Long Telephoto lenses and increasing depth of field?

Tommi K1 wrote:

C Sean wrote:

So the question is when you zoom in close to your subject with a long telephoto lens, no matter how much you stop down, you can only get one subject in focus unless the subjects are perfectly lined up?

I haven't shot properly with Full Frame and less experience shooting with their standard 70-300/100-400 type lenses. However, I know several M43 members mention with long telephoto zooms, you don't need to stop down all the time and therefor it's easier to shoot with long telephoto lenses compared to Full Frame. So is there a long telephoto rule, if you zoom in close, you can only get one subject in focus no matter how much you stop down?

You will get same DOF regardless the focal length, when you have three factors same:

1. Same subject framing
2. Same format
3. Same F-stop

So in this case with m4/3 and example f/5.6, there is no difference do you shoot with 12mm or with 300mm, you are having the same DOF when the subject framing (magnification) is same.

The typical scenario is this, your subject is further but you want the same framing, so you use longer focal length. That will deliver you same DOF as you would get if you would use shorter focal length at the closer distance and frame the subject same size.

If you want multiple different subjects to be framed in same size, then you need to start to play around with multiple factors:

You can only get so far all the magnifications same, but never get the same perspective or background blur, but the DOF will be same.

Yes.

You can restate the usual DOF formulas in terms of magnification rather than subject distance and focal length in which case you find that DOF is a really a function of magnification.
I prefer to think of it this way when I'm in the field using a variety of focal lengths at various distances. Estimating magnification is easier for me than subject distance and focal length. YMMV.