Specifically, the chapter on “Storytelling Apertures”. He describes how to overcome the lack of a depth-of-field scale on SLR lenses by using the distance settings.
He writes; “And, since every storytelling composition relies on maximum depth of field, you would first choose to set your aperture to f/22 and then align the distance above your distance-setting mark on the lens. Your focal length will determine which distance you choose.”
I don’t understand the last sentence. HOW does the focal length determine the distance at which you focus? If you select f/22; at what distance do you focus?
Any help appreciated.
Thx,
Bruceter
May I suggest looking up "Ben Long" on Lynda.com. He has some great courses on basic exposure. Bryan Peterson can be difficult to grasp and understand at times because he goes too quick I think (this was when I watched his course 5 years ago).
Basically this is because of lens compression with zoom lenses. The farther out you zoom (for any given aperture) the scene can be more compressed).
I wouldn't get too bogged down with this. Just remember it like this:
* Large apertures (like f/1.8 and f/2.8) produce shallower depth of field
* smaller apertures (like f/8 or f/11 or f/22) produce deeper depth of field
Where focal length plays a role is as such
* with a larger aperture (like f/2.8), and a short focal length (like 15mm) depth of field is still fairly large (larger than the example below)
* with a larger aperture (like f/2.8) and a longer focal length (like 200mm) your depth of field is decreased because of the compression.
He is basically telling you to get the entire scene in focus, shoot at f/22 and probably a medium focal length, like 35mm or 50mm. Unless you're shooting a flat subject, you should try to focus about 1/3 into the frame (what you see in the view finder) to get maximum DOF because generally 1/3 of the scene in front and 2/3 of the scene behind where you focus, will be in focus (and fall within the DOF). f/22 is pretty forgiving in many cases because it's DOF is generally pretty big, especially at shorter focal lengths and by this I mean you can be off a little on where you focus, say at 15mm at f/22 and most of the scene will still appear in focus.
Another way to look at this is like this... you're shooting with a 50mm lens and you focus on the subject ( the person):
f/2 is shallow depth of field (think of a person standing 50 ft in front of a car with its lights on. the person will be sharp, and you will see the lights from the car but they will be blurred. YOu might not be able to tell the lights are from a car or if it's one or two cars.
f/8 - The person is still in focus, the lights on the cars are more defined, but still blurry. You might be able to see that it's a car behind them but it will still be at least slightly out of focus.
f/16 - The person is still in focus, the car may mostly be in focus but slightly blurred.
f/22 - The person and the car and everything around it and the person would be pretty much in focus.
Hopefully these examples also illustrate what DOF and aperture does.
As a side note, He has some short video clips on Youtube if you Google them. Sometimes its easier to see him demonstrate the differences in a video. There are also a ton of videos that cover this subject too.