Hyperfocal Distance and Depth of Field

[Daniel Browning]

Great post, electric eel. One brief comment:

Btw- depth of field is 1/3 in front of the focus mark and 2/3 behind, so if you focus at 30' , the depth of field would extend from 20' to 50', this is just a hypothetical example.

That's true near the hyperfocal distance but for other distances, the DOF can be the other way around (2/3 in front and 1/3 behind), it depends on the specifics.

[electric eel]

Thanks Daniel, I wasn't aware of the switch, I'll definitely want to learn more about that, if you have any examples could you post?

[Daniel Browning]

Sorry, my mistake. It doesn't become the other way around, but it does slowly go from 50/50 out to 1/3, then 1/100:


http://www.dofmaster.com/dofjs.html


With Canon 50D, 55mm focal length, f/16, 11 feet subject distance: 2.74 ft in front of subject (33%, 1/3rd), 5.45 ft behind subject (67%, 2/3rds).

The closer you get to infinity, the more it stretches out behind the subject until it gets to infinity:

32-ft subject distance: 15.8 ft in front of subject (1%), 1231 ft behind subject (99%).


The closer you get, the more it becomes 50/50:


3-ft subject distance: 0.24 ft in front of subject (46%), 0.28 ft behind subject (54%).

[electric eel]

Thanks Daniel, I never paid much attention to the tables but it appears they are valuable, have you ever checked the tables against the depth of field markings on a lens, I wonder how accurate the markings are against the tables? Time to drag the older lenses out and check this.