Depth of field confusion ?

I keep hearing about 1/3 fwd (33%) and 2/3 back (67%) with DOF.
But when I use DOF Master at http://www.dofmaster.c​om/dofjs.html
for say:
Canon 450 D
Focal length = 63mm
f = 22
Subject dist = 5.1
I get:
In front subject = 1.8m (23%)
Behind subject = 6.12 m (77%)

Varing to f = 4:
In front of subject 0.45 m (45%)
Behind subject 0.54 m (55%)

Which is correct?

Many thanks in advance.
Richard

People who state that DOF is 1/3 : 2/3 are wrong. It varies heavily with focus distance.

At close distances (relative to the hyperfocal distance) the DOF will be very close to 50:50 split front to back. Keep this in mind when you are shooting portraits or photos of small groups.

As you approach the hyperfocal distance, the ratio of the DOF rear:front approaches infinity (this is obvious as the back distance at the hyperfocal distance goes to infinity, and the ratio of any finite number to infinity is also infinite).

What he said. the 1/3 and 2/3 thing is the roughest of guides. The actual amount will vary with the focal length, aperture and distance you are focussing at.

Right, urban legend that 1/3 -2/3 split. Congrats on not swallowing that BS and using your own observations with a DOF calculator to discover the urban legend. I can pretty easily show you a 0.5% : 99.5% split at about 120'

You guys have no idea how many "Pro's" have told me about the 1/3-2/3 "rule" of DOF. They had me convinced several times over the years...

Jon.

Jon Foster wrote in post #8638041
You guys have no idea how many "Pro's" have told me about the 1/3-2/3 "rule" of DOF. They had me convinced several times over the years...

Jon.

I can buy myself a pipe wrench and have business cards printed for a plumbing business even though I have never apprenticed as one, and tell you the reasons for saving money with plastic tubing for a plumbing system, too!

Jon Foster wrote in post #8638041
You guys have no idea how many "Pro's" have told me about the 1/3-2/3 "rule" of DOF. They had me convinced several times over the years...

Jon.

Well, understand that it's only been recently that a tool to actually do the math has been easily available.

RDKirk wrote in post #8638393
Well, understand that it's only been recently that a tool to actually do the math has been easily available.

What is your definition of recent?

I had spreadsheet software running on my personal machine since 1988, and anyone who can enter a few calculations in a spreadsheet can make their own DOF calculator. I like mine better than the internet ones because I also calculate blur disc diameters to get a feel for background blur levels too.

And.....If one allows for a bit more knowledge it would be no sweat to write a DOF calculator in Fortran 77, although I'll allow that this would be beyond the means of most photographers.

The thumbrule was widely expressed in 1970, when I first heard it...some time before PCs and spreadsheets.

By "recent" I mean since the dofmaster web site was posted.

I would not agree that "anyone who can enter a few calculations in a spreadsheet can make their own DOF calculator" unless one already knows what calculations to enter...which would not have been most photographers--not in 1988 and not even today.

Heck, we have people who can't seem to shake themselves of the "1/focal length minimum handholding shutter speed" thumb rule, when all they need is fifteen minutes play with their digital cameras to find out the truth of that.

And you expect them to delve into mathematics to verify a depth of field thumb rule?

I got into photography back in 1982 when I got my first decent camera (AL-1). Back then anything photography related was voodoo and nobody would talk to you about shooting let alone share anything worth while. So when somebody did say something you thought it was gold. The books available back then (at least to me) were incredibly cryptic too and I think they were sprayed with a sleeping formula of some type that worked on me every time.

Jon.

I feel that all these spreadsheets and rules only confused me when i first started shooting.
I was into them thinking that they would show me the easy way to get good shots but now I just shoot and learn and my pics are where I want them to be .

JeffreyG wrote in post #8638420
What is your definition of recent?

I had spreadsheet software running on my personal machine since 1988, and anyone who can enter a few calculations in a spreadsheet can make their own DOF calculator. I like mine better than the internet ones because I also calculate blur disc diameters to get a feel for background blur levels too.

And.....If one allows for a bit more knowledge it would be no sweat to write a DOF calculator in Fortran 77, although I'll allow that this would be beyond the means of most photographers.

Having recently delved into the equations of DOF, I find the significant issue is the simplications in the equations made for simplification of assumptions, so that even being able to use Excel is insufficient to creating your own with an oversimplified equation!

Wilt wrote in post #8641644
Having recently delved into the equations of DOF, I find the significant issue is the simplications in the equations made for simplification of assumptions, so that even being able to use Excel is insufficient to creating your own with an oversimplified equation!

Thats simple for you to say!

So I thought I would try it for myself.
Set up cards marked (f) 4, 5.6 etc on a railing at distances discribed by DOF Master near and far from a subject. The near cards roughly comply but can not get the far cards at higher f stops to come into focus.

Still confused?
Richard

This is why I stick to the rule of thumb: Figure out what aperture will work best for you, from a bit of experience, and use it. Getting all worked up about stuff is anal unless you have a very specific reason for doing so!