Pure primary color shows other primaries?

hi, i'm trying head around how hsl sliders in lightroom 4.4 control saturation , luminance. in process of doing that, created 4 psds in photoshop, each single layer (i.e. background): of red (255,0,0), blue (0,0,255), green (0,255,0), , gray image (127, 127, 127). when open psds within lightroom, show in histogram having sizeable contribution 2 missing primaries in each: if open blue psd shows red 41.1%, green 18.3%, , blue @ 93.8%, if open red pds shows red 75.4%, green 34.7%, , blue @ 13.7%, if open green psd shows red 61.0%, green 94.2%, , blue @ 37.8%. can please explain what's going on here? i'm not saying how intend use lightroom, created these test images see how extremes of saturation , luminance adjustments affect colors , results got surprised me.

 

first, questions saturation.

 

• let have opened blue psd document. histogram shows red 41.1%, green 18.3%, , blue 93.8%  if drag blue saturation slider way right (i.e. +100), color on screen not change, histogram changes , reflects red 39.0%, green 10.8%, , blue 93.8%. color looks identical, histogram different. happening here?
• also, let have opened blue psd document. expect if grabbed saturation targeted adjustment tool , dragged or down, blue slider change, instead, see both blue , purple saturation sliders changing. why this?
• i similar results regardless of primary rgb color psd open.
• the 1 behavior witnessed within lightroom expected see if dragged blue saturation slider -100, image become gray.

 

now, on luminance.

 

• is luminance synonymous brightness in photoshop? analogous?
• as saturation targeted adjustment tool, when use luminance targeted adjustment tool, instead of seeing blue luminance change, see blue , purple luminance sliders change. why that?
• if drag blue luminance slider +100, color becomes pastel, i.e. though white added color.
• ultimately, have no idea luminance doing in lightroom.

 

 

any , appreciated, thanks!

 

matt

first, should clear saturation not absolute, relative color space. 255/0/0 red in srgb not same 255/0/0 red in adobe rgb. numbers same, color different. inversely, same color have different numbers in srgb , adobe rgb.

 

the lightroom histogram appears give (linear) prophoto readout, if file in different space. (for non-raw files, embedded profile supposedly preserved , not converted linear prophoto, forgot tell histogram...)

 

here's how 255/0/0 red psd reads out in lightroom, in srgb, adobe rgb , prophoto:

 

 

 

 

luminance, in photoshop, not same brightness. brightness 0 - 255 in each rgb channel, combined , averaged. luminance, otoh, equals l channel in lab. difference neatly illustrated here:

 

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