Issues with used Contax 90mm F2.8 Carl Zeiss Sonnar T* M-mount conversion

[ninjin]

For my current trip to Japan I planned to pick up a 90mm M-mount lens that accepts 46mm filters to complete my ideal 28/50/90 set of lenses. While I would have loved for it to be a Zeiss like my other two lenses, I had planned on buying a 90mm Elmarit to use until Zeiss stops obsessing about wide-angle M-mount lenses for their ZM range.

On a Friday evening I dropped by Lemon Camera (レモン社) in Ginza and could not believe my eyes when I saw a Contax 90mm F2.8 Carl Zeiss Sonnar T* M-mount conversion for JPY 69,000 (~USD 600) – as a reference, that is just below 60% of what Japan Exposures would charge for the lens. I did not have a digital body on me and while it certainly did not feel as nice mechanically as a ZM – and certainly nowhere close to a Leica – I could not spot anything obviously wrong with it. Now it was on commission (委託） and plenty of alarm bells went off in my head, so, I promised to come back in a few days with a digital body and try it out proper. Three days later, I was back with my M240 and everything felt fine, sure, the interior was not perfect when I did the “flash light test” there was plenty of dust, but the shots I took looked the way they should – here I made the mistake to shoot only at f2.8 and f4, more on this later. So, I forked over the cash and merrily went home looking forward to learning how to operate a 90mm lens on a rangefinder.

Today I finally had the spare time to take it for a real spin and already the first couple of shots were odd. My wife was putting on make-up in front of the mirror and I saw an interesting new photo opportunity from a distance, selected f4 for a portrait with bokeh, shot, looked, and to my surprise there was some weird white-ish stain towards the centre right edge. There was a bright light in the scene so I figured it may have been some weird flare, but it all made me feel very uneasy – a flare that bad on a late-90s lens? Later outside I took a photo of a crowd watching a performance and a similar white stain was present as if it came from the sky. At this point I had had enough and went into full investigation mode and shot a wall on the nearby mall for all available apertures with no possibility of flares. See the results below (I have attached three photos to future proof this post).

f2.8: http://udon.stacken.kth.se/~ninjin/sonnar_issues/sonnar_f2_8.jpg
f4: http://udon.stacken.kth.se/~ninjin/sonnar_issues/sonnar_f4.jpg
f5.6: http://udon.stacken.kth.se/~ninjin/sonnar_issues/sonnar_f5_6.jpg
f8: http://udon.stacken.kth.se/~ninjin/sonnar_issues/sonnar_f8.jpg
f11: http://udon.stacken.kth.se/~ninjin/sonnar_issues/sonnar_f11.jpg
f16: http://udon.stacken.kth.se/~ninjin/sonnar_issues/sonnar_f16.jpg
f22: http://udon.stacken.kth.se/~ninjin/sonnar_issues/sonnar_f22.jpg

While you can see some dust (look for the black spots) the stain has a mild presence already at f4 and at f22 it is fairly obvious that something is very rotten indeed. I am still a clumsy amateur, but to me the increased presence with higher apertures would indicate that there is something inside the lens that needs to be fixed. Has anyone experienced something similar? I am perfectly willing to try to have it fixed, but it certainly stings not to play around with my new toy and I dread if this lens is past saving.

I have certainly learned my lesson, I am not qualified to judge commission goods and should have stuck to my rule of buying new, used on RFF, or from Map Camera. It costs more – apart from when you buy at RFF – but you do not need to keep your guard up. I should also mention that I in no way blame Lemon Camera for this, I knew what I was in for – I do however doubt that whoever put the lens up for sale through them could not have noticed this as it is effectively a f2.8-only lens at this point.

 

[shawn]

Assuming you aren't getting that with other lenses that should rule out anything on your sensor.

It is odd, maybe some haze/oil inside the lens? Fingerprint inside? Are the aperture blades oily? Did you look with the flashlight in both directions? Having the lens CLA's should help as long as the optics themselves aren't etched/damaged.

Shawn

 

[Larry H-L]

I find it odd that the white stain only appears in a certain area. Haze would most likely cause an overall hazy look.

Do you have a filter or hood on the lens? If so, try shots without them mounted.

Also, check for areas on the back of the lens barrel that might be causing a reflection, such as an unpainted chrome part.

And finally, check inside the mount on your camera, make sure nothing is inside.

 

[ninjin]

Thanks Shawn and Larry, those are some very quick responses.

I did try a few shots with the second love of my life – after my wife – that is, my ZM Sonnar, and things looked fine on those shots. The Sonnar aperture blades are as clean as can be, with only a pinprick of paint loss on one of the blades. All shots I have provided are also without any filters – there was however no hood included. There is an unpainted region at the back of the lens, see the attached photo, but I would at least like to believe that Miyazaki-san over at MS Optical knew what he was doing with the conversion and that it would cause issues such as this. I did try the flash light is both directions and did the same test again just now and cleaned the front and back elements with a microfibre cloth kindly provided by my mother in law. It is however a bit too dark in Japan and I lack a good background to shoot against, but I will try to replicate again now that it is as clean as I can get it as soon as the morning comes.

 

[ninjin]

First batch of “boring” test pictures, sorry for making another post but the limit of three attachments is indeed limiting.

 

[ninjin]

Following the cleaning yesterday, I headed outside to shoot a set of “exciting” wall photos. It is very cloudy today, so no opportunity to shoot the sun and a clear blue sky for testing. I faced three directions, roughly east, south, and north and shot both in portrait and landscape to see if the white stain would remain fixed. Given the results, I would rule out coating damage, element damage, etc. since I suspect those would have remained fixed while switching directions. Instead, I think “the price” may very well go to Larry for his suspicion of this being related to reflections in the unpainted chrome portion at the back of the barrel.

Now, while it is great news that one has a hypothesis that seems to be supported by the evidence, I suspect that fixing this will not be easy. I think I will shoot Hamish Gill at e-mail since he is the only other guy I know that has shot one of these conversions. Perhaps his lens is painted good and proper or looks the same, while it does not have the same issues? He did complain about the ergonomics, which I agree are not the best, but certainly not about terrible optical defects.

 

[rscheffler]

IIRC, there is flocking paper you can buy, used for scientific applications (?) that became a common solution among recent Sony users adapting vintage lenses to the current mirrorless cameras with cheap (and sometimes not so cheap) adapters.

FWIW, I'm not sure that conversion is the one done by MS Optical. I have a G45 converted to M mount with a Fotodiox helicoid conversion, and yours looks very similar. The G90 shown at the Japan Exposures page looks different.

http://www.japanexposures.com/images/2009/01/sonnar90.jpg

Also, given that the shape of the 'flare' is the same in landscape and portrait orientations, I would also guess at some form of internal reflection in the converted portion of the lens. Maybe some carefully applied black primer paint designed for use on metal?

 

[ninjin]

Wow, rscheffler, you are absolutely correct. As this is my first adventure into conversions and I have never been a Contax user, the rather obvious FOTODIOX printed on the helicoid went completely unnoticed – see the additional photos.

Since it is a bit late I only spent a few minutes for instructions on how these are applied, does it require a professional? Will it come loose somehow? I am not sure if I would dare paint it on my own, but if it is useless without it anyway… My biggest fear would be if something comes loose when it is attached to a considerably more expensive digital body.

I still weep a bit over the lost money, but now there is a mystery at hand about an unidentified conversion by an unknown agent – how can one not get excited?

 

[maigo]

IIRC, there is flocking paper you can buy, used for scientific applications (?) that became a common solution among recent Sony users adapting vintage lenses to the current mirrorless cameras with cheap (and sometimes not so cheap) adapters.

Also, given that the shape of the 'flare' is the same in landscape and portrait orientations, I would also guess at some form of internal reflection in the converted portion of the lens. Maybe some carefully applied black primer paint designed for use on metal?

I believe this is the flocking material you are referring to:

http://www.fpi-protostar.com/flock.htm



Sent from my iPhone using Tapatalk

 

[Larry H-L]

If you are able to return the lens to the seller, or trade it for another item, I would do so.

Otherwise, if you are nervous about painting and/or flocking, ask a camera repair service to do it, it should not be expensive.

It is possible that flocking / painting may not totally solve the problem. As a view camera user, I have seen reflections come off of the rear element of glass itself in some lighting conditions. The glossy glass covering on digital sensors can make it more problematic.