Two different codes for 35 summicron

[sonyleica]

Does anybody know why 35 Summicron (IV) has different code than 35 Asph Summicron (the newest version)? What does it effect from different codes in M8?

I accidently purchased two LTM adapters for my 35 UC Hexanon f2 without knowing that those two adapters have actually different codes, one for Cron (IV) and another for the new Cron. Will these two codes give different signatures?

Thanks
DJ

 

[Ben Z]

The reason is probably that the 2 lenses have different amounts of vignetting. I have a Cron (III) and (IV) and I coded them both as (IV) since there is no code for a (III) and they both seem to work fine in terms of correction for the cyan corners from IR filters. I don't know which might be better for your Hexanon, but since you've got both, try them both and see.

 

[zeitz]

The code doesn't just tell what the focal length and aperture are. Also one 6-bit code out of 2 to the 6th power isn't the whole code. The camera also takes into account the frameline actuator on the lens tab. The M8 then makes specific distortion/vignetting/chromatic aberation corrections obtained from an internal table for the particular lens model. So not all 35mm f2 lenses are the same, etc. That is why non-Leica lenses really can't be hand coded. See The Viewfinder, 2^6 = 64, an Academic Inquire by Tsun Tam.

 

[thafred]

hi, since the UC hexanon is said to be the same lensdesign as the Cron IV (the pictures are remarkebly similar in character) i´d take that adapter...Cron ASPH has lesser vignetting and very different aberations than the old double gauss designs

cheers
fred

 

[Ben Z]

The code doesn't just tell what the focal length and aperture are. Also one 6-bit code out of 2 to the 6th power isn't the whole code. The camera also takes into account the frameline actuator on the lens tab. The M8 then makes specific distortion/vignetting/chromatic aberation corrections obtained from an internal table for the particular lens model. So not all 35mm f2 lenses are the same, etc. That is why non-Leica lenses really can't be hand coded. See The Viewfinder, 2^6 = 64, an Academic Inquire by Tsun Tam.

I read that article too, and though I'm not qualified to dispute the science, I can say with confidence what thousands of others have already discovered, namely that non-Leica lenses (as well as older Leica lenses that have no factory-supplied codes) can most definitely be hand coded, that the coding eradicates the cyan corners caused by IR filters on wide angle lenses, and that it causes no bad side effects. Whether that is because the M8 really doesn't do as much with the codes as Mr. Tam speculates (his article does not prove the existence of advanced corrections) or that the popular non-Leica (and older Leica) lenses are closer in performance to the coded models than he speculates (again, he did not test his hypothesis) I don't know. But emprically, hand-coding of non-Leica and non-codable-Leica lenses works just fine. It may be true though, that some experimentation might be required to find (borrowing from the real estate trade) the Best Available. It may be that a code for a 28mm might work better for a 35mm non-coded lens (just an example, not a specific recommendation). The only exception I'm aware of is the 12mm Voitlander lens, which really has to rely on 3rd-party software for the cyan correction.

 

[jaapv]

Sean Reid did comparative tests and non-Leica lenses can be reliably coded to the most similar Leica lens with great results.