LR printing - a bit confused

[davidedric]

Hi,

Almost a follow up to an earlier thread.

I am soft proofing in LR4. I have chosen a monochrome image, and there are NO out of gamut warnings, either on the monitor or the printer.

However, if I toggle between the Perceptual and Relative rendering intents, there is a distinct change in the appearance of the proof image (basically, perceptual appears brighter and a bit more contrasty).

I thought I was beginning to understand this stuff, and I thought the different renderings only affected things if there are out-of-gamut colours, but obviously wrong.

Any help gratefully received.

Dave

[Carl in Louisiana]

Hey Dave, maybe this tutorial will help if I understand your problem correctly.

http://tv.adobe.com/watch/whats-new-...oofing-images/

[Polar01]

Dave: it's monochrome, only 256 shades of grey it can never be out of gamut, out of gamut shows colours that the printer can not actually reporduce so it has to shift the colours to something it can reproduce.
Cheers:

Allan

[davidedric]

Thanks guys,

I think light is slowly dawning - my brain used to work OK once, honest

So. perceptual and relative rendering are colour space conversions, between display and printer. They are not to do with the actual colours present in the image. Hence the two different renderings potentially look different on any image, even if the images colour space is completely contained within both gamuts?

In which case relative colormetric will give the most accurate reproduction, in this case, since it will effectively discard any potential colours outside of the target gamut, and in this case there aren't any? (I'm looking at the diagrams in the CiC tutorial.)

Dave

[Macmahon]

....

So. perceptual and relative rendering are colour space conversions, between display and printer. ...

Not between display and printer colour spaces, but between working colour space - the space in which the image is encoded - and printer colour space, as I understand it

They are not to do with the actual colours present in the image. Hence the two different renderings potentially look different on any image, even if the images colour space is completely contained within both gamuts?
Dave

Yes. The numbers for all colours change under each rendering intent (whether or not the colours are represented in the image: although it's academic if they're not).

In perceptual rendering all colours are 'shrunk', as it were, so that the extreme saturated colours of the image colour space (whether or not they exist in a particular image) are mapped to the most saturated colour of the same hue in the printer space. All colours in an image are shifted whether or not they are outside the gamut of the printer space.

In relative colorimetric rendering, out of gamut colours are not discarded, but are all mapped to the most saturated colour of the appropriate hue in the printer space. As I understand it, whether or not in-gamut colours are shifted under rel.col. rendering depends whether there is a difference in the white points of the image space and the intended output space.

Cheers

Tim

[davidedric]

Not between display and printer colour spaces, but between working colour space - the space in which the image is encoded - and printer colour space, as I understand it

Thanks, Tim, very helpful. Yes, you are right of course. As I understand it, there is one conversion between the working colour space and display device, and another between the working colour space and the printer?

Dave

[Colin Southern]

As I understand it, there is one conversion between the working colour space and display device, and another between the working colour space and the printer?

In a non-soft-proof situation there is one conversion between the internal representation of the image ("working space") and the monitor when you display the image. When you print the image there is a conversion between the internal representation of the image ("working space") and the printer. The printer isn't interested in the conversion that appears on your monitor (and vice-versa) - both the image on the screen and image on the printer are "best effort" real-world approximations of the internal representation of the image (or as we say "the map is not the territory").

When you soft proof though, you're in essence doing a double conversion - but - it still has to physically be reduced to something the monitor is capable of displaying which usually means (in my opinion anyway) that soft-proofing is next to useless in a visual sense because the gamuts of printers and monitors are generally significantly different once you get out of sRGB (although monitors are slowly catching up).

[davidedric]

Thanks, Colin.

that soft-proofing is next to useless in a visual sense because the gamuts of printers and monitors are generally significantly different once you get out of sRGB

I'm just trying to get to grips with using Lightroom for printing (I think you are a CS man, a bit beyond LR ). What LR does give you when soft proofing are a couple of warnings, similar to the highlight and black clipping warnings, that show out of gamut regions for either display or target printer profile. I haven't yet worked out how much use this is!

Incidentally, I was viewing one of the George Jardine videos on LR soft proofing, and I just loved the 3D manipulation that he could do with colour spaces using ColorThink Pro. I had a look and saw the price! DO you know of anything similar? Again, I'm not sure how useful in practice but I did like the ability to see in 3D where the out of gamut issues are.

Cheers,

Dave

[Donald]

This thread just makes me nervous, as I sit here waiting for my Epson R3000 to arrive (Wednesday hopefully). But thanks for asking the questions, Dave.

You always know that you're at the beginning of the learning curve when you are unsure even of what the questions are that you need to ask.

I've put a tag on the thread so that I'll be able to easily find it again when I need it (which I have no doubt I will).

[DanK]

which usually means (in my opinion anyway) that soft-proofing is next to useless in a visual sense because the gamuts of printers and monitors are generally significantly different once you get out of sRGB (although monitors are slowly catching up).

I'm a relative novice in printing my own, but I have not found this to be the case. I have not found soft proofing to be all that valuable when printing to a relatively wide-gamut paper, but I have found it very valuable when printing to matte papers with more limited gamut. It provides a quick way to compare (even if approximately) perceptual with relative rendering. It provides a nice warning about what is out of gamut, although to be frank, I have not often found myself able to compensate well and sometimes use this as a hint to change papers. It also shows how much tonal range and contrast will be lost, and that is easier to correct.

[Colin Southern]

I'm a relative novice in printing my own, but I have not found this to be the case. I have not found soft proofing to be all that valuable when printing to a relatively wide-gamut paper, but I have found it very valuable when printing to matte papers with more limited gamut. It provides a quick way to compare (even if approximately) perceptual with relative rendering. It provides a nice warning about what is out of gamut, although to be frank, I have not often found myself able to compensate well and sometimes use this as a hint to change papers. It also shows how much tonal range and contrast will be lost, and that is easier to correct.

Hi Dan,

I think you might have missed the key word "VISUALLY" from my post. Things like gamut warnings work OK; it's just that visually, I find it next to useless trying to simulate how a wide-gamut CMYK subtractive-colour device will produce a wide-gamut image by simulating it on an RGB additive-colour narrow-gamut device.

[davidedric]

This may be getting a bit surreal, but.......

How do I map my own eyes' gamut? If I have red/green colour blindness, then there must be a problem. But "presumably" I can't see any colours outside my own (rgb?) gamut?

Another glass of wine called for.

Sadly, I have a very poor sense of smell, so I can't appreciate fine wine in the way that I think others can

[Macmahon]

This may be getting a bit surreal, but.......

How do I map my own eyes' gamut? If I have red/green colour blindness, then there must be a problem. But "presumably" I can't see any colours outside my own (rgb?) gamut?

Another glass of wine called for.

Sadly, I have a very poor sense of smell, so I can't appreciate fine wine in the way that I think others can

Heh heh! With you on that Dave... but I drink it 'cos I like the visual on the label!

The out-of-gamut (OOG) warnings on Lightroom's soft-proofing are very useful in the respect that you know what colours you're seeing on the monitor that are not correct and so may look different in print (for most monitors they're in the highly saturated blue/cyans) and which colours you are seeing on the monitor which have been changed for print by the print rendering (often highly saturated red/orange/yellow).

The trouble with soft proofing in general is that you can get an indication which colours are OOG but no indication of how much they're out of gamut.

Funnily enough, print renderings from a decent print profile mean that the colours that are OOG for the printer (well, ink and paper) are treated so cleverly that you need to be pretty savvy (or have a good sense of smell) to notice; whereas colours that are OOG for the monitor can really surprise you when you see them in print.

Years ago I spent a lot of time effort, and no little $$, chasing what I thought was a printing problem, only to discover (after LR 4) that the issue was with my monitor all along.

Colorthink is useful - you can compare the colours in your image with the gamut limits of your monitor, ink/paper, sRGB or any other colour space to see how they'll be clipped or need to be rendered. But, to be honest, I use it more for teaching about this stuff than with real images. Lightroom tells me quite enough.
(I have Colorthink 2, rather than Pro. I don't think it was that expensive.)

OK. All that has persuaded me to open another bottle of burgundy. I need to test its gamut!

Tim

[Colin Southern]

The trouble with soft proofing in general is that you can get an indication which colours are OOG but no indication of how much they're out of gamut.

Just chuck on an adjustment layer (eg saturation or levels) - tweak it - and see how easily the OOG "gives up" - if it's easy then it's not far OOG.

Often though, the print doesn't look at bad as people expect; I commonly get colour issues in places, but generally people don't know how it's supposed to look anyway, so it's not an issue.