Archived posting to the Leica Users Group, 1999/07/07

[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]

Subject: [Leica] Noctilux VS 75mm Now DOF
From: "Robert Rose" <>
Date: Wed, 07 Jul 1999 20:10:31 -0700

There is a dandy depth of field calculator on the Internet at: 

Also, there is a really nice portable version for the Palm at: 
called Focus+

These programs confirm that Jim is correct.  The reason the Summilux has "less" DOF than the Noctilux at the same subject distance is because it has a smaller field of view.  They will give identical DOF at equivalent f/stops only if you move in with the Noctilux to frame the identical image.

Now, to answer Jim's project, I looked at the Leica brochure and found that the Noctilux has a 45 deg field and focuses to 1 meter, while the Summilux has a 31 deg field and focused to .75 meter.

Using the handy calculator, at their respective close focus distances (as reported in the brochure) the Noctilux has a DOF of .9 in and the Summilux has a DOF of .3 in.  Jim is again correct!

BTW, the Summilux focuses to an object of 192 x 288 mm, while the Noctilux only goes to 410 x 615 mm.

Flamers on your marks:  The R lenses can do better on close focus.

I have to get a life.

Bob Rose
Date: Wed, 07 Jul 1999 17:14:43 -0700
From: Jim Brick <>
Subject: [Leica] Re:  ..

I believe DOF is determined by image size. That is, if you set a Noctilux
at f/1.4 and frame a scene, then set a 75 Summilux at f/1.4 and frame the
same scene exactly like the Noctilux (The Noctilux is closer to the scene
than the Summilux in order to have the exact same image on film) the DOF of
both lenses will be exactly the same.

If you stand at exactly the same place and take the photograph, at f/1.4,
with both lenses, the Summilux will record less of the scene than the
Noctilux. 75mm vs. 50mm. The Summilux will have less DOF, in this
circumstance, than the Noctilux.

The f/1.0 DOF statistics belong only to the Noctilux.

The Summilux at f/1.4, focused at it's closest position, might possibly
have less DOF than a Noctilux at f/1.0 focused at its closest position.
Perhaps exactly the same. This is a good project for someone. I believe the
75/1.4 close focus/image size is the best of the M lenses.

I have a photo of a tulip, printed 16x20 on Ciba, that I took with my
75/1.4, at f/1.4, and focused at its closest position. The DOF is literally
the front surface of the tulip. Barely a few millimeters.