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Infinity focussing question

 
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unclened



Joined: 07 Dec 2014
Posts: 7
Location: United Kingdom

PostPosted: Sat Dec 20, 2014 1:22 am    Post subject: Infinity focussing question Reply with quote

I have the Aero Ektar 178 f2.5 and the 135 f4.7 Graflex lens on a Pacemaker Speed Graphic. I'm finding that the focussing margin for infinity focus and objects that are far away is really small. Near focussing is the opposite and has lots of margin. Is this normal? Can I adjust it in anyway to give me more latitude when focussing on faraway subjects?

Thanks in advance for any guidance offered.
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45PSS



Joined: 28 Sep 2001
Posts: 4081
Location: Mid Peninsula, Ca.

PostPosted: Sat Dec 20, 2014 8:11 pm    Post subject: Reply with quote

Normal lens characteristics.
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unclened



Joined: 07 Dec 2014
Posts: 7
Location: United Kingdom

PostPosted: Tue Dec 23, 2014 2:25 pm    Post subject: Reply with quote

thank you, so am I right in understanding that depth of field is does not have linear relationship with subject distance?
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Sirius Glass



Joined: 06 Jun 2010
Posts: 162
Location: Southern California

PostPosted: Tue Dec 23, 2014 9:15 pm    Post subject: Reply with quote

At a given aperture the Depth of Field [DOF] increases as the focus move toward infinity.

For example at a given aperture the lens might focus from 3 feet /1 meter to 15 feet/5 meters when focused to 9 feet/3 meters. Extend the focus to 30 feet/10 meters and the lens might focus from 15 feet/5 meters to infinity.
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