Florescent lights are everywhere – they come in all shapes and sizes, they are inexpensive and they are energy efficient – they are also one of the worst light sources for photography (the bulbs used in street lamps and some industrial warehouses are much worse – but you rarely find those while photographing while florescent bulbs are everywhere).
There are two problems with florescent lights – flicker and color.
Flicker is the worst of the two, florescent lights flicker, they constantly cycle between different intensities and color, each cycle takes 1/50 or 1/60 of a second, depending on where in the world you are.
When your picture captures just part of a cycle you can get a strange color cast, incorrect exposure and even colored bends in you photo.
To demonstrate I’ve the camera to continues shooting mode and a shutter speed of 1/4000 of a second and pointed it at the round florescent bulb that is right above me, I’ve left the shutter button pressed for about 5 seconds and got a lot of pictures of the same light bulb, I’ve combined them for your viewing pleasure (click image to view larger version):
You can clearly see the color of the light changes between pictures and if you look closely you can also see the amount of light the bulb emits changes drastically between shots.
So what can we do? make sure we capture complete flicker cycles, here the electricity frequency is 50Hz (in the US it’s 60Hz, in most of Europe it’s 50Hz) so I’ve set the shutter speed to 1/50 of a second so I capture one complete cycle and re-run the experiment:
Those 16 identical images are different pictures – it’s just that the total amount and color of light of a complete cycle is completely consistent.
And if a shutter speed of 1/50 or 1/60 does not give you correct exposure you can select a longer shutter speed that covers complete cycles – in the US this will be 1/60 for one cycle, 1/30 for two, 1/15 for four, etc. and in Europe it will be 1/50 for one, 1/25 for two, 1/13 for four and so on.
If you remember in the beginning I’ve said the second problem of fluorescent lights is color – so I took just one more picture of that same light bulb, but this time with I’ve set the white balance to daylight:
If you look at the white ceiling around the light bulb you will see it’s green! you can fix this by setting your white balance to fluorescent – but if you have both fluorescent light and daylight or indecent light in the same picture this will cause a strange color cast that’s hard to fix.
If you mix indecent and daylight you can get the indecent to be white and the daylight to be cold blue or the daylight to be white and the indecent to be worm yellow – both will produce acceptable images but if you throw florescent into the mix you get a green cast – and unless you want people’s skin to look sickly green (or you are photographing zombies) you really don’t want a green color cast.
Also, unlike daylight and indecent light (and light emitted by fire) there are some wavelengths of light that are completely missing from fluorescent lights, this will cause some colors to look completely different under daylight or fluorescent lights – and this can’t be fixed by setting the white balance.
Luckily, the color issue with today’s fluorescent lights is not nearly as bad as it used to be and we can expect (or at least hope) this will continue to get better.
That’s it for today, hope this helps you the next time you take photos in a fluorescent-lit room, see you next week.