How Do I Know What the Hyperfocal Distance Is?
I assume you've read last week's newsletter, but in case you want the digest version, here it is: The hyperfocal distance is where you can focus the lens to get the greatest possible depth of field.
Now that you understand the basic concept, you're no doubt wondering how to apply it. After all, knowing that the hyperfocal distance will enable you to capture uniformly sharp photos is pointless if you don't know how to determine the hyperfocal distance to begin with.
Well, I have some good news and some bad news. The good news: This information is readily available. The bad news: You might have to work a bit to get it.
It can help to understand some photography history. Old SLR film cameras used to have depth of field information inscribed right on the lens barrel, making the hyperfocal distance easy to determine on the fly. Check out this photo of my trusty old Minolta 55mm lens, which my dad handed down to me for my first film camera. This lens was probably manufactured in the 60s, making it as old (or older) than me. As you turn the barrel to focus the lens, the diamond-shaped marker showed you the actual focus distance--in this case, it's 10 feet, or 3 meters.
Surrounding the focus diamond are lines that show the depth of field at different f-stops. As you might expect, bigger f-numbers correspond to deeper depth of field. At f/16, you can see that everything from about 7 to 20 feet will be in focus. At f/8, you only get about 8 to 14 feet of sharpness. (It's hard to be precise when reading numbers marked on the side of a lens. I'm approximating.)
Finding the hyperfocal distance on these older lenses was a snap. Focus the lens until the distant depth of field marker for your desired f-stop just touches infinity. That's the greatest possible depth of field this lens can muster at this f-stop, and thus is the hyperfocal distance. In this example, if I focus around 20 feet, the depth of field at f/16 will go from 9 feet to infinity.
I think using these older lenses to visually demonstrate hyperfocal distance is a good way to learn, because it graphically shows that the hyperfocal distance at any given aperture setting is the minimum possible focusing distance at which the depth of field extends to infinity. Obviously, you can still set the focus farther away if you choose to, but if you do that, the range of sharp focus can't get any bigger, and so you're just wasting depth of field "beyond" infinity.
Modern Hyperfocal Cheats
That's nifty if your camera lens has depth of field markings on the barrel, but I am afraid those days are pretty much gone. So how do we figure out the best focusing distance using modern cameras?
Thankfully, there are a few tools at our disposal. You might start with an online depth of field calculator, like the excellent one at DOFMaster.
To use this site, start by entering your type of camera--this step is critical because the size of your camera sensor affects the effective focal length. Then, set the details about the lens you're using, including the focal length and f-stop. Now you'll need to do some fiddling. Enter a subject distance and check the near and far limit on the right side of the page.
If the far limit is not infinity, make it bigger. If it's already infinity, make it smaller. Try a few values until you just hit infinity. Now you know the distance you should focus on to get the best possible depth of field. You can also note the near limit of the depth of field, so you can be sure to position yourself for ideal sharpness of all the important parts of your photo.
Of course, you're not always taking photos within easy reach of your computer, so you can check out an online depth of field guide. If you have a smartphone, there are a wealth of free and inexpensive depth of field guides you can get as well. Recently, I searched for "dof" in my iPhone's app store, for example, and found a dozen candidates. I personally recommend the $2 DOFMaster, from the same folks that bring you the Web site I mentioned earlier. Not only does the program tell you the depth of field for any focusing distance you enter, but it can also display the hyperfocal distance with the tap of a button.
Leap of Faith
Shooting photos the hyperfocal way can be a little scary the first few times you do it. It's a bit of a leap of faith to take a photo when you're not focusing on either your near or far subject, but rather at some indeterminate distance in between. Intuitively, it feels like you'll just end up with an out-of-focus shot. Don't forget, though, that if you're shooting with a digital SLR, you probably have a depth of field preview button that you can use to ensure your photo will be sharp before you take the photo.
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digital photography wiki5
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