Eos RP with adapted wide-angle LM (Zeiss 28mm, Voigtlander 21mm) lenses

All,

A semi-quick follow-up to earlier post about 40mm f/2 Leitz lens, in https://www.dpreview.com/forums/post/62491029

I got hold of my wider lenses, and the conclusion is not as positive as for the normal lens. While the 28mm f/2.8 Biogon does become sharp when stopped down, a colour shift at the corners does not go away (at f/5.6). The 21mm f/4 has worse colour shift at the edge when stopped down to f/8. Both have fatal vignetting at full open, with the 28mm f/2.8 being top to bottom, whereas the 21mm f/4 is dark corners (which surprised me less).

First, the money shots. I'd be lying if I said I didn't think these lenses look very sweet on the Eos RP. The 21mm in particular.

Eos RP with Cosina-Voigtlander 21mm f/4 M Mount on adaptor

Eos RP with Zeiss 28mm f/2.8 Biogon M Mount on adaptor

The test subject was some devotional brickwork close to work, with light not quite constant (passing clouds conspired against me). While the clouds might have taken the edge off the light from time to time, the vignetting is from the lens/camera not from the lighting...

Camera on a tripod, RF lens not on IS, aperture priority auto exposure. Processed lightly in DPP (colour balance and setting sharpening to 2 more than default).

The 28mm at f/2.8 gives a massive sensor top-to-bottom (bottom is on the right, here) vignetting.

Zeiss 28mm, at f/2.8, whole image

We'll skip the corner in full open and go to two whole stops down

Zeiss 28mm, at f/5.6, whole image

Still a colour shift close to the top and bottom edges. Corner is no longer actively soft, though:

Zeiss 28mm, at f/5.6, upper right corner at 100%

The 21mm is a little less weird at full open

Voigtlander 21mm, af f/4, full image

The same sort of colour shift at the edge as on the 28mm, and the softness is fatal (if a little weird - I'm sure I focussed on the top right corner)

The 21mm at two stops down, is more usable with regards to sharpness

Voigtlander 21mm, at f/8, whole image

Vignetting and colour shift rule the day, though

Voigtlander 21mm at f/8, upper right corner at 100%

A little soft, and very vignetted.

For reference, the RF 24-105mm zoom, at 24mm wide open, which does its thing (admittedly with good light)

RF 24-105mm f/4, at f/4, whole image

RF 24-105mm f/4, at f/4, upper right corner at 100%

The 21mm takes normal enough snapshots at f/8, but the colour shift at the corners is distracting

Voigtlander 21mm, at f/8

The 28mm is less distracting

Voigtlander 28mm, at f/5.6

Still some colour shift.

In conclusion, I would say that while I do carry the 40mm when just going out I would not do the same with these wider angle lenses. The eagle-eyed viewer will spot a scratch on the 28mm lens hood which came from a nasty drop, but I don't think that the odd vignetting comes from that. In any case, trying out specific lenses is absolutely essential before considering using them.

Please note that I have taken really very sharp pictures on the Voigtlander 21mm. On film. I love this lens on a rangefinder film camera.

Disclaimer: I do not try to correct for lens errors. I have no idea how well lens correction software would do with these images. If anyone is interested, I would hapily upload the CR3 raw files for playing around with.

Regards

Jens

That's interesting! On the Eos RP I think I'm out of luck - the fully electronic shutter operation is only available in an otherwise fully automatic mode (which excludes the aperture priority needed for manual everything lenses).

A quick test against an interior surface at speed 1/80 does indeed avoid the top-to-bottom vignetting.

I was also wondering how on earth the viewfinder could show a normal looking image and the photo taken be so broken. Now I know - thanks for clearing that up.

Regards

Jens

evil_guy wrote:

Interesting results Jens, thanks a lot for this!

My pleasure, it was interesting.

As a footnote, I wondered if these effects might be as focal length dependent as received wisdom has it. I checked, and the 90mm f/2.8 Elmarit-M does indeed not appear to be afflicted. At 1/4000 and f/2.8 there was no top-to-bottom vignetting and if there were any corner vignetting or colour cast it couldn't be spotted in the camera LCD screen (which was the case with the wide angle lenses).

I'd like to know how Canon's newer bodies, especially R6, do with the adapted rangefinder wideangles. There seems not to be much discussion about that available in general, but the sensor stack of R6 is reported to be thinner than the previous ones (R, RP) which should be a good sign. But how is it in practice?
Have people tried the lenses mentioned in this thread with R6?