Where is infinity?

Started Feb 28, 2013 | Questions thread
EinsteinsGhost
Forum ProPosts: 10,076Gear list
Like?
Re: Where is infinity?
In reply to sybersitizen, Mar 1, 2013

sybersitizen wrote:

EinsteinsGhost wrote:

sybersitizen wrote:

EinsteinsGhost wrote:
... If you focused past HFD (10m, for example), you’d not see any difference (3.60m to infinity will be in focus).

I assume you mean actually turning the focus ring to the 10m mark. If so, you were on solid ground until here, but that part is not right. DOF would now extend from (roughly) 4 or 5 meters to infinity - and actually 'beyond' infinity, meaning some of the distant DOF is being 'wasted'.

No. I don't really use the distance scale on the lens. By 10m, I meant the actual distance (measured or approximated).

The point is: If you refocused the lens from 7m to 10m (with or without markings), what I said above is true.

Are you instead saying that you left the lens alone and only moved the subject from 7m to 10m away from the camera? Of course that will change nothing regarding DOF covered by the lens.

No, I'm simply changing focus to a different distance, to make a point about how DoF will change, until you hit HFD when it goes to infinity. I'm not concerned about focusing at a subject, just the distance to focus.

As in my illustration, 24mm, f/4 on A580 will have an HFD of 7.2m, regardless of where you are focusing. However, if you focus at a point 7.2m away (meeting the HFD criteria), the DoF increases to infinity (and an additional 3.6m of it, from that point towards the camera).

 EinsteinsGhost's gear list:EinsteinsGhost's gear list
Sony Cyber-shot DSC-F828 Sony SLT-A55 Sony Alpha NEX-6 Sigma 18-250mm F3.5-6.3 DC OS HSM Sony 135mm F2.8 (T4.5) STF +12 more
Reply   Reply with quote   Complain
Post (hide subjects)Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark post MMy threads
Color scheme? Blue / Yellow