OT Ostreni a nekonecno (bylo Zkusenosti s fotoaparatem DMC-FZ18E-S Lumix)

Dusan Dolezal duffa@inmail.cz
Středa Červen 11 09:43:45 CEST 2008


Tak jsem dnes nahodou narazil na nejake FAQ ohledne fotaku a byla tam i
otazka na tu moznost "ostrit za nekonecno". To vysvetleni vypada byt celkem
logicke:

"My lens can focus past infinity. Is it broken?

This is perfectly normal. Many AF lenses can focus past infinity, for one or
several of the following reasons:

    * Some zoom lenses vary focus slightly when zoomed to varying focal
lengths. So while they focus to infinity at one position of the focus ring,
they focus past or before infinity at the same position but at a different
focal length.
    * Large lenses can expand with increasing temperature, changing focus as
they expand, and they need the extra focus range to make sure they can be
focused to infinity even after they were exposed to the heat of the sun.
    * Auto-focus can overshoot the infinity mark when it hunts for correct
focus. With some extra room after infinity focus, the AF system can detect
the overshot and has a chance to stop the AF motor before a mechanical end
stop is hit. This reduces mechanical strain and wear of the AF motor and
gearing."

Dusan Dolezal

> -----Original Message-----
> From: hw-list-bounces@list.hw.cz 
> [mailto:hw-list-bounces@list.hw.cz] On Behalf Of Raven
> Sent: Saturday, June 07, 2008 8:23 PM
> To: HW-news
> Subject: Re: OT Zkusenosti s fotoaparatem DMC-FZ18E-S Lumix
> 
> Jelikoz jsem si nebyl zcela jist pockal jsem az budu doma. Toz je to 
> naopak nez uvadis. Nekonecno pro IR je bliz nez pro 
> "normalni" svetlo. 
> Vim, ze pro krajinky jsem tyto veci neresil a proste zatocil 
> objektiv na 
> konec. A zvlast u kratkych ohnisek neni ostreni az tak osemetne.
> Jinak u soucasnych zoomu s aut. ostrenim mas pravdu. Jde to 
> zatocit za 
> nekonecno, zrejme z duvodu nejakych tech. omezenich. Dle meho nazoru 
> naprosto zbytecne.




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