Tuesday, March 15, 2011

Digital Photography Questions Pt. 3, NOW with Two Parts!

Finally, at long last, I'm going to get to answering Shing's question #2, which was, "For shooting small toy/doll house sets, how do you control depth of field to make the background more out of focus?" It only took two massive blog posts and finishing off all of the Earl Grey tea in the house to get there!

(That's right, this is the first part of the third and final installment of my guide to macro photography and selective focus. If you don't like that I didn't break it in to four parts, well, too bad. Get your own blog with blackjack and hookers. Part one talks about basic Canon DSLR zoom lens choices. Part two talks about basic technical concerns with macro photography.)

What we are talking about in this final section is termed "selective focus," which is simply using a lack of focus control the look of the image. And in the case of Marlowe, Shing is looking for more ways to make the background less in focus. Let's look at a one of her images (used with permission) to see what we're working on.

"Marlowe could never finish enough beer to attain a full set of beer goggles." © 2011 Shing Khor

(She might not be James Casebere but she's already doing a damn good job, so I'm just going to ramble about lots of different tools and methods she could try.)

Here are some basic ways to control depth of field: 

1)  First, on any camera/lens combo, if you want to decrease depth of field you need to set the aperture to the lowest possible number (which to be confusing is the largest physical opening in the mechanics of the lens). 

In real terms, f/4 has a much more narrow depth of field than f/22 would. The easiest way to make your camera use smaller apertures is that instead of using the "P" or "Auto" setting on the camera, you use the "Av" setting on the control dial. This shooting mode lets you pick a specific aperture to use and then the camera automatically picks the correct shutter speed to match it, but never varies the aperture for the exposure. So if you want lot's of blur, set it as low as your lens will go and leave it there. 

*Note!* Remember to change this back to P or Auto after your shoot! There is nothing worse than shooting tons of random photos of buildings and streets and landscapes and fashion and realizing you had your lens set to f/4 so only people's noses are in focus, or the mail box… Not that I've done this… 

Let's look at a couple of examples!

This first image is shot (on a tripod, with a timer...) at 40mm with f/4, 1/6 shutter, and ISO 100.

Now, the exact same frame but at f/22.

If you click the images and zoom in, you can see that the f-stop is the foremost thing to impact the depth of field in an image!

2) If narrow depth of field is really really important, you might actually want to buy a prime lens. 

Backing up from my recommendation in my zoom lens post, assuming money is no option, if you really wanted to be able to put the most area out of focus with a zoom lens, you would want to buy the Canon 16-35 f/2.8L lens. The difference between f/2.8 and f/4 is actually somewhat significant. 

But there is a cheaper and more useful way to have the same ultra-narrow depth of field. What you'll want to do is buy one of those general zooms I talked about and then spend some bucks bucks to buy a prime lens (a non-zoom lens). 

Nice zoom lenses might go down to f/4, but even a moderately priced prime lens can go down below f./2, which is MUCH more narrow depth of field, despite the small numerical difference (almost four times as narrow, because the f/ number goes in odd intervals. A single doubling/halving step is f/8 to f/11, or f/1.4 to f/2). The Canon EF 28 f/1.8 will go super narrow! A similar but cheaper lens is the 50mm f/1.4. It's a bit longer, which will change the character of the shot, but that is a razor thin depth of field. 

Of note to artists is that prime lenses usually have much better out of focus rendering. That is called "bokeh" in photo-parlence. "Bokeh", which was coined by Daido Moriyama and his circle of friends in 1960's Japan, describes the kind of character of each lens in the areas that are out of focus. Prime lenses almost always look more pleasing and interesting in the out-of-focus areas than zoom lenses. http://en.wikipedia.org/wiki/Bokeh

3) Another strategy for being able to make the focus area smaller is to work closer to the subject with the camera. At 22 mm with f/4 where the lens is 6 inches from the subject will provide much less in-focus area (1" at best) than shooting 22mm f/4 from a distance of 20 inches and cropping the image in post. The closer you can jam your lens to the point of it's minimum focusing distance (the distance where it can't focus on a subject any closer) the less apparent depth of field you will get.

Here's a couple examples:

22mm @ f/4, 2/5 shutter, ISO 100, with the lens 6 inches from the focus point.

22mm @ f/4, 2/5 shutter, ISO 100, 20 inches from the focus point, cropped to match the framing.

You can see how the pink dino and the Totoro are both way more in focus on the cropped shot, even though all I did was move the camera back about a foot!  

4) For the purpose of shooting super close to objects a "macro" lens might provide the best results! These lenses are designed to be able to focus closer to a subject than normal. Most of normal lenses have a minimum focusing distance somewhere between 16" and 3 feet (the longer, more zoom, and cheaper the lens the further the minimum distance will be usually). But "macro" lenses will actually let you focus in such a way that you can get just about as close to 1:1 as you might need (that is, a penny is taking up one penny worth of space on the sensor or film!) The a good one for Canon is the EF-S 60mm f/2.8 Macro. It's not too expensive either!

Or, if you get a general zoom and want to do macro work with that lens, you can use an extension tube to shoot closer than normal. They lock in to place between the lens and body, effectively changing the focusing geometry to make the lens focus closer which basically turns regular lenses in to macro lenses. You'll have to play with which one will work best for each of your specific projects since they come in different values for more or less macro. This one tends to work pretty well. 

I shot all of the macro shots of the hentai origami for my upcoming "Japonisme" project with a 17-40 f/4L and a generic macro extension tube, if you're curious. They look amazing, so getting macro extenders are a very viable option.  

"Sailor Moon Hentai Origami" 2010 by Eron Rauch (39mm f/16 1 sec. ISO 100)

In the next section coming tomorrow morning we'll have more photos, more about lenses, and even a little bit about lighting! 

1 comment:

  1. Thanks for this Eron, it's really useful tutorial I'll surely make used of.