color errors

Forum|Forum|6 years ago
November 1, 2019
2 replies
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How to get printer (Epson ET-2650) to print accurate images of what's shown on Photoshop screen (computer a Dell Inspiron with Windows 10)--both in terms of hue and of light/darkness. Ror example, Is Epson sRBY the correct setting? Or perhaps Epson Standard RBY--Gamma 1.8?

How to

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davescm

Community Expert

Color management is simple. To get correct matching colour, within the limitations of inks, you need three things.

1. A monitor profile, set in your system, that describes your specific monitor. Most do this with a calibration device.

2. A document profile e.g. sRGB or Adobe RGB which describes how the colours in your document should be displayed.

3. A printer profile, specific to your printer, ink and paper combination. Some make their own with specialised hardware and software, but in many cases they can be downloaded from the paper manufacturers.

With those in place color management works.

Dave

A

Adobe@123Author

Participant

Photoshop asks for printer model and type of paper--never saw anything about ink. In any case those 3 steps may be easy for you, but not for someone like me.

davescm

Community Expert

In step 3 the profile will not mention the ink, but if you use a profile for say Epson Premium Glossy photo paper on a specific Epson printer - then use 3rd party inks then the profile is no longer valid.

See if this helps explain further :

Digital images are made up of numbers. In RGB mode, each pixel has a number representing Red, a number representing Green and a Number representing Blue. The problem comes in that different devices can be sent those same numbers but will show different colours. To see a demonstration of this, walk into your local T.V. shop and look at the different coloured pictures – all from the same material.

To ensure the output device is showing the correct colours then a colour management system needs to know two things.

1. What colours do the numbers in the document represent?
This is the job of the document profile which describes the exact colour to be shown when Red=255 and what colour of white is meant when Red=255, Green = 255 and Blue =255. It also describes how the intermediate values move from 0 through to 255 – known as the tone response curve (or sometimes “gamma”).
Examples of colour spaces are (Adobe RGB1998, sRGB IEC61966-2.1)
With the information from the document profile, the colour management system knows what colour is actually represented by the pixel values in the document.

What colour will be displayed on the printer/monitor if it is sent certain pixel values?
This is the job of the monitor/printer&paper profile. It should describe exactly what colours the device is capable of showing and, how the device will respond when sent certain values.
So with a monitor profile that is built to represent the specific monitor (or a printer profile built to represent the specific printer, ink and paper combination) then the colour management system can predict exactly what colours will be shown if it sends specific pixel values to that device.

So armed with those two profiles, the colour management system will convert the numbers in the document to the numbers that must be sent to the device in order that the correct colours are displayed.

So what can go wrong :

The colours look different in Photoshop, which is colour managed, to the colours in a different application which is not colour managed.
This is not actually fault, but it is a commonly raised issue. It is the colour managed version which is correct – the none colour managed application is just sending the document RGB numbers to the output device regardless without any conversion regardless of what they represent in the document and the way they will be displayed on the output device.
The colour settings are changed in Photoshop without understanding what they are for.
This results in the wrong profiles being used and therefore the wrong conversions and the wrong colours.
If Photoshop is set to Preserve embedded profiles – it will use the colour profile within the document.
The profile for the output device is incorrect.
The profile should represent the behaviour of the device exactly. If the wrong profile is used it will not. Equally if the settings on the device are changed in comparison to those settings when the profile was made, then the profile can no longer describe the behaviour of the device. Two examples would be using a printer profile designed for one paper, with a different paper. A second example would be using a monitor profile but changing the colour/contrast etc settings on the monitor.
The monitor profile is set in the operating system (in Windows 10 that is under Settings>System>Display >Advanced) which leads to a potential further issue. Operating system updates can sometimes load a different monitor profile, or a broken profile, which no longer represents the actual monitor.

Colour management is simple to use provided the document profile is correct, always save or export with an embedded profile, and the monitor/printer profile is correct. All the math is done in the background.

I hope that helps

Dave