Manual color-temperature

[vvizard]

If one where to use this, how should it be used? Should one just "know" what the color-temperature for a given scene is? Or is this metered with equipment? Some time ago, I was driving Toyota's new lineup of cars: Avensis, Rav4, Corolla, Yaris, while my sisters ex-boyfriend (a photographer) was hanging out of the car in front, shooting them. Every now and then, he tok his cam down, pointed some other device at the car I was driving, at the sky, at the asphalt, and whatnot, then he did "something" with the cam, and continued to shoot. He was shooting film (medium/large I think). But I didn't ask what the "device" was for, cause I had very little clue about photography at that time. Could this have been something to meter color-temperature? If so, how much does those devices cost, and what to search for at B&H?

If what he used wasn't for this, I would still be interested in oppinions on what it might have been, and of course, then what I should use (or how I should learn) how to set manual color-temperature..

[leony]

What the photog used was an incident light meter - he was just making sure the exposure was proper for the amount of light. If you're shooting in a studio, and are using strobes, that are gelled so that all of them produce the same color temperature, you pull out a very expensive color temperature flash meter and meter the color ballance. Then you set that on your camera. Then of course the problem is how color-accurate the rest of your workflow is. This is, by the way, the reason why all catalogs in the retail and fashion industry where color is critical are still shot with film.

~ L.

[vvizard]

Does this mean that his little "gadget" was just checking exposure in the same way as when we "normal" folks half-press our shutter, so the cam can figure out what exposure is needed? If so, why? Aren't the cams good enough in "guessing" this, or could it be that his film-cam (Hasselblad I think) can't figure out exposure by itself?

And what exactly can be read from such a light-meter? Does it show working shutter/aparture combination, or is it just one number on a scale that means nothing to most of us others? :)

I'm sorry if I'm asking foolish questions, I'm just trying to learn this thing, and would like to know what equipment that exist, and can be used. I would be very mad if I after a couple of years found out that I had spoiled many shots because of errors that could easily been corrected by a $20 plastic-box =) (not saying they actually are this cheap though =))

[Jesper]

vvizard wrote:
Does this mean that his little "gadget" was just checking exposure in the same way as when we "normal" folks half-press our shutter, so the cam can figure out what exposure is needed? If so, why? Aren't the cams good enough in "guessing" this, or could it be that his film-cam (Hasselblad I think) can't figure out exposure by itself?

There are cameras (especially medium and large format cameras like Hasselblad makes them) that don't have a light meter like modern, automatic cameras. The light meter does what you do when you half-press the shutter; it measures the amount of light.

And what exactly can be read from such a light-meter? Does it show working shutter/aparture combination, or is it just one number on a scale that means nothing to most of us others? :)

It shows a number that you can only decode using a secret formula that only Real Pro's know... :) just joking... It depends on the light meter. On the ones I've used you can set a desired shutter speed and it shows you the matching aperture for the measured amount of light or vice versa. It can also show the EV (exposure value) number, which starts to sound like that secret magical number.... explanation of EV values: http://photonotes.org/cgi-bin/entry.pl?id=EV

By the way, a separate light meter is not only useful if your camera doesn´t have a built-in; it's also useful photography with studio flashes, for example. I'm doing a portrait and model photography course; there we use a light meter to measure the output of the flashes before making the photo.

Like light meters, you can also get devices to measure the color temperature.

With your 10D, if you want really accurate colors, you can use custom white balance. See page 52 of the manual of your 10D...

[gsrossano]

There are meters that measure color temperature. Search B&H for "color temperature meter". They used to be stand alone gizmos, but now they are built into regular incident light meters and flash meters also. They are fairly expensive. About $1000 US.

Standarized light sources have a color temperature specified in degerees Kelvin (K). If you know the color temperature of the source (and have only one type of light source) you can dial it into the camera. If you have something neutral to take a reading off of with the camera you can use the custom white balance. If you have different light sources miixed together or flourescent light the color temp can be all over the place.

One final wrinkle, some artificial light sources vary in color on a very short time scale. For exposure times shorter than 1/125 sec the color will vary from frame to frame no matter what you do.

[rdenney]

vvizard wrote:
If one where to use this, how should it be used? Should one just "know" what the color-temperature for a given scene is? Or is this metered with equipment? Some time ago, I was driving Toyota's new lineup of cars: Avensis, Rav4, Corolla, Yaris, while my sisters ex-boyfriend (a photographer) was hanging out of the car in front, shooting them. Every now and then, he tok his cam down, pointed some other device at the car I was driving, at the sky, at the asphalt, and whatnot, then he did "something" with the cam, and continued to shoot. He was shooting film (medium/large I think). But I didn't ask what the "device" was for, cause I had very little clue about photography at that time. Could this have been something to meter color-temperature? If so, how much does those devices cost, and what to search for at B&H?

If what he used wasn't for this, I would still be interested in oppinions on what it might have been, and of course, then what I should use (or how I should learn) how to set manual color-temperature..

In many cases, you'll never know the color temperature of a given scene, even if you have a colorimeter. The reason is that most artificially lit scenes have a variety of color temperatures in them, and finding the right balance is more of an aesthetic choice than an objective setting. Thus, I shoot RAW. One of the real advantages of shooting RAW is that you can adjust the color temperature after the fact. That way I can adjust the color balance so that it is what looks best. If you need it to be precisely corrected, shoot an image in the same light of a Kodak gray card, and adjust the color temperature setting when converting from RAW so that the gray card is 128, 128, 128. It will establish a precisely neutral mid-tone, and come out that way if your monitor and printer are properly calibrated.

Architectural photographers in the pre-digital days would often take multiple exposures of interior scenes in their view cameras. They would cock the shutter and expose the scene lit by just the tungsten lights, using the appropriate correction filter. Then they would recock the shutter and shoot again with just the flourescent lights, with the filter to correct the flourescent to the color balance of their film (usually daylight). They might have left the camera sitting there for a couple of hours after making an exposure with a little entering daylight, again with any needed filters, before waiting for darkness to make those artificial light exposures.

We can simulate the same thing by making an image with each light source (leaving the camera unmoved on a tripod, of course). We correct each image when converting from RAW so that they all have the color cast that we want, and then stack them on separate layers in Photoshop to make a composite image. It's kind of fun if you are into that sort of thing.

Rick "admittedly answering a 10-cent question with a 10-dollar bill" Denney