Depth of Field questions..

photoguy99 · Dec 24, 2014

The thing is nobody actually does understand the calculations in any useful way. Sure I can laboriously work through the calculations but they don't make any useful sense until I boil them down to rules of thumb.

As evidenced by thread after thread not very many people understand it at all. And yet lots of people seem to be able to take photos.

Pilots might understand some crap about attached turbulent flow and its relationship to lift but it sure as hell doesn't help them fly planes.

Just take some pictures and look at them. We're not flying airplanes here, anyways. We're taking photos.

Designer · Dec 25, 2014

photoguy99 said:
.. they don't make any useful sense until I boil them down to rules of thumb.

We don't need no stinkin' rules of thumb.

Ysarex · Dec 25, 2014

photoguy99 said:
The thing is nobody actually does understand the calculations in any useful way.

That's just flat-out wrong.

photoguy99 said:
Sure I can laboriously work through the calculations but they don't make any useful sense until I boil them down to rules of thumb.

The few DOF equations that might be worth working through are no more than 6th grade math. If that's laborious for you or beyond your understanding, I can refer you to places where you can get help.

Here's a rule of thumb story: 39 years ago I got my first job in the photo industry working in a camera store. I was already an avid enthusiast taking lots of photos and already brimming over with the standard rules of thumb. For example I was well acquainted with the 1/3 -- 2/3 rule of thumb for DOF distribution. One day I was holding a lens with a DOF calculator inscribed on the barrel and I noticed that focused near hyperfocal distance the DOF distribution was nothing near a 1/3 -- 2/3 split. I'd been taught otherwise and so I asked the store manager who was a very competent photographer. He reached behind his desk and took down a book called the Leica Manual. 40 years ago that was an old copy of the Leica Manual. He handed it to me and told me to read it.

One fallacious rule of thumb after another began to collapse as I turned the pages (Warning! 6th grade math was in the book). Rules of thumb were often just plain wrong or so crude as to be harmful rather than helpful. DOF for example does distribute unevenly around the plane of focus, but it sure isn't 1/3 -- 2/3.

+ How could I be worse off for understanding that now?
+ How would I be better off if I still thought the false rule of thumb applied?
+ How is it I didn't see that the rule of thumb was wrong looking at my photos?
+ Maybe I would have seen it eventually but I hadn't at that point. But it wasn't helpful for me to see and understand the math, and speed up the learning process?

Answer those questions.

The 1/3 -- 2/3 DOF distribution rule of thumb is just as prevalent now as it was when I was new at this, and it's just as fallacious. 40 years ago I learned better by understanding and seeing some simple math in a well written photo manual. That ruined me right? I should have stayed ignorant and I'd be much happier today, right? I might even to this day still believe the 1/3 -- 2/3 DOF rule of thumb and I'd be a better photographer if I did, right?

No one in this thread or others ever suggested that you should only understand DOF in theory and never experience it in practice. Only you seem to have this either/or problem where you reject understanding theory as useless. Of course you have to take the photos and see it in practice. Can you learn to manipulate the phenomenon without understanding the theory? In time yes. But knowledge of the underlying theory does not hobble your ability to learn in practice it enhances your ability to learn in practice as the practice validates the theory and the theory improves practice precision.

Joe

photoguy99 · Dec 25, 2014

Merry Christmas!

Designer · Dec 25, 2014

We're happy as clams, snapping away at anything and everything. No silly rules for us, no sir! No education either for that matter. We just snaps 'em and posts 'em.