Color space when exporting from RAW

Marcin S wrote: Thank you for you helpful replies. Now I know a little bit more about it. But still, this is not completely clear to me. My main question is: when exporting a photo, does Lightroom convert to a profile or assign a profile? Both.    What you mean by both? How should I interpret it? I cannot choose "convert" or "assign", so how they both work together? What does it mean for me wanting to process photo and print in Lab? I can only add, that those 3 photos which I exported to JPEG with 3 different colour spaces, they look different when viewing outside of Lightroom, ie. IrfanView. But when importing those JPEGs into Lightroom, differences are extremly slight. Is that because Lightroom operates in ProPhoto, which covers all colour spaces which I used, and other programs work in sRGB and those photos differently? And the last question for now: will the hardware calibrator help in monitor which is, let's say, medium cost and medium quality? I mainly use it for preparing photos to put them on the website gallery, but would be nice if I could print better ones with a bit of certainty about what I will get from Lab. Many thanks!! Marcin

When you export a photo from LR, it converts to the colour space you select (e.g. sRGB) and embeds the appropriate profile in the exported file. 

If your monitor were calibrated and profiled, and you view with a colour-managed viewer then images should look pretty much identical no matter which colour space you export in.  (W7 Photo viewer is colour managed, the XP equivalent isn't, Mac s/w generally is.  IE and Chrome aren't properly colour managed, Firefox is for all images, Safari is for images with embedded profiles.  Other viewers vary.)  With colour-managed viewers, the only difference should be with very highly saturated colours outside sRGB colour space (and then only if your monitor can display those colours). 

LR is colour managed.  If the monitor isn't calibrated/profiled then I think LR assumes the monitor has a colour space equivalent to sRGB (which is generally roughly right but won't be accurate).  Internally LR uses ProPhoto RGB colour space in develop module, but uses Adobe RGB in Library, and previews are stored in Adobe RGB.  However, the colour space LR uses won't explain why other viewers show things differently.  It's simply that LR is colour managed (which means it converts to/from the image colour space), and I guess the other viewers you're using aren't; they just throw RGB data at the screen without converting. 

Is it worth calibrating and profiling your monitor?  Quite possibly.  Does the colour and brightness vary with viewing angle as you move your head from side to side?  If so, it may be TN technology, and perhaps not worth profiling.  If it looks reasonably stable with different viewing angle then probably yes.