Color spaces: processing, exporting, printing

[Downrigger]

This may be trivial to some, but I’m still struggling with it, and perhaps a few others are, so I post this in hopes I get some useful clarifications. I’ve read the C&C tutorial and had a tad of instruction on this but I’m still short of a full deck on it.

When I bring a RAW file into Lightroom, as I understand it I am working with an image in a large-gamut RGB space in LR, and it is on the screen on my Mac, which is a calibrated but provides a smaller, restricted portion of the Adobe RGB space (I was told about 70% of it at a recent class).

Fine. I get it looking the way I like it.

When I export JPEGs for screen, I assume I might as well export in the same color space I was in when I post-processed, so as not to compress or rearrange any of my hues… so, I guess ???AdobeRGB???.

More importantly though, if I export to print, most labs are going to work in sRGB, so my post processing work in a larger space will get smushed either if I export as sRGB, or if the lab converts my image to sRGB when they receive it. (I think if I had a large space inkjet I could avoid this… not there yet).

In both instances it seems to me I’d be better off working in sRGB for my post processing and thus would know how my image will look in that smaller space, and therefore on print paper, if I order one (and also, assuredly on other peoples' screens). But I can’t figure out how to work in sRGB space in LR, in any case.

I'll appreciate any challenges to my premises, or easy answers.

[xpatUSA]

This may be trivial to some, but I’m still struggling with it, and perhaps a few others are, so I post this in hopes I get some useful clarifications. I’ve read the C&C tutorial and had a tad of instruction on this but I’m still short of a full deck on it.

When I bring a RAW file into Lightroom, as I understand it I am working with an image in a large-gamut RGB space in LR

Correct, for the purposes of your thread.

and it is on the screen on my Mac, which is calibrated but provides a smaller, restricted portion of the Adobe RGB space (I was told about 70% of it at a recent class).

There are several Adobe RGB spaces, e.g. 'Melissa', Adobe Wide, Adobe RGB (1998) so can't help with that statement.

Fine. I get it looking the way I like it.

When I export JPEGs for screen, I assume I might as well export in the same color space I was in when I post-processed, so as not to compress or rearrange any of my hues… so, I guess [???Adobe RGB (1998)???].

We do not know what color space your Mac screen uses - but I'll guess that it is sRGB, now that Macs have aligned with the rest of world. The assumption, though, is incorrect. If you are exporting "JPEGs for screen" (especially for other people's screens), sRGB is highly recommended. And if you do export as sRGB JPEG, your image will be compressed and re-arranged - whether you like it or not

More importantly though, if I export to print, most labs are going to work in sRGB, so my post processing work in a larger space will get smushed either if I export as sRGB, or if the lab converts my image to sRGB when they receive it.

Correct.

In both instances it seems to me I’d be better off working in sRGB for my post processing and thus would know how my image will look in that smaller space, and therefore on print paper, if I order one (and also, assuredly on other peoples' screens). But I can’t figure out how to work in sRGB space in LR, in any case.

Yes, I don't use LR myself but most editors allow the user to select a "working space" such as sRGB, for example. You need to ask that question in another thread or maybe a LR user will tell you how to, in this thread. Anybody?

It's not easy to explain, anything to do with color management is hard going.

When you intend to save a file for viewing on-screen only, select sRGB as your "working space" and Adobe will show the review image on-screen as if someone had opened your file on their cheap uncalibrated 6-bit LCD monitor. IOW, it's trying to show you how it would look. So, if it looks good to you after editing but before saving, it will likely look good on my NEC Multisync, too.

If, on the other hand, you edited a highly-saturated flower shot to perfection in ProPhoto working space and then 'saved as' a sRGB JPEG, disappointment will surely follow - in the form of clipped colors causing low color contrast or even blotching.

Of course, JPEGs can be saved with the super-wide ProPhoto space but that .icc profile had better be 'embedded' in the file and anything which opens that file had better be color-managed . . and how someone else's stuff will render your finely-crafted image will certainly not be under your control.

Complex subject, I hope I have helped a bit . .

[Mike Buckley]

Lightroom uses ProPhoto RGB in the Develop module. (If that can be changed, I haven't found where to change it). It uses Adobe RGB in other modules. This Adobe web page provides more details about that.

[ajohnw]

From what I gather Lightroom's works space is ProPhoto. This means that as you adjust images no information of significance can be lost even though you can't see the hidden bit depth on the screen. PP moves it in and out of the screens colour space. There is a complication however that would take too many words to explain in any detail and doesn't really have any impact on what I have just said. Colour management converts between gamuts.

Sounds to me like your are viewing in sRGB so no way should you save as aRGB of any form. Only jpg - other than if lightroom like many packages has some mechanism for saving everything including the current state of your work flow. I'd guess it does this by saving a small file that will be loaded each time you load a raw that has had any work done on it so this option doesn't exist.

You should have lightroom set up to output sRGB which is probably it's default. You should only set say aRGB if you are using an aRGB monitor. Several people on here assume that they are working in sRGB output using PS etc but repeatedly put out aRGB images on the web. I've seen no signs of that from Lightroom people. As mentioned when posting on the web currently it's best to post sRGB if you want people to see what you see when you adjust images. There is a simple reason for this. While browsers are now colour managed and will convert between gamuts colours exist in both that can't be displayed in the other. 3x10bit aRGB more or less takes care of that but as far as I know there is no way of posting it in a meaningful manner. The web doesn't support it.

Going back a bit. to simplify Your screen covers 70% aRGB which sounds like sRGB to me. If you try to work in aRGB you are effectively manipulating colours you can't see.

Looking for info on the web it seems Lightroom automatically picks up the monitor profile you generated when you calibrated your monitor which from what you have said aught to be sRGB. You needn't worry about anything else - just save as standard jpg.

If you had an aRGB monitor and that profile installed it would work in that or you could tell the OS to load the sRGB one and it would use that one.

There is another aspect to remember about aRGB and sRGB jpg's. They can both contain the same NUMBER of colours but the spacing in aRGB is wider. This isn't really the same as what is often meant by deeper colour gamuts. If you work in aRGB in this mode banding is more likely. If for some reason an aRGB image like this happens to get displayed on an sRGB monitor without gamut conversion it will tend to have flat muted colours - bit like say a Constable painting effect.

If you need more clarification ask and I'll try but I don't think pointing you at comprehensive colour management details would help with basic miss understandings. I've also lost a link that truly spells it out without worrying about which gamuts are being used where. The main point concerns workspace gamut as it's often called does not relate to the screen output gamut. All sorts of workspace data handling formats are possible.

John
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[Polar01]

Ted when working in LR in development the colour space is ProPhoto from some readings it was stated that it is not a true ProPhoto work space but one called Melissa. When images LR are not in development but another section (say print) the colour space is Adobe sRGB.

Cheers: Allan

PS this can be seen the link that Mike gives in post #3

[Downrigger]

Lightroom uses ProPhoto RGB in the Develop module. (If that can be changed, I haven't found where to change it). It uses Adobe RGB in other modules. This Adobe web page provides more details about that.

Yes, Mike, thanks, and I see the prophoto data onscreen in a somewhat constrained aRGB that my mac provides. But as I understand it, I do not have the option of post processing color in the same color space that I will be exporting in (sRGB almost always). I'm understanding that this means that once the image leaves lightroom, I am at the mercy of the software's color management as to how the colors I chose during PP are rendered in the sRGB JPEG that I send out to you folks, the printer, SmugMug... whomever.

Maybe, this, like a lot of things, pertains to fine tuning issues not relevant to my level of work, but I get the sense (as in John's helpful post) that smushing colors from a large space to a smaller ones can have real world/ordinary guy consequences.

[ajohnw]

Yes, Mike, thanks, and I see the prophoto data onscreen in a somewhat constrained aRGB that my mac provides. But as I understand it, I do not have the option of post processing color in the same color space that I will be exporting in (sRGB almost always). I'm understanding that this means that once the image leaves lightroom, I am at the mercy of the software's color management as to how the colors I chose during PP are rendered in the sRGB JPEG that I send out to you folks, the printer, SmugMug... whomever.

Maybe, this, like a lot of things, pertains to fine tuning issues not relevant to my level of work, but I get the sense (as in John's helpful post) that smushing colors from a large space to a smaller ones can have real world/ordinary guy consequences.

No Mark. That isn't so. the workspace gamut as I hope Adobe call it, prophoto, floating point colour what ever has no bearing at all on the profile the software uses to display the image. Software translates the gamut between the one used by workspace and the one used by the screen.

According to the web Lightroom asks the operating system what display gamut it is using - you have profiled your monitor so that is sRGB ( I hope) and it will display on that basis. Actually it probably loads and uses the profile you generated. Some packages assume that the display is profiled correctly - that can get complicated if the wrong one is selected.

The reason for the larger gamut in the workspace is pretty simple really. Say it was set to sRGB and some PP step multiplied a series of value in the image by 1.5. Some would correspond with values that are available in sRGB which is 3x8bit deep colour channels some wouldn't. As the sRGB can't hold the odd ball values they have gone and can't be obtained again. If a deeper colour space is used for the workspace they are retained so further changes can be made - they can even be adjusted back to where they were - the ultimate test. That isn't possible when the depths are the same. The data in the workspace of the deeper gamut might be retained as say either 3x16bit or 3 x 32 bit floating point. This means that data can't be lost. The actual gamut that the work space uses isn't really relevant only the fact that it's deeper than the displayed one. Where a gamut is used in the workspace eg prophoto software converts it to the display gamut. There is plenty of info on gamut conversions and their generation on the wiki but there isn't much point in going into detail only being aware of what goes on.

ProPhoto is chosen because it more or less covers all colours we can see so can hold any colour. To do this as we use a mix of 3 colours it has to use 2 what are called imaginary colour that we can't see at all. I suspect this is the area that causes some confusion. Not the fact that it uses imaginary colour but the fact that it can contain all colours. What it does in practice is retain fractional bits of the display profile colours so that at that level the image can be manipulated without any loss of data. As above if the bit depth of the 2 were the same data could be lost with no way of getting it back. Multiple pp steps will gradually loose more and more data. I should add that some packages have worked purely in 3x8 bit colour channels for donkies years without significant problems but it needs more care especially when converting the higher bit depth available from a raw file into that colour space. Some packages I use do not care about the workspace gamut at all. They just keep the data at a greater bit depth than needed - usually as 3x32 bit floating point in what ever gamut the screen is being run at. This does exactly the same thing and could even hold a prophoto image's data. ProPhoto images are only of interest to people who own a prophoto printer and they have to be adjusted on a monitor without being able to see all of the colours they contain. That becomes apparent when they are actually printed. Same if you try to work in aRGB on an sRGB screen. Not a good idea at all and there is no saying what it will look like when some one displays it on an aRGB monitor.

John
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[xpatUSA]

Ted when working in LR in development the colour space is ProPhoto from some readings it was stated that it is not a true ProPhoto work space but one called Melissa.

Thanks Allan,

Yes, I already knew about Melissa and did already mention it in my earlier post. It's ProPhoto with sRGB gamma (2.4 plus a linear bit) instead of ProPhoto's 1.8. From memory, 'Melissa' is used internally and is never applied to an actual saved image output, only for viewing. I have an even vaguer memory that it is signed 16bit i.e. 15bit compared to unsigned ProPhoto.

All classic Adobe - which is why I avoid their stuff whenever possible

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[ajohnw]

Thanks Allan,

Yes, I already knew about Melissa and did already mention it in my earlier post. It's ProPhoto with sRGB gamma (2.4 plus a linear bit) instead of ProPhoto's 1.8. From memory, 'Melissa' is used internally and is never applied to an actual saved image output, only for viewing. I have an even vaguer memory that it is signed 16bit i.e. 15bit compared to unsigned ProPhoto.

All classic Adobe - which is why I avoid their stuff whenever possible



I find that a little odd but, since I've never used LR, I can't argue . . .

I very much doubt it forces aRGB as if some one wanted sRGB jpg's it would be a disaster displaying them as if they were aRGB images and the other way round. On the other hand Adobe might adopt a colour management will cope approach but as both gamuts contain colours the other can't show that sounds NVG and extremely bad practice to me.

John
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[xpatUSA]

I very much doubt it forces aRGB as if some one wanted sRGB jpg's it would be a disaster displaying them as if they were aRGB images and the other way round. On the other hand Adobe might adopt a colour management will cope approach but as both gamuts contain colours the other can't show that sounds NVG and extremely bad practice to me.
John
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I just deleted my "find it a little odd" comment, the only reason being that the poster was just quoting Adobe's help file which was linked to earlier.

I still find it a little odd but I did not wish to cause further confusion in this thread. Besides which, in a previous life here, I've found that disagreeing with the mighty Adobe in these fora can get some less-than-friendly responses

[Mike Buckley]

I'm understanding that this means that once the image leaves lightroom, I am at the mercy of the software's color management as to how the colors I chose during PP are rendered in the sRGB JPEG that I send out to you folks

I think you have for more reason to be concerned about all those folks viewing your images on monitors that are not profiled and calibrated using web browsers that aren't color-managed and even when they are do a horrible job of managing it. You have no control over that.

You have only two points of control: how the image looks on your monitor and how the image looks on a print that you find acceptable. All other viewings of your image are completely beyond your control, so don't worry about it.

[davidedric]

H Mark,

I might have missed something in the thread, but in Lightroom that is exactly what soft proofing is for, so far as prints are concerned. Your print lab (or your printer manufacturer if you are printing yourself) can provide you with a profile, which you select when soft proofing. You have the option of either perceptual or relative colormetric when rendering from your wide colour space into the printed one. Clicking on "simulate paper and ink" ,aka make my picture look c***, gives the best approximation on your monitor of how the print will look.

Dave

[ajohnw]

I just deleted my "find it a little odd" comment, the only reason being that the poster was just quoting Adobe's help file which was linked to earlier.

I still find it a little odd but I did not wish to cause further confusion in this thread. Besides which, in a previous life here, I've found that disagreeing with the mighty Adobe in these fora can get some less-than-friendly responses

Yes I know Ted. me too as they say. I still find it doubtful and the other point of course is that gamut conversion can still take that to to sRGB and of course the added complication is that gamuts can be stored at all sorts of bit depths - Adobe should state which one they use really othewise it's meaningless.

This elaborates on why I mentioned that working space gamuts are irrelevant as software converts as needed and the important aspect is that is that it holds a higher precision than the screen / final output. aRGB can be retained in 3x16bit or even 3 x 32 bit floating point format. As the span of the gamut is greater than sRGB it can hold that. As it is also has more precision than available aRGB bit depths it can hold these as well without loosing any information as the file is PP's. Why do this - probably so that people have to buy PS etc if they want to work in prophoto. If stingy they might hold data in 3 16bit aRGB channels but I suspect as it's now fashionable they use 32 bit floating point. 3x16bit processing might offer the advantage that processing will be faster. Rumour has it that actually they use signed 16 bit colour channels a lot. That effectively means that the use 15 bit precision. This may be what they do now or maybe they just did this in the past and now use 32bit fp. Pass unless I saw their raw software I wouldn't comment. One thing for sure a 3x8bit or even 3x10bit aRGB workspace would be very likely to cause problems when working on jpg's. Especially 8 as that isn't really possible. Even 10 sounds dubious.

John
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[pnodrog]

The thread seems to be ignoring the fact that Colour Management along with good profiles and setting the intent when converting to a more restricted colour space is meant to relieve us of all this worry.....

All you can do is always work in the widest colour space available regardless of your monitor (who knows someone may buy you a better one next week) and cross your fingers that the colour management system works.

If you lower your PP to match an existing monitor or printer means when you upgrade or as advances are made you may need to revise all the work you have done. If you have discarded the colour information it cannot be recovered by moving back to a larger colour space.

[ajohnw]

The thread seems to be ignoring the fact that Colour Management along with good profiles and setting the intent when converting to a more restricted colour space is meant to relieve us of all this worry.....

All you can do is always work in the widest colour space available regardless of your monitor (who knows someone may buy you a better one next week) and cross your fingers that the colour management system works.

If you lower your PP to match an existing monitor or printer means when you upgrade or as advances are made you may need to revise all the work you have done. If you have discarded the colour information it cannot be recovered by moving back to a larger colour space.

That is the sort of comment that does cause confusion. For instance it is completely impossible to map the complete colour span of an aRGB accurately into an sRGB image as it just doesn't cover all of the the colours. Similarly 8 bit aRGB in other words aRGB jpg's currently can't show some colours that exist in sRGB. The are jpg standards that will hold all sorts of gamuts but currently not much use is made of them.

John
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[pnodrog]

That is the sort of comment that does cause confusion. For instance it is completely impossible to map the complete colour span of an aRGB accurately into an sRGB image as it just doesn't cover all of the the colours. Similarly 8 bit aRGB in other words aRGB jpg's currently can't show some colours that exist in sRGB. The are jpg standards that will hold all sorts of gamuts but currently not much use is made of them.

John
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I am sorry if it confuses you. Look forward to seeing your solution.

How long to you think monitors with only sRGB will be manufactured? I just recommend that everyone keep thier files and PP efforts in a colour space that is reasonably future proof.

[Downrigger]

Thanks all:

I am more than satisfied that stirred up in a bowl in poured in a pan the responses to my question bake up to a pretty good cake. Mike's response is reassuring (short of nihilistic), I am getting into the John/l. Paul dialectic - though unresolved, it helps. And Ted, thanks to you too, I hope to grasp this as well as you someday, maybe after a brain transplant. I will keep doing what I am doing (shoot raw, process in LR, export as sRGB JPEGs usually) and, now, with less trepidation. And I will pay more attention to soft proof to reassure myself that my images reflect my intent.

[xpatUSA]

The thread seems to be ignoring the fact that Colour Management along with good profiles and setting the intent when converting to a more restricted colour space is meant to relieve us of all this worry.....

. . . . and then you woke up

All you can do is always work in the widest colour space available regardless of your monitor (who knows someone may buy you a better one next week) and cross your fingers that the colour management system works.

Yep, that is the safe course, without doubt. Being a foveonista, I convert from raw in Sigma Photo Pro (SPP). In SPP, the converted "working file" (never seen) is in Kodak linear ROMM, 16-bpc. For 'important' work, I'll take care of exposure and a few other things if necessary, and save as 16-bpc ProPhoto TIFF for opening in RawTherapee (RT) whose default working space is proper ProPhoto (not Adobe's bastard cousin) and whose processing is 32-bit floating point, AFAIK. RT also allows conversion to other spaces using perpetual rendering intent provided that the sRGB profile has the proper AtoB tables, e.g. ICC V4. No tables, no perpetual rendering. This comment does not apply to printer output files. Not saying this workflow is better than anyone else's, but it sure is simple and easy for me to understand.

If you lower your PP to match an existing monitor or printer means when you upgrade or as advances are made you may need to revise all the work you have done. If you have discarded the colour information it cannot be recovered by moving back to a larger colour space.

Files edited in RT remain unchanged. They do however gain a sidecar file of type .ppt which is applied when the file is re-opened. Said file .ppt can be viewed and even edited in a text editor. The saved file can also optionally be given a side-car file which I'm sure would be useful to some.

[ajohnw]

I am sorry if it confuses you. Look forward to seeing your solution.

How long to you think monitors with only sRGB will be manufactured? I just recommend that everyone keep thier files and PP efforts in a colour space that is reasonably future proof.

t doesn't confuse me at all - just others including you by the sound of it.

I only output sRGB images so am well aware of the fact that aRGB images can look different when colour managed into sRGB.in a browser as they are posted at times. If I printed images myself, or at all I would be aRGB capable.

You have hit on the reason I don't use aRGB at all, things are very likely to change at some point. Probably to 3 10bit colour channels or it mght get computerised and go to some binary friendly number such as 16 even though few cameras can make any use of it. 32 bit is even a possibility also floating point. The catch with that area as far as the web is concerned is bandwidt but some operating systems can already support bigger numbers. They have probably gone further than needed to avoid doing the work again - ever. This area isn't that straight forward anymore. I have been away from windows for a long time now but assume they have introduced transparency as well. What they do is have 3x8 colour and use the extra 8 bits in a 32 bit set up for transparency. The next logical step is 64bit. even though much of it may not be used.

Then comes monitors. Now LED backlights are used there is probably zero difference in the cost of aRGB monitors against sRGB. There may never have been really only the quantities sold might have influenced price. Currently true 10 bit channel monitors are more than thin on the ground. Instead the vast bulk use 8 plus another 2 which are dithered. I have personal feelings about that word from PC colours of the past. Probably baseless in this case but ...............

The real killer in this area is the shear number of sRGB images on the web compared with the tiny number by people who will mostly be photographers who use aRGB which is fully understandable if they use it for printing as it helps make up for the lack of dynamic range this medium has. More so near ProPhoto etc.

If things change to some significant degree all sorts of things might happen. For instance say the sRGB gamut was simply extended so that it covered a larger gamut. It would still display current sRGB images correctly and the new ones. The sort of effect this would have can be seen currently by viewing and adjusting images in 10bit aRGB. From comments it's wonderful. Trouble is that is all that can be done with them at the moment is viewing as far as I am aware.

The next question is if things change what will it go to. aRGB? Actually I suspect that is doubtful as there are some more powerful forces such as microsoft about. They already have some interesting image format standards. Then there are the international colour organisations and personally I wouldn't forget the TV people. One suits all would make a lot of sense. aRGB has one advantage as many cameras will take aRGB jpg's. You should try adjusting one compared with sRGB. Manufacturers love situations that eventually cause people to upgrade so even that aspect is dubious.

Really the most future proof image format is sRGB and it's likely to remain like that for some time.Shear numbers will ensure that.

Keeping all data in an image - that is the raw file or maybe converting to adobe dng. That has been released freely as an attempt to get camera manufacturers to standardise as I understand it. aRGB too primarily aimed at printing, a clone of another complete with a mistake. Hopefully all raw file processing packages people use keep the processing steps as well so that images can simply be reloaded and further adjustments made if needed.

Next time I buy a monitor it will be aRGB capable as my favourite manufacturers has started putting 6+2 panels out rather than true 8. One thing I will,be interested in is what 10bit aRGB images actually look like. I'll be using a format that is intended to enhance dynamic range after a fashion and I wonder if I will want to knock it back as it may look odd on a screen. At times I need to get a life and instead wonder about things like that. This is why I also look around to see if there are any deeper colour image formats that look like they will come to the fore as well. Doesn't look like it to me. Only more complex colour management so that the few who don't use sRGB can get by and accept that others may be presented with something other than what they saw when the prepared it.

One thing for sure it's an interesting area. I recently came across a web page that claimed that a recent popular fashion colour couldn't be accurately recorded on a camera. True - pass, problem with the web and it might have been posted by some one who due to their job has very very acute colour vision.

John
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[ajohnw]

I should have added a foot note to that. The way gamuts are manipulated they can all in principle contain any bit depth. The span of the colours is set by the gamut not it's bit depth. For instance prophoto could be covered with 3 8 bit colour channels but the steps would be rather big. Equally well it could be covered by 3 x 64bit and the steps would probably be smaller than they need be. So aRGB can be kept in all sort of depths, even in floating point. Savinf 3x10 is more sensible than 3x8 in terms of retaining information but still doesn't hold all of the information in a raw file on many cameras.

John
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