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How to Take Better Photos, Pt 2

April 5, 2009

Okay. In the last post I discussed why you should buy a DSLR if you’re serious about taking better photos. This time around, we’ll walk through some key terms so you can get past feeling all intimidated and start taking some seriously rockin’ pics.

Four Key Terms

Every time you bring that camera up to take a shot, it calculates several settings in an attempt to get everything just right. But what it thinks is just right isn’t always what’s best. If you take the effort to understand what the settings mean and how you can manipulate them, you can turn a decent photo into an awesome one.

While there are literally a dozen or more settings you can fuss with, we’re going to focus on the main four – focal length, ISO, shutter speed and aperture. Even if you don’t mess with them, knowing what they are and what they do can make you a smarter – and therefore better – photographer.

Focal Length

The focal length refers to the distance (in millimeters) from the optical center of the lens to the camera’s image sensor. By changing the focal length, you are in effect changing the field of view or picture angle, which basically means how much of the image in front of you is being captured.

But who cares?

In practical terms, focal length is a measure of how zoomed in you are.

On a 35mm camera (such as a film camera or fancy full-frame DSLR), a focal length of 50mm is considered “normal” because it captures images the way we see them with our naked eye, with a picture angle of around 45 degrees. On DSLRs with APS-C sized sensors (which is to say most of them), the “normal” focal length is closser to 30mm.

It may help to think of that picture angle as a slice. Focal lengths higher than 50mm zoom in and, in effect, capture a narrower slice of what you can see. Conversely, focal lengths lower than 50mm capture a broader slice. 

It’s also worth noting that the picture angle applies not only to your subject, but to the background as well. If you’re shooting with a wide-angle lens with a focal length of 24mm, you’re going to capture a wider swath of background, so you’ll need to be closer to your subject if you want to fill the frame. If you’re shooting with a telephoto lens at 150mm, you’re going to capture a narrower slice of background. Because this narrower slice is magnified to fill the frame, it will appear blurred out. It’s not really any more blurred out, it’s just that a narrower selection is magnified, and so it appears blurrier. Nevertheless, this is a neat optical illusion that makes telephotos a good solution for portraits where you don’t want the background intruding on the subject.

Here are some examples at 10mm, 30mm, and 250mm. Click on any of them to see them bigger:

A basic knowledge of focal length comes in especially handy when you’re shopping for lenses, as it lets you tell at a glance what kind of lens you’re dealing with and how far it will let you zoom in and out.

ISO

I grew up in an analog world of VHS players and cassette decks. I learned to type of a friggin’ typewriter, and I learned to shoot with film cameras. And in the world of film, one of the first things you learn is that different films have different speeds, represented by an ASA number. 

Films with low ASA numbers, such as Fuji Velvia 50 or Kodachrome 100, offered stunning detail and intense colors, but they required really good light if you wanted to shoot without a tripod.

Higher ASA films – up to 1200 and 3600 – excelled in low light, but at the expense of quality. The colors weren’t as vivid, and the higher the ASA, the grainier the image.

ISO is basically ASA for the digital world. Digital cameras don’t use film (duh), but the ISO approximates the old speed ratings by telling the image sensor what it’s priorities are. Lower ISOs sacrifice speed for color and clarity, while higher ISOs do the opposite. 

The frustrating thing about digital is that high ISO shots exhibit something called chroma noise, which is basically multi-colored speckling. Whereas film grain could be wielded for artistic effect, chroma noise just sucks.

Chroma noise is also more prevalent on sensors with higher pixel densities. This is one of the reasons why high megapixel point and shoots suck in low light. Thanks to their larger sensors, DSLRs typically have lower pixel densities than point and shoots, and perform better in low light situations, but even then shooting at anything above 800 can be chancy unless you’re willing to drop $2300 on a low light superstar like the Nikon D700.

A good rule of thumb – set your camera to the lowest ISO you can and step it up as needed.

Shutter Speed

Now we’re getting to the good stuff. Most DSLRs worth their salt (and a few higher-end point and shoots) let you select either shutter or aperture priority (represented by an “S” and “A” on the mode dial). Most people avoid these like the plague because they have no idea what they mean. But it’s really not that complicated, and once you have a handle on what shutter speed and aperture are, and how they effect your shooting, you can use them to your advantage.

Let’s start with shutter speed.

When you press the shutter button on your camera, the shutter opens, exposing the image sensor to light. Shutter speed is the extent of time the shutter is open. That’s it. 

Faster shutter speeds can freeze action, but they require either a) good lighting, b) higher ISO, or c) a large aperture setting. 

At slower shutter speeds, the camera’s shutter remains open longer. This lets it capture more light, and thus bring out more detail in low light shots, but it also captures whatever happens for the entire time the shutter is open. Thus movement turns into blur. 

If you’re trying to shoot action, be it a sporting event, air show, or a rampaging toddler, go for faster shutter speeds. If you’re shooting a landscape or something, shutter speed isn’t as important, but be warned – go for too slow a shutter speed and you’ll need to shoot from a tripod, or else you’re entire image will come out blurred.

Aperture

Last but certainly not least, we come to aperture.

Aperture refers to the size of the shutter opening through which light passes. For some reason, larger apertures (i.e. larger openings) are denoted by smaller numbers, as the following chart from DPReview illustrates:

I won’t go into all the boring technobabble of what aperture does. All you need to know is this:

1) A larger aperture lets more light pass through to the sensor. Light is good. A larger aperture setting will let you shoot at a lower ISO and with faster shutter speeds in lower light. This is why I love my 30mm f/1.8 prime lens. It’s fast enough that I can shoot indoors at ISO 100 and still capture Nolan blur-free. It’s also why lenses with large apertures are commonly referred to as “fast” lenses. 

2) The larger the aperture, the shallower the depth of field. But wait, what the %#*#@ is depth of field?

Depth of field refers to how much of the image is in focus. A deep depth of field will capture everything from the foreground to infinity in perfect focus. Progressively shallower depths of field will increasingly blur out everything in front of and behind the focal plane. This blurred effect is referred to as “bokeh”, but you should only call it that if you want to sound like a pretentious douchebag.

This first picture was taken with a point and shoot, and demonstrates a situation where you want a deeper depth of field. But hey, you won’t always have the U.S. Capitol as your backdrop.

This next shot was taken with my Nikon D80, and shows just how shallow you can go with depth of field. If you click on the picture and follow the link back to Flickr, you can see that Nolan’s hands are in sharp focus, but that even his face is a little blurry. That’s how ridiculously shallow you can go. 

Remember, a larger aperture equals speed plus a shallower depth of field, and a smaller apeture, well, you’re smart enough to figure it out.

Wrapping Up

With even a basic understanding of these four key concepts, you can take your photography to the next level. To recap:

– Focal length is a measure of how zoomed in you are.

– ISO is essentially a speed rating. Keep it as low as you can given shooting conditions.

– Use a faster shutter speed to freeze action. Use a slower shutter speed to bring out details in lower light.

– A larger aperture gives you speed and a shallow depth of field.

Depending on the type of shot you’re going for, you can set your DSLR to either shutter or aperture priority, or go balls to the wall with full manual, which lets you set both according to your wishes.

Now go forth and shoot.

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2 Comments leave one →
  1. April 5, 2009 9:21 pm

    I like that shot in front of the Christmas tree.

  2. April 18, 2009 9:14 am

    Excellent once again!

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