Noctilux -- "slight focusshift"

The recent discussion about Erwin's reviews reminded me about his Noctilux <a href="http://www.imx.nl/photosite/leica/mseries/testm/M10-50.html">review</a>. While I appreciate all his efforts his review of the Noctilux leaves me hanging a bit. The most disturbing part is this focus shift or Blendendifferenz. He documents it, but then doesnt really translate his flat plane test chart numbers into real 3D world DOF consequences. What I would like to know is what does the focus shift mean to someone shooting at 1.5 meters and f2 for instance. Does that means I have to move the focus 2 centimeters closer? further away? or is the focus shift less than a centimeter?<br>Has anyone run these figures and can post the results here? Thanks...

Theory is all well and good, and there might in fact be a focus

shift, but people are using this lens at full aperture for real

photography with success. I would think that a focus shift is less

of a problem than a less than perfect rangefinder. On the LUG I have

read several post about how everything was great when the user only

had a 35mm lens, but upon getting a 50mm Noct' or a 75mm Summilux, it

was clear that their rangefinder was not correct. Below are some

shots from one person that posted these series on the LUG

demonstrating the use of the Noctilux at f/1.0. If there is a focus

shift, it doesn't show up here with these three dimensional

subjects. Maybe it would be a problem for a flat test pattern shot,

but only lens testers do those kinds of pictures. These photos are

slow to load due to the resolution, but they show off the lens pretty

well.

 

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<a href="http://www.shinozuka-family.com/f1"> series 1 </a>, <a

href="http://www.shinozuka-family.com/bokars/"> series 2 </a>,

<a href="http://www.shinozuka-family.com/chess/">series 3</a>

Russell,

 

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As I understand it, the focus shift only applies when stopped down.

You should have no problems between F1 and F4, but at F5.6 and

smaller the plan of focus shifts. Can't remember the exact reason

though.

 

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The biggest problem is the limited depth of field wideopen up close

with the Noctilux. Again no problem when you are centering your

subject directly over the focus rectangle, but if you recompose your

image after focus as I often do with my portraits, then the plane of

focus will appear to be closer than your point of intended focus.

 

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I over come this by focusing on my subjects eyes, recomposing and

then 'tweeking' my focus ring to a point closer than the original

focus corresponding to the depth of field marker distance. It is

almost failsafe for me.

 

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I love my Noctilux but only because I nail my focus everytime with

this method.

 

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Haven't noticed the focus shift effect much as I mainly shoot between

F1 and F2.

 

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Good luck

Why not defeat this problem by composing first and then

focussing on the eyes?

Albert, in the very process of moving the viewfinder back to the

desired composition after focusing, a subtle change in camera to

subject distance occurs. It's referred to as "cosine error" because

the ratio of the two distances is equal to the cosine of the angle

through which the camera is moved. There is an earlier thread or two

on this.

 

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Actually, it looks like we have two different topics going here, both

under the heading of focus shift. Shift of focus, as I believe E.

Puts used it, refers to the fact that the point at which the lens is

focus drifts somewhat as the aperture is stopped down. Not much of

an issue with a 50mm Summicron; but with the lens designer having to

juggle so many variables to correct an f/1 lens, evidently some shift

of focus had to be accepted.

Al, thanks for showing your 3 series of NOCT- photos. They show

nicely what a good photographer with a terrific lens/ camera combo

can accomplish.

 

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There are simply not enough photos around on this LEICA- site, IMO.

 

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Thank you again for sharing.

 

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Best regards

Thanks for the answers guys, but that's not it yet... Please read

Erwin's article. There is no focus shift at f1. where it gets "ugly"

is in the f1.4 through f4 range. And it's not a condition of focusing

on in the center and recomposing. But Erwin does a better job of

explaining it than I can.<br>What I am after is how much of a focus

shift it there at something like f2 and close focus. If the focus

shift is only 1/8th of an inch then I can live with it since the DoF

at f2 and close focus is much more than that. Thanks...