Please could someone explain(in simple terms) how the depth of field scale works on my 50mm 1.4 summilux.

-- John (johnsmith@aol.com), January 27, 2002

Answers

Is this another one of those 'how stupid can I be and get away with it' questions?

-- Craig (craigsmith@hotmail.com), January 27, 2002.

Read it out of the manual:

http://members.fortunecity.com/canoneos/manuals/leicam4p161 7.jpg

-- John Collier (jbcollier@powersurfr.com), January 27, 2002.

Is this argument restricted to members of the Smith family or can anyone join in?

To answer John (Smith's) question: as you may be aware, the narrower the lens aperture (i.e. the higher the f-stop number), the greater the DOF. On the lens barrel there is a DOF scale to assist you in knowing the zone that will appear acceptably sharp. It has to be read in conjunction with the distance scale. This is particularly useful with rangefinder cameras because there is no way of previewing the DOF.

You will notice that the DOF scale has a pair of markings for each f- stop. Every point on the distance scale that falls between the pair of markings that corresponds to the aperture you select will be acceptably sharp. This makes use of an optical illusion, since there is actually only one plane of true focus but our eyes are fooled into seeing sharpness fom the front to the back of the so-called DOF.

Its most common use is probably in selecting the hyperfocal distance. To do this, you adjust the lens focus so that the infinity mark coincides with the right-hand mark on the DOF scale (when viewed from above with the lens facing away from you) for your selected aperture. Everything will be then acceptably sharp, from infinity down to the point on the distance scale that coincides with the left-hand DOF scale marking for the same aperture. It's also useful, of course, in setting a deliberately shallow DOF when you don't want a distant background to be sharp.

-- Ray Moth (ray_moth@yahoo.com), January 28, 2002.

Ray: Thank-you for offering a proper response instead of rude like previous answers. Not everyone is gifted enough to have the patience to look things up, others not familiar with the site do not know how to look up previous threads while some of us did not get the manuals with our used equipment.

:)

-- M.A. Johnson (logical1@catholic.org), January 28, 2002.

Hi John! Keep in mind that your lens's DOF scale is based on "acceptable" parameters of sharpness. With this in mind, my own DOF procedure is as follows: When I'm photographing dynamic subjects using DOF to aid focus, where critical DOF sharpness isn't absolutely essential, I go ahead and rely on the DOF scale. When I'm doing a landscape or other "static" subject, especially if using a tripod and a high-res film, I try to use the next lower number-pair on the DOF scale than the actual lens setting. In other words, if the lens is set at f/16, I'll use the f/11 indicators on the DOF scale. This helps to ensure that my 11X14 or larger print is as sharp as originally intended.

-- John Layton (john.layton@valley.net), January 28, 2002.

John Layton has hit on one of the key points. The DOF scale is based on acceptable sharpness for an 8X10 print viewed from about 18 inches. The actual calculation of DOF limits on the lens would change if you wanted it for a 5X7 or a 24X30 print. The correct thing to rememeber is that the lens is accurately focussed for exactly one distance at any given time. Other distance may or may not be within acceptable limits to be considered "in focus". There are some good links on the web if you search long enough. I have them at work but not here.

-- mark (Leica_CL@hotmail.com), January 28, 2002.