Question about RGB output profiles in RawTherapee

Processing
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Hi, I am a new convert from LR, which I used for many years. I have really been enjoying learning about and using RawTherapee, to a large degree thanks to Andy Astbury’s excellent videos on YouTube. I have also been referencing RawPedia.

In any case, for a quick project (12-month calendar) the printer insists that files be submitted as 8-bit JPG or TIFF in sRGB (I would prefer to use Adobe or ProPhoto–I do have a wide gamut monitor). Hence, I am wondering which of the sRGB color spaces available in “Output Profile” would yield best results. RawPedia states, “The recommended output profile when you’re saving to an 8-bit format and/or publishing to the web is RT_sRGB”. Hence, I assume that RTv4_sRGB is the correct choice here.

There is also:

No ICM: sRGB output
RTv2_sRGB
sRGB color space profile

I also grabbed ICM profiles from Chromsoft, but I don’t think these apply here.

It would seem that Perceptual rendering intent would be best here, given that this is only an 8-bit image and I want to avoid posterization.

Any comments or suggestions would be appreciated!

Thanks,
Kevin

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This is indeed correct. Good luck with your project!

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Perceptual or Relative colorimetric choice will depend on the type of paper, ink quality and the printer itself, so a test with both intents is suggested.

And it would be better exporting to tiff, so no compression is applied to the image.

Anyway, I think @Andy_Astbury1 would be able to offer better advice here

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Thanks guys! I am going to try using Printique for the 12-month calendar (10"x10"). Neither they nor BayPhoto accept 16-bit files! Not sure why. This is a calendar of France (trip we took in 2019). I did an Ireland calendar a couple years ago using LR.

I am trying to do most color and tone adjustments in the L*AB panel, but am very new at this approach. I am having a little trouble replicating the sharpness and hues I obtained from some of these same images using LR. I realize this is a huge jump in processing method and will take some practice!

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Ah, BayPhoto - I take it you are west coast US!

So, checking out their website:

Screenshot 2020-12-16 at 10.29.52
Screenshot 2020-12-16 at 10.29.52976×840 115 KB

Firstly, files need to be 8bit - there is little difference between TIFF and JPEG if the files are 8bit, as both files would only contain 256 variations of tonal range per channel - so JPEG is perhaps most expedient from that PoV.

If you did opt for TIFF then there must be NO LAYERS, MASKS or other spare alpha channels - in other words FLATTEN IMAGE in Photoshop terms.

Next, colour space.

They specify sRGB or AdobeRGB - do NOT send them images in any other colour space. And that means RTv4_sRGB too!

RTv4_sRGB and say Rec709 are equivalent to sRGB, and won’t make your images any different in appearance or values, but the colour space tags (the profile name) is very different from sRGB so their RIP will reject them.

This is the one danger with RT if you do not understand colour management TOGETHER with global photo industry standards. The ‘stills’ industry generally uses just two standard colour spaces for image delivery:
sRGB
AdobeRGB1998

And so the plethora of output profiles available in RT are meaningless, and downright confusing for a lot of people.

One of my videos on YT shows how to install sRGB (industry standard tag), AdobeRGB1998 and ProPhoto (gamma corrected Melissa/Lightroom output equivalent) into RT.

then jump to

If you still have Lightroom on your system then I would prep your raw files in RT then save them in the ProPhotoRGB colour space, then import those images into Lightroom and soft-proof them all for sRGB, then export them out of Lightroom as sRGB JPEGs to a folder you can upload to BayPhoto - it’s a logical process.

Finally rendering intent - 99% of the time Relative Colormetric with Black point compensation is the one to go for.

But for goodness sakes do not send them images tagged with the RTv4_sRGB space as it will confuse them :smiley:

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This is not what the website says. “Other color spaces can be embedded, but our processess may not be able to reproduce all the colors within larger gamuts, such as ProPhoto RGB”. In other words, they most likely internally, silently convert. Since the gamut of RTv4_sRGB is identical to that of sRGB, there should be zero problems leaving that profile as the embedded one.

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Understand one thing - RTv4_sRGB is a tag colour space that NOTHING outside of RT understands!
On a print rip that’s just going to flag up as ‘unknown space’. This means that someone has got to manually change it.
Some print rips might have an algo that can recognize REC709 or REC2020 tags as they are both international standards, and so might be able to auto-switch to sRGB IEC 61966-2-1:1999.

It’s not the colour space itself that could cause a problem, just the RTv4 tag.

So just output sRGB IEC 61966-2-1:1999 from RT - the image metadata will carry that tag and so avoid the possibility of a problem - why risk causing a problem when you don’t have to??

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You probably have more experience in dealing with physical printing than I have, but I have a very hard time believing this is true. The de facto standard, Photoshop, but also GIMP and other software, is perfectly capable of handling embedded ICC profiles correctly (regardless of their tag name). They are perfectly capable of converting profiles to another suitable working profile, pretty much automatically.

Of course you can export with the ‘real’ sRGB profile from RT directly and maybe avoid trouble, that’s definitely true.

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Correct! But just like Photoshop, a print rip won’t understand the tag and so will stop its job and ask the operator what to do. If he opts to convert to the rip working space then it’ll read the metadata and apply it - and everything will be golden!
But what happens if the rip operator is taking his morning break on the toilet?
The rip just sits there waiting for his input - meanwhile the other 1000 images in the rip queue are being held up.
So just use the sRGB IEC 61966-2-1:1999 output profile instead of RTv4_sRGB and avoid any potential problems in the first place - for Goodness sakes it’s not rocket science.

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Indeed, this is the ‘engineering’ part of digital imaging - communicating clearly with all the parts of the gonkulator. May not be the ‘best’ way, but it’s the most effective…

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I would say it depends on the quality level selected for the JPEG and the image content as well, as it uses lossy DCT compression that can introduce the typical blocky artefacts sometimes. If you have to go with JPEG, then use 95 to be absolutely safe. Otherwise, TIFF gives you lossless (both LZW and ZIP/deflate), or no compression for maximum quality preservation.

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My bad!
All my jpegs for digital delivery are at 100% as standard, just to get the best jpeg conversion - I wrongly assume that everyone else would do the same :crazy_face:

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What a perfect one word description Glen - love it!

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https://www.webster-dictionary.org/definition/gonkulator

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Thanks for the answers gentlemen.

Yes, I am actually on the West Coast (SoCal–the very WORST part, but I’ll spare you my rant about that. Suffice it to say, I left my heart in San Francisco!)

In any case, I am looking at having the calendar done by Printique–any thoughts about them, or opinions vs BayPhoto? I am surprised that neither of these services pitching themselves to pros and serious amateurs accept 16-bit files.

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Which part? I’m in Pasadena.

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LOL, I’m in Pasadena too! (I meant that SoCal is the worst part of the West Coast, not that I live in the worst part of SoCal.)

I do like Pasadena–a whole lot more than the rest of SoCal. I was born and raised here BTW, lived 4 years in Canada, 10 years in SF Bay area. During the pandemic, we miss eating at our favorite restaurants: Russell’s, Mi Piace, Bistro 45, etc.

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Ah well, I really like SoCal, but I grew up in the central valley. I shoot a lot in the desert, so Pasadena is a nice place to live, I can just shoot right over the mountains and I’m there.

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I haven’t explored the deserts too much despite living fairly near. We usually head up the coast to the SF Bay area or Central Coast. We love the beaches, redwoods, and wine country.

Ever seen Troy Paiva’s photography?? Very interesting and visually arresting urban exploration and desert photography. https://lostamerica.com

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Yes, Troy’s work is a major influence on me. In fact, I’ve been shooting out here recently: https://lostamerica.com/2020/06/08/the-dunes-abide/ that house is now just a roof, completely eaten by the sand.