candreyo
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 p.7 #14 · Front-End Filter Improves Corner Smearing | |
Greetings All,
Just wanted to update some of you, I've finally gotten all my Zeiss ZM wide angle lenses to work absolutely superb with my Sony A7Rii.
For people's info, the following Planoconvex/ Proxar lenses were used to get me there, and what I had to do to in terms of removing internal shims to get them to focus to infinity and focus accurately on Leica M rangefinders. I used OptoSigma Planoconvex and Zeiss Proxar lenses. With the Zeiss Proxar lenses, I removed them from their Hasseblad bayonets. Both types of lenses were held in place with the appropriate step up or down filters. In the case of the Biogons, I used a 46mm to 55mm step up, and the 18mm Distagon, I used a 58mm to 55mm step down. Testing them out, they seem to be at least as flare resistant as without having them on. The OptoSigma lens is multi coated, and with the Zeiss Proxars, I believe they have the T* coatings.
Zeiss ZM 28mm Biogon: added a 1m Zeiss Proxar lens to the front, and unscrewing the rear element with camera spanners, I removed 2 internal brass shins
Zeiss ZM 25mm Biogon: added a 1.5m OptoSigma Planoconvex lens to the front, then unscrewing the rear element, removed 3 internal brass shims
Zeiss ZM 18mm Distagon: added a 0.5m Zeiss Proxar lens, then again unscrewing the rear retention ring, removed all shins (2 small and 2 thick brass shims)
I was then able to achieve infinite focus with the corrections lenses attached, and rangefinder focus worked accurately. I tested rangefinder focus with a calibrated Leica M 240.
With the attached correction lenses on all lenses tested above, the corner smearing is nearly gone. The sharpness boost is quite substantial, and I hope to post photos at a later date.
One thing to note, with the 18mm Distagon, it has changed the field of view slightly. I'd say the lens has now become a 19mm lens, if this makes sense. I have a Voigtlander 21mm lens I compared it to, and with the Proxar lens attached, it is still wider then the 21mm lens, but definitely has lost some of its field of view. I'd say it's closer to a 19-19.5mm lens now.
I'm happy to live with this, as the corner are so sharp now, even with the Proxar attached, that I wouldn't go back. I compared the corrected Distagon to the uncorrected version. The outer 20% of the lens was blurry without the Proxar. With the Proxar on, nothing is really blurry except the outer 2% maybe. Even if you say I lost about 5% of the total image field, I will take this, as I still gain a massive boost in the other 15% of the outter image.
The Proxar lens on the Distagon has had another unexpected affect also, the focus field was curved prior to correction, so that the corners were in a different focus field as opposed to the centre, it was not flat at all. With Proxar attached, the focus field is as flat as can be.
This also happened to the Biogons aswell with the correction lenses installed on the front, the focus field became more flat.
Cost of these conversions was:
1x OptoSigma 1.5m Planoconvex: 86.00 GBP
1x Zeiss Proxar 1.0m in B57 Hasselblad mount (used off eBay): 7.33GBP
1x Zeiss Proxar 0.5m in B57 Haselblad mount (off eBay again): 7.33GBP also
2x 46mm to 55mm step up rings: 1.99GBP each
1x 58mm to 55mm step down ring: 3.39GBP
2x 55mm UV filters (need the internal retention rings to use in the step up filters): 1.99 ea.
I did not need a rentention ring on the 18mm Distagon, as the step down filters internal diameter had a lip below the 55mm thread which had a smaller inside diameter then 55mm. I instead laid the lens against the front of the 18mm Distagon, placed a strip of nitrile rubber completely around it to hold it in the centre, and used the step down ring to lock it in place against the Proxar lens. I really didn't need the rubber strips, but wanted to ensure the lens was in the centre before screwing down the step down ring onto it.
So, for roughly 125.00GBP, I was able to correct 3 different Zeiss ZM lenses.
This is much cheaper then the Kolar Mod, and the great thing is, all this is easily reversible, and I would argue the results are as good as the Kolari Mod would be, if not better. I can reverse the mod in probably less then a few minutes by simply removing the correction lenses and reinstalling the shins. Shin removal and install is very easy on these Zeiss ZM lenses.
If anyone has ever had a Jupiter 3 or 8, you'll know how easy it is to adjust by simply unscrewing the front of the lens away from the body, revealing the shins.
The Zeiss lenses are similar, but instead of unscrewing the front, the rear ring needs removing with camera spanners, exposing the shins that way.
My native Sony FE lenses also get to use the sensor with the filter stack they were designed for.
If anyone is interested in adapting any of their Zeiss ZM lenses in this fashion, just let me know, and I'm more then eager to assist in any way I can.
I'm very excited an inexpensive cure has been found for my wide angle Zeiss ZM lenses that is non destructive, completely reversible and works extremely well.!😀
Hope this helps!
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