Mercury Vapor vs. Metal Halide
These two are both Thorn, one a 250W 240V 'Kolorlux' MBF/U mercury, and the other a 400W 240V MBI/H 'Kolorarc' phosphored metal halide. Both are almost new lamps.
This was an experiment to see if I could capture the difference in colour temperature between the two lamps as they warmed up.
This picture showed something I wasn't really expecting- the 400W MBI lamp (at the back) is noticibly green...the reason for this is that it's not being burned exactly horizontally- it is designed to be burned within 15 deg. of horizontal but in practice a much smaller angle will affect it- I propped it up exactly horizontally after I shot the video, tried it again and it was white with not a hint of green. The mercury lamp doesn't care! It's phosphor is less opaque than the MBI lamp, you can just see the arc through it...
Here's the video
Click here for the video (Realvideo) if you don't want to use the mp4 version.
It is only about a minute and a half long- the first 30 secs are in 'real' time, then it speeds up so the next 5 minutes are compressed into one. The time is bottom right of the frame (Realvideo version only).
Notice the mercury lamp (at the front) is noticably red when it is warming up- the colour that the phosphor contributes to the light output. The phosphor of the metal halide lamp might not be a phosphor at all- it might just be a diffuse translucent coating...I'm not sure.
It is only about a minute and a half long- the first 30 secs are in 'real' time, then it speeds up so the next 5 minutes are compressed into one. The time is bottom right of the frame (Realvideo version only).
Notice the mercury lamp (at the front) is noticably red when it is warming up- the colour that the phosphor contributes to the light output. The phosphor of the metal halide lamp might not be a phosphor at all- it might just be a diffuse translucent coating...I'm not sure.