Photo tungsten filters--why not filter the light bulb?

Factual Questions
1

Tungsten-filament incandescent light bulbs give off a color that is skewed to the orange. Human vision adjusts for it but consumer camera print film is balanced for daylight. So if you take a picture illuminated only by tungsten lighting, everything looks orange. You can buy a filter for the lens that compensates for this balance, making it look to the film like daylight.

Why don’t tungsten light bulbs have the glass tinted the same color as a photographic tungsten filter? That would yield artificial light that is close to daylight, looking “whiter”, even to the human eye.

2

Rather than increase the expense of every light bulb produced in the world, it is far more cheaper to simply alter the spectrum of light entering your camera’s lens.

3

I can think of two reasons.
[list]
[li]First of all people like the yellow ‘warm’ light. Strange, but I guess it reminds us of firelight. There is no light as romantic as candles![/li][li]Economy. Such a filter would absorb quite a lot of light, and reduce the amount of light emitted. Incandescent bulbs are already ineficient enough, there’s no reason to make them more so.[/li]
[/quote]

4

I didn’t really mean to ask, “Why don’t the light bulb manufacturers make life easier for the photogs,” I meant to ask, “Wouldn’t it be an advantage for any application to have light bulbs that are more like natural daylight?”

5

I have not used any in 15 years or so, but blue tinted, or “daylight” photo floods were/are available. The ones I used were about 250 watt and could be used in sockets with attached reflectors. You had to be sure to use ceramic sockets rather than those with cardboard insulation as commenly found in household lamps. I also used tham in my copy stand light units.

You might find them at “Porter’s” a camera store based in Iowa.

Slide films balanced for incadecent bulbs is also available.

6

They also have ‘natural light’ light bulbs but they cost more

7

You can also simply purchase tungsten balanced film. Problem solved.

For any type of situation where a “real” photography would be controlling the scene, filtering the studio lights is indeed a common practice. But this is not feasable for non-set-up-beforehand-photography.

8

You can also purchase gels- floppy plastic sheets of filtering material- for incandescents. The problem is that normal household lights are SO far down the Kelvin Color scale, that to filter them back to daylight would cut out SO much of the available light as to make them almost useless.

Yes, you can buy photofloods. They burn HOT, and don’t last long, but they deliver daylight. And, you can buy stuff like the Duro-Test full-spectrum light bulbs.

See, it’s not just the Kelvin Color scale rating, but the degree of spectrum. These guys make full-spectrum bulbs- GREAT stuff to work under 12 hours a day in an office. I shot a job at the factory years ago, wonderful stuff. Truly amazing.

Anyway. The film comercially sold in most places is, as mentioned, daylight color temperature. ( See the charts below). You can either filter the lens, or deal with the off-colored look.

Tungsten Light- 3,400 Degrees Kelvin

MOST Fluorescents- Cool White- 4,200 Degrees Kelvin

Daylight at high noon in North America ( for those in the know and feeling picky ) - 5,600 Degrees Kelvin

Household Incandescents- below 2,900 Degrees Kelvin. Brually “warm”. See, the higher the number, the cooler the light on film. For example, on an overcast day at dusk, I could get a reading of over 6,500 Degrees Kelvin on a color meter from the cold colored light left in the sky.

Et cetera.

Cartooniverse

9

Another application where tugnsten films are appropriate is photos taken with a microscope. No daylight invovled. Filters in the scope can accomodate rather than a filter in the glass of the bulb. You might have need for different filters and not want the bulb to be filtered.

10

There are applications for filtering the light sources. Filmmakers sometimes use sheets of colored gel with the exact same color filtration properties the OP describes. Mostly they’re used for balancing the color of mixed light sources, like when you have a room lit by standard movie floods but you have large picture windows admitting daylight. You just cover all the windows with the gel, it corrects the daylight to match the interior lighting. And boy is that expensive, the sheets of gel cost a LOT.
But nowadays, this is rarely used unless you have some exterior action or scene that must be visible through the window. Mostly they shoot scenes at night to kill the sunlight, and just supply “daylight” from a lights mounted outside the windows.