Forget The Calculator and Look at Cause and Effect.
Work to understand the cause and effects associated with DOF, the associated variables and manipulating them. The three variables that come into play are:
- Aperture
- Focal Length
- Distance to subject
For Example:
Generally speaking, to create a
Shallower Depth of Field you do the following:
- Use your longest Focal Length, like 200 mm.
- Get as close as you can to the subject and still be able to focus.
- Use a wide open aperture, like f/2.8.
Generally speaking, to create a
Deeper Depth of Field you do the following:
- Use your shortest Focal Length, like 24 mm.
- Get far from your subject.
- Use a narrow aperture, like f/18.
Here’s an example for what's meant by Depth of Field.
It’s my own, unpatented test…one that you will never, ever read about in any of the medical or scientific journals.
Here’s the setup.
- 30D with 70-200L, tripod mounted, positioned 5 feet away from the DVD box.
- The Swiss miss box was positioned directly behind the DVD box, which is 1 inch deep.
- Used the left-point focus, on the DVD box for all the shots.
- First shot at f/2.8
- Second shot at f/4
- Third shot at f/9
- Fourth shot at f/13
Notice how on the f/2.8 shot the Swiss miss box is Out Of Focus, blurry.
Notice how on the f/13 shot the Swiss miss box is pretty much in focus.
- By using a wide open aperture like f/2.8, you can blur the shot immediately behind the focus point.
- By using a narrow aperture like f/13, you can create a deeper depth of field, allowing more of the shot to be in focus, creating a much deeper focal plane.
Notice I used you. That’s because you are in control of the camera and it’s settings, not some DOF Calculator. 
The Depth of Field is something that you would set creatively.
- Depth of Field can be shallow.
- Depth of Field can be deep.
In the end you can select how you want your image to look, what aspects you want to be in focus or out of focus. There is no magic set parameters… just your imagination with regards to how you see the photo.
Another example:
With these two photos, if you had to choose, which one do you prefer most?
Because remember that you can alter the three variables:
- Aperture,
- Focal Distance, and
- Focal Length
to whatever you desire. This will allow you to blur backgrounds/foregrounds or other certain aspects within an image.
Forget about using the DOF calculator. Understand cause and effects.
Aperture f/14, Focal Length 100 mm, Focusing Distance about 9"
Aperture f/2.8, Focal Length 100 mm, Focusing Distance about 9"
Notice how on the f/2.8 shot the DOF is very shallow.
Notice how on the f/14 shot the DOF is deeper.
Again:
- By using a wide open aperture like f/2.8, you can blur the shot immediately behind the focus point.
- By using a narrow aperture like f/14, you can create a deeper depth of field, allowing more of the shot to be in focus, creating a much deeper focal plane.
Don't let that damn calculator and all the associated theoretical mumbo-jumbo math get you all twisted around an axle.
Bottom line...find a flower of your own, go out and set your camera on a tripod and take a bunch of shots and manipulate the three variables, and look at cause and effect.
Once you understand the relationships, you won't need no stink'n calculator.
Best regards, Mike
--
B.R.A.S.S. (Breathe, Relax, Aim, Sight, Squeeze)
