Why open a Jpeg in a RAW PP like ACR

Ed Grenzig · Feb 23, 2008

Andrew
This is a great link with tons of useful information on DNG.
I just spent 1 hr reviewing some of it and have a lot of reading to do.

I am now starting to see and understand the difference between RAW mosaic (CFA), demosaiced RAW (linear DNG (possibly rgb)) forms of image data.
Very interesting information.
Thanks again for the link.
Ed

andrewD2 said:
http://www.barrypearson.co.uk/articles/dng/linear.htm

Its a good question you ask ed although probably more important if
you are actually converting jpgs to dng files rather than just
working on jpgs in ACR (so you know what programs can use them).
If you are working on them directly in ACR it doesn't matter so much
if there is an internal conversion before applying of settings.

I'm not sure I fully understand what you are trying to explain in the above 2 comments. Any clarification will be appreciated.--Ed

andrewD2 said:
Andrew

andrewD2 · Feb 23, 2008

Ed Grenzig said:
Ed Grenzig said:

Its a good question you ask ed although probably more important if
you are actually converting jpgs to dng files rather than just
working on jpgs in ACR (so you know what programs can use them).
If you are working on them directly in ACR it doesn't matter so much
if there is an internal conversion before applying of settings.

Click to expand...

I'm not sure I fully understand what you are trying to explain in the
above 2 comments. Any clarification will be appreciated.--Ed

Just that there are more practical concerns if you are converting from jpg to linear DNG and storing your files in that form. Implications for filesize and having to make sure all your software can read that format. Can Photomatix for example?

Andrew

Jeff Schewe · Feb 23, 2008

Ed Grenzig said:
Can you site any references which state the DNG file is a linear RBG
file. My references state that the data contained in a DNG file is
RAW data either in mosaic (CFA) form or in demosaiced form.

Considering that Z works on the Camera Raw engineering team, I'm pretty sure he doesn't need to "site" anything when he tells you that a DNG saved out of Camera Raw (or Lightroom) is doing so in a linear gamma, RGB form. Now, if you mean "cite" then I suppose Z could actually tell you where in the code is was : )

When you convert raw files, you have the opportunity to convert the file either as an undemosiced raw file or a linear demosaiced file. The demosiaced file is a rendered file and thus no longer "raw" but since it's not yet in a gamma space has a lot more flexibility to additional processing.

That's the process CR & LR take when processing a jpeg (or tiff) out as a DNG file...it ain't "raw" but high bit depth, linear RGB file.

However, considering the optimal nature of Camera Raw's processing pipeline, doing tone & color correction to a jpeg inside of Camera Raw can end up producing arguably better processed images than if you left the jpeg as a jpeg and processed in Photoshop...so, for that reasons and the other mentioned by Z, using Camera Raw (or Lightroom) to process camera jpegs can be a workflow enhancement.

--
Regards,
Jeff Schewe

Ed Grenzig · Feb 23, 2008

Jeff Schewe said:
Ed Grenzig said:

Can you site any references which state the DNG file is a linear RBG
file. My references state that the data contained in a DNG file is
RAW data either in mosaic (CFA) form or in demosaiced form.

Click to expand...

Considering that Z works on the Camera Raw engineering team, I'm
pretty sure he doesn't need to "site" anything when he tells you that
a DNG saved out of Camera Raw (or Lightroom) is doing so in a linear
gamma, RGB form. Now, if you mean "cite" then I suppose Z could
actually tell you where in the code is was : )

I apologize if I came across as testing Z's knowledge. It was not my intent, and I was unaware of his credentials.

Jeff Schewe said:
When you convert raw files, you have the opportunity to convert the
file either as an undemosiced raw file or a linear demosaiced file.
The demosiaced file is a rendered file and thus no longer "raw" but
since it's not yet in a gamma space has a lot more flexibility to
Additional processing.

I had a gut feeling that this may be the case, but not enough knowledge on the subject to be certain. It makes sense and I have learned a lot from your post, as well as other posters in this thread.

Jeff Schewe said:
That's the process CR & LR take when processing a jpeg (or tiff) out
as a DNG file...it ain't "raw" but high bit depth, linear RGB file.

Yea, I am understanding this difference now, but not when I started the thread. This is what I wanted to learn. So thanks for the clear understanding.

Jeff Schewe said:
However, considering the optimal nature of Camera Raw's processing
pipeline, doing tone & color correction to a jpeg inside of Camera
Raw can end up producing arguably better processed images than if you
left the jpeg as a jpeg and processed in Photoshop...so, for that
reasons and the other mentioned by Z, using Camera Raw (or Lightroom)
to process camera jpegs can be a workflow enhancement.

You present very good and important information in this paragraph. I do not think many of the forum readers appreciate this advantage that you point out. I thought this may be the case, but again was not sure, based on my limited image data processing knowledge.

You are very clear and concise in your explanations, are you a technical writer?

Thanks again,
Ed

Jeff Schewe said:
--
Regards,
Jeff Schewe

Ed Grenzig · Feb 23, 2008

Z

Jeff pointed out to me that you work on the Camera Raw engineering team, and have extensive knowledge on the subject matter. I also interpreted his comment to indicate that I may have been testing, or questioning your knowledge of the posted subject, by asking for references and/or articles, as in my post below.

I apologize if my reply was possibly presented in this fashion, since it was not intended this way. I will certainly be more careful in the future, when choosing my words.
Thanks for your time spent.
Ed

Ed Grenzig said:
Z (is real) said:

The purpose of working on JPEG and TIFF in Camera Raw and Lightroom
is the workflow. If you like the workflow of those applications,
being able to use them regardless of the file format you have is an
advantage. (E.g. many compact digital cameras only support JPEG and
not a raw format. We wished to allow people who shoot with those
cameras to use Lightrom.)

Saving out JPEG as DNG is not particularly winning as the file size
will be much bigger. The way it works is that the JPEG data is
converted to a linear RGB DNG.

Click to expand...

Can you cite any references which state the DNG file is a linear RBG
file. My references state that the data contained in a DNG file is
RAW data either in mosaic (CFA) form or in demosaiced form. See my
above post
http://forums.dpreview.com/forums/read.asp?forum=1006&message=26902811
What is a linera RGB file?

Ed Grenzig · Feb 23, 2008

Jim

I appreciate your response.

For your better understanding for the reason of my post, what I am also trying to learn and understand is the following:

Digital images can exist in many different formats such as, RAW, linear RGB (possibly high bit depth, linear RGB), RGB, CMYK, Lab, and possibly others ( I am still learning so I am sure there are other formats). When we now perform PP adjustments to our images, which image formats are the best for which type of PP adjustments that we wish to make? Can we convert our image data between these various formats (with or without loss of data?) to take advantage of the best PP results.

Jeff started to touch on this with his comment:

Jim Hess said:
However, considering the optimal nature of Camera Raw's processing pipeline, doing tone & color correction to a jpeg inside of Camera Raw can end up producing arguably better > processed images than if you left the jpeg as a jpeg and processed in Photoshop...so, for that reasons and the other mentioned by Z, using Camera Raw (or Lightroom) to process > camera jpegs can be a workflow enhancement.
Regards,
Jeff Schewe

As you can see, Jeff states that “tone and color” correction can yield arguably better results when performed on our image data in "linear RGB" format (in ACR)than when performed on an RGB format in(PS). To me, this is important and very useful information.

This is why I am trying to understand more about opening jpeg’s in ACR, and how this affects the image data. Jeff, Z ,you, and others have cleared a lot of this up for me.
Thanks ---Ed

Jim Hess said:
With the advent of ACR 4.0, it is no longer just a raw editor. It
goes far beyond that. ACR uses the same engine as Lightroom, and so
that expands the capabilities that it has.

Just because ACR opens a JPEG or a TIF image that does not make that
data raw image data. Particularly in the case of JPEG images, the
data has already been highly compressed and reduced to 8 bits.
However, because of what happens when a JPEG image is saved by the
camera, JPEG images don't even have the full 8 bits of data. Raw
images are typically 10 bit, 12 bit, and there are now a few cameras
that produce 14 bit raw images. The advantage of this is there is so
much more image data that it is possible to recover more highlights
and shadows than is possible to do in a JPEG image.

When you open a JPEG image into the ACR environment, you are
introducing it into a 16-bit ProPhoto environment. In this
environment is possible to do adjustments without doing any more
damage to the image. But you are still editing image data that has
been highly compressed, and had other in-camera processing applied to
it. You have actually baked the white balance and the JPEG gamma
into the image. Yes, I understand that you can adjust the white
balance on JPEG images in ACR, but it's more limited just like
everything else in more limited. You will never have the flexibility
and depth of adjustment available to you that you have when working
with raw images taken by the camera.

What I have written here is a condensation of information from the
book I have mentioned in previous threads. The book also says that
they haven't decided if editing JPEG and TIF image is in the ACR is a
good thing. But since Lightroom offers that capability Adobe decided
to allow it in ACR as well.

Personally, I like using ACR on my JPEG images. But it's ludicrous
to even think that the data is raw data just because it is opened in
ACR. It isn't. It's all about workflow and being able to apply
adjustments to many images at the same time. If ultimate image
quality is your goal, then you should shoot raw images in the first
place so you can take full advantage of everything ACR has to offer.

Jim Hess · Feb 23, 2008

Ed,

I don't know if you are aware, but Jeff (who has given you some excellent answers) is the author of the book I have suggested that you get. Well, to be precise, he is the one who revised the book for CS3. Bruce Fraser was the original author, but I'm afraid he lost a battle with cancer.

Anyway, the book provides so much good information that I have seen it suggested that the book is a must for anyone who is serious about shooting raw images and using ACR. I realize that some of my answers are not complete. But that is because I don't fully understand all the intricacies yet. When I realized that Jeff had entered the discussion I wanted to hide because I may have made things a little too simplistic. But get the book. It isn't huge. I purchased mine at Borders book store using a 40 percent off coupon, and it cost me less than $30.

Jeff Schewe · Feb 23, 2008

Ed Grenzig said:
You are very clear and concise in your explanations, are you a
technical writer?

Well, I did coauthor Real World Camera Raw for Photoshop CS3...so yeah, I guess I count as a technical writer...

; )

The ability to process jpegs & tiffs really started in Lightroom before Lightroom and Camera Raw's pipelines were joined. While it DOESN'T give as much flexibility and latitude as processing actual raw files, the advantages of the pipeline are that ALL of the resulting image adjustments are made at once in an optimal order inside the CR/LR pipeline and allows for non-destructive, parameteric edits of jpegs & tiffs.

But note that once originally processed out of the camera as jpegs, the white balance and gamma curves are baked it so you don't have as much power to edit extreme highlight detail as you would with actual raw files. So, while Camera Raw does offer workflow and optimized editing of jpegs & tiffs, it doesn't alleviate the fact that jpegs are already baked images. For max flexibility, I would still suggest shooting raw files where possible.

--
Regards,
Jeff Schewe

Ed Grenzig · Feb 24, 2008

Jim

I did not know it until Jeff stated this in his 2nd post. I did notice how clear, concise and to the point he was, in his first post, which is a rare and unique quality. His wording displayed a sense of extensive knowledge and confidence on the subject. So I guess it’s all coming together for me now. (Should I ask for another reference? Only kidding!, Ha!)

I am definitely going to look into the book “RealWorld Camera Raw with Photoshop CS3”. I do enjoy digital imaging technology very much and would like to learn more. Hopefully this book will also touch on my question about PP in different image formats, for the best PP results.
Regards,
Ed

Jim Hess said:
Ed,

I don't know if you are aware, but Jeff (who has given you some
excellent answers) is the author of the book I have suggested that
you get. Well, to be precise, he is the one who revised the book for
CS3. Bruce Fraser was the original author, but I'm afraid he lost a
battle with cancer.

Anyway, the book provides so much good information that I have seen
it suggested that the book is a must for anyone who is serious about
shooting raw images and using ACR. I realize that some of my answers
are not complete. But that is because I don't fully understand all
the intricacies yet. When I realized that Jeff had entered the
discussion I wanted to hide because I may have made things a little
too simplistic. But get the book. It isn't huge. I purchased mine
at Borders book store using a 40 percent off coupon, and it cost me
less than $30.

Ed Grenzig · Feb 24, 2008

Jeff

Thanks for your reply and taking the time to clearly explain the technical points as you have.

I am going to take a close look at “Real World Camera Raw for Photoshop CS3” since it sounds very interesting, as well as recommended by others.

A quick Google search on your name has indicated quite an extensive back ground and present involvement in the digital imaging arena. I am a little embarrassed that I was not familiar with your extensive involvement, but I am very new to this field. I am sure I will find a lot of other material to reference, that you have been involved with. So please excuse my ignorance in previously asking “are you a technical writer?” (Well, it probably got a few chuckles!)
Thanks again.
Ed

Jeff Schewe said:
Ed Grenzig said:

You are very clear and concise in your explanations, are you a
technical writer?

Click to expand...

Well, I did coauthor Real World Camera Raw for Photoshop CS3...so
yeah, I guess I count as a technical writer...

; )

The ability to process jpegs & tiffs really started in Lightroom
before Lightroom and Camera Raw's pipelines were joined. While it
DOESN'T give as much flexibility and latitude as processing actual
raw files, the advantages of the pipeline are that ALL of the
resulting image adjustments are made at once in an optimal order
inside the CR/LR pipeline and allows for non-destructive, parameteric
edits of jpegs & tiffs.

But note that once originally processed out of the camera as jpegs,
the white balance and gamma curves are baked it so you don't have as
much power to edit extreme highlight detail as you would with actual
raw files. So, while Camera Raw does offer workflow and optimized
editing of jpegs & tiffs, it doesn't alleviate the fact that jpegs
are already baked images. For max flexibility, I would still suggest
shooting raw files where possible.

--
Regards,
Jeff Schewe

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