What could be causing weird reds?

[Stuarte]

On the odd occasions where I have a picture with very strong reds, they look wrong on my combination of LR + Mac (both MacBook Pro and iMac).

These photos (below, neither with serious artistic intent ) gives an idea of what I'm talking about.  Any ideas what might be causing it?  I shoot with an EOS 5D

[jjj]

If you mean they don't look like the Jpegs produced by camera, nothing unusual there, oranges also fare poorly I find. You can calibrate ACR/LR using something like the Fors script, which you'll find refernces to on LL. Search forum [or web] to find out more.
I gather you get 'better' colours using Canon's DPP, but then there are workflow issues compared to LR.

[The Vulcan]

Take a look at this thread - might be helpful

http://luminous-landscape.com/forum/index....showtopic=17064

[Nat Coalson]

I've repeatedly seen that doing Fors calibration results in a huge improvement in the "baseline" defaults for images from a specific camera. I have presets saved for all the cameras I've used over the past 5 years.

Generating the necessary Calibration settings is not difficult but does require an X-Rite Color Checker and some knowledge of Photoshop and ACR to get the correct results.