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Philips CPO-TW 60W Light emission spectrum of the 60 W Philips CosmoWhite at nominal power (top, 60 W) and at reduced power (bottom, 36 W), showing a sharp decrease of calcium and cerium iodides' emissions. Despite this dramatic change, this dimmable lamp features a very stable light color temperature of around 2740 K across its wattage range. Keywords: Miscellaneous

Philips CPO-TW 60W


Light emission spectrum of the 60 W Philips CosmoWhite at nominal power (top, 60 W) and at reduced power (bottom, 36 W), showing a sharp decrease of calcium and cerium iodides' emissions. Despite this dramatic change, this dimmable lamp features a very stable light color temperature of around 2740 K across its wattage range.
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Lamp/Fixture Information
Manufacturer:Philips
Model Reference:CPO-TW 60W
Lamp
Lamp Type:Ceramic metal halide
Filament/Radiator Type:Thermal discharge in argon, mercury and metal iodide vapors (Na, Tl, Ce, Ca)
Base:PGZ12
Shape/Finish:Tubular clear
Electrical
Wattage:60 / 36 W (top/bottom)
Voltage:95 / 92 V (top/bottom)
Current:0.65 / 0.38 A (top/bottom)
Optical
Lumen Output:7.20 / 3.24 klm (top/bottom - initial levels)
Lumen Efficacy:120 / 90 lm/W (top/bottom - initial levels)
Colour Temperature:2760 / 2715 K (top/bottom)
Colour Rendering Index:73 / 62 Ra8 (top/bottom)
File information
Filename:CPO_60W.jpg
Album name:Max / Spectra
Keywords:Miscellaneous
Filesize:239 KiB
Date added:07 Jul 2025
Dimensions:1500 x 1021 pixels
Displayed:474 times
Software:Adobe Photoshop CS5 Windows
URL:https://trad-lighting.net/gallery/displayimage.php?pid=908
Favourites:Add to Favourites

Comment 1 to 6 of 6
Page: 1

Tuopeek   [Mon 07 Jul 2025 at 19:28]
Interesting, you say the light colour remains stable as the red end of the spectrum seems to reduce considerably.
Max   [Mon 07 Jul 2025 at 20:10]
So does the blue (Ca) and green (Ce) parts of the spectrum, hence why the measured CCT drops by 45 K only (see data below the description, I measured those). The CosmoWhite is one of the few dimmable CMH lamps developed by Philips, and a consistent light color was one of the key design requirements. Since this is an outdoor lamp, efficacy is more important than CRI and that's why the latter is quite low, and drops noticeably at lower power (a direct consequence of the loss of red).
AgentHalogen_87   [Tue 08 Jul 2025 at 16:42]
I removed a cosmo lantern a couple of years ago with a 45W CPO-TW ballast saying it was permanently dimmed to 55% power. I wish I'd saved that ballast as I've not found another since. But do you have any insight on how a lamp would behave on a ballast like tat?
Max   [Wed 09 Jul 2025 at 06:55]
It's difficult to say. Was the ballast really stuck at 55% power at all time, even during the first 2-5 minutes after ignition, or just during the steady-state regime? The latter case would not be a problem for the lamp as it is designed to operate at reduced power as long as it is started and run up properly (i.e., at full power).
AgentHalogen_87   [Sun 13 Jul 2025 at 15:38]
I unfortunately don't recall. It probably did warm up to full brightness then dim down after. I've been searching for another ever since, still haven't found one Confused
Max   [Mon 14 Jul 2025 at 09:47]
That's not a common system indeed.

Comment 1 to 6 of 6
Page: 1