Aperture & DOF

We all know the relation between aperture & DOF. However, I find the relation is rather a weak one. Meaning, unless you go from extreme to another, e.g from f4 to f16+, the effect is rather weak. I also found that distance to subject and distance to background play a bigger role in changing the DOF.

Would be nice if you can share your thoughts and experiences on the subject.

Thanks

Your're right. Subtle changes in aperture will produce subtle changes in depth of field, and vice versa.

Here's a DOF calculator you can play with that illustrates this:

http://www.dofmaster.c​om/dofjs.html

Thanks Belmondo,

I'm aware of the technical calculations and all (though never got a good grip of it) but in real life situations, the correlation between aperture & DOF is not as strong as you are lead to believe. Except when using a long tele or a macro lens, or that's what I found.

The thing that's stunning to me is how narrow the depth of field can be at what I consider to be normal apertures, say f/8 for example.

I have a very long lens that has to be focused manually. (600mm) According to that calculator, the depth of field of an object 100 feet away shot at f/8 is only plus/minus 2 feet. At f/45., the maximum aperture, it's plus/minus 1.1 feet. At least I understand why so many of my shots are out of focus.

Or try a macro. The differences are in mm's not even cm's.

Here's a shallow DOF - 300 mm at f/4, from about 15 feet away:

http://www.pbase.com …m/image/3817732​3/original

56K beware, its a full-sized image.

Note the in-focus line of dust on the table. AF point was the front face of the battery around the 100% text.