QUOTE(Vincent Pang @ Jun 30 2009, 12:33 PM)
i still don't get why one part of the tube was yellow and not both sides since the tube is round...
Some knowledge of an SLR's focal-plane shutter would help explain that. chucky mentioned this earlier.
Normally, your first shutter opens, exposes the scene for N seconds, and the second shutter closes after it. Let's say it takes 1/100s for a shutter to open and close across the frame.
What happens if you take a 1s exposure? The first shutter opens, and one second after, the second shutter closes.
What happens if you take a 1/200s exposure? The first shutter opens, and 1/200s after, the second shutter closes.
What's the difference? In the 1/200s case, the first shutter is still opening halfway as the second shutter is closing. So at any one time, only a maximum of half the frame is exposed. In addition, one side of the frame is delayed from the other side.
Like this:

So when you took that photo, you managed to capture varying phases of the fluroscent light phosphors in a single frame. One side of the light is yellow and the other not as a consequence of 1) the shutter exposing your photo in a horizontal slit moving down/upwards, and 2) your diagonal orientation of the lights.
In short, there's a solid reason explaining why your photos turned out that way, and it doesn't have anything to do with the filters.
Here ya go -
http://en.wikipedia.org/wiki/Focal_plane_shutter
Added on June 30, 2009, 11:48 amQUOTE(chucky @ Jun 29 2009, 03:46 PM)
1. Shooting fluorescent lighting is bad if you wanna compare colour, because depending on which phase of the 50 Hz you are shooting, you will get different colour white balance.
2. (FYI the fluorescent lighting is flickering at a frequency of 50Hz because that's what our power supply is running at.)
Sorry if this has been pointed out before...
1. Only matters if you're doing high speed shooting.
2. Electronic ballasts for fluorescent lights switch at about 20,000Hz. They're more energy efficient and have instant startup too