Very interesting results with a 50/1.5 ZM Sonnar on a Hexar RF, a heavenly match!

[awilder]

I recently purchased a ZM 50/1.5 C Sonnar (f/1.5 optimized) to use on my Hexar RF as discusssed earlier in this thread: http://www.rangefinderforum.com/forums/showthread.php?t=54418

Results greatly exceeded my expectations, making this potentially one of the best camera-lens matches I've ever used. First, regarding near focus accuracy, I couldn't ask for much better. The following images are taken at 1 meter at f/2, f/2.8 and f/4. There is a slight amount of front focus at f/2, possibly related to the slightly deeper film channel of the Hexar RF but it's not very bad at all. By f/2.8 and f/4, things really improve and there is no nasty focus shift well behind the subject.

 

[aizan]

looks like the lens is optimized for f2.8. you sure it's been optimized for f1.5?

 

[awilder]

Next I shot some pictures at a long distance to make sure there were no front focus issues at wider apertures with the Hexar RF and this lens. Image sharpness was great and as good or better than my former 50 Summilux on my MP. Here is a full frame image at f/2 with the Sonnar on my Hexar, a center crop and a left edge crop.

 

[awilder]

Same setup at f/4 shown as a center crop, tight center crop (for additonal detail) and left crop.

 

[awilder]

For comparison, here are 50 mm Summilux crops at f/2 of the same subject earlier in 2007. The lighting is different especially on the house at the left edge but the idea is to compare sharpness.

 

[awilder]

Lastly, here are the Summilux crops at f/4 as shown in a similar setup.

 

[awilder]

Azian, the lens was ordered from Tony Rose as f/1.5 optimized and I believe he checks them out on an M8 to verify this. The front focus at f/2 is probably a result of the design of the Hexar with it's 0.04 mm deeper film channel allowing for motorized advance but effectively allowing the film extra room to move backward against the pressure plate. As seen here with a comparison between the f/2.8 and f/1.5 optimized Sonnars: http://www.rangefinderforum.com/forums/showthread.php?t=51742, mine seems to front focus less at f/2 than the f/2.8 optimized version at the same opening shown in the above post.

 

[Krosya]

Summilux shots look better to me.

 

[mfogiel]

This is a "f2.8" lens, but due to the Hexar you have about 3 cm front focus at f2.0 and 1 cm of backfocus - totally covered by the dof- at f4.0. I'd suggest to shoot it at f 2.8 onwards at infinity, and for the close subjects just remember about the rule to focus slightly behind at the widest apertures. I find that this lens has such an "abrupt" oof passage at close distances, that the effect while shooting at f2.8 is ideal: you get a very sharp plane of focus and a superb and creamy background blur. For best portraits shoot BW400CN or Portra 400 NC.

 

[awilder]

Mfogiel, I agree that on the Hexar RF, the lens behaves more like your the f/2.8 version albeit with a little less front focus at f/2 than with your M7. However, I suspect that once I get my MP back from service and repeat the test, the narrower film channel will push the film slightly more forward resulting in focus similar to your f/1.5 version. I did briefly try what I thought was an f/2.8 optimized version, but on my Hexar it front focused quite alot at all distances and needed to be stopped down to f/4 and smaller for good results. Sharpness compared to the pre-asph. Summilux was similar at f/2 and f/4 but the Sonnar appears to be a bit sharper at the left edge shot at f/4 due to better correction of astigmatism.

 

[awilder]

I reshot the same test chart on my MP and the results are pretty much the same. This tell me it's more correctly an optimized f/2.8 version. Also other test shots demonstrate the Hexar's film plane focus matches that my Leica MP spot on. To be honest, if it were an f/1.5 optimized version, sharpness would suffer from f/2.8 through f/5.6 at all distances since focus shift affects all focused distances, not just close ones. That's because the lens cam is perfectly parallel rather than a hand finished slope like the Leica C lenses for the CL. This means that there is no extra focus compesation at near, only what normally occurs when the lens and cam move in unison with close focus.