DOF question (Page 2): Your true plane of focus is the mirror - look at the mirror frame - slightly out of focus? The reflection in the mirror, even though way behind, is still at the...

Georgia Peddler Loc: Brunswick, GA

Your true plane of focus is the mirror - look at the mirror frame - slightly out of focus?
The reflection in the mirror, even though way behind, is still at the focal plane of the mirror.
Wierd stuff, eh? Have you ever seen the set of mirrors photo where each reflection goes on and on for infinity with pics of mirrors?

infocus Loc: Australia

AlyG wrote:

I took this shot at f/5.6 focal length 32mm(appox) and was wondering if anyone had a definitive reason for why the reflection in the mirror wasn't affected by the shallow setting. The DOF in the mirror appears to be much deeper. Opinions and thoughts welcomed. A friend and I have been going around and around for 2 days on this! lol

Great shot though. Everyone else has answered your question. I thought I'd just tell you I like your pic. :thumbup:

MtnMan Loc: ID

AlyG wrote:

I took this shot at f/5.6 focal length 32mm(appox) and was wondering if anyone had a definitive reason for why the reflection in the mirror wasn't affected by the shallow setting. The DOF in the mirror appears to be much deeper. Opinions and thoughts welcomed. A friend and I have been going around and around for 2 days on this! lol

You can think of the convex mirror as like a wide angle lens. It increases the DOF for its view. Suppose it is a .5 wide angle; that increases the DOF for what you see through through the mirror by a factor of two. That doesn't happen for the stuff seen around the mirror.

Your focus appears to be on an object in the mirror that is effectively further away than the mirror itself; maybe around the rear of the cab. The total distance is the distance from your camera to the mirror and then back to its focus point. As noted by others the edges of the mirror are not in focus...the focus point is beyond it.

MtnMan Loc: ID

Georgia Peddler wrote:

Your true plane of focus is the mirror - look at the mirror frame - slightly out of focus?
The reflection in the mirror, even though way behind, is still at the focal plane of the mirror.
Wierd stuff, eh? Have you ever seen the set of mirrors photo where each reflection goes on and on for infinity with pics of mirrors?

I don't think so. I think the focus is on a point in the mirror effectively futher away than the mirror iteself. That is why the edge of the mirror is not in focus.

Georgia Peddler Loc: Brunswick, GA

MtnMan wrote:

quote=Georgia Peddler Your true plane of focus is... (show quote)

I agree - that is what I meant when I spoke of the reflection in the mirror being sharp and the mirror edge itself slightly out of focus. Pretty wierd, eh? But very logical

Bangee5 Loc: Louisiana

There is nothing worst than to prove your own self wrong.

Bangee5 Loc: Louisiana

There is nothing worst than to prove your own self wrong.

(don't know if this is going through, might have posted twice.

Shirt in focus

frame in focus

Background in focus

Georgia Peddler Loc: Brunswick, GA

You are correct - no way out, eh?
Maybe if I had thrown in some scientific heebeegeebee it would have been better.

MtnMan Loc: ID

Bangee5 wrote:

There is nothing worst than to prove your own self wrong.

(don't know if this is going through, might have posted twice.

Great illustration of what is happening.

Proving yourself wrong and accepting it is the greatest thing going. That is what science is all about. Nice work.

GoofyNewfie Loc: Kansas City

Bangee5 wrote:

quote=GoofyNewfie quote=Bangee5 You are focused ... (show quote)

Are you wearing your glasses backwards?
The frame and mirroR are in the same plane and both are out of focus!

paulw Loc: nottinghamshire

you are focusing on the mirror at the optimum focal point bot what are seeing is the reflectin off the mirror you are not capturing what the mirror is looking at just the )picture ) in the mirror does that sound right?

AlyG

Chinaman wrote:

Because you focused on the person reflected in the mirror. The mirror itself and background are out of focus. Aperture sizes, point of focus and distance from object of focus are 3 elements that affect DOF.

this is helpful, thank you!

AlyG

I've taken mirror pictures before, where just one thing in the reflection is in focus and everything else in the room is out of focus, but all those mirrors were hanging on the wall, no real background. I think one thing that makes this picture different is that there is a big background behind the mirror.

AlyG

If I ever set this up again, I think I'll put something interesting (a clown juggling..., Bigfoot...) behind the truck :)

Ugly Jake Loc: Sub-Rural Vermont

It's the mirror not being flat - remember, focus is when the reflected light is focused on your sensor / film, it has nothing to do with the subject. This mirror is a crude lens, but it does have an effect.