depth of field

greenspun.com : LUSENET : Pentax 67 SLR : One Thread

Does anyone know what the depth of field is for my Pentax 67, 45mm, 135mm f/4, and 200mm lenses, or can you tell me how to figure it out for each f-stop?

thanks Don Boyd

-- Don Boyd (dwodon@azstarnet.com), December 02, 2000

Answers

It would be easier to answer your question based on the existing DOF scale on the barrel. The 45mm DOF scale can be used as shown except that it is sharper to put infinity one stop more conservative than the aperture setting. In other words, the aperture is at f/22 but you would set the infinity mark on f/16 on the DOF scale. If you get into a bind, you could set infinty at f/19 and still do OK. Don't own the 135 but the 200 is again similar to the 45mm. You need to set the DOF one stop more conservative than the aperture setting. Many of the Pentax/Takumar lenses are like this. If you use the DOF scale exactly, subjects at infinity will be soft. SR

-- Steve Rasmussen (srasmuss@flash.net), December 03, 2000.

You must use the center of the infinity mark when setting your DOF. SR

-- Steve Rasmussen (srasmuss@flash.net), December 04, 2000.

Steve, thanks. Which point on the infinity symbol can I safely use when referencing the f-stop? Don

-- Don Boyd (dwodon@azstarnet.com), December 04, 2000.

Pentax state that temperature affects the focusing scale - which is apparently why the focusing goes beyond infinity on some long focal length lenses (so that there is room to expand into). Might this not affect the use of the focusing scale for DOF? If you use the middle of the infinity mark, this will equate to different actual focusing points depending on temperature...

-- Ed Hurst (BullMoo@hotmail.com), February 08, 2001.

Moderation questions? read the FAQ