Sean Reid's observations on M mount lenses on the G1

[petermcwerner]

Peter do you have results from other R lenses?

The 100mm/2.8 APO macro is fine, but no surprise for long lenses. I have published an example picture some time ago in a thread on this forum.

As far as wide angles are concerned, I only have an old 28mm and the 35mm Schneider shift lens, of which I already published examples here. This one too has no problem. Otherwise the 21-35 zoom covers all my WA needs. I could try the 35-70/2.8 and 35-70/4, I do not think there is much point in testing longer lenses, they should most probably work; the problem is really with wide angles.

 

[mazor]

Hey just wondering is it possible that the Leica m lens have soft corners, as the G1 does not have angular microlens? I know that the Leica M8 although having a smaller crop factor, does sport angular microlens.

Mazor

 

[marknorton]

Hey just wondering is it possible that the Leica m lens have soft corners, as the G1 does not have angular microlens? I know that the Leica M8 although having a smaller crop factor, does sport angular microlens.

Mazor

It's not the lens, it's that the G1 sensor was not designed with M lenses in mind and what Leica has been telling us for years - that M wide-angles are a problem - is true. It would be interesting to know whether the latest wide-angles are any better than the 28m Summicron which was designed pre-M8.

Thanks to everyone for these tests, a lot of work and Kamera Kat is certainly patient!

 

[mazor]

thx marknorton for that info. I think with M lens, this soft corner effect is more extreme due to the close distance of the lens to the film plane meaning low angle non parallel light hitting the sensor. this was not a problem in the past with film, but with digital, parallel light hitting the sensor is important, hence why M8 has angular microlens on the sensor that allow the catching low low angle light and re angle it to hit the sensor correctly

Mazor

 

[vanhulsenbeek]

.............this soft corner effect is more extreme due to the close distance of the lens to the film plane meaning low angle non parallel light hitting the sensor......................
Mazor

Mazor,
Could you explain why that phenomenon causes a soft effect, or smearing and not only vignetting?

My WATE lens is just as far from the sensor as the kit lens is.

 

[Per Ofverbeck]

Mazor,
Could you explain why that phenomenon causes a soft effect, or smearing and not only vignetting?

My WATE lens is just as far from the sensor as the kit lens is.

For the first part, I ask the same question. Even if the light hits the microlenses obliquely, each microlens serves one pixel only, and one pixel has no resolution, thus cannot be soft. Contrast loss through bleeding OK, vignetting surely, but not real loss of resolution.

About the distance from the sensor, it´s not the rear glass surface that´s important, but the exit pupil. Look through the kit lens (or any lens) from behind; you´ll see a circle of light (often filled with a tiny upside-down view of the world in front of the lens). This is the exit pupil, and in the kit lens, it is situated quite some distance into the lens (it moves with zooming). Since it is a virtual image, its position cannot be measured directly, but a rough visual comparison is possible. Regrettably, I don´t own a WATE...

 

[monza]

As far as wide angles are concerned, I only have an old 28mm and the 35mm Schneider shift lens, of which I already published examples here. This one too has no problem. Otherwise the 21-35 zoom covers all my WA needs. I could try the 35-70/2.8 and 35-70/4, I do not think there is much point in testing longer lenses, they should most probably work; the problem is really with wide angles.

I am presuming that the nature of a wide angle lens designed for an SLR (i.e., retrofocus) makes for a more telecentric lens design. Not being any sort of expert in optics, I don't know if retrofocus by it's nature implies telecentric, or if that is just happenstance.

I have a 20/3.5 Olympus Pen F lens, which of course was designed for an SLR, but does that mean it's a retrofocus design? The Pen F has a relatively short lens flange distance; it is more along the lines of a rangefinder in that regard. Being a half frame, everything is smaller, so maybe it is still retrofocus, just on a smaller scale.

Leica M 27.95mm
Canon screw 28.8
Hexar RF 28.00
Leica screw 28.8
Olympus Pen F 28.95
Contax G1 29

All those cameras are rangefinders except for the Pen.

By comparison, the flange distance for SLRs start at about 40mm and go up:

Konica AR 40.5mm
Canon R/FL/FD 42
Minolta MD 43.72
M42 screw 45.46
Contax/Yashica 45.5
Olympus OM 46
Nikon F 46.5
Leica R 47

I'm curious if the longer flange distance of the Leica R by its nature 'helps' R lenses when used on the G1. Although Carl's test seems to show excellent performance of the Canon 24mm which has a 5mm shorter flange distance, so maybe this has nothing at all to do with flange distance and everything to do with lens design.

Perhaps the ultimate test is to try one of the newly designed Leica optics such as the 21/1.4, which were designed for digital. Although I can't see many people using such a lens on a G1 in the real world.

 

[mazor]

Mazor,
Could you explain why that phenomenon causes a soft effect, or smearing and not only vignetting?

My WATE lens is just as far from the sensor as the kit lens is.

basically this smearing can indeed be caused by non angular microlens found in the M8. Basically when the light hits at the sharper angle thanks to a closer to film plane design of range finders, the light hits more than one microlens at one time instead of a single one. Ideally if the light is hitting the sensor perpendicular there will be no stray light going hitting the other parts of the sensor, hence why the center of the frame when using M lens would not exhibit this smearing.

A possible solution I can think of to correct for this phenomena on the G1 would be to use a corrective lens in the adapter, that would essentially correct the extents of the lens to hit the G1 sensor parallel. Negatives of such a solution would possibly reduce light passing though to the sensor, hence loss of possible 1 stop of light, and obviously with any addition of optics, can affect the quality of the overall image, and the worst case is that there would be possibly a multiplier factor addition to the already 2x crop factor.

Obviously the ultimate solution would be to get an M8.2 which we know optimise's light hitting the sensor with the aid of angular microlens, and for those that put on the 6 bit encoding strips, the M8.2 will correct for vignetting and other issues with wide angle lens seamlessly.

Mazor