JPEG is wrong. When you half the exposure, while in the RAW file the
digital value will be halved, this does not happen in JPEG. The values
would be (approximately) 255, 186, 135, 99, 72, 52 etc. The JPEG has
twenty different tonal values four stops down and five stops down from
peak white, and 69 different tonal values between peak white and one stop
down. You article gives 16 and 128 shades for these values.

David
Anonymous
August 31, 2005 7:13:20 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

David J Taylor wrote:

> ron wrote:
>
>>David,
>>
>>The 255 light levels have to do with tonal range not dynamic range.
>>The article assumed a 5 stop dynamic range camera. That is fixed. The
>>camera can not exceed that. The gamma curve can make the image more
>>contrasty and make it appear to the eye that there is more dynamic
>>range. However, that will simply readjust the spread of the 255 light
>>levels (compressing some and spreading out others), but there will
>>still only be no more than 255 light levels in a JPEG file. The
>>article is correct.
>
>
> The way I'm understanding it, "Figure 4: Shades vs. Stops of Light" for
> JPEG is wrong. When you half the exposure, while in the RAW file the
> digital value will be halved, this does not happen in JPEG. The values
> would be (approximately) 255, 186, 135, 99, 72, 52 etc. The JPEG has
> twenty different tonal values four stops down and five stops down from
> peak white, and 69 different tonal values between peak white and one stop
> down. You article gives 16 and 128 shades for these values.
>
> David
>
>

Ron:
Concerning your writeup at http://ronbigelow.com/articles/raw/raw.htm

See Figure 7 at:

Dynamic Range and Transfer Functions of Digital Images
and Comparison to Film
http://www.clarkvision.com/imagedetail/dynamicrange2

While in a jpeg file there can be no more than 255 levels, those levels
do not have to be linearly distributed. In fact they are not, just as
Figure 7 above shows. Note in that figure the dynamic range of the
jpeg and the raw file cover the same range, except for a slight increase in
noise at the low end. Of course, the 12-bit raw has more precision, and that
is the main difference between the two.


You might also check out:

Digital Camera Raw versus Jpeg Conversion Losses
http://www.clarkvision.com/imagedetail/raw.versus.jpeg1

The statements about digital camera dynamic range of the "better cameras"
have about 5 stops is incorrect. The better cameras (e.g. DSLRs) are
Poisson statistics limited (meaning photon statistics limited by the sensor's
given quantum efficiency). The sensors have over 12-bits dynamic range
and thus are limited by the 12-bit ADC. See Table 3 at:

The Signal-to-Noise of Digital Camera images
and Comparison to Film
http://www.clarkvision.com/imagedetail/digital.signal.t...

Roger
August 31, 2005 7:31:06 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Tnx for article, it's great. I'm reading the rest of your work...

"ron" <ron@ronbigelow.com> wrote in message
news:1125464806.813111.116210@g47g2000cwa.googlegroups.com...
>I have written Part I of an article titled "Why Raw". The article can
> be found on my web site at:
>
> http://ronbigelow.com/articles/raw/raw.htm
>
>
> Other articles can be found on my site at:
>
> http://ronbigelow.com/articles/articles.htm
>
>
> Comments are always welcome.
>
September 1, 2005 1:29:33 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

ron wrote:

> I have written Part I of an article titled "Why Raw". The article can
> be found on my web site at:
>
> http://ronbigelow.com/articles/raw/raw.htm
>
>
> Other articles can be found on my site at:
>
> http://ronbigelow.com/articles/articles.htm
>
>
> Comments are always welcome.
>

Thanks again.

I only have one comment: It would be cool if you made your articles in
an easy to print format, like pdf. I wanted to read it this morning,
but was running a little late.... I could've printed it and read it
during my lunch break.

--
Slack
Anonymous
September 1, 2005 3:04:32 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

In message <1aiRe.99663$G8.11733@text.news.blueyonder.co.uk>,
"David J Taylor"
<david-taylor@blueyonder.co.not-this-bit.nor-this-part.uk.invalid>
wrote:

>There is a major error in the article, section Raw Advantage #2: Bits,
>making the comparison between JPEG and RAW quite incorrect. The data in
>JPEG files has a gamma correction of (typically) 2.2 applied, which means
>that it can accommodate a far greater dynamic range than just 255 linear
>light levels. The difference between RAW and JPEG in is the accuracy of
>light level representation, not in the dynamic range.

An 8-bit TIFF has more potential shadow detail than a 12-bit RAW file.
It is not usually realized, however, as 8-bit TIFFs generally come from
12-bit RAW files.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
September 1, 2005 3:26:41 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

In message <1125495824.741798.263850@g47g2000cwa.googlegroups.com>,
"ron" <ron@ronbigelow.com> wrote:

>David,

>The 255 light levels have to do with tonal range not dynamic range. The
>article assumed a 5 stop dynamic range camera. That is fixed. The
>camera can not exceed that.

To say that a camera has 5 stops of dynamic range and no more assumes a
certain quality standard. With a definition that gives 5 stops for
DSLRs, you are talking about a standard of very high quality shadows.
The fact is, there is no hard, concrete limit on the dynamic range of an
image if your quality standards are flexible; the quality simply
deteriorates as you go deeper and deeper into the shadows, until noise
dominates and the signal is vague and lost in the chaos.

>The gamma curve can make the image more
>contrasty and make it appear to the eye that there is more dynamic
>range. However, that will simply readjust the spread of the 255 light
>levels (compressing some and spreading out others), but there will
>still only be no more than 255 light levels in a JPEG file. The article
>is correct.

A JPEG can only express 256 light levels for each color channel. Most
of the values less than about 50 only occur by demosaicing and
sharpening when they come from a 12-bit RAW file. If you took each RAW
color channel and made a bitmap from it in 8-bit gamma-adjusted space,
with no sharpening or softening applied, most of the values below 50
would not be used at all. The histogram would be spaced like this:

| | | | | | | ||||||||||||

The section to the right, where the histogram is full (without gaps) is
the range where the 12-bit RAW has more level-definition than the 8-bit
gamma-corrected space. The rightmost section has several RAW values
becoming a single 8-bit value.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
September 1, 2005 10:59:56 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

JPS@no.komm wrote:
[]
> An 8-bit TIFF has more potential shadow detail than a 12-bit RAW file.
> It is not usually realized, however, as 8-bit TIFFs generally come
> from 12-bit RAW files.

You mean that the 8-bit TIFF is gamma-corrected as well as the JPEG, and
that at the range in the TIFF from lowest brightness levels to the highest
exceeds that of a 12-bit RAW file?

12-bit - 4096 linear levels from 0 to 4095 - range 4095:1

8-bit gamma corrected, 255 levels from 5E-6 to 1 (or 0.001 to 255) - range
200,000:1

David
Anonymous
September 1, 2005 3:18:01 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Slack <slacker7_ReMoVe_ThIs@scglobal.net> wrote:

>I only have one comment: It would be cool if you made your articles in
>an easy to print format, like pdf. I wanted to read it this morning,
>but was running a little late.... I could've printed it and read it
>during my lunch break.


If you are so unhappy, why don't you ask Ron for a refund?

;-)
Anonymous
September 1, 2005 8:49:05 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

On Wed, 31 Aug 2005 21:29:33 -0700, in rec.photo.digital.slr-systems Slack
<slacker7_ReMoVe_ThIs@scglobal.net> wrote:

>I only have one comment: It would be cool if you made your articles in
>an easy to print format, like pdf. I wanted to read it this morning,
>but was running a little late.... I could've printed it and read it
>during my lunch break.

FWIW, some newer printers have a util to help print web pages. What's the
problems with the pages that you couldn't print them? Too wide, choose
landscape. Otherwise you can use Adobe Acrobat to print through Distiller
to PDF. if you want something like this.
----------
Ed Ruf Lifetime AMA# 344007 (Usenet@EdwardG.Ruf.com)
See images taken with my CP-990/5700 & D70 at
http://edwardgruf.com/Digital_Photography/General/index...
September 1, 2005 8:58:06 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Ed Ruf wrote:

> On Wed, 31 Aug 2005 21:29:33 -0700, in rec.photo.digital.slr-systems Slack
> <slacker7_ReMoVe_ThIs@scglobal.net> wrote:
>
>
>>I only have one comment: It would be cool if you made your articles in
>>an easy to print format, like pdf. I wanted to read it this morning,
>>but was running a little late.... I could've printed it and read it
>>during my lunch break.
>
>
> FWIW, some newer printers have a util to help print web pages. What's the
> problems with the pages that you couldn't print them? Too wide, choose
> landscape. Otherwise you can use Adobe Acrobat to print through Distiller
> to PDF. if you want something like this.
> ----------
> Ed Ruf Lifetime AMA# 344007 (Usenet@EdwardG.Ruf.com)


Actually, that is what I tried to do and my printer is brand spanking
new (Dell 3100cn).

Some of the graphics were getting split between two different pages.
Some of the gray side bars in the 2nd half of the article got all
jacked up: overlapping with the main text. I tired playing around
resizing the print, but no joy. I tried to print via two web browsers,
FF & Mozilla.... maybe that was the problem??

What is Distiller? I'm always willing to learn new stuff.

--
Slack
Anonymous
September 2, 2005 1:09:30 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

David J Taylor wrote:
> JPS@no.komm wrote:
> []
>> An 8-bit TIFF has more potential shadow detail than a 12-bit RAW
>> file. It is not usually realized, however, as 8-bit TIFFs generally
>> come from 12-bit RAW files.
>
> You mean that the 8-bit TIFF is gamma-corrected as well as the JPEG,
> and that at the range in the TIFF from lowest brightness levels to
> the highest exceeds that of a 12-bit RAW file?
>
> 12-bit - 4096 linear levels from 0 to 4095 - range 4095:1
>
> 8-bit gamma corrected, 255 levels from 5E-6 to 1 (or 0.001 to 255) -
> range 200,000:1

The problem is that the TIFF comes from the same 12 bit source.

-Mike
Anonymous
September 2, 2005 1:09:31 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

Mike Warren wrote:
> David J Taylor wrote:
>> JPS@no.komm wrote:
>> []
>>> An 8-bit TIFF has more potential shadow detail than a 12-bit RAW
>>> file. It is not usually realized, however, as 8-bit TIFFs generally
>>> come from 12-bit RAW files.
>>
>> You mean that the 8-bit TIFF is gamma-corrected as well as the JPEG,
>> and that at the range in the TIFF from lowest brightness levels to
>> the highest exceeds that of a 12-bit RAW file?
>>
>> 12-bit - 4096 linear levels from 0 to 4095 - range 4095:1
>>
>> 8-bit gamma corrected, 255 levels from 5E-6 to 1 (or 0.001 to 255) -
>> range 200,000:1
>
> The problem is that the TIFF comes from the same 12 bit source.
>
> -Mike

Yes, I appreciate that. I just wanted to confirm precisely what John was
saying, as it's important that the information on Ron's page is correct.

David
Anonymous
September 2, 2005 1:10:37 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

In message <MFxRe.100197$G8.94336@text.news.blueyonder.co.uk>,
"David J Taylor"
<david-taylor@blueyonder.co.not-this-bit.nor-this-part.uk.invalid>
wrote:

>You mean that the 8-bit TIFF is gamma-corrected as well as the JPEG, and
>that at the range in the TIFF from lowest brightness levels to the highest
>exceeds that of a 12-bit RAW file?

From what I've seen and heard, a TIFF is more likely to be literal in
it's 2.2 gamma in the shadows, whereas a JPEG is more likely to render
the deeper shadows even deeper, to hide noise.

>12-bit - 4096 linear levels from 0 to 4095 - range 4095:1

Yes, literally; level 4095 is 4095 times as bright as level 1.

>8-bit gamma corrected, 255 levels from 5E-6 to 1 (or 0.001 to 255) - range
>200,000:1

In therms of luminance, it is actually (255^2.2):1 or 196,965:1.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
September 2, 2005 1:48:31 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Tony Polson wrote:
> Slack <slacker7_ReMoVe_ThIs@scglobal.net> wrote:
>
>> I only have one comment: It would be cool if you made your articles
>> in an easy to print format, like pdf. I wanted to read it this
>> morning, but was running a little late.... I could've printed it
>> and read it during my lunch break.
>
>
> If you are so unhappy, why don't you ask Ron for a refund?
>
> ;-)

He's such a nice bloke, I think he would give double your money
back. :-)

-Mike
September 2, 2005 1:48:32 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

Mike Warren wrote:

> Tony Polson wrote:
>
>>Slack <slacker7_ReMoVe_ThIs@scglobal.net> wrote:
>>
>>
>>>I only have one comment: It would be cool if you made your articles
>>>in an easy to print format, like pdf. I wanted to read it this
>>>morning, but was running a little late.... I could've printed it
>>>and read it during my lunch break.
>>
>>
>>If you are so unhappy, why don't you ask Ron for a refund?
>>
>>;-)
>
>
> He's such a nice bloke, I think he would give double your money
> back. :-)
>
> -Mike
>
>
I'm such a valued customer, he gave triple my $$ back. So there :-D

--
Slack
Anonymous
September 2, 2005 7:35:01 AM

Archived from groups: rec.photo.digital.slr-systems (More info?)

> Actually, that is what I tried to do and my printer is brand spanking
> new (Dell 3100cn).

you're printer driver should have a print-to-fit option. it's fairly
common. else, some of the alternative browsers will actually resize the
page graphics and all (not just the font like IE).

--
Mark

Photos, Ideas & Opinions
http://www.marklauter.com
Anonymous
September 2, 2005 10:58:04 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

JPS@no.komm wrote:
> In message <MFxRe.100197$G8.94336@text.news.blueyonder.co.uk>,
> "David J Taylor"
> <david-taylor@blueyonder.co.not-this-bit.nor-this-part.uk.invalid>
> wrote:
>
>> You mean that the 8-bit TIFF is gamma-corrected as well as the JPEG,
>> and that at the range in the TIFF from lowest brightness levels to
>> the highest exceeds that of a 12-bit RAW file?
>
> From what I've seen and heard, a TIFF is more likely to be literal in
> it's 2.2 gamma in the shadows, whereas a JPEG is more likely to render
> the deeper shadows even deeper, to hide noise.
>
>> 12-bit - 4096 linear levels from 0 to 4095 - range 4095:1
>
> Yes, literally; level 4095 is 4095 times as bright as level 1.
>
>> 8-bit gamma corrected, 255 levels from 5E-6 to 1 (or 0.001 to 255) -
>> range 200,000:1
>
> In therms of luminance, it is actually (255^2.2):1 or 196,965:1.

Thanks, John. Our understanding is the same, then. I only quoted
200,000:1 simply because if I quoted the exact number I expected someone
to think I was being pedantic! I can appreciate that JPEG might be
optimised in a slightly different way to TIFF so that errors are masked.

By the way (for anyone else who's still reading), this 2.2 gamma figure is
what some cameras call the "contrast" setting - use a smaller number when
converting from linear to JPEG and you'll get more contrast, a larger
number gives less contrast.

David
Anonymous
September 2, 2005 12:25:01 PM

Archived from groups: rec.photo.digital.slr-systems (More info?)

David J Taylor wrote:

>Slack wrote:
>[]
>
>
>
>>What is Distiller? I'm always willing to learn new stuff.
>>
>>
>
>http://www.adobe.com/products/acrdis/main.html
>
>
>
>
Open Office can export to PDF and its free!
A
Anonymous
September 3, 2005 12:49:37 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

In message <0KSRe.100820$G8.39510@text.news.blueyonder.co.uk>,
"David J Taylor"
<david-taylor@blueyonder.co.not-this-bit.nor-this-part.uk.invalid>
wrote:

>JPS@no.komm wrote:

>> In therms of luminance, it is actually (255^2.2):1 or 196,965:1.

>Thanks, John. Our understanding is the same, then. I only quoted
>200,000:1

Sorry; I didn't even notice that you wrote that. I read it fast, and
somehow thought you were writing about 255:1.

>simply because if I quoted the exact number I expected someone
>to think I was being pedantic! I can appreciate that JPEG might be
>optimised in a slightly different way to TIFF so that errors are masked.

>By the way (for anyone else who's still reading), this 2.2 gamma figure is
>what some cameras call the "contrast" setting - use a smaller number when
>converting from linear to JPEG and you'll get more contrast, a larger
>number gives less contrast.

Most JPEG conversions, I think, vary the gamma across the histogram.
This is important if you want to keep middle grey standard, but expand
or compress contrast relative to it.

I really wish I had a greyscale wedge the quality of the Gretag-MacBeth
color checker, but with about 10 stops of grey rectangles with steps of
about 1/6 stop, or even a pie wedge to discount light roll-off.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
September 3, 2005 12:24:54 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

JPS@no.komm wrote:
[]
> Most JPEG conversions, I think, vary the gamma across the histogram.
> This is important if you want to keep middle grey standard, but expand
> or compress contrast relative to it.

Yes, there may also be an attempt to keep a little of the specular
highlights, for example.

> I really wish I had a greyscale wedge the quality of the
> Gretag-MacBeth color checker, but with about 10 stops of grey
> rectangles with steps of about 1/6 stop, or even a pie wedge to
> discount light roll-off.

Could you make something out of a light box and some grey film in multiple
layers? I guess that wouldn't be accurate enough, though.

David
Anonymous
September 3, 2005 11:00:48 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

<JPS@no.komm> wrote in message
news:63ehh1dvt37988c5bh8vr0a1p8kfg47ist@4ax.com...
> In message <0KSRe.100820$G8.39510@text.news.blueyonder.co.uk>,
> "David J Taylor"
> <david-taylor@blueyonder.co.not-this-bit.nor-this-part.uk.invalid>
> wrote:
>
> >JPS@no.komm wrote:
>
> >> In therms of luminance, it is actually (255^2.2):1 or 196,965:1.
>
> >Thanks, John. Our understanding is the same, then. I only quoted
> >200,000:1
>
> Sorry; I didn't even notice that you wrote that. I read it fast, and
> somehow thought you were writing about 255:1.
>
> >simply because if I quoted the exact number I expected someone
> >to think I was being pedantic! I can appreciate that JPEG might be
> >optimised in a slightly different way to TIFF so that errors are masked.
>
> >By the way (for anyone else who's still reading), this 2.2 gamma figure
is
> >what some cameras call the "contrast" setting - use a smaller number
when
> >converting from linear to JPEG and you'll get more contrast, a larger
> >number gives less contrast.
>
> Most JPEG conversions, I think, vary the gamma across the histogram.
> This is important if you want to keep middle grey standard, but expand
> or compress contrast relative to it.
>
> I really wish I had a greyscale wedge the quality of the Gretag-MacBeth
> color checker, but with about 10 stops of grey rectangles with steps of
> about 1/6 stop, or even a pie wedge to discount light roll-off.
> --
>
> <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
> John P Sheehy <JPS@no.komm>
> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><

Re the grayscale you desire ... get a Kodak Q-13 "Kodak Color Separation
Guide and Gray Scale-Small," costs something like US$20 at places such as
B&H.

http://www.bhphotovideo.com/bnh/controller/home?ci=1&sb...
tialSearch=yes&O=SearchBar&A=search&Q=*&bhs=t&shs=Kodak+Q-13&image.x=10&ima
ge.y=5

They are literally an "industry standard," and have been used as such for
over fifty years.
Anonymous
September 4, 2005 4:52:14 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

In message <ApmSe.707$Sx4.18@trnddc06>,
"RSD99" <rsdwla.NOSPAM@gte.net> wrote:

>Re the grayscale you desire ... get a Kodak Q-13 "Kodak Color Separation
>Guide and Gray Scale-Small," costs something like US$20 at places such as
>B&H.
>
>http://www.bhphotovideo.com/bnh/controller/home?ci=1&sb...
>tialSearch=yes&O=SearchBar&A=search&Q=*&bhs=t&shs=Kodak+Q-13&image.x=10&ima
>ge.y=5
>
>They are literally an "industry standard," and have been used as such for
>over fifty years.

I already have this, and the quality is poor. It is glossy, and they
grey rectangles are reddish. You have to use special lighting for the
glare not to be an issue.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
September 4, 2005 5:09:11 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

"RSD99" <rsdwla.NOSPAM@gte.net> wrote in message
news:ApmSe.707$Sx4.18@trnddc06...
SNIP
> Re the grayscale you desire ... get a Kodak Q-13 "Kodak Color
> Separation Guide and Gray Scale-Small," costs something like
> US$20 at places such as B&H.
>

Unfortunately the range they cover is too small for a decent DSLR.

The one you'll need is e.g. the Stouffer T4110:
http://www.stouffer.net/TransPage.htm#transmission%20st...

It covers a range of approx. 10000:1 or 13.5 stops. That should be
enough to be able to determine the dynamic range with a single
exposure.

Bart
Anonymous
September 4, 2005 5:09:12 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

In message <431a2d19$0$11061$e4fe514c@news.xs4all.nl>,
"Bart van der Wolf" <bvdwolf@no.spam> wrote:

>
>"RSD99" <rsdwla.NOSPAM@gte.net> wrote in message
>news:ApmSe.707$Sx4.18@trnddc06...
>SNIP
>> Re the grayscale you desire ... get a Kodak Q-13 "Kodak Color
>> Separation Guide and Gray Scale-Small," costs something like
>> US$20 at places such as B&H.
>>
>
>Unfortunately the range they cover is too small for a decent DSLR.
>
>The one you'll need is e.g. the Stouffer T4110:
>http://www.stouffer.net/TransPage.htm#transmission%20st...
>
>It covers a range of approx. 10000:1 or 13.5 stops. That should be
>enough to be able to determine the dynamic range with a single
>exposure.

That looks interesting. Do you have one? Is glare an issue?
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
September 4, 2005 5:24:12 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

In message <cfhkh1h01b4tjtd9ulu7g7jdfssg0j5f5f@4ax.com>, I,
JPS@no.komm wrote:

>Is glare an issue?

I guess not, as long as they are illuminated from behind; they are
transmission wedges.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <JPS@no.komm>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
Anonymous
September 4, 2005 11:29:04 AM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

JPS@no.komm wrote:
> In message <cfhkh1h01b4tjtd9ulu7g7jdfssg0j5f5f@4ax.com>, I,
> JPS@no.komm wrote:
>
>> Is glare an issue?
>
> I guess not, as long as they are illuminated from behind; they are
> transmission wedges.

The company seems to make both transmission and reflection wedges, quite
reasonably priced (I would have said) if you don't want hand calibration.

http://www.stouffer.net/

David
Anonymous
September 5, 2005 6:39:30 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

<JPS@no.komm> wrote in message
news:ivikh1hed1jt4nht133efhmgspttjmlj4q@4ax.com...
> In message <cfhkh1h01b4tjtd9ulu7g7jdfssg0j5f5f@4ax.com>, I,
> JPS@no.komm wrote:
>
>>Is glare an issue?
>
> I guess not, as long as they are illuminated from behind; they are
> transmission wedges.

Actually to get the best results, one should *only* have back-lighting
for such dense areas as the target offers. Any light striking it from
the front will reduce contrast a little. Of course, if the amount of
backlighting is much larger than any ambient light to the front, there
is no issue. That means that it's best to shoot the target with the
front shielded from ambient light, and the back only lighted by a
lightsource that's shielded from lighting anything else than the
target.

Bart
Anonymous
September 5, 2005 7:21:45 PM

Archived from groups: rec.photo.digital.slr-systems,rec.photo.digital (More info?)

<JPS@no.komm> wrote in message
news:cfhkh1h01b4tjtd9ulu7g7jdfssg0j5f5f@4ax.com...
> In message <431a2d19$0$11061$e4fe514c@news.xs4all.nl>,
SNIP
> That looks interesting. Do you have one? Is glare an issue?

I have one from Kodak that covers 10 stops, but that is too limited
because the channels are not equally sensitive, which requires
combining different exposures to clip on the bright side, and be noise
limited by dynamic range on the dark side.

I'm in the process of ordering the T4110, and I'm building a dedicated
lightbox/contraption with masked opaline glass as a diffusor, and a
kind of ambient-light shade on the front. The Imatest software I use
will also allow to make sure that the illumination of the target is
uniform, and I can measure/calibrate the target (in place)
transmission and spectral characteristics with the Eyeone Photo's
Spectrophotometer.

I'm experimenting with the lightsource to use, but I'll probably
either end up with 5300K or 6500K fluorescent tube lighting (which
makes it hard to restrict lighting to only the target holder), or a
shielded electronic flash rear window. It'll probably be the flash
exposure (more consistent/repeatable and shorter exposure times).

Bart
!