Choosing the Right Fluorescent Tube
Virtually all Fluorescent tubes have two pins at either end of the tube.
T2 Tubes - 7mm
These are relatively new on the maket, they are only 7mm in diameter.
T4 Tubes - 12mm
These are commonly used in undercabinet fittings and are 12mm in diameter. Be careful when ordering these tubes, as they are not standardised, so lengths can vary from make to make.
T5 Tubes - 16mm
These are the most common slimline tubes, diameter is 16mm.
T8 Tubes - 25mm
Standard size 25mm diameter tubes. Commonly used in ceiling mounted fluorescent fittings.
T12 Tubes - 38mm
The largest tubes are 38mm diameter. These tubes are being phased out by most manufactures, but can be replaced with the slimmer T8 tubes in most cases.
Fluorescent tubes colours
Fluorescent tubes come in a range of different colour temperatures, the chart below gives the most common codes.
Standard (Halophosphate) fluorescent tubes have a colour rending index of 50-70% whereas the Triphosphor fluorescent tubes have a colour rendering index of 85%.
Extra Warm White
The numbers in the above table show the colour code reference that your bulb will say on it. eg. F18W/35 refers to the 18 watt halophosphate fluorescent tube with the colour 35 (White).
Colour Rendering Definition
The Colour Rendering Index is an industry standard reference to a bulb on how well it renders colours of objects it is illuminating. Codes range from 0 to 100, the higher the number the more vivid and lively things look under that light. The lower the CRI rating the more ghostly (faded, dead) objects appear.
If you want your colours to look natural, then high CRI is required. High CRI bulbs generally cost more to buy and cost more to operate as they have low lumen output per watt consumed. Low CRI bulbs put out low quality light, but are very cheap to operate as they have high lumen output per watt consumed.