The 75 lux has a very shallow DOF at full aperture, and here is what I am wondering: when you take a portrait at F1.4, and you want the focus on the eyes, you move the camera so that the eyes are in the rangefinder patch to focus accurately. And you then recompose (unless you want the eyes right in the middle of the picture but it is seldom the case). Given the limited DOF, don't you then lose accurate focusing (since you move the camera to recompose)? How can you make sure the focus will be perfect and still have the right composition?

-- Marc A. Pilgrem (mpilgrem@hotmail.com), April 25, 2002

Answers

there was a long discussion about this topic. Martin Tai had an extensive explanation on how this can be achieved...i tried to search this site using google but i can't find it...maybe someone else can...

-- Dexter Legaspi (dalegaspi@hotmail.com), April 25, 2002.

http://www.greenspun.com/bboard/ q-and-a-fetch-msg.tcl?msg_id=004sHD

-- JM Woo (wooismyid@nospam.yahoo.com), April 25, 2002.

That's all I needed. Thank you !

-- Marc A. Pilgrem (mpilgrem@hotmail.com), April 25, 2002.

wow, this must be a record for a thread, active for more than a year. martin tai must be commended for keeping/correcting his data up to date.

can't write much more, i now have a headache looking at his diagrams and formulas. :*)

-- Steve (leitz_not_leica@hotmail.com), April 25, 2002.

Whew... makes you want to have a groundglass. ;-)

-- Gary Voth (garyvot@vothphoto.com), April 25, 2002.

I hate math!!!

Even my boyfriend has a hard time with the information. He says it must be the format of the presentation.

Martin can you please explain it for dunces like myself? Some of my photos are blurry, maybe because we are doing a compositional series of the system of thirds in my class and the focused part (eyes) moved. By the way, reading here and relating to the class, I have been very popular. There are many of my classmates here now. But, they don't own Leicas yet. I am the only one.

My camera is the M3 and my lens is a 50 Summicron. I assume your formulas take into account the different viewfinders? Please make it easy.

Regards, Allison

-- Allison Reese (a_b_reese3@hotmail.com), April 25, 2002.

Allison, judging by that photo.net thread, this is one topic you may not want to give Martin any encouragement on ;-)

The concept is very simple. Here is an example.

You facing someone and focusing on one of their eyes using the central spot of the viewfinder. Picture in your minds eye an imaginary wall falling through that eye, parallel to the camera. Everything on that "wall" will be in focus.

Now swing the camera around slightly to get that focused eye to the rule of thirds point in your viewfinder. The imaginary in- focus "wall" swings with your camera, moving away from the eye. Result? The eye has fallen away from the in-focus "wall".

Now if you have stopped down, and there is plenty of depth of field, you may not notice at all. But if there is very little, the eye will be out of focus. Its a rare problem in portraiture though, occuring with close ups, wide open in dim available light...

-- Mani Sitaraman (bindumani@pacific.net.sg), April 25, 2002.

Mani's right: with the 75mm at f/1.4 and close focusing distances, re- framing is very likely to produce "focus change." But there are easy work-arounds: use faster film, a smaller aperture, or stand back a bit further.

-- Andrew (mazurka@rocketmail.com), April 26, 2002.

Revisiting THAT thread reminds me of the story of the millipede who forgot how to walk because some worm asked him which leg he put forward first.

Don't lose sight (pun intended) of the objectives (pun intended again).

-- Erik (supercalifragilisticpolymathicgenius@hotmail.com), April 26, 2002.

"Use smaller aperture" yes, but how "small" is "small" ?? F8 ? f 16 ?

For example, with R 28 f/2.8 lens, if center focus distance = 0.3 meter, after recompose the object to the side, what "small " aperture you think will be enough to cover the focus shift ?

I have a simpler method using table approach See my article:"Leica M & R Recompose focus Guide" http://groups.yahoo.com/group/Leicafile/files/articles/recompose.html

-- martin tai (martin.tai@capcanada.com), April 27, 2002.

Martin,

This a really useful table and article. Good work, and thank you for helping us all!

-- Mani Sitaraman (bindumani@pacific.net.sg), April 27, 2002.

thank you Mani

Indeed, table is a better way than math.

I choose to post the article to a site where I can update the content ( I have revised three times already ). Otherwise, the thread will be too looooong, like the other thread.

-- martin tai (martin.tai@capcanada.com), April 29, 2002.