Linear Processing of RAW Image Files .

luis-a-guevara · October 24, 2008

Some images carry their message in their lower tones and some do it with their midlle tones and highlights, like this one:

<img src="http://d6d2h4gfvy8t8.cloudfront.net/8079820-lg.jpg" alt="This image was shot RAW and processed as a 16 Bit LINEAL RAW in Adobe

Prophoto Color Space with a Custom Gamma 1.0 profile to properly render the extended amount of upper Tones." height="1005"

width="1492" border="0">

Normal RAW processing spreads the image tones evenly across its Dynamic Range , thus , abnormally ,compressing the highlights

and expanding the Shadows , something that will not work well with this type of imagery .

Linear processing workflows , instead ,compress the shadows and devote the rest of the Color Space to Midtones and highlights

making it the perfect Complement to this type of imagery ,that results from frontal lighting.

I am inviting all members to discuss this advanced technique and share their experiences with the rest of us.

ellis_vener_photography · October 24, 2008

Choosing a linear response curve is an option in all versions of Adobe Photoshop Lightroom. For some iamges it is useful for making the photo look the way yu want it to look.

roger_smith4 · October 24, 2008

That's a very delicately lit image, nice work with it. Can you say more about the workflow you use for "linear processing?"

I use Lightroom and generally use the "linear" setting for curves but I'm not sure if that's doing what you describe.

luis-a-guevara · October 24, 2008

Sure Roger , that is the whole idea of this posting. This image was processed using dcRAW-X which is an alternate RAW converter for the Macintosh , but versions exist for other platforms . It was output as a 16 Bit Linear PSD file . The file was opened in photoshop CS3 and asigned a Custom Adobe Prophoto profile that was only modified by changing its Gamma setting to 1.0.

If you dont use a Custom Profile , since Linear RAW files are not Tagged to any color space , Photoshop , unless instructed to do otherwise, will convert them to the working Color Space , and if none has been selected in the preferences it would default to sRGB , the most restrictive color space. In essence turning the LINEAL raw back to a plain vanilla NON LINEAR RAW file with the sRGB Gamma value of 1.8 , not different than what the camera would have produced .

I use Lightroom and its Linear option, but it does not work out the same . When I opened the image in Photoshop seem to have followed the same process that I just described , since Photoshop obviously knows about Lightroom exotic options . The only difference , if any, is that you dont have to asign a Linear Custom Profile.

When I open dcRAW-X files the situation is very different , the images are dark and the Histogram is concentrated at the lower end , as any Linear image should . When you asign or convert to the Custom Linear Profile of Gamma 1.0 you are not really changing the distribuition of Tones , but giving meaning to its Colors . You will have to do a Manual Tone Mapping (Or Re Mapping if you wish ) to expand the tones that have been concentrated in the Shadow portion of the Histogram .

I will be creating a Tutorial that I will post in my website when ready.

frans_waterlander · October 25, 2008

Luis,

Most image editing programs have a curve function with linear being the default and tweaking it is easy to do. So what exactly is the point you are trying to make? It seems to me that you are reinventing the wheel.

luis-a-guevara · October 25, 2008

Hi Frans . Those curves that you are refering to are really just describing the behavior of the Midtones of the

image, in fact the end points are fixed and your options are limited to defining the Slope of the curve at the Mid

Point , which as you described , by default is lineal , meaning no transformation takes place. However the Data that

you are trying to work on is already non lineal , since as soon as you open it in a RAW Converter , before it is even

separated into our familiar 3 RGB chanels , a Gamma of 0.45 is imposed on it, to counteract the Display Gamma of

2.2 , a very necessary step , since we expect the image to be ,overall ,a lineal representation of the Scene, in spite

that the Display is highly unlineal. If you choose a Midtone Curve of Lineal value , then all the intrinsic non linearity

of the converted RAW file is passed along untouched

What this means is that our RAW Data that was Linearly captured ,thanks to the painstaking efforts of the

Sensors Designers ,is artificially DISTORTED when it hurts the most , right before the Color Channels and the Color

Balance are created from it. The RAW file is just a Matrix of Data with no Color Channels , Color Spaces or even

Color , for that matter.

So what is LINEAR PROCESSING AGAIN?

Simple. I am sure that you will agree that is simple. Linear processing is removing the introduction of this

Inverse Gamma at the point where it hurts the most ,and reintroduce it as one of the last steps , where it hurts the

least.

You can do this in the Adobe products Lightroom and ACR , but only if you go deep into the advanced

preferences for conversion ,and choose LINEAL , instead of the default embed Original RAW file.

This is very different than the tweakings that you are talking about , since by removing the compression of

tones

introduced so early in the process you will have more tones to TWEAK .

So the point that I am trying to make is that when Utmost Image Quality matters , linear processing is the way

to go. Lineal Image Converters , like dcRAW-X and others , not only remove Gamma but also , Compression ,

Sharpening ,Denoising , Antialiasing and Interpolation. What you want is that your chanels are made from data that

has been touched the least . Ideally ,not touched at all. All this , Compression ,

Sharpening ,Denoising , Antialiasing and Interpolation, can be best done taylored to the

image type, under the control of the Artist and not by invisible factory presets that only work for Generic ,Average

Scenes.</

P>

Luis

frans_waterlander · October 25, 2008

Luis,

Maybe you could start by posting an example of an image processed both ways to demonstrate possible advantages.

luis-a-guevara · October 25, 2008

Good Idea . Here you have it one NON LINEAR RAW and the best one , at the end ,the LINEAR RAW:

IN THIS ONE THE TONES HAVE BEEN SPREAD EVENLY ACROSS THE HISTOGRAM BY THE GAMMA

FUNCTION

IN THIS OTHER ONE THE LINEAL RENDERING PUTS THE TONES AS THEY WHERE ON THE ORIGINAL

SCENE:

You tell me which one you like best, bost have the same "tweaking" except for the different Gammas</

P> Luis

Tim_Lookingbill · October 25, 2008

Luis,

Thanks for explaining such a somewhat complicated subject in a not so complicated manner. Very informative.

What versions of ACR can you get this linear output through its preferences?

And what profile did you assign to the bottom image?

Was it the custom 1.0 gamma ProPhoto RGB which can be made using Photoshop's CustomRGB within Color Settings?

How was color temp/white balance applied?

Did you apply further tweaks to contrast after assigning the 1.0 gamma profile to the bottom image before posting it here?

Very interesting. A much better and more accurate looking rendering.

roger_smith4 · October 26, 2008

Would you be willing to post or email the original raw file so I can try it myself and compare?

luis-a-guevara · October 27, 2008

Thanks Tim .

What versions of ACR can you get this linear output through its preferences?

I am not sure when was the first time that ACR included Lineal Output , but I have been using it at least for the last

Versions that started with Photoshop CS2.

Lightroom , as far as I know included the option since V1. But I dont generally use them , like I said I use a program

called dcRAW-X , that I know exactly what it does , being a Programmer myself ,while Adobe products are shielded in

Commercial Secrecy.

Was it the custom 1.0 gamma ProPhoto RGB which can be made using Photoshop's CustomRGB

within Color Settings?

Yes . You go Color Settings , select your desired profile , in this case Prophoto, and then go down to the Gamma

settings , that by default would be 2.2 and type in 1.0. Now Save this alongside all the other profiles with a convenient

name . Foe example I use "Linear Prophoto"

How was color temp/white balance applied?

The Header portion of every RAW image file, contains non user readable Metadata that includes a Sub-section

called "Exif " where all the camera settings in force at the time of the capture are stored . The RAW

converter reads this info and uses it to color balance the image. This particular Image was shot in the shade under a

Blue sky , illuminated by reflected light from the sky , so I had , correspondently set the camera Color Balance to

"Shadow" . As you can see the Non Lineal version shows the Yellow Bias imposed by the

"Shadow" setting , to counteract the Bluish illuminant.

The Lineal RAW image ,instead, does not have the Yellow color bias imposed on it , and therefore contains more

Blue , Truer to the Scene.

Did you apply further tweaks to contrast after assigning the 1.0 gamma profile to the bottom image

before posting it here?

Yes , of course . When you open a Lineal image and assign a Custom profile of Gamma 1.0 three things happen

:

1-You prevent Photoshop preferences settings for Untagged Images from taking effect ( This means assigning the

Users Workspace preference ,if exist , or P.S. default's , sRGB)

2-The colors of the Lineal Image now have a Context that defines the meaning of its color

values.

3-The Most Important Part. No Gamma transformations are applied to the tonal distribution , in essence passing it

right through , as it is , with its original Gamma 1.0

Because of this last part ( Which is at the heart of the reasons why you choose to do a Lineal Processing ) the

image will have a visual aspect that is Lineal , but with the uncompensated Monitor Gamma of 2.2 Riding on it skewing the

Midtones to the Left . (Remember Gamma is the slope of the Levels Curve at its Midpoint ). So Yes , you have to either

Reinstate the Gamma Encoding that you removed early in the Game ,where it hurt the most , or do a Manual

Tone Mapping ( This is better ) Either way you are doing it after the image have already been built from the maximum

data available , which is the point where any Tweaks will hurt the least.( All Tone Manipulations produce data Loss, so you want to

delay them until after the Image has already been created from the RAW Data into 3 RGB channels , on which the Color Balance will be

based upon )

This last part ,Tone Mapping , is something that every good artist would always do to every image , regardless of it

being Linear or Not , to account for each image needs, that are , obviously , different all the time.

The great benefit of this Lineal Processing is that it enables you to use all the Data captured ( Applying

Gamma different than 1.0 ,always shrinks the Tonal Range ) and because the High tones are up to this point ,untouched

, they can deliver a lot more detail ( Shrinking the upper tones means the tonal differences are minimized between

adjacent tones , therefore detail suffers) . This is a good thing because our eyes are less sensitive to detail in

bright lights .

At the end , when your are satisfied with your image , save it as a Master Image in PSD format , then convert it to

Adobe sRGB color space , change image to 8 Bit mode and save it again as JPEG with a

compression of 6 , for web display.

The end result is , like you said "A much better and more accurate looking rendering"

P.S. Roger I am creating a small tutorial using another , similar ,image of the same Scene , that will include a link to

download the RAW file .The other image is already part of <a href="http://www.photo.net/photos/Luis-A-Guevara">my Fine Art Gallery</a>

right here at photo.net . My RAW files are X3f files from a Sigma SD9 camera and Leica lenses , so you will have to

use either Lightroom or Photoshop to do the conversion.

More on this will follow soon.Luis<div></div>

luis-a-guevara · October 27, 2008

Thanks Tim .

What versions of ACR can you get this linear output through its preferences?

I am not sure when was the first time that ACR included Lineal Output , but I have been using it at least for the last

Versions that started with Photoshop CS2.

Lightroom , as far as I know included the option since V1. But I dont generally use them , like I said I use a program

called dcRAW-X , that I know exactly what it does , being a Programmer myself ,while Adobe products are shielded in

Commercial Secrecy.

Was it the custom 1.0 gamma ProPhoto RGB which can be made using Photoshop's CustomRGB

within Color Settings?

Yes . You go Color Settings , select your desired profile , in this case Prophoto, and then go down to the Gamma

settings , that by default would be 2.2 and type in 1.0. Now Save this alongside all the other profiles with a convenient

name . Foe example I use "Linear Prophoto"

How was color temp/white balance applied?

The Header portion of every RAW image file, contains non user readable Metadata that includes a Sub-section

called "Exif " where all the camera settings in force at the time of the capture are stored . The RAW

converter reads this info and uses it to color balance the image. This particular Image was shot in the shade under a

Blue sky , illuminated by reflected light from the sky , so I had , correspondently set the camera Color Balance to

"Shadow" . As you can see the Non Lineal version shows the Yellow Bias imposed by the

"Shadow" setting , to counteract the Bluish illuminant.

The Lineal RAW image ,instead, does not have the Yellow color bias imposed on it , and therefore contains more

Blue , Truer to the Scene.

Did you apply further tweaks to contrast after assigning the 1.0 gamma profile to the bottom image

before posting it here?

Yes , of course . When you open a Lineal image and assign a Custom profile of Gamma 1.0 three things happen

:

1-You prevent Photoshop preferences settings for Untagged Images from taking effect ( This means assigning the

Users Workspace preference ,if exist , or P.S. default's , sRGB)

2-The colors of the Lineal Image now have a Context that defines the meaning of its color

values.

3-The Most Important Part. No Gamma transformations are applied to the tonal distribution , in essence passing it

right through , as it is , with its original Gamma 1.0

Because of this last part ( Which is at the heart of the reasons why you choose to do a Lineal Processing ) the

image will have a visual aspect that is Lineal , but with the uncompensated Monitor Gamma of 2.2 Riding on it skewing the

Midtones to the Left . (Remember Gamma is the slope of the Levels Curve at its Midpoint ). So Yes , you have to either

Reinstate the Gamma Encoding that you removed early in the Game ,where it hurt the most , or do a Manual

Tone Mapping ( This is better ) Either way you are doing it after the image have already been built from the maximum

data available , which is the point where any Tweaks will hurt the least.( All Tone Manipulations produce data Loss, so you want to

delay them until after the Image has already been created from the RAW Data into 3 RGB channels , on which the Color Balance will be

based upon )

This last part ,Tone Mapping , is something that every good artist would always do to every image , regardless of it

being Linear or Not , to account for each image needs, that are , obviously , different all the time.

The great benefit of this Lineal Processing is that it enables you to use all the Data captured ( Applying

Gamma different than 1.0 ,always shrinks the Tonal Range ) and because the High tones are up to this point ,untouched

, they can deliver a lot more detail ( Shrinking the upper tones means the tonal differences are minimized between

adjacent tones , therefore detail suffers) . This is a good thing because our eyes are less sensitive to detail in

bright lights .

At the end , when your are satisfied with your image , save it as a Master Image in PSD format , then convert it to

Adobe sRGB color space , change image to 8 Bit mode and save it again as JPEG with a

compression of 6 , for web display.

The end result is , like you said "A much better and more accurate looking rendering"

P.S. Roger I am creating a small tutorial using another , similar ,image of the same Scene , that will include a link to

download the RAW file .The other image is already part of <a href="http://www.photo.net/photos/Luis-A-Guevara">my Fine Art Gallery</a>

right here at photo.net . My RAW files are X3f files from a Sigma SD9 camera and Leica lenses , so you will have to

use either Lightroom or Photoshop to do the conversion.

More on this will follow soon.Luis

Tim_Lookingbill · October 28, 2008

Luis,

Thanks for the explanation.

I was wondering if you could post the image with just the assigned custom linear ProPhoto RGB profile before any edits so we

can see how much work is involved in this process. I'm amazed at the local contrast detail in the image you posted and I want

to see if it's due to working on the linear data or if you used Highlite/Shadow tool or some kind of sharpening routine.

Also wondering if you're able to bypass the traditional raw converter's internal color table this way and work strictly from the

RGB ratios straight off the demosaiced sensor data. I'm assuming you must be getting different hue/saturation results by

assigning linear ProPhoto RGB to linear data in Photoshop over what you'ld get from a traditional raw converter.

Just liked to see how much off it is.

luis-a-guevara · October 28, 2008

<h2>LINEAL RAW PROCESSING</

©LUIS A GUEVARA luis@sigmacumlaude.com

</h2>

This is one of the most elusive Digital Concepts , because ,when seen globally , all Digital Processing

Systems are Lineal. Otherwise the images we make will not make any sense to us.

We expect a Scene to look the same way whether we look at them through a window , through a Roof mounted

Video camera , at the Computer Screen or in a Print hanged in the wall . This would not be possible if their overall

processing systems did not respect all the tonal relationships of the Scene , such as color balance , Illumination

Dynamic Range , Contrast , Sharpness ,etc. When it does , we say that the system is Lineal and that there are no

distortions introduced by the process itself.

In practice our systems are lineal to a degree that we call "Realistic", and we recognize that some

combinations of Hardware and Software brands produce better "Image Quality" or that there is an

improved "Realism" in their resulting images.

Finally when dealing with this kind of elusive concepts , we can reach another plateau in the Image

Reproduction arena, that is referred to as "Three Dimensionality".

When the image quality achieved is so highly realistic we say that it has achieved "Three

Dimensionality" , that is ,it can fool the eye into believing that is real.

The European <a href="http://en.wikipedia.org/wiki/Renaissance" target="_blank">Renaissance</a> painters

refereed to this concept ,as "<a href="http://en.wikipedia.org/wiki/Trompe_l’oeil" target="_blank">Trompe-l'œil

</a>" (trick the eye")

<h3>So what do we mean by Lineal Processing as opposed to Lineal Systems?</h3>

Simple. Although as a whole all the elements of an Imaging System behave Linearly , their individual

Components are mostly Non Lineal , but their non linearity has been compensated at different points to achieve the

final desired overall System Linearity. The tool used to do this is called Gamma Encoding.

Gamma is nothing but the slope of a function graph that describe the relationship between the input and the

output of a system or a system element.

<img src="http://www.sigmacumlaude.com/LINEAL ROOT/gamma.gif" alt="Gamma" width="250" height="234" /

>The image shown is a Monitor Gamma Curve that is definetily non linear and non uniform

Gamma 1.0 , on the other hand ,means that the output divided by the input equals ONE. No transformation

takes place , and we call it LINEAL. The output equals the input.

We certainly want linearity in all our overall systems , be they music amplifiers or Digital Cameras .However in

Digital Imaging this is harder to achieve because our Computer Monitors , Cameras LCD Displays , and all Printing

Devices are Highly Non Lineal . Monitors for example have a Gamma of 2.5 and more, but our

Camera Sensors are very Lineal with a Gamma very close to 1.0 , so how do we conciliate this disparity ?

Simple , again , but largely unknown to most people, in spite that this has been with us since the creation of

Video Cameras :

<h4 class="style1"> An artificial Gamma Correction is introduced to the Captured RAW Data that is exactly the

inverse of the Display Gamma so that the overall effect is that they cancel each other out.</h4>

Since today imaging systems operate within Standardized Color Spaces , each one designed with its own

Target Display Gamma , of which the most ubiquitous is the sRGB Color Space that was designed to represent the

Gamma of the Average , Uncalibrated , PC CRT Monitor , of Gamma 2.2 , then the inverse of this 1/2.2=0.45 , is applied, as a transformation function, to the RAW data ,DURING ITS CONVERSION from

RAW DATA to Displayable Image File .

This is done in the RAW developer, as a first step , right before before any other necessary processes of the

conversion from data to image ,have taken place.The following graphic

illustrates how the two ,opposite curves combine , mathematically, to produce a Mean Value of 1.0 , the straight

Gray Line you see in between .

<img name="" src="http://upload.wikimedia.org/wikipedia/en/5/5a/Gamma06_600.png" width="529" height="479"

alt="" />

<a href="http://en..org/wiki/Gamma_wikipediacorrection" target="_blank">http://en.wikipedia.org/wiki/

Gamma_correction</a>

That is ,our RAW Data that was Linearly captured ,thanks to the painstaking efforts of the Sensor

Designers , is artificially DISTORTED when and where it hurts the most , right before Color Channels and Color

Balance are created from it.

The RAW file is just a Matrix of Data with no Color Channels , Color Spaces or even Color , for that matter.It is

not an image file. For more on RAW , please see my article "The Raw Story" at: <a href="http://

www.sigmacumlaude.com/The_Raw_Story.aspx" target="_blank">http://www.sigmacumlaude.com/

The_Raw_Story.aspx</a>

<h3> SO , WHAT IS THIS LINEAR PROCESSING AGAIN? </h3>

Simple. I am sure that you will agree that is simple. Linear processing is avoiding the introduction of this Inverse

Gamma at the point where it hurts the most ,to reintroduce later, where it hurts the least ,as one of the last steps of

the Image Optimization , rather than at the Image Creation. A big substantial

Difference.

Of course we must reintroduce it , to achieve again the necessary overall System Gamma of 1.0. If we don't ,

we will end up with an image that possess the same Gamma as the display does , that is G2.2 , which for most

people is VERY DARK AND CONTRASTY and TOTALLY UNUSABLE. ( Please take a mental note of this ,

because when you process Lineal Images and you forget to reintroduce the compensating Gamma of 0.45 , your

image will be like that , dark and concentrated at the lower tones.)

For example , this is a RAW image , converted into a LINEAL Photoshop file,that was opened without

assigning it a Custom Lineal Profile. As you can see because is missing the Gamma encoding , the image looks

dark , because nothing is counteracting the Monitor Gamma.

As you can see its color settings are indicating sRGB , my preference as a Workspace for

those images that don't come with a Gamma Tag. SRGB has a Gamma of 2.2 , so we end up

with 2.2 + 2.2 = 4.4 , instead of the desired Gamma 1.0 . No wonder it looks so dark and Contrasted.

<img src="http://www.sigmacumlaude.com/LINEAL ROOT/CUSTOM PROFILE 1 STEP a.jpg" width="1049"

height="694" />

When I change it to Adobe Prophoto , that has a Gamma of only 1.8 , as seen here , the Colors get better , but theTones , although slightly brighter ,are still wrong and harsh .Detail is

poor in the HIGHLIGHTS and barely acceptable in the Mid Tones . But clearly we are moving in the right direction.</

p>

.<img src="http://www.sigmacumlaude.com/LINEAL ROOT/CUSTOM PROFILE STEP 3.jpg" width="1049"

height="694" />

NOW THIS IS THE SAME IMAGE , AFTER CHANGING THE PROFILE TO MY CUSTOM PROFILE , THAT I

HAVE NAMED AS "LINEAR PROPHOTO" As you can see here the Custom Profile is nothing but a

Prophoto RGB profile where the Gamma was changed to 1.0:

<img src="http://www.sigmacumlaude.com/LINEAL ROOT/CUSTOM PROFILE STEP 4.jpg" width="1049"

height="694" />

This a very impressive Visual difference , that comes from the fact that all instructions that the camera writes

to the Metadata of the RAW file have been stripped from it , by my LINEAL CONVERTER OF

CHOICE ,<a href="http://www.frostyplace.com/dcraw/index.html"> "DCRAW-X"</a>

This 16 Bit Photoshop PSD file was created, directly, in Adobe PROPHOTO RGB Color Space , without even

opening the image in a Viewer , so that I could quickly get to open it in Photoshop in the most Pristine condition

possible.

Some people do not believe this , so here you have a screen shot of the RAW file Metadata , as presented by

Photoshop CS4;

This is the Metadata of the Lineal PSD image .It is very short containing mostly creation information Please

notice how both Photoshop and Camera RAW frames are showing the File number IMG30989.psd :

<img src="http://www.sigmacumlaude.com/LINEAL ROOT/Pasted Graphic 1.gif" width="850" height="829" /></

p>

FOR COMPARISON , HERE IS THE EXTENSIVE METADATA FOR THE SAME IMAGE , THIS TIME AFTER

A NON LINEAL , ORDINARY <a href="..">A.C.R</a>. CONVERSION: ,

YOU CAN CLEARLY SEE ALL THE EXTRA INSTRUCTIONS , HIGHLIGHTED IN BOLD, and

the file number in RED

<?xpacket begin="" id="W5M0MpCehiHzreSzNTczkc9d"?>

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THIS SECOND METADATA EXAMPLE IS SO LONG THAT I COULDN'T MAKE A SCREEN SHOT OF IT AND

HAD TO COPY AND PASTE , INSTEAD.

So the point that I am trying to make is that when Utmost Image Quality matters , linear processing is the way

to go. Lineal Image Converters , like dcRAW-X and others , not only remove Gamma but also , Compression ,

Sharpening ,De noising , Anti aliasing and Interpolation. What you want is that your color channels are made from

data that has been touched the least . Ideally ,not touched at all.

All this , Compression , Sharpening ,De noising , Anti aliasing and Interpolation, can be best done tailored to the

image type, under the control of the Artist and not by invisible factory presets that only work for Generic ,Average

Scenes.

If you want to download the 7 MB IMG30989.X3F Zip file, to try all this by yourself , please <a href="http://

www.sigmacumlaude.com/LINEAL ROOT/IMG30989.X3F.zip">click here</a> , but please remember that all this

document is copyrighted.

roger_smith4 · October 28, 2008

The image 30989.x3f looks like a very different image than the one you posted in this thread. Is that intentional? It also appears to be somewhat blown out. I don't see this image anywhere in your photo.net or pbase or deviantart gallery to compare your processing with mine.

Am I missing something?

Your images are very strong, by the way.

I'd really love the raw version of the image at the top of this thread to compare.

frans_waterlander · October 29, 2008

Luis,

I hate to rain on your parade, but something doesn't add up in your story. If as you say "linear processing workflows compress the shadows and devote the rest of the Color Space to Midtones and highlights" then, if further processing is applied correctly (meaning the finished image should show no changes in tonality and color as compared to "normal" processing) this would result in less posterization/more detail in the midtones and highlights at the expense of more posterization/less detail in the shadows. However, that's not what your examples show; they show dramatic differences in tonality and color; that's NOT what linear processing should result in. Somewhere along the line you are introducing these dramatic changes in tonality and colors and either a) that's unintended but needs to be resolved or b) you want that in addition to the linear processing characteristics but then you would need to make that abundantly clear. As is stands right now, you are causing changes you don't realize or you are not telling the whole story.

Tim_Lookingbill · October 29, 2008

Luis,

Good work. I take it this was your tutorial you were planning on posting.

The only raw converter I have where I can actually get this dark linear unprocessed rendering is in Raw Developer (Mac only).

Its core algorithms were built upon DCRAW. I never thought of using RD's Unprocessed setting because I didn't know what

source profile to assign because I was with the understanding that digital sensors have no color space. I'm going to give it a try

on one of my own Pentax PEF's and see what I get.

I can't find a setting in ACR 3.7, the only version I have at the moment which came with CS2 that gives the same dark

rendering as Raw Developer.

What peaks my interest in your process is the unusual and quite unique and beautiful color renderings in the images here and

in your gallery and was wondering if this is due to the linear process, dcRAW-X or the camera sensor RGB spectral response

and lens combo.

However, what I don't understand about your images is why there are so many posterization artifacts along high contrast

edges and within tonal transitions in out of focus bokeh backgrounds.

luis-a-guevara · October 29, 2008

Hi again Tim .

Good work. I take it this was your tutorial you were planning on posting.

The only raw converter I have where I can actually get this dark linear unprocessed rendering is in Raw Developer (Mac

only). Its core algorithms were built upon DCRAW. I never thought of using RD's Unprocessed setting because I didn't know what

source profile to assign because I was with the understanding that digital sensors have no color space. I'm going to give it a try on one

of my own Pentax PEF's and see what I get.

</blockquote>

Thanks . The setting for conversion in ACR is buried as an option for SAVING as DNG ! While you are in the Conversion Screen ,

click "Save Image..." at the bottom and the "Save Options " will pop up.

Choose Format > Digital Negative andnew options will appear for DNG , that are "Embed Original

RAW" ,or "Convert to Linear Image"B , as you can see highlited in Yellow here:

Nobody knows exactly what they mean by "Lineal Image" since Adobe is very Cryptic about it. To me Lineal means not

only NO GAMMA , but no Compression , Sharpening ,Denoising ,

Antialiasing and no Interpolation, as well as no Vignetting or Chromatic corrections .

This is the only way that our color channels can be made from undisturbed data , meaning that it has been touched the least .

Ideally ,not touched at all.

I can't find a setting in ACR 3.7, the only version I have at the moment which came with CS2 that gives the same dark rendering as

Raw Developer.

Like I said I use DCRAW-X , a free Lineal Converter for MacIntel that does strip Gamma and Color profiles. You can download it for

free at <a href="http://www.frostyplace.com/dcraw/index.html">http://www.frostyplace.com/dcraw/index.html</a>

What peaks my interest in your process is the unusual and quite unique and beautiful color renderings in the images here

and in your gallery and was wondering if this is due to the linear process, dcRAW-X or the camera sensor RGB spectral response and

lens combo.

</blockquote>

Well , clearly, the image quality of the Foveon sensor ,paired to Leica or other German lenses , is much superior to unmodified

cameras or Bayer sensor, in terms of 3 Dimensionality and richness of color, and that is why I sell Converted cameras and Mount

Replacement kits at <a href="http://www.sigmacumlaude.com">Sigma Cum Laude</a> , but as your intuition is telling you

this Synergetic combination only comes alive with Linear processing .

However, what I don't understand about your images is why there are so many posterization artifacts along high contrast

edges and within tonal transitions in out of focus bokeh backgrounds.

</blockquote>

I have not seen any of this , but it could be that I am using a Color Managed Browser at a 24 Million Colors depth ,on Mac OSX

Leopard , with a Color calibrated 23inch Apple Cinema Monitor . Some of my images are very large , in the order of 900 mB , and when

compressed as JPEG do suffer a lot . Unfortunately there are no ways around that.However do look at your Display preferences to see

if you are in Millions or only in Southends. Many Mac models use main memory shared with the Monitor , so if you are low on it it might

automatically bring down the Display Resolution.

Tim_Lookingbill · October 29, 2008

Well I gave it a try and it seems Raw Developer's creator Brian Griffith's internal color table profile is more accurate in

rendering skintone and other primary colors for my Pentax K100D PEF's. I could not get Luis's color style in my renderings, so

it's probably due to a combination of his camera's Foveon sensor, lens and dcRAW-X native output profile. Not sure.

In email exchanges with Brian Griffith, Raw Developer's creator, I was discussing creating my own source profile using RD's

custom ICC color matrix profile creator and Brian indicated that the color space of my Pentax, according to his research on

Japanese based Bayer sensors, was closer to NTSC. And he was kind of right. I found assigning a linear version of Joseph

Holmes Ekta Space RGB gave more accurate looking results than a linear NTSC on the majority of images. Assigning linear

ProPhoto RGB gave the typical over saturated magenta hue to skintones to my PEF's.

The only advantage using linear process for me is being able to use better color and tonal editing tools and faster live preview

updating in Photoshop over doing it in Raw Developer but I don't have access to RD's noise and chroma artifacts tools which is

very useful.

Tim_Lookingbill · October 29, 2008

You haven't seen these artifacts?

Here's two screenshots of images in your gallery as viewed on my i1 Display calibrated 20" G5 iMac with S-IPS panel in Mac OS

10.4.11 in Safari:

Tim_Lookingbill · October 29, 2008

Whoops! Some kind of server glitch occurred. Here goes again.<div>

00RK81-83623684.jpg.c93ea00141fbb8c415619dab698cdc4a.jpg

</div>

Tim_Lookingbill · October 29, 2008

Here's the second one...<div>

00RK84-83623784.jpg.9a29934d7918be4250270a838a8d82a8.jpg

</div>

luis-a-guevara · October 29, 2008

You haven't seen these artifacts?

Sorry those images were not converted using a linear process . But I will make it a point to develop those two in DCraw-X and

present the results a some point.

luis-a-guevara · October 29, 2008

Roger Smith , Oct 28, 2008; 09:24 p.m.

The image 30989.x3f looks like a very different image than the one you posted in this thread. Is that intentional? It also

appears to be somewhat blown out. I don't see this image anywhere in your photo.net or pbase or deviantart gallery to

compare your processing with mine.

Am I missing something?

Your images are very strong, by the way.

I'd really love the raw version of the image at the top of this thread to compare.

Roger like I said that image is already in my Fine Art Gallery so I decided to give everybody a chance to work on a

new image , before I presented you with my own rendering of it.

You are not missing anything , Lineal RAW images will enable you to utilize the FULL DYNAMIC RANGE that you

captured , so that gives you an extra Stop of room over the highlights that you can , and SHOULD capture by adding

extra exposure , unless you wanted them waisted as usual. So all my images have an intentional , lets call it

overexposure , of about 2/3 of a stop , because they are intended for Lineal processing.

From the point of view of Lineal Processing that is PROPER EXPOSURE , but if you process it normal it will look

overexposed because it is HITTING THE LIMITS OF THE CONVENTIONAL PROCESS.

Frans Waterlander , Oct 29, 2008; 12:21 a.m.

Luis,

I hate to rain on your parade, but something doesn't add up in your story. If as you say "linear processing

workflows compress the shadows and devote the rest of the Color Space to Midtones and highlights" then, if

further processing is applied correctly (meaning the finished image should show no changes in tonality and color as

compared to "normal" processing) ........

</blockquote>

DONT WORRY FRANS , YOUR POINTS ARE WELL TAKEN and they are indeed indicating that you are taking my

statements seriously and ,thinking hard

What happens here has to do with the fact that the order of things in the process DOES have an influence on the

outcome . I explain:

DEMOSAICING , or the creation of the 3 color channels. is done NOT FROM THE ORIGINAL CAPTURED DATA

but from DATA THAT HAS ALREADY BEEN ALTERED by GAMMA . It is from this , somewhat distorted Color

Channels that Color Balance will be determined. more so ALL THE SUBSEQUENT STEPS OF IMAGE CONVERSION

will build on this Gamma encoded Data , incrementing the deviation , since every step is modifying data that was

already modified by the previous step.

All Sensors will go through Interpolation of the 3 Color Channels , Anti Aliasing filtering , and , to counteract it, some

degree of Sharpening , followed by Contrast and Saturation enhancements , before finally compressing the data into the

chosen camera Color Space, as a RAW data file.

If you apply Gamma AFTER the Demosaicing and color balance have taken place you will have a very different result

because all this

additive deviations from the original data,will be acting on pristine data. If you remove Gamma and leave out

Compression and Color Space

you will achieve greater dynamic range with more highlight detail and richer color .

However, that's not what your examples show; they show dramatic differences in tonality and color; that's NOT

what linear processing should result in. Somewhere along the line you are introducing these dramatic changes in tonality

and colors and either a) that's unintended but needs to be resolved or b) you want that in addition to the linear

processing characteristics but then you would need to make that abundantly clear. As is stands right now, you are

causing changes you don't realize or you are not telling the whole story.

</blockquote>

On the contrary . Your statement reflects that you are taking Linearity as something that should be happening

between the final image and the initial image, and therefore because the RAW file I provided , as seen

through your processing looks very different to my final image you think it is not lineal , however the Linearity I

am interested on is in reference to the original Scene , the RAW file is just a means to an end. You cannot

possibly know the validity of this , because you never saw the scene. If we were just interested on being

faithfull to the way our RAW files look ,we will not be looking into this or any other process and we will be all happily

busy doing conversions the old way.

The confirmation of the advantages of lineal processing lies in the fact that you CANNOT arrive to the same rendering

of tones I made from that RAW file , unless you process it Linearly and Display it using a Lineal Prophoto Profile of

Gamma 1.0

....................this would result in less posterization/more detail in the midtones and highlights at the expense

of more posterization/less detail in the shadows.

This is an exellent point and very valid one . A 12 Bit Linear binary file of recorded intensity values will have 2048

levels available for the upper highlight stop , that if you can use it, (And you can if you use Linear processsing) will give

you a lot of tones for very delicate highligts with lots of detail and color nuances, but at the other end of a typical Six

stop Dinamic Range , you will only have 64 Tones to describe your shadows , leading to posterization and loss of detail

in the shadows.

That is why my opening statement was :

"Some images carry their message in their lower tones and some do it with their midlle tones and

highlights, like this one:

Normal RAW processing spreads the image tones evenly across its Dynamic Range , thus , abnormally

,compressing the highlights and expanding the Shadows , something that will not work well with this type of imagery

.

Linear processing workflows , instead ,compress the shadows and devote the rest of the Color Space to

Midtones and highlights making it the perfect Complement to this type of imagery ,that results from frontal

lighting."

Image IMG30989.X3F is another image carrying its message with its upper tones and therfore benfited in an

inimitable way from Lineal Processing:

<img name="" src="http://www.sigmacumlaude.com/for forum/IMG30989FinalCropped W logo .jpg"

width="1180" height="1150" alt="" />

</blockquote>

frans_waterlander · October 29, 2008

Luis,

You have not convinced me one bit. The 2 side-by-side images early on in this thread show tremendous color and tonality shifts. So, either your first image is the most true to reality and the second one, obtained with linear processing, shows horrendous color and tonality shifts or the second image is the most true to reality and the first one, obtained with "normal" processing, shows horrendous color and tonality shifts. So what it comes down to is that either your "normal" process is way out of whack or your linear process is way out of whack.

This also would mean that untill you find out which process is out of whack your comparison between the two processes is meaningless.

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