Hell is Digital Photography (part 1)

Saturday, May 10, 2003

Or: I Went To DemiCon and All I Got Was 800 Crappy-Looking Photos

Yes, you read the title right, I said "hell". After writing in the journal entry about how I was switching from film photography back to digital because of the problem of getting good pictures, you have to be wondering what I'm bitching about now. And I have an answer for you.

In a word: "White Ballance".

Okay, so that's two words, so sue me.

You have to ask yourself when you are taking pictures with any kind of camera, film or digital, video or still: "What color is that white thing, really?" I'm not kidding. It looks white to you, because your brain has grown up knowing that white is white, and when it sees something that it knows is supposed to be white, your brain adjusts your perception so that what you think you see is white.

We learn in art and physics classes that white is really a color that is made by reflecting all colors equally. But what if the light that is being reflected equally has more blue in it than red or green? You will see a blueish-white thing, or a light blue thing. Your brain though, will "color correct" to be white.

Once you know what you are looking for, you can actually see this. On a bright, clear, summer day at noon, find a tree or something that provides complete shade. Stand in the shade, and look at a piece of paper or something that is white. At first, you will see white. But look closely, and you will realize that the piece of paper is actually a light blue. This is because the nice "white" light comming directly from the sun is blocked by whatever is creating the shade, and the piece of paper is actually being lit by the blue sky all around (we said a "clear" day above, which should be read: "no clouds").

This is white ballance, an effort to define what color a white object will actually be, and correct it so that it will look white. This is important, because digital cameras, and film cameras for that matter, don't have a brain like yours. They will put on film, or record digitally, what color something really is with zero regard to your brains sensibilities about what white really looks like.

Thus it is, when you take a night shot of street lights, they all come out green. When you take pictures lit by incandescent lighting, every shot comes out redish-orange.

In a effort to comensate for this effect, some scientist somewhere defined a "color tempurature" scale, so that they could specify what "tempurature" the light was, and adjust for that "tempurature" so that white looks like white. The idea is to take a blackbody radiator and heat it up, and record what tempurature it has to be to radiate "white light", or variations on the theme. Color temp is specified in degrees kelvin. If you don't remember highschool physics, kelvin is like celcius, but 0 is at absolute zero, or -273 degrees celcius.

Now, "white light" still needs to be defined, so what happened is that someone -- probably an intern -- got sent to Washington DC on a bright, clear, summer day, stand on the Plaza there at exactly noon, and recorded the light coming down, and called that light "white light", which turned out to be 5500 degrees kelvin. Meaning that it is totally arbitrary.

But, 5500K is still an important number, because "color corrected light" in a photographic sense is 5500K, and most speedlights, strobes, and flash kits are going to be calibrated to pump out that kind of light.

But as with many things in this world, not all is as it seems. In photography, "warm colors" are redish, and "cold colors" are blueish. But warm colors are color temps that are below 5500K, which normal people would think of as a "cooler temp", and cool colors are colors above 5500K, which normal people would think of at hotter. I will not try to explain this one.

So, what to do? As I pointed out above, even film suffers from white balance problems. Film is designed to look good in a specific color temp. You will often see "Daylight" film, or "Tungsten" film. Daylight film is film designed to render color temps of 5500K to 6000K as pure white, and Tengsten film will render color temps around 3200K as white. Florescent lights don't fit into this scheme really well, they are not blackbody radiators, and radiate light in rather specific narrow bandwidths.

Photographers traditionally get along with this color temp thing by carrying around a small collection of filters designed to turn whatever light they have into 5500K light.

In the digital world though, we have the chance to do this adjustment on the fly as the camera records the picture. The CCD or CMOS sensor that actually records the picture doesn't know, natively, what white actually is, like film does. It just records a bunch of numbers, and the computer in the camera adjusts them in whatever way it sees fit for "white balance", and puts the result on the memory card. Most digital cameras have a way of setting the "white balance", or have a "auto" setting that will calculate it on the fly. While digital cameras have gotten pretty good at this, they all still have a certain amount of trouble with incandescent and tungsten lighting.

My Nikon D100 got almost every picture wrong that didn't get taken with flash. The color temps in most of the rooms was somewhere around 2500K, which is probably the result of using a zillion, clear, 40 Watt light bulbs in the chandeliers.

In our next installment, I'll go into exactly how I've been getting reasonable pictures out of a bunch of orange photos.