Just obtained my two F20T12 Grey end capped Philips lamps, and my Sylvania GTE lamp, all three Halophosphate Cool White.
Swapped out both of the LPF Trigger Start ballasts that came with the F20T12 fixtures I've got, for the cold temp versions, successfully.
I was in the middle of comparing the brightness levels of the LPF and HPF ballasts at one point though, but that was short lived... found
out the hard way that not only are both of my F20T12 Philips lamps used, one of them was actually right at EOL. The end blackening did not
indicate this, but then again, both lamps have electrode filament shield guards.
The lamp that went EOL was actually on my HPF Trigger Start ballast as it did so. Rough start up, with very bright filament glow as soon as
the lamp fired up successfully. The filament hotspot glow disappeared for a while, so I automatically assumed it was a broken filament. Wrong...
the filament was still intact but completely spent... so, complete hotspot movement occurred, the end blackened completely, and the lamp went EOL.
Brilliant orange flashing at the bad end as expected... but it dimmed down to start-up stage, just like any other HPF Rapid Start ballast. Not much
flash with this lamp.
Switched the EOL lamp over to the LPF ballast and not surprisingly, it just sits there and rectifies... nothing more.
To my surprise, the brightness level of the LPF Trigger Start ballast was almost comparable to the HPF cold temp Trigger Start ballast, but of
course, the HPF one was still a tad bit brighter.