It is meant for infinity shooting with Optosigma 5m lens in front of ZM 35mm 1.4.
Any feedback is welcome, as I didn't have that many shots to check its quality and
it might only work well for my combination of Step-Up and Step-Down rings.
Recently I got a cheap used ELPRO4. It has a 55mm retention ring that can catch 50mm diameter PCX.
Here is my setup. Now I can use G21's original front cap.
G Biogon 21mm + 55mm Blank Filter + SLB-50-1500PM(reverse orientation,rubber tape adhered on the edge for centering) + ELPRO4's Retention Ring
MIRANDA1 wrote:
I find it interesting that you were not able to reach infinity by removing all the front shims on the ZM, I've had no issue with that with 3 different adapters that I've tried, Voigtlander, Novoflex and the TAP and the ZM 25.
In respect to the OptoSigma filters for the ZM 25, I don't recall anyone testing that combination, can you send the link? I would be very interested in seeing those results for sure.
I got as far as removing 3 of 4 front shims plus one from the rear. Still no infinity even with Hawk's adjustment. Busy at the moment but may return to take out all 4 of the fronts (and put the rear back, these shims may have no effect on infinity focus).
The 25ZM shows improvement in corner sharpness at all focal lengths on the AR7ii with the Optosigma 1500 at medium distance (and attains infinity with 3 front shims removed). Not to the same extent as the Contax G28 but still very noticeable. There doesn't seem to be vignetting with the same 46-55, 55-52, 52-58 filter adapter combo as for the G28.
It may take a while to post any results, please be patient. The variables keep piling up.
I pulled my ZM 25 apart today. I have a front silver in the front and a gold and bronze in the rear. I tried pulling the silver in front and put back in the bronze in the rear. To short of the hard stop. So I put the silver back in and pulled the bronze from the rear. So my final look is 1 silver in front and a bronze,gold in rear. I'm still playing to see if I can improve the right side more. It does look better but I'm stubborn as hell. I won't give up . Lol
I also switched out my Fotosy adapter for the one I have on the 85. It's newer
MIRANDA1 wrote:
I think the difference between my Hoya setup and your is that mine is in the original Hoya filter holder, did I understand you correctly saying that you mounted your Hoya lens in a Tiffen filter mount, not sure if that's a factor or not.
polylepis wrote:
I got as far as removing 3 of 4 front shims plus one from the rear. Still no infinity even with Hawk's adjustment. Busy at the moment but may return to take out all 4 of the fronts (and put the rear back, these shims may have no effect on infinity focus).
The 25ZM shows improvement in corner sharpness at all focal lengths on the AR7ii with the Optosigma 1500 at medium distance (and attains infinity with 3 front shims removed). Not to the same extent as the Contax G28 but still very noticeable. There doesn't seem to be vignetting with the same 46-55, 55-52, 52-58 filter adapter combo as for the G28.
It may take a while to post any results, please be patient. The variables keep piling up....Show more →
I look forward to your test results. In respect to the impact of the front shims on infinity focus, on my lens they have an absolute impact on infinity focus, when I remove the 4 front shims infinity focus is at the 5m marking on the lens with the voigtlander adapter, adding an additional bronze shim brings infinity to the hard stop. What adapter are you using for your tests?
I attached polyvinyl tape on the circumference of the PCX so that it is firmly fixed inside bottom part of the 55mm blank filter.
The PCX can't touch G21's front plate but is very close to (almost touch) G21's first lens vertex.
tormoder wrote:
@HaruhikoT@:
For this setup, is the filter "resting" directly against the front plate of the lens or the bottom part of the blank filter?
MIRANDA1 wrote:
I look forward to your test results. In respect to the impact of the front shims on infinity focus, on my lens they have an absolute impact on infinity focus, when I remove the 4 front shims infinity focus is at the 5m marking on the lens with the voigtlander adapter, adding an additional bronze shim brings infinity to the hard stop. What adapter are you using for your tests?
A Hawk's adjustable. The test with 4 front shims out won't happen for a week, have to run down to the desert (flowers).
Mail from China (=eBay) arrived and I finally got 55-52mm step-down ring. I build different "filter stack" for ZM25:
1. ZM25 lens
2. 46mm - 55mm step up ring
3. Proxar 1.0m lens
4. 55-52mm step down ring
5. 52mm UV filter retention ring
==> there is almost no vignetting with this filter stack. However if I add any step-up ring or filter there will be hard vignetting.
HaruhikoT wrote:
I attached polyvinyl tape on the circumference of the PCX so that it is firmly fixed inside bottom part of the 55mm blank filter.
The PCX can't touch G21's front plate but is very close to (almost touch) G21's first lens vertex.
Thanks for the info. Is the tape only for centering, or also to avoid the PCX from falling through the blank filter?
The reason I ask is because I attempted to use the frame of an original Contax G 55mm filter, but the bottom part is approx. 50.5mm wide, and too wide to hold the PCX.
Can't recall if you guys looked at the 35/2.5 VM - I tried a like-new copy out this afternoon on my A7RII and it looked like the same issues as the 35/1.4 ZM - great center, but blurry corners that only clean up to usable at f/8.
If it hasn't been looked at already, does anyone think this lens could benefit from the weak front element treatment?
It probably depends. If you can get reasonably sharp corners by refocusing for the corner, it would imply a field curvature problem which might be close enough to the field curvature problem of the lenses being discussed here. If the corners are just mush no matter where you focus, then probably not. The difficulty with that lens is it doesn't really have a strong reputation for peripheral sharpness.
In any of your wider aperture test photos, could you see any indication of field curvature or anything towards the edges acceptably sharp, though not in the intended plane of focus?
If it is a matter of field curvature, whether the solution here works, I wonder if it matters the direction of field curvature? My understanding is the lenses being discussed here, the field curvature bends away from the camera (towards infinity) moving towards the image edges/corners.
The tape is not only for centering, but also to avoid from falling through.
tormoder wrote:
Thanks for the info. Is the tape only for centering, or also to avoid the PCX from falling through the blank filter?
The reason I ask is because I attempted to use the frame of an original Contax G 55mm filter, but the bottom part is approx. 50.5mm wide, and too wide to hold the PCX.
I’ve been following this thread and the one about the Kolari thin mod for months and I still haven’t made my mind about them. Both have pros and cons, so it’a question of choosing my poison ( luckily, not a very lethal poison).
Playing devil’s advocate, don’t you think that if a simple front filter is all we need to get the best from RF wides on Sony A7x cameras, Zeiss would have released E-mount versions of their Biogons with a built-in front filter and call it a day ?. Why going with all the the trouble of designing from scratch Loxias and Batises ?
On the other part, as Groucho said, who are you gonna believe, me or your own eyes? . Those ugly ducklings that were the Biogon G21 and G28 on Sony sensors, suddenly morphed into magnificent swans thanks to a PCX element. Likewise for the ZM25, the ZM35..
cross posting this with the ultra thin filter stack thread since it seems relevant – here is a contax g 28/2.8 comparison between stock a7, kolari UT a7, and reversed optosigma pcx 1.5m filter on stock a7. i shot the kolari UT a7 + g28 combo focused in the center, outer midzone, and corner to give a feel for the level of field curvature remaining. i only focused the pcx filter shots in the center because i didn't see any real difference between focus locations moving outward with the pcx filter. the kolari is clearly better in the center and midzone, but it's quite close in the extreme corner.
Your results with PCX last week show good details in the midzone, but this time those branches look just out-of-focus. Perhaps PCX is slightly decentered this time?
