jlehet wrote:
I got my two front filters for the CV35 1.7 and the new-to-me G28. (I have had and loved the CV 35 for about a year, got the G 28 on account of this experimentation).
The G 28 won't focus to infinity with my Fotodiox Pro adapter, so I ordered a Kippon. Hopefully that will work.
The CV is a little more disappointing, as I've been using it with a Hawks V for the year. I can't set the Hawks to be short enough for this hack. I also had a Fotodiox M adapter around, and tried that, but of course no go. Going to have to find an adapter for that....Show more →
try the cheap ~$10 ebay m to e-mount adapters, they tend to be pretty short. if you by 3 one is almost certain to work.
Has anyone used the front-end fix with any of the above, in particular the CV Voigtlander Nokton 35mm f1.4? It's certainly my favorite lens, but the exaggerated corner smearing and field curvature issues on a Sony A7ii have been disappointing for me. If so, does anyone mind walking me through their set-up, including:
1. Which plano convex lens they used? (Brand, thickness, etc.)
2. Which step-up, step-down filters they used?
3. Focus to infinity solution (shims, adapters, etc.)?
No one tested/reported about your listed lenses yet.
For the CV35, if you want to try this solution at your own risk, I can advise you.
1. Optimal corrective lens (PCX)
There is no technical data for CV35, so in order to estimate optimal PCX, I need to check its aperture diameter observed from both side.
Could you take and post pictures of your CV35? For better estimation, please care tips below:
1) Stop down the aperture until you can see whole aperture shape from backside of the lens. Be careful not to stop down too much. F2 or F2.8 should be good.
2) Take pictures of both front side and back side of the lens. Use telephoto (100mm or longer) to avoid perspective distortion.
These are samples (this is my ZM35, not CV).
2. Step-up/down rings
Basically you need those 3 rings:
43-55 step-up
55-52 step-down (50mm diameter 3mm thick PCX should be placed inside this ring)
52-55 step-up
Please note those rings' thickness are slightly different by brands. I recommend "Marumi" brand but others may also work.
For Avenon 21, I think its front element is too large for the 50mm diameter PCX which is currently only one choice for reasonable price. Mechanical vignetting will suffer image corner.
For Canon/Nikkor 50mm 1.4 LTM, perhaps PCX 5m work but I don't have high expectation because similarly designed ZM C-sonnar 50mm 1.5 was tested with PCX 5m and results were not good.
Infinity adjustment is also problematic for these. I cannot recommend you to teardown such precious old lenses.
Out of curiosity, would mounting the pcx at the rear of the lens have the same effect? Or is there a different lens spec that would achieve the same result mounted at the rear?
thrice wrote:
HaruhikoT thank you for everything so far!
Out of curiosity, would mounting the pcx at the rear of the lens have the same effect? Or is there a different lens spec that would achieve the same result mounted at the rear?
Thanks,
Dan
This has been asked at least once (by me) and the answer was no - it would not produce the same effect.
Has anyone used the front-end fix with any of the above, in particular the CV Voigtlander Nokton 35mm f1.4? It's certainly my favorite lens, but the exaggerated corner smearing and field curvature issues on a Sony A7ii have been disappointing for me. If so, does anyone mind walking me through their set-up, including:
1. Which plano convex lens they used? (Brand, thickness, etc.)
2. Which step-up, step-down filters they used?
3. Focus to infinity solution (shims, adapters, etc.)?
Likely you aren't interesting in replacing your CV 1.4; but if you like that lens Cosina have announced a new version of it for E mount, which is supposed to deal with the filter stack issues (it'll still have whatever issues are associated with it's compact and 'classic' design, but presumably you like those!)
Please help a newbie at this stuff. I just got my "SLB-50-5000PM filter from Opto Sigma in an effort to help my Zeiss ZM 35/1.4 lens. I decided first to mount it in a cheap 52mm UV filter that I bought. I removed the retaining ring and put the opto-sigma filter in and found that it would not stay in the filter as it is just a tiny bit smaller than the 52mm UV filter that was in there. Am I misunderstanding how to secure the opto-sigma filter or did I get a bum 52mm filter or do I need a different size? Thanks for any help for this lens modification newbie.....
@Luvwine, my configuration is a 49>55mm step up filter, then a 55>52 step down filter, and then I put my Opto Sigma lens in, put rubber band shims on the side of the lens to keep it in place, and then I put a 52mm retaining ring on it to hold everything in place. My step-up and step-down filters are from Sensei. My 52mm retaining ring came from a Amazon Basics 52mm UV filter. I created a quickie graphic on how I oriented my rubber band shims, which can be found here: https://flic.kr/p/R7FjJ2. I think others developed other solutions, but this worked for me.
scrappydog wrote:
@Luvwine@, my configuration is a 49>55mm step up filter, then a 55>52 step down filter, and then I put my Opto Sigma lens in, put rubber band shims on the side of the lens to keep it in place, and then I put a 52mm retaining ring on it to hold everything in place. My step-up and step-down filters are from Sensei. My 52mm retaining ring came from a Amazon Basics 52mm UV filter. I created a quickie graphic on how I oriented my rubber band shims, which can be found here: https://flic.kr/p/R7FjJ2. I think others developed other solutions, but this worked for me....Show more →
I have the step up and down filters--same set. It was the rubber band part I missed. I guess I could use tiny pieces of electrical tape too. Will try to figure something out. Thx!
Luvwine wrote:
I have the step up and down filters--same set. It was the rubber band part I missed. I guess I could use tiny pieces of electrical tape too. Will try to figure something out. Thx!
I only used the rubber bands because the filter will move around without them, and they keep the filter centered. I made them approximately 2mm x 2mm square because the Opto Sigma is 3mm wide and I did not want the shims to poke out and impede the retaining ring from making a tight seal against the lens. So far, it has worked well. Good luck!
Luvwine wrote:
Please help a newbie at this stuff. I just got my "SLB-50-5000PM filter from Opto Sigma in an effort to help my Zeiss ZM 35/1.4 lens. I decided first to mount it in a cheap 52mm UV filter that I bought. I removed the retaining ring and put the opto-sigma filter in and found that it would not stay in the filter as it is just a tiny bit smaller than the 52mm UV filter that was in there. Am I misunderstanding how to secure the opto-sigma filter or did I get a bum 52mm filter or do I need a different size? Thanks for any help for this lens modification newbie........Show more →
Centering of the lens element will not help if the retaining ring inner diameter is larger than 49.95mm. There is lots of variation on retention ring inner diameters, for example I have now purchased >25pcs 55mm filters and 6 of them have small enough inner diameter. However it's not possible that 52mm filter retaining ring has too big inner diameter; the thread inner diameter is less than 52mm, and it's not very likely to have inner diameter larger than 49.95mm.
So most likely in your setup the retention ring just did not go deep enough. When the retention ring is pressing the OptoSigma lens it will not move, and does not matter is lens centered or nor, it will not move. Naturally optically it does matter, so centering is needed to get best optical results).
Luvwine wrote:
I have the step up and down filters--same set. It was the rubber band part I missed. I guess I could use tiny pieces of electrical tape too. Will try to figure something out. Thx!
My setup for a Contax G28, is also 46-55 step-up + 55-52 step-down. Put the PCX lens inside and secure it with a 52-55 step-up ring, so I can use hoods or lens caps of 55mm size
I circled the sides of the filter with double sided tape which is aprox.0.5mm. thick ( I didn’t peel off the protective paper on the outer side). This way, the diameter of the Optosigma increases from 50mm to aprox.51mm. and fits snugly into the female threads of the 55-52 step down ring. I expect that many types of electrical insulating tape or similar would do fine as well. Beware though. Special care must be taken to avoid the adhesive tape to make contact with the filter front. It might be very difficult to remove sticky residues without damaging the filter coatings.
Question about the 5m PCX: I know this is supposed to help corner resolution, but the thing that bothers me the most about the A7's performance with this CV in particular is that it exaggerates the field curvature problem that it has. Will the 5m PCX help with that?
The idea is to bring the field curvature in line with the original lens design.
For the 35/1.4 CV that means a W shaped plane of focus unfortunately. It will correct the curvature introduced my the sony sensor stack though. raydeng wrote:
Thanks @HaruhikoT@!
Question about the 5m PCX: I know this is supposed to help corner resolution, but the thing that bothers me the most about the A7's performance with this CV in particular is that it exaggerates the field curvature problem that it has. Will the 5m PCX help with that?
