Difficulty with focusing

[maximusmini]

Hi everyone

A newbie needs some help.

I have an old Summilux 50 (1960s 2nd version I think) on my M4 and have a problem with focusing up close (<1.5m), especially when I shoot at f2 or f1.4.

I have 2 questions:

1) I tried to take a pic of my cat at about 1m, and lined up the RF split image (using the top edge of the nose where it meets the eye as a guide).

At 1.4, I found that my point of focus ended up about 1 to 1.5 inches in front of where I thought it would be (ie. the face wasn't in sharp focus but the area in front of it was).

This lens has a min focus of 1m, but when i turn the focus ring all the way, it goes beyond the 1m marking (the lens barrel also moves). In this case, I turned the focus ring all the way, then moved back, until the RF split image lined up.

Assuming it was my cat's face that I wanted in focus, am I doing something wrong? Or should I get the body or lens checked or calibrated?

2) Does anyone have any idea at f1.4 or f2, and focusing down to 1m, what the depth of field for this lens is?

Please help.

Tim

 

[RML]

Unless you test it with a stationary subject and your camera on a tripod, in clear light and good contrast, there's no way to tell whether it was you, your camera or the cat.

 

[waileong]

1. Put your camera on a tripod, tape a newspaper to the wall, measure the distance accurately from the newspaper to the film plane with a yardstick or measuring tape, then focus the lens and compare. This will tell you if your focus is in order. Try with different lenses and you will see if it's the camera or the lens that needs adjustment.

2. Search the net for a DOF calculator.

 

[Artorius]

Pocket PC

Pocket PC

If you have a Windows PPC, here is what I use;
http://home.comcast.net/~jonsachs/

Excellent program and FREE.

 

[maximusmini]

Much thanks for the help people. 🙂

 

[pvdhaar]

Using the top of the RF spot to align vertical edges does pose a problem for some real life situations. But the same would hold for using the bottom RF edge.. Had you used the bottom edge in the same situation, you might have found the focus to lie behind the intended point instead..


This all happens when you're not shooting exactly perpendicular to the plane that the edges are in. In other words, if your camera is tilted, then you'll notice differences in alignment between top and bottom of the RF spot..

You can check this if you draw a line on a wall, and focus with a tilted camera. You'll even see the line as an X in the RF spot if you tilt the camera enough..

Under real life conditions, you can best focus by lining up the middle of the dual images.

 

[maximusmini]

Thanks for your help Peter.