Outputing Files To ProPhoto RGB in ACR

[danpbphoto]

How do you check that the ouput of ACR to CS4 is ProPhoto RGB?
Is this done within Adobe Bridge? I think it is by the fact that when I go Bridge>File Open in ACR..it does so but it appears the defaul color space as indicated at the blue workflow space beneath the image show "Adobe RGB(1998)." My understanding from numerous articles was that Adobe ACR's native color was PP RGB.
PLEASE excuse what most will think is elementary, I indeed thought it was that until I started to see grave problems in working profiles versus what was printed.
Thanks!
Dan

PS I may have answered my own question by clicking and seeing the "Workflow Option dropdown menu"

[FranciscoDisilvestro]

Correct, you set the output color space with the Workflow Option Dropdown menu.

ACR native space is ProPhotoRGB (or maybe the same gamma 1.0 version used by lightroom) but it works like "soft-proof" with the color space you select in the workflow option.

Also remember that the Histogram correspond to the color space that you select there (so if you select sRGB or AdobeRGB it could show clipped channels because of saturation that are not clipped in ProPhotoRGB)

[danpbphoto]

Many thanks...