Leica SE 18mm Service

[giordano]

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Alan I have no experience regarding the Canon lens whatsoever. It may be great on a dSLR, I have no clue nor opinion there.

The size constraint to work well on an M is obvious of course as is that a T/S cannot work on a rangefinder camera. I'm not an optical designer either. A pretty reasonable assumption that the Peter Karbe and his team are expert though and as a customer, I personally support their approach. Are you suggesting that the Canon design could be modified to do a better job? Have you any basis for that?

 

Alan can speak for himself, but it's certainly (a) possible to make an 18mm lens with less distortion than the Super Elmar and ( possible to do so by modifying the optical design of the 17mm Canon TSE (that's obvious: even without shifting, it covers a wider angle with less distortion).

 

Assuming (a pretty safe assumption) that the Leica lens design team knows its stuff, they could have done (a) if they'd really wanted to - so we can infer that some other factor(s) - e.g. size, weight, cost, not blocking the rangefinder windows - intervened.

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[AlanG]

Maybe what needs to be mentioned is there is nothing special in the lens design of a TS lens other than the shorter focal length ones are very "wide angle" in order to produce a larger image circle in order to accommodate the tilt and shift displacements. Thus an even less radical design (not as wide angle) could be used for a non TS lens of the same focal length if it only has to cover 24x36mm. And a TS lens could be used on a rangefinder via trial and error.

 

But clearly Leica made its choice on the 18 3.8 so I don't see what would be wrong with removing the distortion in post processing if it bothers anyone.

[lars_bergquist]

But clearly Leica made its choice on the 18 3.8 so I don't see what would be wrong with removing the distortion in post processing if it bothers anyone.

 

Or using a different lens with less distortion. Or is that heresy?

 

The old man home from the brand wars

[gvaliquette]

IThis is the kind of distortion that will need a special correction profile. (I don't know what aperture was used but perhaps the distortion improves a bit when stopping down.) The distortion is wavy and progresses towards the edges.

 

Alan:

 

Distortion does not vary with aperture. If it did, sharpness would be severely impacted, as the various parts of the lens would project a different image on the film or sensor!

 

Guy

[AlanG]

Alan:

 

Distortion does not vary with aperture. If it did, sharpness would be severely impacted, as the various parts of the lens would project a different image on the film or sensor!

 

Guy

 

You are correct and I was wrong for thinking the aperture would matter. So making software correction for the distortion shouldn't be too hard to employ once the lens has been tested.

[hoppyman]

John that is rather the point. Those factors and many more must be taken into account in the design of an M lens. Whether or not that Canon design could be modified to work on an M is moot in any event.

Alan can speak for himself, but it's certainly (a) possible to make an 18mm lens with less distortion than the Super Elmar and ( possible to do so by modifying the optical design of the 17mm Canon TSE (that's obvious: even without shifting, it covers a wider angle with less distortion).

 

Assuming (a pretty safe assumption) that the Leica lens design team knows its stuff, they could have done (a) if they'd really wanted to - so we can infer that some other factor(s) - e.g. size, weight, cost, not blocking the rangefinder windows - intervened.

[menos I M6]

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The Super-Elmar-M 18 mm Asph primarily is an M lens—that is to say, SHARP and SMALL. You simply can't have a lens that covers a 24 × 36 mm frame with an angle of view of 100° that is tack-sharp across the whole field and small and distortion-free. The Canon TS-E 17 mm is sharp and virtually distortion-free—but definitely not small.

 

Generally, Leica accepts fairly high amounts of distortion in their wide-angle lenses (and often the unpleasant and hard-to-remove wave-form kind) in order to optimize other aspects. Zeiss wide-angle lenses usually have less distortion but they are bigger, and/or have more curvature-of-field, and/or vignette more, and/or are not so sharp at the frame's corners. The art of lens design is to find a good compromise. And each lens desiger has different ideas, preferences, and priorities.

 

The Voigtländer 15 Heliar is a phenomenal lens by comparison. It is much tinier, lighter, a lot less expensive and of course, doesn't show the slightest such an extreme distortion.

 

I too did not believe, this modern Leica lens could produce such an extreme amount of distortion and I would be very unsatisfied by finding this out after paying the high price for the 18mm Leica, whereas a 15mm Heliar costs just 300 − 400 EUR !!!

 

Thanks for this thread! I indeed lightly thought about adding the 18mm at one time to my lens bag - glad, I didn't do it.