One of the most common questions when someone starts using a little advanced camera is about what color space to use. Most compact cameras do not raise this question, but the most sophisticated and the reflex, we can choose to work in AdobeRGB or sRGB .

The color space is like the palette available to the painter to paint your picture. Depending on what colors may be better or worse represented scenes. It is not, as is sometimes read in many colors, they all have the same amount (16.7 million when working with 8 bits per color) but how they are distributed.

Simplified to give an example we could have two spaces understandable "gray" which only had four rings. Where Agris would call pure white, pure black and two gray, 33% and 66%. In what could be called sGris four gray to 20%, 40%, 60% and 80%. Then we would say that is broader than Agris sGris as they could be more tones that are at the ends. However, his tones are further apart than those of sGris. This makes it impossible to sGris represent some shades (white and black).

Basically that's the difference between AdobeRGB and sRGB , the first is broader and may pose a greater range of colors, especially in cyan and green. In any case, both are far from being able to represent all the colors the human eye can see.

Color spaces are represented as triangles contained within the CIELab diagram, allowing to easily compare their amplitudes. AdobeRGB covers 50% of visible colors represented in CIELAB.

Moreover, since both spaces have the same number of colors, it is clear that AdobeRGB two contiguous colors are further apart than in sRGB, which can be harmful when it comes to represent smooth gradations.

But the reason for choosing one or another color space is closely linked to the possibilities of the medium we use to view the photos. In principle we should start from the assumption that all computer monitors are incapable of representing anything wider than sRGB. Not in vain this space is created HP and Microsoft in 1996 for use in CRT monitors. Currently this is not true and there are models that cover the AdobeRGB, but they are few and are not common. In addition, Web browsers do not usually support more colors than the sRGB, with the exception of Safari and the forthcoming version 3 of Firefox. Therefore, when we go to post pictures on the net will be required to use sRGB. Otherwise the colors will look different than we expected. View current developments in monitors and browsers, it is likely that in a few years you have to change this recommendation and we can use AdobeRGB for web images.

Systems instead of printing can reproduce much more range, and may comprise AbobeRGB (in fact, that space was created for printers), so that when we go to send to print an image, we use it, provided they confirm before the laboratory that their equipment is used. If in doubt, sRGB is the lowest common that always works, even at the cost of color gamut.

If printing at home we can believe that because these are used CMYK inks with the printer, but is wrong. What matters is not the ink but color management that makes the driver and that is in RGB. Only printers with the prepress RIP processor using a CMYK model. Therefore the conversion to CMYK space, much smaller even than the sRGB, is justified only when it is sending four color printing press.

In the second part of this article we will see the difference that color spaces to reveal a RAW file.

Other articles in this series:

1. "AdobeRGB or sRGB? (I) (This post)
2. "AdobeRGB or sRGB? (II)
3. "AdobeRGB or sRGB? (YIII)