Talk:Focus (optics)

Lining up images in an SLR
In an SLR, there is usually a circle at the middle of the viewfinder divided in half horizontally. When the subject is out of focus, the upper and lower half of the image within the circle don't line up; one is shifted left, the other right. What is this device called? How do they work? —BenFrantzDale 01:44, 21 February 2006 (UTC)


 * That's called a split-image rangefinder (called a split prism in the focusing screen article). It works by showing you the image through the left side of the lens on top, and the right side of the lens on the bottom (or vice versa).  When they line up, rays from the two sides of the lens converge at the focal plane, and all is happy.  Dicklyon 18:01, 10 May 2006 (UTC)

Merge
Focal and image points in optics are far too important a concept to be relegated to a subsection of Lens (optics). I have boldly removed that merge tag. If you disagree with this, feel free to add it back and we can discuss it. Principal focus should definitely be merged/redirected to here, though.--Srleffler 14:38, 2 March 2006 (UTC)

Amazing picture!
I've have to say this. That computer generated picture is cool! —The preceding unsigned comment was added by 203.206.86.161 (talk) 12:33, 2 March 2007 (UTC).

hyperfocal distance
It might be useful, especially to newby photographers to explain hyperfocal distance: that distance setting at which everything is acceptably sharp from half-way between camera and hyperfocal distance to infinity.--Jim Stinson 00:46, 11 July 2007 (UTC)


 * Try hyperfocal distance. Dicklyon 03:40, 11 July 2007 (UTC)

As a verb, to focus, focusing
The disambiguation page for focusing leads here (in the case of optics). This page describes focus as a noun: a point where light is directed by a lens or mirror. It does not discuss the act of focusing (focus as verb). I assume focusing involves moving the lens relative to the image plane (to minimize Circle of confusion)? The hyperfocal distance page talks about what happens when focusing at different distances (with a fixed aperture size and focal-length), but it does not describe how to focus at different distances. Is this discussed somewhere on wikipedia? Hydradix (talk) 11:47, 30 June 2018 (UTC)


 * The Manual focus page talks about focusing, mostly in terms of mechanics of different cameras. Unfortunately it doesn't clearly define focusing or include any diagrams, equations, or references.  Nonetheless, I added it to See Also of this page. Hydradix (talk) 12:07, 30 June 2018 (UTC)

About what is image focus and object focus
Pls give answer asap 117.99.228.8 (talk) 15:03, 10 May 2022 (UTC)