Home · Register · Software · Software · Join Upload & Sell

Moderated by: Fred Miranda
Username  

  New fredmiranda.com Mobile Site
  New Feature: SMS Notification alert
  New Feature: Buy & Sell Watchlist
  

FM Forums | Sony Forum | Join Upload & Sell

1       2       3              70      
71
       72              92       93       end
  

Front-End Filter Improves Corner Smearing
  
 
Fred Miranda
Offline
Admin
Upload & Sell: On
p.71 #1 · p.71 #1 · Front-End Filter Improves Corner Smearing


Guy, reversed look noticeably better, especially wide open.


Mar 22, 2017 at 05:45 PM
GMPhotography
Offline
• • • • • •
Upload & Sell: On
p.71 #2 · p.71 #2 · Front-End Filter Improves Corner Smearing


So I went into Ace hardware in the plumbing section. I came real close to getting the exact size but its like 47mm in diameter . So what I did was cut it in half laid it in on top of the step up ring 49-55 than put the PCX 5000 in it. What it does is cut down all the extra room and made it tighter in the mount. Still a touch of play but damn close to sitting still and not getting far off center. If your careful once you have it set than you can lay down your retaining ring on it. So for me it worked. I did the ZM 35 lens. Once I get the ElPro 3 for the 25 I will do the same.

Here is the part number







Mar 22, 2017 at 06:10 PM
GMPhotography
Offline
• • • • • •
Upload & Sell: On
p.71 #3 · p.71 #3 · Front-End Filter Improves Corner Smearing


Fred Miranda wrote:
Guy, reversed look noticeably better, especially wide open.


Thanks Bud i will switch it back to reversed and I got infinity finally. One Gold from Rear and one bronze from front is right smack on the hard stop now. I may go run another test in 1/3rds of a stop in reverse mode.

In all honesty this is worlds better than with out it. I am freaking thrilled now and for everyone else I believe the PCX is the going to be the ticket on the 28 also.



Mar 22, 2017 at 06:14 PM
GMPhotography
Offline
• • • • • •
Upload & Sell: On
p.71 #4 · p.71 #4 · Front-End Filter Improves Corner Smearing


Fred love to see you buy the 28mm again and I can send this rig for the PCX 2500 over for testing


Mar 22, 2017 at 06:15 PM
Fred Miranda
Offline
Admin
Upload & Sell: On
p.71 #5 · p.71 #5 · Front-End Filter Improves Corner Smearing


GMPhotography wrote:
Fred love to see you buy the 28mm again and I can send this rig for the PCX 2500 over for testing


I'm still looking for a mint ZM 28/2.8. If anyone comes across one, let me know.



Mar 22, 2017 at 06:27 PM
tormoder
Offline

Upload & Sell: Off
p.71 #6 · p.71 #6 · Front-End Filter Improves Corner Smearing


Samuli Vahonen wrote:
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.


I found that using the 46-55|55-52|52-55 setup caused some additional vignetting with my G28. Using a 52-retaining ring instead of the 52-55 fixed it in my case.



Mar 22, 2017 at 08:18 PM
artur5
Offline
• • •
Upload & Sell: Off
p.71 #7 · p.71 #7 · Front-End Filter Improves Corner Smearing


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


Yeah, a close shave. I checked my empty filters and they both have 4.5mm. of usable threads. Those PCXs are 3mm. thick so 1.5mm left for screwing the retaining ring, which is a bit more than 1mm. thick



Mar 22, 2017 at 08:24 PM
artur5
Offline
• • •
Upload & Sell: Off
p.71 #8 · p.71 #8 · Front-End Filter Improves Corner Smearing


For a PCX filter in a 55mm step-up ring you need O-rings of 54mm. ext diam x 2 mm. thick

https://www.amazon.com/10Pcs-Sealing-Gasket-Washer-Automobile/dp/B00858B8TQ/ref=sr_1_4?ie=UTF8&qid=1490215266&sr=8-4&keywords=o+ring+54mm



Mar 22, 2017 at 08:44 PM
GMPhotography
Offline
• • • • • •
Upload & Sell: On
p.71 #9 · p.71 #9 · Front-End Filter Improves Corner Smearing


Yea Arthur the ones I bought are 47mm, biggest they had so I cut it in half and laid it in. It works , not moving.


Mar 22, 2017 at 08:58 PM
Samuli Vahonen
Offline
• • • •
Upload & Sell: Off
p.71 #10 · p.71 #10 · Front-End Filter Improves Corner Smearing


tormoder wrote:
I found that using the 46-55|55-52|52-55 setup caused some additional vignetting with my G28. Using a 52-retaining ring instead of the 52-55 fixed it in my case.

Vignetting and color errors I referred in text you quoted is due to sensor design, it has nothing to do with mechanical vignetting. The A7r v2 back illuminated sensor handles the extreme ray angles better as shown on this and other threads on FM.


About mechanical vignetting with G28: I have 46-58 -> 58-55 -> Amazon Basics 55mm filter retention ring pressing down the PCX lens sitting in 46-58 step-up ring => no mechanical vignetting. However if I add 55-82mm step-up for ND filter etc. it adds very little mechanical vignetting. Amazon basics 52mm filter UV-filter retention ring is pretty close to perfect: a) it's beveled b) pretty thin (1.92mm - Elpro E55 retention ring is 3.54mm) c) inner diameter is 49.82mm

NOTICE! I first ordered one Amazon Basics 55mm UV, which had 49.82mm inner diameter and hold OptoSigma 50mm PCX lens perfectly in place. As it was perfect I ordered 3 more. And just writing this forum post I measured them and "tested" against OptoSigma PCX and it seems that ALL filters arrived in 2nd batch have retention ring with too large inner diameter to hold OptoSigma 50mm diameter lenses... 2nd batch filters seem to have retention ring inner diameter 50.02-50.11mm. So the hunt for perfect 55mm retention ring is not over yet!


So if there is knowledge of which 55mm UV filter has thin retention ring with inner diameter of ~49.8mm I would be very interested.

Samuli



Mar 22, 2017 at 09:21 PM
 

Search in Used Dept. 

        


Samuli Vahonen
Offline
• • • •
Upload & Sell: Off
p.71 #11 · p.71 #11 · Front-End Filter Improves Corner Smearing


FYI about OptoSigma Europe: My 2nd order for 2000mm and 2500mm seems to take longer; I got confirmation today and it says that shipping happens 28th April. Last order was faster, just few weeks.

Samuli



Mar 23, 2017 at 08:04 PM
GMPhotography
Offline
• • • • • •
Upload & Sell: On
p.71 #12 · p.71 #12 · Front-End Filter Improves Corner Smearing


Mine came the other day without notice ahead of what they said. Passing on the good karma


Mar 23, 2017 at 08:06 PM
artur5
Offline
• • •
Upload & Sell: Off
p.71 #13 · p.71 #13 · Front-End Filter Improves Corner Smearing


Samuli Vahonen wrote:
FYI about OptoSigma Europe: My 2nd order for 2000mm and 2500mm seems to take longer; I got confirmation today and it says that shipping happens 28th April. Last order was faster, just few weeks.

Samuli

Same here. I ordered PCX1500 + PCX5000 on March 13th. and scheduled shipping is for April 21th.



Mar 23, 2017 at 08:18 PM
DavidBM
Online
• • • •
Upload & Sell: On
p.71 #14 · p.71 #14 · Front-End Filter Improves Corner Smearing


GMPhotography wrote:
Thanks Bud i will switch it back to reversed and I got infinity finally. One Gold from Rear and one bronze from front is right smack on the hard stop now. I may go run another test in 1/3rds of a stop in reverse mode.

In all honesty this is worlds better than with out it. I am freaking thrilled now and for everyone else I believe the PCX is the going to be the ticket on the 28 also.


Guy the PCX may well get the 28 to near native performance; but the lens itself is quite a bit less impressive than the 25 (despite being an easier to design FL - it's just an older design and one which prioritizes compactness over resolution)

Maybe it's worth messing with for the sunstars - there's currently no other 10 blade option at 28mm that I'm aware of - but we can't expect miracles here.



Mar 23, 2017 at 08:59 PM
Fred Miranda
Offline
Admin
Upload & Sell: On
p.71 #15 · p.71 #15 · Front-End Filter Improves Corner Smearing


DavidBM wrote:
Guy the PCX may well get the 28 to near native performance; but the lens itself is quite a bit less impressive than the 25 (despite being an easier to design FL - it's just an older design and one which prioritizes compactness over resolution)

Maybe it's worth messing with for the sunstars - there's currently no other 10 blade option at 28mm that I'm aware of - but we can't expect miracles here.


Although I agree that the ZM 25 is superior to the ZM 28, we can't come to a definite conclusion just by comparing MTFs. The ZM 28 has stronger field curvature and the weaker MTF probably accounts for that.

The same could be said for the ZF 28/2 Distagon's MTF.



Mar 23, 2017 at 09:19 PM
Phillip Reeve
Offline
• • • •
Upload & Sell: Off
p.71 #16 · p.71 #16 · Front-End Filter Improves Corner Smearing




DavidBM wrote:
Maybe it's worth messing with for the sunstars - there's currently no other 10 blade option at 28mm that I'm aware of - but we can't expect miracles here.

There is also the CV 2/28 which has FC issues as well.



Mar 23, 2017 at 09:29 PM
Fred Miranda
Offline
Admin
Upload & Sell: On
p.71 #17 · p.71 #17 · Front-End Filter Improves Corner Smearing


Phillip Reeve wrote:
There is also the CV 2/28 which has FC issues as well.


The Ultron 28/2 is quite good at f/5.6 towards the corners. The issue is FC mitigation and I'm sure the right PCX will improve this quite a bit.



Mar 23, 2017 at 09:37 PM
GMPhotography
Offline
• • • • • •
Upload & Sell: On
p.71 #18 · p.71 #18 · Front-End Filter Improves Corner Smearing


The ZM 25 is really nice now. Fred's after the 28mm. I'm betting with the PCX 2500 the 28 may come to life. I easily picked up 2 stops in the corners. If Fred gets one either I or he will test it with my PCX 2500 we both have a Hawk adapters we could test without taking any shims out. I just bought a Hawks for the 25 too. No matter what combination I try with the 25 I can't hit the hard stop. I either come up short or too long adjusting with shims. So I will dedicate a Hawks to it and finish the infinity adjustment. My ZM 35 has a Hawks as well. I'm deadly on the hard stop there.


DavidBM wrote:
Guy the PCX may well get the 28 to near native performance; but the lens itself is quite a bit less impressive than the 25 (despite being an easier to design FL - it's just an older design and one which prioritizes compactness over resolution)

Maybe it's worth messing with for the sunstars - there's currently no other 10 blade option at 28mm that I'm aware of - but we can't expect miracles here.



Edited on Mar 23, 2017 at 09:40 PM · View previous versions



Mar 23, 2017 at 09:38 PM
DavidBM
Online
• • • •
Upload & Sell: On
p.71 #19 · p.71 #19 · Front-End Filter Improves Corner Smearing


Fred Miranda wrote:
Although I agree that the ZM 25 is superior to the ZM 28, we can't come to definite conclusions just by comparing MTFs. The ZM 28 has stronger field curvature and the weaker MTF probably accounts for that.

The same could be said for the ZF 28/2 Distagon's MTF.


Agreed; but my sense of of the difference wasn't based only on MTFs, but on having thought when playing with the digital M system (I borrowed a bunch of M stuff before getting Sony gear while looking for a FF system for wilderness work that was smaller than Canon FF) that the 25 was astonishingly good, and the 28 fine, but nothing special. But that was pretty informal.

So yes the MTFs might be largely different because of field curvature. But the MTF is at infinity, so if its not like some FC which is mainly at shorter distances and calms down at infinity. If we can mitigate the native field curvature (as against the induced FC) it will be by focussing for a compromise setting -- but that of course, while it gives better results overall, is trading off centre resolution for evenness.

None of this is to say the 28 is not worth pursuing with a PCX, or that it definitely won't turn out to be a good solution. But just that it needs to be pursued in the spirit of experiment, rather than in the confident hope that it'll end up giving great results like the 25 can...

(but here's a wild thought - with these front filters we are basically playing at lens design by adding elements. I wonder if we can simulate what it would take to modify the *native* field curvature by adding an element, effectively doing what Zeiss would have done if their brief/budget/design goal had been different....)



Mar 23, 2017 at 09:38 PM
GMPhotography
Offline
• • • • • •
Upload & Sell: On
p.71 #20 · p.71 #20 · Front-End Filter Improves Corner Smearing


David I'm losing nothing on center at all with the PCX 2500 and the 25 but gaining a load in the corners. Basically what these PCX lenses are doing is essentially flatening out the field curvature . Optically that is.


Mar 23, 2017 at 09:43 PM
1       2       3              70      
71
       72              92       93       end






FM Forums | Sony Forum | Join Upload & Sell

1       2       3              70      
71
       72              92       93       end
    
 

You are not logged in. Login or Register

Username     Reset password