[finaldesignrb]

Why did the Apo Lanthar 90mm f3.5 lens become so unexceptional in sharpness when mounted on the Nex? 3 stars optical rating. It tested so well, 4.5 stars optically, in the Nikon APS-C photozone review. Is this going to happen with every lens we put on the Nex? Your theory, Klaus? In contrast, the Sony 50mm f1.8 did not take quite so much of a hit upon migration to the Nex.

[genotypewriter]

[quote name='RussellB' timestamp='1291875585' post='4893']

Why did the Apo Lanthar 90mm f3.5 lens become so unexceptional in sharpness when mounted on the Nex? 3 stars optical rating. It tested so well, 4.5 stars optically, in the Nikon APS-C photozone review. Is this going to happen with every lens we put on the Nex? Your theory, Klaus? In contrast, the Sony 50mm f1.8 did not take quite so much of a hit upon migration to the Nex.

[/quote]

Since they're both SLR lenses, I expect the resolution conversion numbers when put on the Nex to be fairly close with a bit of room for experimental error.



I found a similar weirdness in the 17L test:

http://forum.photozone.de/index.php?/topic/514-ts-e-17l-photozone-results-error/



GTW

[Klaus]

[quote name='genotypewriter' timestamp='1291881284' post='4894']

Since they're both SLR lenses, I expect the resolution conversion numbers when put on the Nex to be fairly close with a bit of room for experimental error.



I found a similar weirdness in the 17L test:

[url="http://forum.photozone.de/index.php?/topic/514-ts-e-17l-photozone-results-error/"]http://forum.photozo...-results-error/[/url]



GTW

[/quote]



The M mount version of the Lanthar is different to the SLR version ...

[joachim]

[quote name='Klaus' timestamp='1291884592' post='4895']

The M mount version of the Lanthar is different to the SLR version ...

[/quote]



I doubt the optical design differs between the two. Rangefinder 90mm lenses have a lot of clearance between the last piece of glass and the sensor/film. You can easily fit a mirror in there.



On the other hand, I don't see any disagreement between the two tests. The numbers are actually very close. It might be that the 10MP of the Nikon D200 coincides with the MTF50 of that lens, and the higher resolution of the NEX outresolves that lens.

[Brightcolours]

[quote name='joachim' timestamp='1291905526' post='4905']

I doubt the optical design differs between the two. Rangefinder 90mm lenses have a lot of clearance between the last piece of glass and the sensor/film. You can easily fit a mirror in there.



On the other hand, I don't see any disagreement between the two tests. The numbers are actually very close. It might be that the 10MP of the Nikon D200 coincides with the MTF50 of that lens, and the higher resolution of the NEX outresolves that lens.

[/quote]

Nice that you doubt that, however a simple look at the lenses in both reviews already will show that both lenses are of a slightly different design. One only has to look at the difference in how they extend during focussing.







The basic design may be the same, but they are different in detail. Also notice the reversal of focus and aperture ring between the two designs.

SL (II): 0.5m MFD

M-mount: 1m MFD



(showing the basic design to be the same

[joachim]

[quote name='Brightcolours' timestamp='1291906406' post='4906']

The basic design may be the same, but they are different in detail. Also notice the reversal of focus and aperture ring between the two designs.

SL (II): 0.5m MFD

M-mount: 1m MFD



(showing the basic design to be the same





[/quote]



Hi,



Thanks for replying to my post.



I am writing about the glass, and that is essentially all Klaus is testing (unless the barrel is not holding the glass in the proper place).



Have a look at what you posted - the optial designs look the same. For sure the barrels (the brass stuff) are different. The close focus is part of the brass stuff, the SLR lens has a longer helicoid. If you study the various incarnations of 90/2.8 for Leica M and R over the decades you will learn that they sold the same glass for both systems.



Considering the differences you point out in the brass stuff, you can point out similar differences between old Nikon AF-D and Canon EF:



mechanical AF vs motor in lens

mechanical aperture vs electrical aperture

aperture ring vs aperture control in body only



Still everyone would have been surprised if a lens available in both mounts (e.g. Tamron) would perform extremely differently between the two mounts.

[finaldesignrb]

[quote name='Klaus' timestamp='1291884592' post='4895']

The M mount version of the Lanthar is different to the SLR version ...

[/quote]

Klaus, you answered this question so perfectly that am now feeling dumb for asking. And, want that SLR lens now, not just for the all-aperture goodness, but also for the real nice performance at small F11 and F16 apertures too. Your careful comments about the lens's strengths and weaknesses much appreciated.