sRGB vs ProPhoto RGB on an Epson 3800

[Abitconfused]

When printing the same colorful image to my Epson 3800, I see almost no difference between an image processed (using 16-bit) and printed in the ProPhoto color space and the same image converted (Photoshop CS6 Edit > Convert to Profile) to sRGB and printed using the same driver presets and paper. Shouldn't there be some difference?

[Simon Garrett]

If you mean it's printed from Prophoto RGB or sRGB, and in each case using colour management, and using a printer profile, then no - they shouldn't look different. That's what colour management does: convert from any colour space to the device colour space, so the colour is "right" on the device.

[Abitconfused]

OK, well I suppose the printer profile, what there is, must be in the printer driver? How can a sRGB image be "improved" to have the same width and breadth colors as a ProPhoto image?

[Simon Garrett]

OK, well I suppose the printer profile, what there is, must be in the printer driver? How can a sRGB image be "improved" to have the same width and breadth colors as a ProPhoto image?

You can't improve sRGB colours to be like ProPhoto. You can't add colours that aren't there.

sRGB and ProPhoto RGB can be represented thus:




All the colours in sRGB are inside the smaller triangle. Compare that to the PhoPhoto RGB with a much bigger range of colour. It contains all the colours of sRGB, and a lot more. But the additional colours are all highly saturated colours which, in practice, aren't all that common in nature.

What that means: most colours in most images are within the sRGB triangle, and will look the same whether they image is represented in sRGB or ProPhoto RGB. The only difference is that very highly saturated colours won't look quite so bright in sRGB. But if you start with an image in sRGB, you can't add colours that aren't there. Well, I suppose you could convert the image to ProPhoto RGB, which in itself won't change the look, and you could then screw up the saturation to "create" highly-saturated colours that weren't there in the sRGB version, but it won't be natural.

[Abitconfused]

I think I get it. We adjust such things as contrast, saturation and exposure in ProPhoto RGB to give us room to maneuver but the final print will not necessarily have more colors than is within the sRGB color space. But you won't lose colors using ProPhoto RGB whereas if you edit in the sRGB color space colors can "fall off the edge." Correct?

[Manfred M]

Ed - regardless of which colour space you are using, you are still limited by your printer's capabilites based on the paper you are using. If you are using a colour managed workflow, your Photoshop printer software (Color managed by Photoshop setting) will do all the conversions for you.

Just because your camera can record it, doesn't mean that your computer screen / printer can reproduce it.

[Abitconfused]

As I understand it now, we generally use a larger color space when adjusting images to retain as much color information as possible. Then output the file within a color space suitable for our needs i.e. sRGB for the internet or ProPhoto RGB to a printer such as the Epson 3800. Is this correct?

[Simon Garrett]

As I understand it now, we generally use a larger color space when adjusting images to retain as much color information as possible.

That's right.

Edited to add: I think we sometimes get a bit obsessive about wide colour spaces. I use ProPhoto RGB for editing as I use Lightroom, and that's what it uses. However, most pixels in the large majority of images have colours within sRGB. Colours outside sRGB are all pretty highly saturated colours which aren't that common in nature. Furthermore, our eyes aren't very sensitive to differences in highly saturated colours. In any case, most monitors can't do more than sRGB, and many printers can't.

I have two monitors: one wide gamut (colour space larger than Adobe RGB) and one with a colour space close to sRGB. In Lightroom, most of the 35,000 raw images I have in the catalogue look virtually identical on the two monitors. In other words, there are no visible areas of colour outside sRGB colour space. Sure, I can create highly saturated blobs of colour in ProPhoto RGB in Photoshop, and they look quite different on the two monitors. But real photographs: the difference is usually hard to discern.

Then output the file within a color space suitable for our needs i.e. sRGB for the internet or ProPhoto RGB to a printer such as the Epson 3800. Is this correct?

With a colour-managed work flow, it doesn't really matter what colour space you keep the image in. Colour managed programs alter the RGB values to be suitable for the output device in use. For example, if the monitor has been calibrated and profiled, there will be a profile for the monitor. A profile contains (among other things) a measurement of the colour space of the device.

So colour-managed programs take the image, get the profile for the image (typically embedded in the image file), get the profile for the monitor (by asking Windows or Mac OS for the profile) and then map RGB values from the image colour space to the monitor colour space. The colour displayed will then be right, in so far as the monitor is able.

People not using colour management, which means most photographers and everyone else, don't generally have profiles for the monitor, and often don't use colour managed browsers. That means the program just sends the RGB values straight to the monitor without any change. However, most monitors have a colour space approximately sRGB. So if you send sRGB images straight to the monitor without alteration, then on most monitors the colours will be approximately correct. Hence, when hosting images on the web, the best bet is to use sRGB. It doesn't matter for people with colour-managed browsers and calibrated/profiled monitors, but most people haven't, and sRGB gives approximately correct colour on typical unmanaged unprofiled monitors.