Aperture & DOF

[aam1234]

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

[Belmondo]

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.com/dofjs.html

[aam1234]

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.

[Belmondo]

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.

[aam1234]

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

[Tom W]

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

http://www.pbase.com/photosbytom/image/38177323/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.