Hi,

I have a photo in which the red channel is blown out and the others are fine.Since it's a RAW file I can adjust the exposure so that there's no red channel clipping and I'll end up with two images which I'd like to combine.

Now how do I replace the red channel from the file where it's not blown with the other "bad" red channel?

It depend on picture how You should do the channel mixing but try this
new adjustment layer:channel mixer
mode luminosity

saby

Assuming your using Photoshop - open the channels up select the good red channel - copy to clipboard. Open the bad red channel and paste.

Or in simple terms copy and paste.

Christine

Sorry I miss understood if You can get a good one from raw it's just copy and paste as Christine wrote

saby

Thanks Xaran. Your tip is great and it works really well. I knew there's a simple way to do this. Regards, Ljupco