Straightforward color management explanation needed

[bbc]

Hi,

 

I shoot slide film and have it scanned to a CD at the lab I use. I then edit them in

Photoshop and send them to print.

 

I'm a bit confused by colour management. I know why it's needed - due to different

devices having different gamuts, colour management is used to ensure that your print

comes out as close as possible to what you see on the screen. I kind of understand it and

what's involved, but I think I need a very straightforward explanation of what needs to be

done and why.

 

 

 

 

1. First of all, monitor calibration. Why? On my iBook there are various options when

calibrating the monitor and I don't fully understand why I need to calibrate it. There is

already a preset profile for the monitor.

 

(a) why would I need to use any other settings (specifically the native white point)?

 

(b) does my room's lighting (e.g. tungsten, fluorescent, daylight) determine the need to

calibrate the monitor?

 

 

 

 

2. Secondly - monitor profile/working space.

 

a) for an image with a embedded profile, should I convert it to my monitor's profile upon

opening it, or keep the embedded profile?

 

b) for images without embedded profiles, should I assign the monitor profile to them?

 

c) The images on my CD's are in RGB colour space. At what point in the editing process

should I convert them to CMYK? Or should I just ask the lab to give me CMYK images if

that's possible?

 

 

 

 

3. Thirdly - printer profiles. I've been told that, before making adjustments to the image, I

should

 

a) make a duplicate,

 

b) then apply a soft proof to it (view > proof > custom and then choose the printer

profile), so that I can see what it will look like when printed.

 

c) Then, once the soft proof is applied, I should start making the adjustments (e.g. levels,

saturation, colour balance etc.).

 

d) Once I get the image looking how I want it, I then convert it to the printer profile, save

it, and then print.

 

Is this correct?

 

 

 

 

Cheers,

 

- Lee

[andrew_rodney1]

> 1. First of all, monitor calibration. Why? On my iBook there are various

> options when calibrating the monitor and I don't fully understand why I need

> to calibrate it. There is already a preset profile for the monitor.

 

Because every display is different and they change over time. The same set of numbers will

look differently on different displays and even the same display over time.

 

It's like asking, why replenish a film line? It falls outside spec (calibration).

 

> (a) why would I need to use any other settings (specifically the native white

> point)?

 

For an LCD, you don't. But what IS the native white point? The ICC profile will record this

data for correct previewing inside ICC aware applications like Photoshop. The actual

calibration isn't as critical as the profile that describes the current behavior of the device

for the CMS.

 

> (b) does my room's lighting (e.g. tungsten, fluorescent, daylight) determine

> the need to calibrate the monitor?

 

It affects your perception of the display and the print.

 

> 2. Secondly - monitor profile/working space.

>

> a) for an image with a embedded profile, should I convert it to my monitor's

> profile upon opening it, or keep the embedded profile?

 

No, never. That's a highly device dependent color space. All RGB working spaces are the

opposite. They are not based on any single device.

 

> b) for images without embedded profiles, should I assign the monitor profile

> to them?

 

Maybe. It depends on if the image came from a device that's anything like your display.

Probably not. First question is why did you get a bloody untagged file? What did someone

give you RGB mystery meat? Then, where did it come from and do you have a profile that

accurately tells Photoshop what the numbers in the file really means. That's all a profile

does. What does R255/G45/B89 look like? No way to say unless you ALSO define the color

space those numbers belong to. That's what the profiles do. The give the numbers a scale,

a meaning.

 

> c) The images on my CD's are in RGB colour space. At what point in the

> editing process should I convert them to CMYK? Or should I just ask the lab to

> give me CMYK images if that's possible?

 

What RGB color space? There are millions of them.

 

What CMYK device? You need a profile to produce the right set of RGB numbers (or CMYK

numbers) for the specific device.

 

> 3. Thirdly - printer profiles. I've been told that, before making adjustments

> to the image, I should

>

> a) make a duplicate,

 

Yes.

 

> b) then apply a soft proof to it (view > proof > custom and then choose the

> printer profile), so that I can see what it will look like when printed.

 

Yes

> c) Then, once the soft proof is applied, I should start making the

> adjustments (e.g. levels, saturation, colour balance etc.).

 

Yes.

 

> d) Once I get the image looking how I want it, I then convert it to the

> printer profile, save it, and then print.

 

Yes. Keeping the original RGB data alone for all other devices you wish to output to then

going through the process over again. You don't want to edit the numbers based on one

device (unless that's the ONLY device you'll ever send the numbers to which is unlikely).

[rhaytana__tim_adams_]

If I can ask a follow-up, specifically to Andrew Rodney, one of the more obviously knowledgeable folks to be found here:

 

My rough impressions are:

 

1. You calibrate the monitor, but the monitor's ICC profile isn't usually assigned to anything. It just corrects what's seen onscreen.

 

2. The film scanner or other acquisition device has or can have an ICC profile.

 

3. The image is tagged with a broad gamut profile (such as Adobe RGB or ProPhoto) as it is brought into Photoshop.

 

4. It is converted to the printer ICC profile before printing (or printed to the printer's profile, if that's a more appropriate terminology.)

 

Does that eighty word overview convey the essentials, or have I missed something crucial? (And if I'm wandering off topic here, please forgive me.)

[bbc]

Thank you both very much for your replies. Much appreciated - I understand the process a

lot better now.

 

Andy - I'm feeling a bit dumb as I had a late night and an early morning. One more

question I need to ask is about Photoshop > Color Settings.

 

Working space - I have the choice to use Adobe RGB, which in the PS help file is described

as the largest recommended RGB working space and suited for print production with a

broad range of colours. I'm not sure whether I should use this instead of my "Color LCD

Calibrated" working space. The two are very different; I'm a bit lost as to which

one I should choose and why.

 

Thanks again for your replies,

 

- Lee

[bbc]

Last question, I promise. You can ignore the above question if you want to. The Help file

says: "Some RGB working space options are device-dependent (such as a monitor-profile-

based working space) and some are device-independent (such as Adobe RGB, Apple RGB,

and sRGB). It's probably best to use a device-independent working space for most image

editing."

 

That seems to answer the above question; I take it that using Adobe RGB as my working

space is the best thing to do. However, I'm confused as to whether I choose 'Preserve

Embedded Profiles' or 'Convert to Working RGB' in Color Management Policies.

[ellis_vener_photography]

<I>1. You calibrate the monitor, but the monitor's ICC profile isn't usually assigned to

anything. It just corrects what's seen onscreen.</I><P>

Yes this is correct the monitor's profile is assigned just to the signal going o the

monitor.<P>

 

<I>2. The film scanner or other acquisition device has or can have an ICC profile.

</I><P>Yes. it is an image generating device. Scanners come with generic profiles for

that

make and model of scanner. Whether that generic profile is accurate for that specific

scanner is the question. Creating a profile for an individual scanner is the ideal

solution.<P>

 

 

 

<I>3. The image is tagged with a broad gamut profile (such as Adobe RGB or Pro Photo)

as

it is

brought into Photoshop.</I><P>

Workspaces like Adobe RGB (1998), sRGB and Pro Photo are not exactly "broad gamut

profiles and should not be thought of in that way. Workspaces are a special over class of

colorspaces -- They are ideals where equal amounts of information in the three color

channels -- Red, Green, and Blue -- produce a neutral gray without a color bias in any

direction. Image making and reproduction devices -- cameras, scanners, monitors and

printers can't do this. This is why they need device specific calibration & profiling. The goal

of profiling (also known as characterization) is to examine the native state of the input or

output of the device, determine the limits of that device and then to apply a custom set of

algorithms o the signals coming from or going to a device to correct the performance

of the device back as closely to neutral as the device as is possible. More importantly the

goal is to be able to make sure that no matter what monitor or printer or printing method

( and by printer and printing method I mean: a printer, a specific set of inks or dyes and a

single paper stock) is used to reproduce the image that the results should --within the

limitations of that device and method match up. if you are only ever going to use one

scanner , one monitor and one printer and somehow are blessed with devices whose

performance over time will never change (in the case of printers this includes inks and

paper stock; in the case of monitors it means that the performance of the monitor

components will never change as they age)) then you would be extremely lucky and would

not need to be so concerned with all of this. Once you grasp the idea that changing inks,

paper or printer /printing method and that the components in your monitor are going to

age you understand the necessity of accurate calibration and profiling -- if you are

concerned with the idea that you want to be able to accurately reproduce an

image.<P><I>

4. It is converted to the printer ICC profile before printing (or printed to the printer's

profile, if that's a more appropriate terminology.)</I><P>Yes.

[andrew_rodney1]

-->That seems to answer the above question; I take it that using Adobe RGB as my

working space is the best thing to do. However, I'm confused as to whether I choose

'Preserve Embedded Profiles' or 'Convert to Working RGB' in Color Management Polici

[rhaytana__tim_adams_]

Thank you, Ellis Vener, for your thoughtful response. I have read and read about color management and have scratched my head for an overview that I, at least, can understand, and now I think I have one. I'm grateful.