Hello to you all,
I'm wondering how to simulate in Photoshop the Adobe Lightroom Split toning for grayscale colorizing (for those who don't know it, Lightroom has a channel mixer grayscale conversion followed by a Highlights/Shadows hue/sat sliders) and I need help...
The first obvious way (two sat colorizing adj. layers with alpha mask: select, color range, highlights the first and shadows the second) gave horrible posterisation, compared to the Lightroom smooth result.
So I tryed again the two sat adj layers with different alpha mask (a luminosity mask and an inverted one) but again no luck. Better, but not as subtle effect as Lightroom's one -- and if you switch the sat layers you get different colors!
I can't figure out how to proceed... I'd like to avoid messing around with duotones etc. It must be an easier way, but I'm not able to find it.

Any clue? All suggestions greatly appreciated!
Best regards,
unDavide