{"id":1506,"date":"2008-11-10T10:55:29","date_gmt":"2008-11-10T14:55:29","guid":{"rendered":"http:\/\/www.starkeith.net\/coredump\/?p=1506"},"modified":"2012-01-21T17:35:06","modified_gmt":"2012-01-21T22:35:06","slug":"depth-of-field-experiments","status":"publish","type":"post","link":"https:\/\/www.starkeith.net\/coredump\/2008\/11\/10\/depth-of-field-experiments\/","title":{"rendered":"Depth of Field Experiments"},"content":{"rendered":"

I’m a sucker for certain “classic” photography effects. You’ve probably already seen the results of my obsession with the silky-waterfall effect<\/a> and my experiments with macro mode<\/a>, but there was another effect I have been trying to master – getting the “out-of-focus background” effect by controlling the depth of field.<\/p>\n

For those that aren’t familiar with the term, “depth of field” refers to the amount of a picture that’s in focus. As usual, Wikipedia has an excellent article on the topic if you’re after more detail<\/a>. The trick with cameras is that depth of field is controlled largely by the aperture you’re using when you take a picture. A larger aperture (smaller f-number) gives a shallower depth of field, and a smaller aperture (larger f-number) gives a greater depth of field. (Confusing, I know.) The theoretical “perfect” pinhole camera has an infinite depth of field, meaning everything is in focus no matter how far away, but in reality there is no such thing as a “perfect” camera, so every picture-taking device – including your own eyes – has some sort of depth of field, even if it’s very large.<\/p>\n

Anyway, although you’d think that with photos you always want everything to be in focus, the fact is that you can use blurring to sort of “focus” on one thing – blurring out the background, for example, is often used with portraits to keep the focus on the person.<\/p>\n

Now, knowing the relationship between aperture and f-numbers should let me create this effect whenever I want – in theory. In practice, I’ve had some trouble getting it “right.” Oh, I got some nice blurring when I used macro mode – which basically gives my camera a very, very, very small (shallow) depth of field, but it also meant that I could only focus on things very, very, very close to the camera. Useful for closeups of flowers – not so useful for anything else.<\/p>\n

So the other day I sat down and decided to try some experiments. To gauge the results, I needed something that stretched away from the camera for some distance, so I could gauge what was in focus and what was out of focus.<\/p>\n

Taking a tip from some photography sites which used a similar example, I set up my dining room table with a bunch of bottles of wine from my wine rack. This is what it looked like to start with:<\/p>\n

\"wine<\/a><\/p>\n

This was taken in manual mode on my camera, but I got the settings by using “Program” mode and just depressing the shutter button half-way so the camera gave me it’s “recommended” exposure settings. They are (for the curious): Exposure of 1\/8 second, and aperture of f\/2.7 (the largest aperture my camera has).<\/p>\n

At first, I was a little disappointed – after all, the background is out of focus, but not by very much. The effect I wanted wasn’t very pronounced, and I knew it had to be possible – but what was I doing wrong?<\/p>\n

Somewhere along the way (probably in The Digital Photography Book by Scott Kelby<\/a>) I had read about portrait photographers using a “short zoom lens” (85-100mm focal range) because it produced such nice results for portraits – which, as I said earlier, often utilize a shallow depth of field to produce a blurred background that helps draw attention to the person in the picture.<\/p>\n

“Well hey,” (I said to myself), “I’ve got a zoom lens on my camera that I think can do at least some of that focal range.”\u00a0 So I tried zooming in a little. The results? Have a look:<\/p>\n

\"wine<\/a><\/p>\n

Well now – that’s much more like it! The bottles at the back are very much out of focus – more so than in the first picture. I might be onto something here!<\/p>\n

Now, although the above picture turned out quite nice, I did make the mistake of letting the camera auto-focus for me – that’s why the “Fools Bay” botle is in focus instead of the first (closest) bottle. (My camera at the time was set to auto-focus on whatever was bracketed in the middle of the picture.) So, time to switch to manual focus!<\/p>\n

\"depth<\/a><\/p>\n

Ahhh, much better.<\/p>\n

Now, it’s worth noting a few things about these last 2 photos:<\/p>\n