1.4/50 Sumilux ASPH Back Focus: How much is still acceptable

[adietrich]

Hi,

I just got back my 1.4/50 Sumilux Asph from Leica USA. It seems to me that there is still some residual back focus. The attachments show a focus test chart, distance 40in at f2.0.

Before I send back the lens I would like to ask: "How much is still acceptable?"

Thanks!

Regards,
Arne

 

[adietrich]

1.4/50 Sumilux ASPH: another example

1.4/50 Sumilux ASPH: another example

This is a more realistic example: I focus on the "front eye", and the "back eye" turns out to be in focus.

-a

 

[Never Satisfied]

Arne, if I spent that much on a lens like that, to my mind it should be spot on. How well does your body focus other lenses??

Andrew.

 

[Tom A]

Considering what they charge for the 50f1.4 Asph - there should be no backfocus. Did you send the camera along with the lens? There could be a "mating" problem between the body/lens.
I haven't really heard about it with Summilux 50 Asph - but it is fairly common with Noctiluxes and 75f1.4 Summiluxes. Shooting close with even a f1.4 wide open does not leave much room for error in rangefinder adjustment, camera support etc. I assume you used a tripod for the test so we can eliminate body-movement (exhaling/inhaling etc).

 

[adietrich]

Considering what they charge for the 50f1.4 Asph - there should be no backfocus. Did you send the camera along with the lens? There could be a "mating" problem between the body/lens.
I haven't really heard about it with Summilux 50 Asph - but it is fairly common with Noctiluxes and 75f1.4 Summiluxes. Shooting close with even a f1.4 wide open does not leave much room for error in rangefinder adjustment, camera support etc. I assume you used a tripod for the test so we can eliminate body-movement (exhaling/inhaling etc).

Hi Tom, Andrew,

Thanks for your quick reply. I sent in the lens only because the other lens looked OK to me. So maybe the other lens and the range finder are both off.

For the test chart I used f2, flash, a tripod, and a wire release for good measure. ;-)

Big picture: This time the body goes back with the lens.


Regards,
Arne

 

[35mmdelux]

Get rid of that albatross and send it to me.

 

[john_s]

I had a 35mm Summilux ASPH that frontfocused quite a lot. My local Leica importer (Adeal, Melbourne) was good enough to send it to Solms for adjustment and it came back with documentation to that effect. It still frontfocused just as much as far as I could tell, using a test very like yours. It did so on two M bodies and a Voigtlander R3M. Since those three bodies all focus my 50mm Summilux ASPH almost perfectly, and since the 50mm is the lens I use the most, I sold the 35mm to a dealer to whom I told the whole story. Two of the bodies and both lenses I bought new. I really don't know what to make of all this, except that the whole rangefinder system is fraught with small errors and if you're unlucky the errors all go in one direction resulting in a very expensive system that gives results worse than many a cheaper system (e.g. autofocus Nikon, which I now use for wide angle use).

I should add that I wouldn't do anything until trying the test at some other distances. It might be fine at two or three metres.

 

[mfogiel]

In principle, the "acceptable" amount of misfocus must be within the DOF, so you should shoot another test wide open, and see. For what I see, you are already borderline at f2.0, so wide open the focus zone will be outside the intended focus plane. These problems can be magnified if a) you use a digital camera, which has a more shallow dof at equivalent apertures, because the sensor does not have the emulsion depth, b) if you wear glasses or position your eye off the center in the VF when making the test. As Tom said, you should send the camera together with the lens, and pretend a perfect focus alignment.

 

[waileong]

The prob is usually not with the lens. The body has to be calibrated.

 

[awilder]

Here's an example of my 50/1.2 Hexanon focused at 1 meter and shot at f/2: http://photo.net/photodb/photo?photo_id=8924468
DOF appears to be reasonably sharp at a little over 22 mm on either side of focus. This is consistent with the stated dof charts for this setting and closely matches to what Leica also states on their dof chart for the 50 Summilux ASPH. I don't know why, but the dof shown in your example is about half that stated at f/2 for 1 meter. Must be the better correction and focus isolation of the aspheric design allowing for less aberration at the focus point but greater softness beyond the point of oerfect focus. Another possiblity is that the test chart is not at a perfect 45 degree angle to the camera.

 

[horosu]

As far as I know this lens doesn't show focus shift at all. Mine is spot on wide open and I often am amazed by its sharpness.

Horea