Opening raw files in CS

J
Posted By
jytzel
May 23, 2004
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908
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I was wondering if there is any benifit of using CS RAW dialogue for correcting raw images (contrast, exposure, etc.) Would it jus be better, or at least the same, not to use any of those corrections and applying the ordinary corrections (curves, levels, etc.) in Photoshop?

thanks

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L
Lionel
May 23, 2004
Kibo informs me that (Jytzel) stated that:

I was wondering if there is any benifit of using CS RAW dialogue for correcting raw images (contrast, exposure, etc.) Would it jus be better, or at least the same, not to use any of those corrections and applying the ordinary corrections (curves, levels, etc.) in Photoshop?

In general, it’s better to do as many of your adjustments as possible in the RAW dialog. The advantage is that the RAW converter has more data available to it at that point, & it get stripped out when the image is transferred to the main program.


W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est —^—-^————————————————— ————
AM
Alfred Molon
May 23, 2004
Jytzel wrote:
I was wondering if there is any benifit of using CS RAW dialogue for correcting raw images (contrast, exposure, etc.) Would it jus be better, or at least the same, not to use any of those corrections and applying the ordinary corrections (curves, levels, etc.) in Photoshop?

In my opinion it’s best to do all optimisations before JPEG compression. Besides if you optimise the RAW file all optimisation parameters (WB, exposusre, shadows, contrast, etc.) are stored in the Exif data and can be retrieved later – something you cannot do if you optimise with ordinary corrections.


Alfred Molon
——————————
http://groups.yahoo.com/group/Olympus_405080/
Olympus 5050 resource – http://www.molon.de/5050.html
Olympus 5060 resource – http://www.molon.de/5060.html
Olympus 8080 resource – http://www.molon.de/8080.html
J
jytzel
May 23, 2004
Lionel …
Kibo informs me that (Jytzel) stated that:

I was wondering if there is any benifit of using CS RAW dialogue for correcting raw images (contrast, exposure, etc.) Would it jus be better, or at least the same, not to use any of those corrections and applying the ordinary corrections (curves, levels, etc.) in Photoshop?

In general, it’s better to do as many of your adjustments as possible in the RAW dialog. The advantage is that the RAW converter has more data available to it at that point, & it get stripped out when the image is transferred to the main program.

But the image is still in RAW format even after it is transfered to the main program, rigth?
DK
David Kilpatrick
May 23, 2004
Jytzel wrote:

Lionel …

Kibo informs me that (Jytzel) stated that:

I was wondering if there is any benifit of using CS RAW dialogue for correcting raw images (contrast, exposure, etc.) Would it jus be better, or at least the same, not to use any of those corrections and applying the ordinary corrections (curves, levels, etc.) in Photoshop?

In general, it’s better to do as many of your adjustments as possible in the RAW dialog. The advantage is that the RAW converter has more data available to it at that point, & it get stripped out when the image is transferred to the main program.

But the image is still in RAW format even after it is transfered to the main program, rigth?

no. the moment it opens in the CS main window, it’s Photoshop data, 8-bit usually, and all the information you had access to in the raw file is no longer there. You can’t make further exposure adjustments, white balance changes etc, without losing data.

Do all this in the raw conversion stage.

David
N
nomail
May 23, 2004
David Kilpatrick wrote:

I was wondering if there is any benifit of using CS RAW dialogue for correcting raw images (contrast, exposure, etc.) Would it jus be better, or at least the same, not to use any of those corrections and applying the ordinary corrections (curves, levels, etc.) in Photoshop?

In general, it’s better to do as many of your adjustments as possible in the RAW dialog. The advantage is that the RAW converter has more data available to it at that point, & it get stripped out when the image is transferred to the main program.

But the image is still in RAW format even after it is transfered to the main program, rigth?

no. the moment it opens in the CS main window, it’s Photoshop data, 8-bit usually, and all the information you had access to in the raw file is no longer there. You can’t make further exposure adjustments, white balance changes etc, without losing data.

Not neccessarily. You can also output the data in 16 bits format, in which case you haven’t lost anything and you could make your corrections in Photoshop if you like.


Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/
AM
Alfred Molon
May 23, 2004
Johan W. Elzenga wrote:

Not neccessarily. You can also output the data in 16 bits format, in which case you haven’t lost anything and you could make your corrections in Photoshop if you like.

Well, if you choose your black and white points in such a way to clip away some of the histogram (you might want to do that to have stronger colours and/or a more vibrant image) you cannot go back without losses. The best idea is to do all image processing at the RAW stage.

If you want to make some changes to the image later, you can again start with the RAW image, because the JPEG file contains all information about the paramaters you used for the RAW conversion (in File Info). —

Alfred Molon
——————————
http://groups.yahoo.com/group/Olympus_405080/
Olympus 5050 resource – http://www.molon.de/5050.html
Olympus 5060 resource – http://www.molon.de/5060.html
Olympus 8080 resource – http://www.molon.de/8080.html
N
nomail
May 23, 2004
Alfred Molon wrote:

Johan W. Elzenga wrote:

Not neccessarily. You can also output the data in 16 bits format, in which case you haven’t lost anything and you could make your corrections in Photoshop if you like.

Well, if you choose your black and white points in such a way to clip away some of the histogram (you might want to do that to have stronger colours and/or a more vibrant image) you cannot go back without losses.

That’s obvious, but not very realistic. If you plan to do your corrections in Photoshop, it’s obvious that you will *NOT* clip anything while opening the RAW file. Choosing black and white points will *ALSO* be done in Photoshop in that case.


Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/
AM
Alfred Molon
May 23, 2004
Johan W. Elzenga wrote:

Well, if you choose your black and white points in such a way to clip away some of the histogram (you might want to do that to have stronger colours and/or a more vibrant image) you cannot go back without losses.

That’s obvious, but not very realistic. If you plan to do your corrections in Photoshop, it’s obvious that you will *NOT* clip anything while opening the RAW file. Choosing black and white points will *ALSO* be done in Photoshop in that case.

It is possible to do all optimisations at the RAW stage – white balance, white and black points, saturation, sharpness, contrast, noise and CA reduction etc. That’s the beauty of RAW – further processing after the RAW converter stage is not necessary.


Alfred Molon
——————————
http://groups.yahoo.com/group/Olympus_405080/
Olympus 5050 resource – http://www.molon.de/5050.html
Olympus 5060 resource – http://www.molon.de/5060.html
Olympus 8080 resource – http://www.molon.de/8080.html
N
nomail
May 23, 2004
Alfred Molon wrote:

Johan W. Elzenga wrote:

Well, if you choose your black and white points in such a way to clip away some of the histogram (you might want to do that to have stronger colours and/or a more vibrant image) you cannot go back without losses.

That’s obvious, but not very realistic. If you plan to do your corrections in Photoshop, it’s obvious that you will *NOT* clip anything while opening the RAW file. Choosing black and white points will *ALSO* be done in Photoshop in that case.

It is possible to do all optimisations at the RAW stage – white balance, white and black points, saturation, sharpness, contrast, noise and CA reduction etc. That’s the beauty of RAW – further processing after the RAW converter stage is not necessary.

I know that, and that’s the way I work myself. But that’s not what the discussion is about, though. The discussion is about that is not BETTER to do all the optimisations at the RAW stage, it’s a matter of choice. If you open the file in 16 bits in Photoshop, you *CAN* do it there if you want. After all, Photoshop has more uptions than the RAW opener has. It’s up to you to use what you like best.


Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/
L
Lionel
May 24, 2004
Kibo informs me that (Jytzel) stated that:

Lionel …
Kibo informs me that (Jytzel) stated that:

I was wondering if there is any benifit of using CS RAW dialogue for correcting raw images (contrast, exposure, etc.) Would it jus be better, or at least the same, not to use any of those corrections and applying the ordinary corrections (curves, levels, etc.) in Photoshop?

In general, it’s better to do as many of your adjustments as possible in the RAW dialog. The advantage is that the RAW converter has more data available to it at that point, & it get stripped out when the image is transferred to the main program.

But the image is still in RAW format even after it is transfered to the main program, rigth?

Nope. When you hit that "Ok" button, the image is converted into Photoshops internal format.


W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est —^—-^————————————————— ————
L
lars
May 24, 2004
Alfred Molon …
Jytzel wrote:
I was wondering if there is any benifit of using CS RAW dialogue for correcting raw images (contrast, exposure, etc.) Would it jus be better, or at least the same, not to use any of those corrections and applying the ordinary corrections (curves, levels, etc.) in Photoshop?

In my opinion it’s best to do all optimisations before JPEG compression. Besides if you optimise the RAW file all optimisation parameters (WB, exposusre, shadows, contrast, etc.) are stored in the Exif data and can be retrieved later – something you cannot do if you optimise with ordinary corrections.

Just come across this article which might be of interest for the readers of this thread
http://www.creativepro.com/story/feature/21351.html

Lars Ekdahl
webmaster http://www.ekdahl.org/digital.htm
W
westin*nospam
May 25, 2004
(Johan W. Elzenga) writes:

David Kilpatrick wrote:

I was wondering if there is any benifit of using CS RAW dialogue for correcting raw images (contrast, exposure, etc.) Would it jus be better, or at least the same, not to use any of those corrections and applying the ordinary corrections (curves, levels, etc.) in Photoshop?

In general, it’s better to do as many of your adjustments as possible in the RAW dialog. The advantage is that the RAW converter has more data available to it at that point, & it get stripped out when the image is transferred to the main program.

But the image is still in RAW format even after it is transfered to the main program, rigth?

no. the moment it opens in the CS main window, it’s Photoshop data, 8-bit usually, and all the information you had access to in the raw file is no longer there. You can’t make further exposure adjustments, white balance changes etc, without losing data.

Not neccessarily. You can also output the data in 16 bits format, in which case you haven’t lost anything and you could make your corrections in Photoshop if you like.

Unless, of course, there are problems like overexposure or out-of-gamut colors that get clamped.


-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.
DO
Darryl Okahata
May 25, 2004
westin* (Stephen H. Westin) writes:

Not neccessarily. You can also output the data in 16 bits format, in which case you haven’t lost anything and you could make your corrections in Photoshop if you like.

Unless, of course, there are problems like overexposure or out-of-gamut colors that get clamped.

True. However, with Canon 300D/10D RAW data, "slightly blown highlights" can often be corrected.

[ That’s because the "overexposure" exists only in the thumbnail/LCD jpeg preview image, and may not actually exist in the 300D/10D RAW data, because RAW data has almost another full f-stop of headroom above the processed Canon jpeg image. ]


Darryl Okahata

DISCLAIMER: this message is the author’s personal opinion and does not constitute the support, opinion, or policy of Agilent Technologies, or of the little green men that have been following him all day.
N
nomail
May 25, 2004
Stephen H. Westin <westin*> wrote:

no. the moment it opens in the CS main window, it’s Photoshop data, 8-bit usually, and all the information you had access to in the raw file is no longer there. You can’t make further exposure adjustments, white balance changes etc, without losing data.

Not neccessarily. You can also output the data in 16 bits format, in which case you haven’t lost anything and you could make your corrections in Photoshop if you like.

Unless, of course, there are problems like overexposure or out-of-gamut colors that get clamped.

I don’t see the difference. Overexposure (meaning washed out highlights) is beyond repair in the RAW opener too. You cannot repair what isn’t there anymore. And out of gamut clamping will occur when the file is read into Photoshop in a (too) small color space. This will happen no matter where you do the corrections.


Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/
W
westin*nospam
May 25, 2004
(Johan W. Elzenga) writes:

Stephen H. Westin <westin*> wrote:

no. the moment it opens in the CS main window, it’s Photoshop data, 8-bit usually, and all the information you had access to in the raw file is no longer there. You can’t make further exposure adjustments, white balance changes etc, without losing data.

Not neccessarily. You can also output the data in 16 bits format, in which case you haven’t lost anything and you could make your corrections in Photoshop if you like.

Unless, of course, there are problems like overexposure or out-of-gamut colors that get clamped.

I don’t see the difference. Overexposure (meaning washed out highlights) is beyond repair in the RAW opener too.

As someone else pointed out, that’s not true. Most raw files contain a broader brightness range than is normally represented in the converted image. With Kodak DSLR’s, you can pull back two full stops!

You cannot repair what isn’t
there anymore. And out of gamut clamping will occur when the file is read into Photoshop in a (too) small color space. This will happen no matter where you do the corrections.

Not if you change color balance so as to bring the image within gamut. Imagine an image that was shot with an electronic flash with white balance set by mistake to tungsten. Everything will be shifted towards blue; objects in the image that started as a saturated blue may be beyond gamut. Switching to "flash" white balance during the raw conversion will allow the converted image to represent these colors better.


-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.
W
westin*nospam
May 25, 2004
Darryl Okahata writes:

westin* (Stephen H. Westin) writes:

Not neccessarily. You can also output the data in 16 bits format, in which case you haven’t lost anything and you could make your corrections in Photoshop if you like.

Unless, of course, there are problems like overexposure or out-of-gamut colors that get clamped.

True. However, with Canon 300D/10D RAW data, "slightly blown highlights" can often be corrected.

But only in the raw conversion: if you convert with default parameters, the information is gone.
j
<snip>


-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.
N
nomail
May 25, 2004
Stephen H. Westin <westin*> wrote:

I don’t see the difference. Overexposure (meaning washed out highlights) is beyond repair in the RAW opener too.

As someone else pointed out, that’s not true. Most raw files contain a broader brightness range than is normally represented in the converted image. With Kodak DSLR’s, you can pull back two full stops!

It all depends what a "converted image" is. You seem to be talking about an 8 bits per color image, I’m not. I’m talking about a 16 bits image, as I have stated from the start. Those two stops will be in the 16 bits converted image too, providing that you didn’t unneccessarily clip them when you opened the file.

Clipping may happen using the RAW opener for the following reason: Photoshop’s RAW opener has default settings that are NOT zero. Use the default settings and you may indeed get clipping. Set all settings to zero (except of course for color temperature, you cannot set that to zero) and you will have no washed out highlights in the resulting 16 bits image. But if you still do, the RAW opener won’t be able to fix that either, because the information simply isn’t there.

And out of gamut clamping will occur when the file is
read into Photoshop in a (too) small color space. This will happen no matter where you do the corrections.

Not if you change color balance so as to bring the image within gamut. Imagine an image that was shot with an electronic flash with white balance set by mistake to tungsten. Everything will be shifted towards blue; objects in the image that started as a saturated blue may be beyond gamut. Switching to "flash" white balance during the raw conversion will allow the converted image to represent these colors better.

I still disagree. If you open the file in Photoshop in a color space that is as wide or wider than your camera’s color space, I see no reason why correcting the white balance in the RAW converter should be better than doing so in 16 bits in Photoshop. Besides, the ONE thing you HAVE to do in the RAW opener anyway is setting a white balance. After all, you cannot open an image without any white balance at all. So yes, setting/correcting the white balance would be something one would normally do in the RAW opener, even if all other corrections were -for whatever reasons- made in Photoshop.


Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/
DO
Darryl Okahata
May 25, 2004
westin* (Stephen H. Westin) writes:

Unless, of course, there are problems like overexposure or out-of-gamut colors that get clamped.

True. However, with Canon 300D/10D RAW data, "slightly blown highlights" can often be corrected.

But only in the raw conversion: if you convert with default parameters, the information is gone.

How is the RAW conversion being done? While I do not have PS CS, I’ve been told that converting from RAW to 48-bit Adobe PSD will not result in loss of information. I don’t see how converting RAW (12-bits per channel) to 48-bit PSD (16-bits per channel) could result in loss of information.

[ I’m talking about using dcraw to do the conversion to 48-bit PSD, where the default PSD conversion settings do not do any brightness or gamma adjustments. ]


Darryl Okahata

DISCLAIMER: this message is the author’s personal opinion and does not constitute the support, opinion, or policy of Agilent Technologies, or of the little green men that have been following him all day.
W
westin*nospam
May 25, 2004
(Johan W. Elzenga) writes:

Stephen H. Westin <westin*> wrote:

I don’t see the difference. Overexposure (meaning washed out highlights) is beyond repair in the RAW opener too.

As someone else pointed out, that’s not true. Most raw files contain a broader brightness range than is normally represented in the converted image. With Kodak DSLR’s, you can pull back two full stops!

It all depends what a "converted image" is. You seem to be talking about an 8 bits per color image, I’m not. I’m talking about a 16 bits image, as I have stated from the start. Those two stops will be in the 16 bits converted image too, providing that you didn’t unneccessarily clip them when you opened the file.

You’ve never actually tried this, have you? Notice that an image converted to 16 bits is just as bright as if you convert it to 8 bits. That means the same camera value is being mapped to the maximum. You can, however, move the exposure slider to -1.0 and recover highlight information. I just tried this with Photoshop CS on a Canon CRW image with overesposed highlights. Converting to 16 bits doesn’t change the histogram; the same pixels are blown out. I can’t move the "Levels" slider beyond 255 to get beck the pixels that were clamped to maximum. And yes, I understand that 255 on the Levels dialog really means 32768 on a 16-bit image. If those bright pixels are mapped to, say, 40,000, the information is gone. If, however, I convert to 8-bit mode and move the exposure slider to -2.0, some of the blown pixels can be saved.

Clipping may happen using the RAW opener for the following reason: Photoshop’s RAW opener has default settings that are NOT zero. Use the default settings and you may indeed get clipping. Set all settings to zero (except of course for color temperature, you cannot set that to zero) and you will have no washed out highlights in the resulting 16 bits image.

No, that’s not correct. Setting exposure to -2.0 will preserve the full brightness range. Leaving it at zero will, in general, clip some bright values.

But if you still do, the RAW opener won’t be able to fix that either, because the information simply isn’t there.

Really, there is information in the raw file that doesn’t make it into Photoshop with the default settings, or with setting everything to zero. Would you like me to dump a raw file to show you?

And out of gamut clamping will occur when the file is read into Photoshop in a (too) small color space. This will happen no matter where you do the corrections.

Not if you change color balance so as to bring the image within gamut. Imagine an image that was shot with an electronic flash with white balance set by mistake to tungsten. Everything will be shifted towards blue; objects in the image that started as a saturated blue may be beyond gamut. Switching to "flash" white balance during the raw conversion will allow the converted image to represent these colors better.

I still disagree. If you open the file in Photoshop in a color space that is as wide or wider than your camera’s color space, I see no reason why correcting the white balance in the RAW converter should be better than doing so in 16 bits in Photoshop.

And which color space would that be? Why do you think that any color space exists that includes the entire raw gamut of your camera? How do you know what the camera raw gamut is?

Besides, the ONE thing you HAVE to do in the RAW opener anyway is setting a white balance.

Or let it default to the setting of the camera at capture time.

After all, you cannot open an image without any white balance at all.

Trust me; you wouldn’t want to.

So yes,
setting/correcting the white balance would be something one would normally do in the RAW opener, even if all other corrections were -for whatever reasons- made in Photoshop.


-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.
W
westin*nospam
May 25, 2004
Darryl Okahata writes:

westin* (Stephen H. Westin) writes:

Unless, of course, there are problems like overexposure or out-of-gamut colors that get clamped.

True. However, with Canon 300D/10D RAW data, "slightly blown highlights" can often be corrected.

But only in the raw conversion: if you convert with default parameters, the information is gone.

How is the RAW conversion being done?

1. Read raw data values from the file. These may be 10 or 12 bits.

2. Convert raw data to linear. A CCD is inherently linear, but many cameras apply a nonlinear transfer function to save bits. And the Canon D60, for example, seems to be slightly nonlinear.

3. Transform color. This includes not only white balance correction, but also color space conversion.

4. Demosaic: fill in the missing color values, since each sensel picks up only a single color (except for Foveon-based cameras).

5. Correct for display gamma. All common color spaces include a nonlinear transfer function that compensates, at least approximately, for the display nonlinearity.

While I do not have PS CS,
I’ve been told that converting from RAW to 48-bit Adobe PSD will not result in loss of information. I don’t see how converting RAW (12-bits per channel) to 48-bit PSD (16-bits per channel) could result in loss of information.

It’s actually intentional. If you take some value less than the sensor maximum and scale that up to the maximum pixel value, you retain the ability to compensate for some degree of overexposure. Different cameras do this differently; the Kodak DSLR’s probably provide the most headroom.

Oh, by the way, you don’t get a full 16 bits per channel in Photoshop; the value range is 0:32768, which is 15 bits and one extra value.

<snip>


-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.
AM
Alfred Molon
May 25, 2004
Stephen H. Westin <westin*> wrote:

2. Convert raw data to linear. A CCD is inherently linear, but many cameras apply a nonlinear transfer function to save bits. And the Canon D60, for example, seems to be slightly nonlinear.
3. Transform color. This includes not only white balance correction, but also color space conversion.

4. Demosaic: fill in the missing color values, since each sensel picks up only a single color (except for Foveon-based cameras).

Wouldn’t step 4 have to happen before step 3 ?


Alfred Molon
——————————
http://groups.yahoo.com/group/Olympus_405080/
Olympus 5050 resource – http://www.molon.de/5050.html
Olympus 5060 resource – http://www.molon.de/5060.html
Olympus 8080 resource – http://www.molon.de/8080.html
DO
Darryl Okahata
May 25, 2004
westin* (Stephen H. Westin) writes:

(Johan W. Elzenga) writes:

It all depends what a "converted image" is. You seem to be talking about an 8 bits per color image, I’m not. I’m talking about a 16 bits image, as I have stated from the start. Those two stops will be in the 16 bits converted image too, providing that you didn’t unneccessarily clip them when you opened the file.

You’ve never actually tried this, have you? Notice that an image converted to 16 bits is just as bright as if you convert it to 8 bits. That means the same camera value is being mapped to the maximum.

I think he’s talking about converting 12-bit (per channel) RAW data directly into 16-bit (per channel) data and not 8-bit data.

[ And, I think a key, unstated assumption here is that the CAMERA’S HISTOGRAM (not CS PS) is saying that the highlights are blown, which means that they might not really be blown — see below. ]

You can, however, move the exposure slider to -1.0 and
recover highlight information. I just tried this with Photoshop CS on a Canon CRW image with overesposed highlights. Converting to 16 bits doesn’t change the histogram; the same pixels are blown out. I can’t move the "Levels" slider beyond 255 to get beck the pixels that were clamped to maximum. And yes, I understand that 255 on the Levels dialog really means 32768 on a 16-bit image. If those bright pixels are mapped to, say, 40,000, the information is gone. If, however, I convert to 8-bit mode and move the exposure slider to -2.0, some of the blown pixels can be saved.

Going off on a tangent: while this may be true in PS CS, the jpeg (8-bit) conversion in a Canon 300D/10D is quite different (note that the camera shows a jpeg thumbnail image in the LCD display, even when shooting RAW, and that the camera’s histogram appears to be that of the jpeg, and *NOT* RAW, data). The Canon in-camera jpeg conversion will blow jpeg highlights long before they are really blown in the RAW data. The red channel is the worst; someone estimated that the red channel blows (clipped to 255) around 1350 (out of 4K values). The blue and green channels blow around 2100.

So, if the camera’s histogram says that the highlights are blown, they are blown in the jpeg, and might not really be blown in the RAW data.


Darryl Okahata

DISCLAIMER: this message is the author’s personal opinion and does not constitute the support, opinion, or policy of Agilent Technologies, or of the little green men that have been following him all day.
W
westin*nospam
May 26, 2004
Alfred Molon writes:

Stephen H. Westin <westin*> wrote:

2. Convert raw data to linear. A CCD is inherently linear, but many cameras apply a nonlinear transfer function to save bits. And the Canon D60, for example, seems to be slightly nonlinear.
3. Transform color. This includes not only white balance correction, but also color space conversion.

4. Demosaic: fill in the missing color values, since each sensel picks up only a single color (except for Foveon-based cameras).

Wouldn’t step 4 have to happen before step 3 ?

Yup. My mistake.


-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.
W
westin*nospam
May 26, 2004
Darryl Okahata writes:

westin* (Stephen H. Westin) writes:

(Johan W. Elzenga) writes:

It all depends what a "converted image" is. You seem to be talking about an 8 bits per color image, I’m not. I’m talking about a 16 bits image, as I have stated from the start. Those two stops will be in the 16 bits converted image too, providing that you didn’t unneccessarily clip them when you opened the file.

You’ve never actually tried this, have you? Notice that an image converted to 16 bits is just as bright as if you convert it to 8 bits. That means the same camera value is being mapped to the maximum.

I think he’s talking about converting 12-bit (per channel) RAW data directly into 16-bit (per channel) data and not 8-bit data.

So was I, hence the phrase "an image converted to 16 bits". I should have said "a raw image converted to 16 bits". By point is this: if you take the same raw file and conver twice in CS, once in 16-bit mode and once in 8-bit mode, the "Levels" histograms will be essentially identical on the screen. That is to say, the same raw value that is converted to 255 in the 8-bit image will be converted to 32,768 in the 16-bit image; any raw value greater than that will be clamped to 32,768 (or 255). You don’t gain any headroom simply by using 16 bits.

[ And, I think a key, unstated assumption here is that the CAMERA’S HISTOGRAM (not CS PS) is saying that the highlights are blown, which means that they might not really be blown — see below. ]

That’s what I mean: the normal raw conversion for any camera will actually lose the highest raw values from the sensor. The "exposure" slider lets you recover these values, and there’s no other way to do this.

You can, however, move the exposure slider to -1.0 and
recover highlight information. I just tried this with Photoshop CS on a Canon CRW image with overesposed highlights. Converting to 16 bits doesn’t change the histogram; the same pixels are blown out. I can’t move the "Levels" slider beyond 255 to get beck the pixels that were clamped to maximum. And yes, I understand that 255 on the Levels dialog really means 32768 on a 16-bit image. If those bright pixels are mapped to, say, 40,000, the information is gone. If, however, I convert to 8-bit mode and move the exposure slider to -2.0, some of the blown pixels can be saved.

Going off on a tangent: while this may be true in PS CS, the jpeg (8-bit) conversion in a Canon 300D/10D is quite different (note that the camera shows a jpeg thumbnail image in the LCD display, even when shooting RAW, and that the camera’s histogram appears to be that of the jpeg, and *NOT* RAW, data). The Canon in-camera jpeg conversion will blow jpeg highlights long before they are really blown in the RAW data. The red channel is the worst; someone estimated that the red channel blows (clipped to 255) around 1350 (out of 4K values). The blue and green channels blow around 2100.

So, if the camera’s histogram says that the highlights are blown, they are blown in the jpeg, and might not really be blown in the RAW data.

Exactly what I’m trying (unsuccessfully) to say: the default conversion (and Photoshop’s default conversion is, I’m sure designed to mimic what Canon does in this respect) will lose some values. The point of those sliders is to let you intervene in the process and recover this information, which can’t be recovered after the conversion.


-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.
DO
Darryl Okahata
May 26, 2004
westin* (Stephen H. Westin) writes:

I think he’s talking about converting 12-bit (per channel) RAW data directly into 16-bit (per channel) data and not 8-bit data.

So was I, hence the phrase "an image converted to 16 bits". I should have said "a raw image converted to 16 bits". By point is this: if you take the same raw file and conver twice in CS, once in 16-bit mode and once in 8-bit mode, the "Levels" histograms will be essentially identical on the screen. That is to say, the same raw value that is converted to 255 in the 8-bit image will be converted to 32,768 in the 16-bit image; any raw value greater than that will be clamped to 32,768 (or 255). You don’t gain any headroom simply by using 16 bits.

True, but the "headroom" is in the camera, not PS CS. By shooting RAW, you gain a little headroom in the camera, to (hopefully) avoid blown highlights. If you can avoid blowing the highlights in the RAW data (the camera’s LCD histogram may still say that the highlights are blown, though), then none of the values will be converted to 255/32768 in PS CS.

Exactly what I’m trying (unsuccessfully) to say: the default conversion (and Photoshop’s default conversion is, I’m sure designed to mimic what Canon does in this respect) will lose some values. The point of those sliders is to let you intervene in the process and recover this information, which can’t be recovered after the conversion.

[ I don’t have PS CS, so take the following with the appropriate chunk of salt. ]

While this may be true of the PS CS converter, others seem to be using a different approach to RAW & PS CS: they do not use the RAW converter in PS CS. Instead, they use dcraw (which is free, third-party software — not Canon’s) to do a plain linear conversion (no brightness or gamma correction) of the RAW data to 48-bit PSD data, and then read the PSD file into PS CS.

Note that, even though the *camera* may say that the highlights are blown, they may only be blown in the camera’s LCD jpeg preview, and may not be blown in the RAW data. Because of this, there is no clipping (by dcraw — I have no idea what PS CS does) or loss of information during the dcraw conversion process. This is because, assuming that nothing in the RAW data is blown, all of the RAW data are below the maximum value (and because no gamma or brightness correction is done).


Darryl Okahata

DISCLAIMER: this message is the author’s personal opinion and does not constitute the support, opinion, or policy of Agilent Technologies, or of the little green men that have been following him all day.
N
nomail
May 26, 2004
Stephen H. Westin <westin*> wrote:

I think he’s talking about converting 12-bit (per channel) RAW data directly into 16-bit (per channel) data and not 8-bit data.

So was I, hence the phrase "an image converted to 16 bits". I should have said "a raw image converted to 16 bits". By point is this: if you take the same raw file and conver twice in CS, once in 16-bit mode and once in 8-bit mode, the "Levels" histograms will be essentially identical on the screen. That is to say, the same raw value that is converted to 255 in the 8-bit image will be converted to 32,768 in the 16-bit image; any raw value greater than that will be clamped to 32,768 (or 255). You don’t gain any headroom simply by using 16 bits.

No, indeed you don’t and that is not what I meant either. I realize that I haven’t been clear enough. What I meant is this:

If you open a RAW image in 16 bits rather than 8 bits, you can do all the *FURTHER* corrections in Photoshop, without losing data by doing so. Why would you want to do that? The RAW opener does not have anything like ‘Shadow/Highlight’ or Adjustments Layers with layer masks, for example, so there can be many reasons why someone may prefer to use Photoshop for fine tuning the image. Personally, I make as many corrections as I can in the RAW opener, but I still use 16 bits output, because I may indeed want to do some extra work involving Adjustment layers and/or the Shadow/Highlight correction. Only when I’m really satisfied with the results, I convert to 8 bits. I believe that gives the best possible results. It’s not either/or, it’s and/and.

Exactly what I’m trying (unsuccessfully) to say: the default conversion (and Photoshop’s default conversion is, I’m sure designed to mimic what Canon does in this respect) will lose some values. The point of those sliders is to let you intervene in the process and recover this information, which can’t be recovered after the conversion.

I think it’s a matter of semantics. What is ‘the default conversion’ anyway? I don’t think there is anything like that. There is only the conversion using default values, but we agree that those aren’t always the best settings for every image. You should obviously convert the RAW file without causing any unnecessary clipping in the first place. Usually, if your image was correctly exposed, that simply means you set the correct white balance and you can leave everything else at zero. However, if your image was overexposed, you may indeed have to set the exposure at -1 or -2 in order not to cause any EXTRA clipping. So be it.


Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/
W
westin*nospam
May 26, 2004
Darryl Okahata writes:

westin* (Stephen H. Westin) writes:

I think he’s talking about converting 12-bit (per channel) RAW data directly into 16-bit (per channel) data and not 8-bit data.

So was I, hence the phrase "an image converted to 16 bits". I should have said "a raw image converted to 16 bits". By point is this: if you take the same raw file and conver twice in CS, once in 16-bit mode and once in 8-bit mode, the "Levels" histograms will be essentially identical on the screen. That is to say, the same raw value that is converted to 255 in the 8-bit image will be converted to 32,768 in the 16-bit image; any raw value greater than that will be clamped to 32,768 (or 255). You don’t gain any headroom simply by using 16 bits.

True, but the "headroom" is in the camera, not PS CS. By shooting RAW, you gain a little headroom in the camera, to (hopefully) avoid blown highlights.

Right. And the controls in the raw importer let you retrieve the extra highlight information.

If you can avoid blowing the highlights in the RAW
data (the camera’s LCD histogram may still say that the highlights are blown, though), then none of the values will be converted to 255/32768 in PS CS.

By default, some of the values *will* be converted to the maximum. That’s one big reason why there are adjustments possible during the conversion process.

Exactly what I’m trying (unsuccessfully) to say: the default conversion (and Photoshop’s default conversion is, I’m sure designed to mimic what Canon does in this respect) will lose some values. The point of those sliders is to let you intervene in the process and recover this information, which can’t be recovered after the conversion.

[ I don’t have PS CS, so take the following with the appropriate chunk of salt. ]

While this may be true of the PS CS converter, others seem to be using a different approach to RAW & PS CS: they do not use the RAW converter in PS CS. Instead, they use dcraw (which is free, third-party software — not Canon’s) to do a plain linear conversion (no brightness or gamma correction) of the RAW data to 48-bit PSD data, and then read the PSD file into PS CS.

Note that, even though the *camera* may say that the highlights are blown, they may only be blown in the camera’s LCD jpeg preview, and may not be blown in the RAW data. Because of this, there is no clipping (by dcraw — I have no idea what PS CS does) or loss of information during the dcraw conversion process. This is because, assuming that nothing in the RAW data is blown, all of the RAW data are below the maximum value (and because no gamma or brightness correction is done).

Yup. I’m pretty sure dcraw, at least when asked for linear output, won’t try to emulate the default tone mapping of the camera firmware or manufacturer’s software. But that, of course, demands a fair amount of postprocessing to create a viewable image.


-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.
W
westin*nospam
May 26, 2004
(Johan W. Elzenga) writes:

Stephen H. Westin <westin*> wrote:

I think he’s talking about converting 12-bit (per channel) RAW data directly into 16-bit (per channel) data and not 8-bit data.

So was I, hence the phrase "an image converted to 16 bits". I should have said "a raw image converted to 16 bits". By point is this: if you take the same raw file and conver twice in CS, once in 16-bit mode and once in 8-bit mode, the "Levels" histograms will be essentially identical on the screen. That is to say, the same raw value that is converted to 255 in the 8-bit image will be converted to 32,768 in the 16-bit image; any raw value greater than that will be clamped to 32,768 (or 255). You don’t gain any headroom simply by using 16 bits.

No, indeed you don’t and that is not what I meant either. I realize that I haven’t been clear enough. What I meant is this:

If you open a RAW image in 16 bits rather than 8 bits, you can do all the *FURTHER* corrections in Photoshop, without losing data by doing so. Why would you want to do that? The RAW opener does not have anything like ‘Shadow/Highlight’ or Adjustments Layers with layer masks, for example, so there can be many reasons why someone may prefer to use Photoshop for fine tuning the image. Personally, I make as many corrections as I can in the RAW opener, but I still use 16 bits output, because I may indeed want to do some extra work involving Adjustment layers and/or the Shadow/Highlight correction. Only when I’m really satisfied with the results, I convert to 8 bits. I believe that gives the best possible results. It’s not either/or, it’s and/and.

Absolutely. But some folks were insisting that anything that the raw importer does can be done just as well later on. Wait, it was you:

From: Johan W. Elzenga ()
Subject: Re: Opening raw files in CS

View this article only
Newsgroups: comp.graphics.apps.photoshop, alt.graphics.photoshop, rec.photo.digital Date: 2004-05-23 06:10:46 PST

David Kilpatrick wrote:

<snip>

But the image is still in RAW format even after it is transfered to the main program, rigth?

no. the moment it opens in the CS main window, it’s Photoshop data, 8-bit usually, and all the information you had access to in the raw file is no longer there. You can’t make further exposure adjustments, white balance changes etc, without losing data.

Not neccessarily. You can also output the data in 16 bits format, in which case you haven’t lost anything and you could make your corrections in Photoshop if you like.


Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/

See, that’s the focus of the misunderstanding:

"You can also output the data in 16 bits format, in which case you haven’t lost anything and you could make your corrections in Photoshop if you like."

I think you meant something like

"You can also output the data in 16 bits format, in which case you have the capability to preserve everything and you could make your corrections in Photoshop if you like."

See the difference? Just clicking the "16-bit" box isn’t enough: you have to override the default settings to preserve all the extra information.

<snip>

I think it’s a matter of semantics. What is ‘the default conversion’ anyway? I don’t think there is anything like that. There is only the conversion using default values,

…. which is what I meant…

but we agree that those aren’t always
the best settings for every image. You should obviously convert the RAW file without causing any unnecessary clipping in the first place. Usually, if your image was correctly exposed, that simply means you set the correct white balance and you can leave everything else at zero. However, if your image was overexposed, you may indeed have to set the exposure at -1 or -2 in order not to cause any EXTRA clipping. So be it.

Right. But where I came in was the start of the thread:

From: Jytzel ()
Subject: Opening raw files in CS

View this article only
Newsgroups: comp.graphics.apps.photoshop, alt.graphics.photoshop, rec.photo.digital Date: 2004-05-22 18:32:57 PST

I was wondering if there is any benifit of using CS RAW dialogue for correcting raw images (contrast, exposure, etc.) Would it jus be better, or at least the same, not to use any of those corrections and applying the ordinary corrections (curves, levels, etc.) in Photoshop?

Those of us who mentioned operations that require access to the raw sensor data seemed to get an argument. I’m glad that you and I agree.


-Stephen H. Westin
Any information or opinions in this message are mine: they do not represent the position of Cornell University or any of its sponsors.
N
nomail
May 26, 2004
Stephen H. Westin <westin*> wrote:

See, that’s the focus of the misunderstanding:

"You can also output the data in 16 bits format, in which case you haven’t lost anything and you could make your corrections in Photoshop if you like."

I should have said "in which case you do not HAVE TO lose anything". As you may have noticed, English is not my mother tongue. The point is that I was reacting to someone who suggested that the output was 8 bits and that you shouldn’t do corrections in Photoshop because of THAT. This person said: "the moment it opens in the CS main window, it’s Photoshop data, 8-bit usually, and all the information you had access to in the raw file is no longer there". It’s still there if you know how to get it there!

I think you meant something like

"You can also output the data in 16 bits format, in which case you have the capability to preserve everything and you could make your corrections in Photoshop if you like."

See the difference? Just clicking the "16-bit" box isn’t enough: you have to override the default settings to preserve all the extra information.

Wait a second, I never said that you should just hit "OK" when the RAW dialog comes up. I specifically said that you should NOT use the default settings. Anyway, I think we agree that you CAN make all the corrections in Photoshop, providing that you make sure that:

A: You do not unnecessarily clip any data during the conversion; B: You convert to a 16 bits file.

Now where did I read that before?… 😉


Johan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/
M
mail
May 28, 2004
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Jack-of-the-Dust
May 28, 2004
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