Color temperature

[westphoto]

<p>So I was looking at the very green lights outside our door and actually had a good idea for a portrait. My question is what should I expect from fairly green light on daylight balanced film? This isn't green light bulbs, but just some very green halogens or something.</p>

[peterbcarter]

<p>Do a test shot with a digital with white balance set to daylight. It should be close.</p>

[craig_shearman1]

<p>What kind of bulbs are they? Sodium lights (like a street lamp or a big security light) can be green. Fluorescent can also be green. Halogen is usually in the tungsten range (3200K plus or minus, probably a little lower since it's not a photographic lamp) that's on the red size rather than green.<br /><br />Most people cannot tell the color temperatue of a light source just by looking at it since the eye, unlike a camera, compensates. If the light is so green that it looks green to the naked eye, then photos on daylight white balance (digital or daylight film) are going to be very, very green. If you have a digital camera, do some test shots at Peter suggests. Run through the WB options on the camera and see which matches the most.<br /><br />Also keep in mind that green is about the least flattering color you could possibly use for pictures of people. Unless you're shooting Martians, the results are not likely to look good. :)</p>

[westphoto]

<p>Peter, thank you for the obvious solution that I always seem to forget.<br>

Craig, sorry, you're right. They're probably fluorescent, although they're fairly old apartments, so they could even be sodium. I'll take a look at whether or not I can pop the cover off and take a look, because I've been wondering just what would put out so much green myself. And I definitely have the unnaturalness of green in mind. It's certainly just an idea and not a perfectly formed shot in my head. Just trying to flex my creativity and see shots in various forms of light that are easily accessible to me. I'll be sure to post back if anything comes out alright.</p>

[peterbcarter]

<p>Once you know what you are dealing with, you may be able to compensate with your scanning software. I use vuescan and you can adjust the levels of the guns.</p>

[john_shriver]

<p>Some of the non-incandescent bulbs (mercury, sodium) emit very few colors. They aren't "blackbody" radiation so they don't really have a color temperature. In these cases (particularly sodium vapor), monochrome may be the only realistic result.</p>

[glen_h]

<p>Clear (no phosphor) mercury lamps are somewhat green. They have a line spectrum with green and blue (and UV) lines, but not much red. </p>

<p>HPS (high pressure sodium) are a popular pink/orange colored light for street lighting. Due to collision broadening (the atoms collide faster than they can radiate), the spectrum is fairly broad.</p>

<p>LPS (low pressure sodium) has two very narrow and close together yellow lines. They are used for street lighting in San Jose, California. </p>

<p>Color temperature is often used for source that aren't black body, but they have to attempt to be a white light. </p>

[Fotohuis RoVo]

<blockquote>

<p>LPS (low pressure sodium) has two very narrow and close together yellow lines.</p>

 

</blockquote>

<p>590nm +/- 1nm to be precise. Yellow and sold under <em>Osram Duka 10</em> with mechanical aperture to dim.</p>

[bebu_lamar]

<p>With that kind of lighting getting good color balance is impossible not matter is you do post processing or putting color filter on the lens. </p>

[garethspics]

<p>Here's a useful article about colour spectrum. About half way down the page there is a comparison between fluorescent and daylight. Many older fluorescent lights have spikes or gaps in their spectrum which makes them difficult or even impossible to white balance.<br>

http://dba.med.sc.edu/price/irf/Adobe_tg/color/light.html<br>

Fuji used to tout their "4th layer" films which were supposedly able to help in these situations.</p>