The Summar looks as unassuming as the Elmar but is mechanically much more complex. You did an admirable complete dis- and reassembly. But for practical purposes, I don't think you need to go that far. Accessing the helicoid and the aperture ring should be enough. The haze on the lens surfaces facing the aperture blades readily wipes off. The real problem with the Summar is the soft front element. I have never seen one which wasn't heavily scratched. There may be no deep scratches, but a mesh of very fine scratches is enough to make the lens glow heavily in the highlights and dramatically reduce contrast. However, the front element can be repolished quite easily with cerium oxide. With patience you can restore it to good performance. As to coating: The Summar was never sold coated (production ceased in 1939). If you encounter coating, it was applied post-war (starting in 1946) and is most likely a single soft layer which, over time, has become faulty. I don't think you would do a scratched lens a disservice by polishing the coating away: you just end up with a lens as it was originally released. You may also see a bluish tint that looks like (rests of) coating but is an effect of glas oxidization (sometimes referred to as "natural coating"). This oxidization can also occur in a spotlike fashion. Don't try too hard to wipe it off, it should have little effect on the optical performance. -- And, yes, the Summar is a very sharp lense (in the centre).
@@atf2940 I probably had my facts wrong with the coating part. But wouldn't the polishing of the front element pose a risk of changing the curvature of the lens? I mean how can I polish the convex surface evenly?
@@AlinCiortea No risk, no fun ;-) In theory, yes, you run the risk of changing the curvature by hand polishing. In practice you'll be hard put to actually do it in any noticeable way. You are taking off vvvery little material and by constantly rotating the lens element and wiping in a circular fashion you take care of doing it evenly. I am not suggesting that you polish a good enough lens! But many (most?) Summars have been scuffed badly over the years. If so, then you have the choice between preserving a decorative paper weight and trying to to turn the paper weight into a good performer. I have opted for the latter with a 1939 Summar and a 1936 Zeiss Sonnar: still very sharp but hugely improved contrast! In both cases I didn't go all the way to a perfectly smooth surface. It's enough to polish until that milky haze in strong torch light is gone. Stop from time to time and check the cleaned and dry lens. Takes some time ...
@@AlinCiortea Just to help you overcome your risk aversion. Suppose the lens in its badly scuffed state is worth 120 Euros; if you polish it successfully, it would be be 280; if your polishing fails, 80. (Just suppose, but the figures look abt right to me.) You have a choice between KEEP as is and POLISH. For KEEP the expected utility (EU) is 120 (measured in Euros). If you POLISH and your chance of success is 0.8, then the EU of POLISH is 240 (0.8x240 + 0.2x80). Only if your chance of success drops to 0.2 could you just as well flip a coin to decide (0.2x240 + 0.8x80 = 120). Did that help? 😉
The Summar looks as unassuming as the Elmar but is mechanically much more complex. You did an admirable complete dis- and reassembly. But for practical purposes, I don't think you need to go that far. Accessing the helicoid and the aperture ring should be enough. The haze on the lens surfaces facing the aperture blades readily wipes off. The real problem with the Summar is the soft front element. I have never seen one which wasn't heavily scratched. There may be no deep scratches, but a mesh of very fine scratches is enough to make the lens glow heavily in the highlights and dramatically reduce contrast. However, the front element can be repolished quite easily with cerium oxide. With patience you can restore it to good performance. As to coating: The Summar was never sold coated (production ceased in 1939). If you encounter coating, it was applied post-war (starting in 1946) and is most likely a single soft layer which, over time, has become faulty. I don't think you would do a scratched lens a disservice by polishing the coating away: you just end up with a lens as it was originally released. You may also see a bluish tint that looks like (rests of) coating but is an effect of glas oxidization (sometimes referred to as "natural coating"). This oxidization can also occur in a spotlike fashion. Don't try too hard to wipe it off, it should have little effect on the optical performance. -- And, yes, the Summar is a very sharp lense (in the centre).
@@atf2940 I probably had my facts wrong with the coating part. But wouldn't the polishing of the front element pose a risk of changing the curvature of the lens? I mean how can I polish the convex surface evenly?
@@AlinCiortea No risk, no fun ;-) In theory, yes, you run the risk of changing the curvature by hand polishing. In practice you'll be hard put to actually do it in any noticeable way. You are taking off vvvery little material and by constantly rotating the lens element and wiping in a circular fashion you take care of doing it evenly. I am not suggesting that you polish a good enough lens! But many (most?) Summars have been scuffed badly over the years. If so, then you have the choice between preserving a decorative paper weight and trying to to turn the paper weight into a good performer. I have opted for the latter with a 1939 Summar and a 1936 Zeiss Sonnar: still very sharp but hugely improved contrast! In both cases I didn't go all the way to a perfectly smooth surface. It's enough to polish until that milky haze in strong torch light is gone. Stop from time to time and check the cleaned and dry lens. Takes some time ...
@@AlinCiortea Just to help you overcome your risk aversion. Suppose the lens in its badly scuffed state is worth 120 Euros; if you polish it successfully, it would be be 280; if your polishing fails, 80. (Just suppose, but the figures look abt right to me.) You have a choice between KEEP as is and POLISH. For KEEP the expected utility (EU) is 120 (measured in Euros). If you POLISH and your chance of success is 0.8, then the EU of POLISH is 240 (0.8x240 + 0.2x80). Only if your chance of success drops to 0.2 could you just as well flip a coin to decide (0.2x240 + 0.8x80 = 120). Did that help? 😉
@@atf2940 that sounds like some fancy statistical analysis. If I decide (and have permission) to polish it I'll surely post a video :D
@@atf2940BTW, what polishing paste did you use? Polywatch by any chance?