50mm Summilux ASPH Oddity

[Timmyjoe]

Was wondering if anyone else has experience this.

Purchased a new 50mm Summilux ASPH a few days ago, and although it was tack sharp at f1.4, it really softened up at f2, then went back to pretty sharp at f2.8 and tack sharp again at f4. Did this on my M8.2 and my M6 TTL.

Ended up sending it back.

Just wondering if anyone else has experienced this and if it's just one of those weird idiosyncrasies of the new 50 lux ASPH design?

Best,
-Tim

 

[V-12]

Its not really known for it, but your Summilux may be exhibiting focus shift at f/2, where stopping down gradually increases sharpness again because of the increased DOF.

The design of many rangefinder lenses incorporates focus shift, a design flaw, but one that we have to live with and compensate for by knowing when it happens and factoring that in when critcal focusing.

Typically they will be calibrated to be sharp wide open, but at f/2 to maybe f/4 they go soft according to what the rangefinder says, but come back to maximum sharpness at f/5.6, but all suspectible lenses have their own variations. Discovering how much to compensate to get a sharp picture at f/2 can be frustrating on a film camera because of the delay in processing, but after a while you should get used to moving the focus patch a tiny bit one way or the other.

 

[Moriturii]

I suggest you take a picture of a ruler or something that is at a 45 degree angle (something like that) and take pictures at a few aperture levels (no need really to go beyond F8 I would've thought) and you will see the level of focus shift on your lens. Good luck.

 

[philipus]

The 50 asph has a floating group that largely compensates for focus shift, as I understand it. I have never seen this behviour on my copy.

 

[Rowse]

My current copy which I bought 3 months ago is sharp at all apertures including F/1.4. My former copy which I returned was not sharp at all at F/1.4, but was tack sharp at F/2 and all other apertures. It was hazy at F/1.4 and I dont think it was a focus shift issue. My current copy is much sharper at F/1.4. Your copy may be a focus shift issue since it is sharp at the widest aperture, normally it should be the opposite, ie. soft at F/1.4.

 

[ramosa]

I never noticed this with the Lux 50 ASPH that I used to have. Like you, I would have sent it back if it had this problem.

 

[Timmyjoe]

Thanks everyone. I'm sticking with my pre-ASPH lux. It might not be so sharp, edge to edge, like the new one, but have never had any focus shifts issues with it in the twelve years I've had it.

Best,
-Tim