In a simpler definition – A very defined space where exactly this many colours can be displayed/shown, by the device. In other words it is to determine one device’s ability to display the no. of the unique colours (sometimes a part of the device). Be it a computer screen, a mobile phone’s screen, or a tablet’s screen, most of the times it is hardware but in few cases, it is software (for instance – a browser).
sRGB – a colour space jointly created by HP and Microsoft. This profile is the most widely used one for browsers and most of the screens including tablet screens and mobile phone screens. As the below diagram depicts, the largest colour profile next to visually perceivable is ProPhoto RGB, the next smaller one is Adobe RGB and the smallest one is sRGB.
Since sRGB is the most used colour space in the browsers and alike in displays, you are expected to export your images in this colour space, so that the colour you have seen while editing are better displayed by the same file in the other mediums or displays.
Note: Not all the monitors available in the market possess the ability to display all the colours in sRGB. They usually measure it in percentage, for example – 75% of sRGB, 90% of sRGB. If you are a professional you might consider buying a monitor which covers a higher percentage of sRGB, mostly 90% + or even 90% + of Adobe RGB colour space. Dell ultra sharp series monitors have a positive feedback in general.
Adobe RGB – as the name suggests created by Adobe systems and is smaller than ProPhoto RGB but larger than sRGB. Widely printers are using this profile, but it is advisable to check with the printing service provider before sending the files, in which colour space they need. Adobe RGB includes 50% of the colours specified by Lab Colour space.
Many printers and almost all commercial places most likely need the files in this colour space.
ProPhoto RGB – made by Apple, the largest colour profile available, but no devices support this profile yet. Hence if you export your file in this profile, the display medium will convert the file’s colour space into the device’s colour space in a best possible way! and it may show drastic colour differences. ProPhoto RGB includes 90% of all perceivable colours specified by Lab colour space. Currently there are no devices which support this profile. In future, there may.
Note: When you photograph, if you are shooting in RAW mode, you don’t have to worry about which color space to be selected in your camera, because RAW files are only interpreted by the softwares, basically the RAW files contains the data – it is not even a image format. But if you are shooting in jpeg, your color space selection does play an important role. Set Adobe RGB, if the purpose is to send photographs for print. If it is only for web services and display purposes, sRGB is sufficient.
Colour spaces visually explained. Image source – Wikipedia.
All the colour spaces are displayed over the visible colour space to have a better understanding.
If you are using Lightroom to edit your photographs, you do not have to worry about color space as Lightroom is working on the largest colour space ProPhoto RGB. The only place where you have to decide is when you are exporting your file from Lightroom.
Note: When exporting you can apply any of the above colour spaces to your photograph, the thing matters is the purpose of the photograph.
Hope I have made the basic understandings of the colour spaces currently being used. If you have got to say something about colours, comment it. Will be looking forward to it.
Cheers & Happy Photographing.