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Front-End Filter Improves Corner Smearing
  
 
navmannz
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p.70 #1 · p.70 #1 · Front-End Filter Improves Corner Smearing


Fred Miranda wrote:
I wanted to compare the FE 35/2.8 vs ZM 35/1.4 @f/2.8 for astro. That's the aperture where the FE lens shines and I'm expecting to get very similar results. I will post it.


I'll be interested to see, Fred, although its a reasonably academic comparison for me, given that I don't have the FE. The big gain for me is that I can at last shoot stars with my ZM - it was not usable at wide apertures without the filter.



Mar 21, 2017 at 07:31 PM
Parariss
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p.70 #2 · p.70 #2 · Front-End Filter Improves Corner Smearing


rji2goleez wrote:
Nice test and confirmation Fred, thanks. If I may ask, what are folks doing to make th PCX 5cm stay centered and in a fixed position. Mine moves a bit as it is loosely bound between the filter rings. Is it the rings I have or are people doing something to the PCX to keep it from moving?


I used black electrical tape. I cut five strips, a quarter inch in length and with a width somewhat less than the thickness of the corrective lens. I attached these strips to the perimeter of the lens, taking care that they were evenly spaced, and dropped the lens gently into the retaining ring. It's centered, there is no movement of the lens (there was still movement with 4 strips), and I can remove/replace the lens if I need to.

And I do - I need to invert the lens based on Fred and Rob's test results. Now that I'm looking for a permanent fit, I may add a bit of scotch tape to the flat surface of the lens to make sure the retaining ring has solid contact and wedges in the lens. Because the area of the corrective lens that is actually used is smaller than its 50mm, running glue shouldn't be a problem in the heat. I'm thinking of using some Locktite (the minimum hold kind) on the rings to keep the whole assembly reliably together when I remove it for cleaning.



Mar 21, 2017 at 07:41 PM
GMPhotography
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p.70 #3 · p.70 #3 · Front-End Filter Improves Corner Smearing


ZM 25 I could use another ELPro 3 retaining ring if someone sees one cheap. I can still test so not a immediate big deal. Working on infinity 1 Front Gold out but need one more . I'm close maybe the bronze shim. Heading to do that now. But a quick up close looked pretty good. I have convex out right now but may switch that


Mar 21, 2017 at 09:02 PM
Samuli Vahonen
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p.70 #4 · p.70 #4 · Front-End Filter Improves Corner Smearing


Small update from last week and weekend testing & shooting.

  1. Contax G21 and G28 seem to work well with SLB-50-1500PM reversed on stock filter stack cameras (tested A7r and A7v2) as simulated and confirmed in this thread . Final verdict for G21 is not yet out as I did not do any normal shooting (=not infinity, boke involved) with the lens, just infinity shooting, where it seemed to perform fine.
  2. Contax G21 doesn't work with SLB-50-4000PM on Kolari v2 . Discussed this with Hirohiko and the simulations made in post p3 #14 were calculated with 0.8mm filter stack thickness, while the optical thickness of filter stack is ~1.5mm. Hirohiko re-calculated (thanks!!!!) and assuming 1.5mm optical thickess SLB-50-2000PM is optimal, but also SLB-50-2500PM works. ==> made 2nd order to OptoSigma for SLB-50-2000PM and SLB-50-2500PM.
  3. ZM 2/35 Hirohiko simulated (thanks!!!) that SLB-50-3000PM should be optimal for standard cameras. Hirohiko also gave me help to simulate this one on Oslo software, and to me also the SLB-50-3000PM seems optical (but I still struggle with the software and understanding all the parameters). However it did not work in practice - correction is way too weak with SLB-50-3000PM. Not sure why but there must be something wrong on parameters we use to simulate as other simulations seems to be spot on. As correction was not enough I tried moving the lens to one of my Kolari v2 modified A7 bodies and it seems that this combo works well . I did shoot quite a lot my normal boke shooting and landscapes, and it seems that SLB-50-3000PM on Kolari v2 works - however I want to test it with SLB-50-2500PM and SLB-50-4000PM before giving "the final verdict". For me this lens is special due to it's boke and transition from focus to boke, and I'm really looking forward to shoot with this lens on coming spring & summer. Some native field curvature remains in corners, so for people looking "perfect lens" ZM 1.4/35 or Voigtländer are better options - In my opinion unless you like the rendering style of ZM2/35 I would not consider this lens worth the effort.
  4. ZM 4/18 I did test only very shortly with 58mm Hoya +1. For landscape shooting results with standard filter stack camera seem to be OK (hard to say does it correct field curvature when DOF is gigantic due to short focal length). On the few landscape image I shoot corners were sharp when shoot with f/8 and f/11, and I could not detect CA or astigmatism in corners. Naturally 58mm Hoya filter frame is too thick and small vignetting can be seen in corners. I checked and no matter how I skrew the filter in place it always stop in same place --> if this is good solution for this lens optically I'll just cut the filter frame so that it can still hold lens cap but corners don't vignette. I'll try this lens at some point with SLB-50-3000PM which is optimal according to simulation for standard thick filter stack camera - however I can't imagine any way to attach the filter to lens without generating vignetting, testing can be done by 2-sided-tape but any permanent solution will vignette. Also OptoSigma doesn't sell in larger 60mm size suitable focal length, so this one will be challenging.
  5. Both G21 and ZM18 cause very severe vignetting and colour errors on image edges/corners due to extreme ray angle on A7, A7r and A7v2 . I was not planning to get A7r v2 but it seems it's mandatory if I want to use these lenses. G28 is almost as bad, but most likely I can correct it with software. ZM2.8/25 and ZM2/35 better, but will require color correction on A7, A7r and A7v2 regardless is camera Kolari converted or not (assuming you don't want pink/magenta sky in corners etc.). I have not done controlled tests, but A7v2 seems to cause little less color cast than A7 and A7r - also that needs to be tested. Too much testing, too little photography...



It's good to end day by dreaming of going shooting with G21, G28, G45 and G90 on next summer This lens "family" has my favorite rendering style, and it seems it's finally feasible to shoot them with digital camera.

Samuli



Mar 21, 2017 at 09:15 PM
Chuck Coyne
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p.70 #5 · p.70 #5 · Front-End Filter Improves Corner Smearing


My approach is very easy and fast but not so easy to describe.
I cut two small pieces of Scotch double tape (about 2mm) and place them against each other on the step-up ring (where the PCX will sit on). Then I place the PCX lens on it and center it visually as good as possible. I do not press it down yet. Next, I get a small screw driver (about 2mm head) and circle around the empty area around the PCX to make sure it's perfectly centered. Once, I'm done, I press the PCX firmly down and it will no
...Show more

I did the exact same procedure as described above by Fred using double sided scotch tape. I also find that when I use the spanner wrench to really tighten the ELPro3 retaining ring down the PCX filter doesn't move at all. The tape raises the filter just enough to allow the retainer ring to meet it and secure it.
Chuck



Mar 21, 2017 at 10:30 PM
Slingers
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p.70 #6 · p.70 #6 · Front-End Filter Improves Corner Smearing


Another option to stop the PCX movement instead of tape is to use an o-ring like this as a spacer.


Mar 22, 2017 at 05:43 AM
rji2goleez
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p.70 #7 · p.70 #7 · Front-End Filter Improves Corner Smearing




Slingers wrote:
Another option to stop the PCX movement instead of tape is to use an o-ring like this as a spacer.


I like this approach! I went to make an expedited order and they wanted $30 to ship a $5 item for which I only need one from a pack of 10. Quite laughable. I think I can find a local source.



Mar 22, 2017 at 12:54 PM
GMPhotography
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p.70 #8 · p.70 #8 · Front-End Filter Improves Corner Smearing


I tried a rubber band . Just have the wring size. Those O rings should be at a Lowes, Home Depot and ace hardware. I'm going to stop this morning. I'm running out to test my ZM25, double check my ZM 35 reversed and throw the Firin in the bag. I'll go to Lowes if I find the O rings that work I'll post a shot of the packaging. I ordered another El Pro 3 for the 25 so same setup as my 35. I'll get a link to these tests as well. So far the PCX 2500 looks good . Will find out in a few hours

As far as the ZM 25 hood no way I can use it now just need too much space (2 46mm rings) just to clear the inside of the hood. Vignettes badly like that. There is another hood that Zeiss sells that may work.



Mar 22, 2017 at 01:03 PM
Parariss
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p.70 #9 · p.70 #9 · Front-End Filter Improves Corner Smearing



GMPhotography wrote:
I tried a rubber band . Just have the wring size. Those O rings should be at a Lowes, Home Depot and ace hardware. I'm going to stop this morning. I'm running out to test my ZM25, double check my ZM 35 reversed and throw the Firin in the bag. I'll go to Lowes if I find the O rings that work I'll post a shot of the packaging. I ordered another El Pro 3 for the 25 so same setup as my 35. I'll get a link to these tests as well. So far the PCX 2500 looks good
...Show more

My local Lowes and Home Depot had nothing that would work. Please post a SKU if you find something that does.



Mar 22, 2017 at 01:18 PM
GMPhotography
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p.70 #10 · p.70 #10 · Front-End Filter Improves Corner Smearing


It's most likely in the plumbing section. I'll check it out


Mar 22, 2017 at 01:19 PM
 

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rji2goleez
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p.70 #11 · p.70 #11 · Front-End Filter Improves Corner Smearing


GMPhotography wrote:
It's most likely in the plumbing section. I'll check it out


Sometimes Ace and True Value have these . . . I'm out of town right now but interested to learn of a source.




Mar 22, 2017 at 01:29 PM
GMPhotography
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p.70 #12 · p.70 #12 · Front-End Filter Improves Corner Smearing


I'm lucky Ace is about right around the corner


Mar 22, 2017 at 01:37 PM
artur5
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p.70 #13 · p.70 #13 · Front-End Filter Improves Corner Smearing


When my PCXs arrive from Optosigma (some day next month, I hope.. ) I plan to put them in ordinary filter holders. I have already two 52mm. filters with the glass removed. There’re of the type with a screw-in retaining ring. I’ll wrap the periphery of the Optosigmas with double sided scotch tape, so that the original 50mm. diameter of the glass becomes around 51mm. This is the right size to fit inside the male thread of a 52mm. filter. After that, just screwing the retaining ring on top will fix the glass tightly without any play, tilt or decentering. This way, I’ll have those PCXs converted into common 52mm. filters. Much easier to put them in reverse, adapt to different lenses, etc..


Mar 22, 2017 at 02:32 PM
GMPhotography
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p.70 #14 · p.70 #14 · Front-End Filter Improves Corner Smearing


Arthur they maybe too thick to get a ring on it. I'll check I have blank 52.

Out in field just ran Big Bronco. It looks to be working. Light sucks but I can see the improvement



Mar 22, 2017 at 02:38 PM
GMPhotography
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p.70 #15 · p.70 #15 · Front-End Filter Improves Corner Smearing


ZM 25 Holy Crap. Really nice with the PCX 2500. Working on it now. Major improvement


Mar 22, 2017 at 04:28 PM
GMPhotography
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p.70 #16 · p.70 #16 · Front-End Filter Improves Corner Smearing


Im loading the raws right now and will add link. Had some crappy light on Big Bronco. Ill try posting some results here but here are the instructions

So Big Bronco series. The first set is normal with convex out to subject, than second set reversed all 2.8,4,5.6,8,11

Infinity the first set is Reversed than the second set is convex facing subject. I changed it in the field with my spanner wrench and reversed it at Big Bronco. So I only had to do this twice.


https://www.hightail.com/download/dDZIeW45OW4yWGVVbDhUQw

Edited on Mar 22, 2017 at 05:28 PM · View previous versions



Mar 22, 2017 at 04:42 PM
GMPhotography
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p.70 #17 · p.70 #17 · Front-End Filter Improves Corner Smearing


Just a idea Big Bronco top left. Really bad light.

These the convex is facing subject

















Mar 22, 2017 at 04:48 PM
GMPhotography
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p.70 #18 · p.70 #18 · Front-End Filter Improves Corner Smearing


Infinity Front facing extreme upper left. Right side is following along perfectly

















Mar 22, 2017 at 04:52 PM
Fred Miranda
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p.70 #19 · p.70 #19 · Front-End Filter Improves Corner Smearing


I looks significantly better at from f/4 to f/5.6 at infinity at the corners.
I would say f/5.6 is the sweet spot from the samples you posted but I have not seen f/6.3, f/7.1 or f/8



Mar 22, 2017 at 05:17 PM
GMPhotography
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p.70 #20 · p.70 #20 · Front-End Filter Improves Corner Smearing


I just did 5.6,8,11.

Once I get this all fine tuned i will run it again. Im still working on infinity. I actually had to pull a shim in the field just to hit infinity. Im fixing that now.

https://www.hightail.com/download/dDZIeW45OW4yWGVVbDhUQw



Mar 22, 2017 at 05:22 PM
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