If you haven’t been following the blog, I suggest to start with Part 1 of this article, here:
Here are Dave’s Simple Variables of Photography:
- Composition — you have to make the subject of the photo interesting.
- Shutter Speed — how long the light is allowed to hit the sensor (or film).
- Aperture — how wide your camera’s lens opens to let in light.
- ISO Setting — how sensitive your camera’s digital sensor (or film) is to incoming light.
- White Balance — what does the camera interpret as “white?” New in digital; film users need filters.
In the first article, we looked at Composition, Shutter Speed, and Aperture. Now let’s move on with the focus of this article, which will be ISO and White Balance.
This is the sensitivity of your camera’s sensor or film. A low number like ISO 100 or 200 is not very sensitive. Some digital cameras go up to 6400 or more nowadays, which is VERY sensitive (consumer film maxes out around 800-1600).
In film, some emulsions are more sensitive to light than others; however, there is a downside. Faster film, which allows shorter shutter speeds, creates larger “grains” (the smallest chemical “pixels” on the film), effectively reducing the resolution of the film photograph. The grain effect carries over to digital photography as noise. When the sensitivity of the digital sensor is turned up, you get more noise, which looks like static when magnified. It’s especially bad in dark portions of a photo, where a solid black background can look like a starry sky at ISO 6400. Take a look at these two photos from a Nikon D90 (which has very good high-ISO performance compared to most cameras):
At this web-friendly resolution, you don’t notice much at first glance. But look at this zoomed comparison of the two:
The noise is most noticeable in solid color regions, like the background of this photo.
So, how do we use ISO? You should balance it with your “need for speed.” If using a tripod and taking photos of landscapes near dark, use the lowest ISO possible! But if you’re taking sports shots and need a fast shutter speed, you may want to crank up the ISO a bit. This allows you to use a faster shutter speed, because the sensor is more sensitive. What ISO to use also depends on the objective of your photos. If you will use them on the web at low res, a lot of noise will be filtered out when you shrink the photos. But if you want a nice glossy print, or you plan to use the photos at high-res, stick with the lowest ISO that your “need for speed” will allow. Now: just imagine the days of film. You had to finish a roll in order to switch ISO, something that you can now do in a few button presses with any capable digital camera!
Many cameras also have an AUTO-ISO setting, which is great. Just be aware how it works. Check your first few photos in a dark setting by zooming in on them in the camera’s LCD, to make sure the ISO isn’t making your solid/dark colors look like the Milky Way. I have a whole collection of grainy Christmas evening photos with no flash at ISO 6400, which look like this (Canon SD1000 with CHDK hack software):
So, now you are an expert at ISO: which you can cleverly use in conjunction with shutter speed to trade off between increasing picture quality and reducing motion blur.
This is, very simply, what the camera sensor interprets as white. Your eyes do this automatically, but a camera cannot (even though it may get it right sometimes with an “AUTO” setting). Think of it this way: if you are in a dark bar with brick walls and flickering red candlelight, everything is red. But when you look at the napkin, it’s white to you. Even if it looks reddish, your mind interprets it as white! But a camera is not intelligent enough to say, “yeah, the ambient lighting is red, and I know napkins are white, and so I’ll just adjust my perception.”
Now, how do you compensate for this? It’s simple. Most common light sources are leaning a certain way on the spectrum, and most cameras compensate for it.
- Camera flash: very blue tint
- Incandescent light: orange tint
- Shade/clouds (compared to full sun): blue tint
- Fluorescent: green tint
When you pop the flash, the camera removes blue and adds orange to the mix, and the pictures come out OK. The same goes for the other types of lighting. But how does the camera’s AUTO WB setting know what setting to use? As far as I can tell, it guesses based on the incoming spectrum. And very often it’s wrong. Surprisingly, my pocket Canon does a better job than the Nikon D90 D-SLR. I’ve heard it’s common that pocket cameras are better than D-SLR’s when it comes to WB. But even the Canon SD1000 misses sometimes:
Probably the SD1000 auto-selected the daylight setting. Now, many people would not say “this is a bad setting,” simply because they’ve seen too many off-color snapshots and don’t know the difference. Look at it again after changing the camera’s setting to match the lamp’s bulb:
Usually I leave the pocket camera on AUTO and only change it when something looks off. With the D-SLR I set it manually every time I start taking photos, but on my D90 it only takes 2 seconds with the thumb wheel (no menus). Here’s the setting screen on the Canon pocket camera:
Note that you have to go into Manual mode to change these settings on my little Canon. See how orange the picture looks in “Cloudy?” That’s because the camera pushes a lot of orange to counteract the blueness of cloudy photos.
There is also a “Custom WB” setting that most cameras can do, even my small Canon. This sounds complicated, but it’s not. You take a picture of something white, and tell the camera “This is white!” …it automatically adjusts. You can use anything white that you can find, for example someone’s T-shirt or a napkin from the table. Here’s an example of what I did in a red-lit, brick-walled bar:
AWB on the Nikon D90. Everything is completely red, ugh.
Look at the difference after I calibrated on a napkin! The bricks are brick-colored instead of glowing red; the white on my friend’s hoodie is actually white. This Custom WB took about 15 seconds to set up on the camera, and gave me a dozen nice shots of this basement bar meetup.
If using film, you have to go with filters on the lens instead of adjusting a simple menu parameter. But I suppose the folks using film already know enough they won’t be reading this article!
So… there we have it, the most important settings for your camera explained. Hopefully my examples helped to make this easy to understand. If you have any questions or comments, please post them here — I am happy to respond!
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