Re: Cold strong light source

On 2 Dec 2003 10:24:55 -0800, [EMAIL PROTECTED] (Bob) wrote:

>searching for a strong and cold light source bulb, it should emit
>smooth "spikeless" spectrum, ideally as close to equal energy as
>possible, small in size and requiring no or very little ventilation.

Such a bulb does not exist, of course you can run bulbs at high
temperature but it will reduce the life time considerably. Also, bulbs
that emit good color temperature are filtered and the filter typically
reduce the power by 2 fstops so enormous amount of power is needed for
strong illumination levels.

The best light in my opinion is the Osram Dulux L 36W/12-950
fluorescent twin tube, they are continuous spectrum daylight type, not
spiky and they are seriously strong, one such tube is comparable to
something like 1000W of filtered bulb. At about 5400K and 98 CRI they
are very good for color matching and all kind of photographic work,
they provide even, smooth/diffuse illumination due to the very
suitable form-factor, only some 410mm (16") long.

There is for example the Whitestar 12V/50W tungsten halogen (MR16) in
5300K and 6500K CCT, with CRI only at 95 and 12, 24 or 36 degree beam
(6500K is only available in 12 degree). With the filter of course so
comparable to 12.5W bulb without the filter. CCT below 5000K really is
not very useful as  for "cold light" and nowhere near the equal energy
point.

More light power can be had from the multi-metal lamps (like
HQI-Powerstar from Radium and Osram) . These range from 70W to 2000W
or more and there are types with color temp in the range of 5000K to
6000K (with rather high "mired" shift). They need the control gear
like the fluorescent tubes do and they heat up a lot and it is
difficult to obtain smooth, even illumination from the point like
source.

For some reason good daylight sources are not easily available. Even
if you find the tube or bulb then you do not find a luminaire or
fixture to go with them. The alternative is to go and spend a fortune
into dedicated "pro" photographic hardware.

Timo Autiokari