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Archive 2016 · Front-End Filter Improves Corner Smearing

  
 
naturephoto1
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p.4 #1 · p.4 #1 · Front-End Filter Improves Corner Smearing


hiepphotog wrote:
Then the question is how many ZM 35/1.4 users are willing to try out the process so we can meet the MOQ. For a standard size and glass type, custom order piece would not be that bad. Just need to meet MOQ.


There are several questions though, 1) how many of us have the lens for usage on an A7 series camera, 2) how many will need to produced, 3) how much will it cost, and 4) will we observe reflection issues. Then of course there is the issue of needing differnt filters for the different lenses that many of us have, and how costly it would be for filters for all of these lenses. For people with several or many lenses RF WA lenses, it may end up being better and cheaper to just live with the Kolari Modification (though there may also be improved perfromance for lenses with Kolari modded cameras).

Rich

Edited on Oct 08, 2016 at 03:10 PM · View previous versions



Oct 08, 2016 at 11:03 AM
Steve Spencer
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p.4 #2 · p.4 #2 · Front-End Filter Improves Corner Smearing


I would be interested.



Oct 08, 2016 at 01:05 PM
artur5
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p.4 #3 · p.4 #3 · Front-End Filter Improves Corner Smearing


Of course, a non small advantage of the front end solution vs. the Kolari mod is that we won't have to worry about possible sharpness degradation when using native FE glass. Nevertheless, there's no free lunch. We can see in the graphics of the last page the negative impact on the central part of the frame when we add the PCX element. This is quite evident evident in the case of the ZM35/1.4 full open. Let's hope that the meniscus solution turns out to be economically viable, because it looks much better, at least in theory.


Oct 08, 2016 at 01:50 PM
genji
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p.4 #4 · p.4 #4 · Front-End Filter Improves Corner Smearing


Lloyd Chambers published on his blog (not behind the paywall) a post titled Ray Angle From Lens Exit Pupil (Table of Ray Angles for Zeiss ZM Lenses) which lists the chief ray angles for all the Zeiss ZM lenses. The value for the Distagon ZM 35/1.4 is 32.5 degrees. Would I be correct in assuming that one could use the ray angle and frame size to calculate the exit pupil distance?



Oct 08, 2016 at 08:25 PM
HaruhikoT
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p.4 #5 · p.4 #5 · Front-End Filter Improves Corner Smearing


genji wrote:
Lloyd Chambers published on his blog (not behind the paywall) a post titled Ray Angle From Lens Exit Pupil (Table of Ray Angles for Zeiss ZM Lenses) which lists the chief ray angles for all the Zeiss ZM lenses. The value for the Distagon ZM 35/1.4 is 32.5 degrees. Would I be correct in assuming that one could use the ray angle and frame size to calculate the exit pupil distance?


Thank you for the comment.
Exit pupil distance can be estimated from the chief ray angle.

arctan( 34.0 / 21.64 ) = 32.5.
*Note 21.64 is 1/2 of 35mm format diagonal size.

So I got Exit pupil distance = 34.0mm.
Hmm this is so different from last estimated value 27.86mm(Exit pupil diameter 19.9mm estimated from Nanh's photo * fno 1.4), but I don't know why.

With the new condition: Exit Pupil Distance - Focal length = -1.0mm, I run again the simulation.
In this case also, simple PCX doesn't work well at f1.4. So I used meniscus.

[Update] The image here was removed because I found my model had some flaws to handle meniscus lens and the solution is still under investigation.


Edited on Dec 19, 2016 at 08:28 AM · View previous versions



Oct 09, 2016 at 12:35 AM
DavidBM
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p.4 #6 · p.4 #6 · Front-End Filter Improves Corner Smearing


HaruhikoT wrote:



Thank you for the comment.
Exit pupil distance can be estimated from the chief ray angle.

arctan( 34.0 / 21.64 ) = 32.5.
*Note 21.64 is 1/2 of 35mm format diagonal size.

So I got Exit pupil distance = 34.0mm.
Hmm this is so different from last estimated value 27.86mm(Exit pupil diameter 19.9mm estimated from Nanh's photo * fno 1.4), but I don't know why.

With the new condition: Exit Pupil Distance - Focal length = -1.0mm, I run again the simulation.
In this case also, simple PCX doesn't work well at f1.4. So I used meniscus.
https://farm6.staticflickr.com/5713/30120300551_dbc4ccc685_o_d.jpg



Who that is a truly amazing difference! If it works out in practice, and if the meniscus filter can be made for not too staggering a price with good coatings, it would make the ZM 1.4 fen more attractive. Attractive enough to buy...



Oct 09, 2016 at 03:16 AM
realVivek
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p.4 #7 · p.4 #7 · Front-End Filter Improves Corner Smearing


DavidBM wrote:
Who that is a truly amazing difference! If it works out in practice, and if the meniscus filter can be made for not too staggering a price with good coatings, it would make the ZM 1.4 fen more attractive. Attractive enough to buy...


Wouldn't be easier to impress upon Zeiss to come up with a Sony version?

The Leica version is not exactly a super seller for them , I would suspect.


Without the RF coupling, it should also be cheaper than the ZM version.



Oct 09, 2016 at 05:01 AM
DavidBM
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p.4 #8 · p.4 #8 · Front-End Filter Improves Corner Smearing


realVivek wrote:
Wouldn't be easier to impress upon Zeiss to come up with a Sony version?

The Leica version is not exactly a super seller for them , I would suspect.


Without the RF coupling, it should also be cheaper than the ZM version.


Well, it'll be a long time before there's a Loxia remake. That would be the best solution optically - though I doubt that s 1.4/35 would be any cheaper than the ZM given the pricing of slower Loxias.

But there is one quite big advantage of the ZM version: you can autofocus it on the TechArt. Which doesn't matter for landscape etc, but for wide open informal portrait use is a real benefit, as I've found using it with various M and other mount lenses.



Oct 09, 2016 at 05:29 AM
realVivek
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p.4 #9 · p.4 #9 · Front-End Filter Improves Corner Smearing


Good point! The techpro adapter changed the game.


Oct 09, 2016 at 05:31 AM
Makten
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p.4 #10 · p.4 #10 · Front-End Filter Improves Corner Smearing


Very interesting solution!

But... Wouldn't this screw up the ability to focus at infinity? I mean, a positive lens (albeit much stronger) is often used for closeups, and with one of those mounted, you can't focus to infinity.



Oct 09, 2016 at 07:56 AM
Steve Spencer
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p.4 #11 · p.4 #11 · Front-End Filter Improves Corner Smearing


Makten wrote:
Very interesting solution!

But... Wouldn't this screw up the ability to focus at infinity? I mean, a positive lens (albeit much stronger) is often used for closeups, and with one of those mounted, you can't focus to infinity.


I think you are right Marten, but given that it would just be a front end attachment you could just take it off for infinity shooting. As Fred has demonstrated this lens does very well at infinity stopped down to f/5.6 for smaller, so the front end attachment would be just for closer in shooting.



Oct 09, 2016 at 08:44 AM
Makten
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p.4 #12 · p.4 #12 · Front-End Filter Improves Corner Smearing


Steve Spencer wrote:
I think you are right Marten, but given that it would just be a front end attachment you could just take it off for infinity shooting. As Fred has demonstrated this lens does very well at infinity stopped down to f/5.6 for smaller, so the front end attachment would be just for closer in shooting.


Well, that would be too inconvenient for me, I think. Unless the difference in focus is so tiny that most lenses would reach infinity anyway (because most of them go past infinity to begin with).

The one lens I have that could benefit from such an add-on lens, is the Leica 40/2 Summicron-C. The front lens is so tiny that a much smaller filter/lens could be used, which would be nice (and perhaps cheaper). This lens is terrible at infinity though, so if it's not possible to reach infinity with the filter/lens attached, it would be useless.



Oct 09, 2016 at 08:59 AM
EDBR
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p.4 #13 · p.4 #13 · Front-End Filter Improves Corner Smearing


Very nice solution, let’s put these lenses glasses on :-)

Tried out the 28 and 21mm Contax G lenses and returned them because they where soft in the corners. I knew the cause was the sensor-filter but change the sensor-filter with a thin filter seems not possible in Europe. The 35mm and 45mm are ok when stopped to f8-f11.
So very impressive results with the 21 & 28mm !!!!!!!
It’s indeed a very nice solution, thinking of ordering them back. Like very much these little lenses because they have a lot of IQ/size and price. IQ is even better than the many, much more expensive and new lenses.

Kolari solution: In Europe we pay a lot of taxes on “change + sending-costs” , around +33%-40% in total. Not counting “time on the way” + “time blocked by our customs”. So didn't follow this possibility.

So the questions:

1. Mr HaruhikoT, do you have an idea if the filter from the A7R2 has the same thickness ?

2. Other approach, do you think it’s possible to set this kind of correction glas in the adapter, between lens and A7 body ?
Tried this out once with my 14mm Samyang + a filter to reduce light pollution, but it changed completely my 14mm (regarding focus and induced some astigmatisme)

3. Would the use of these filters give me better results for the Contax G 35mm ( at < f8), what would be the filter to use

By the way, looked to the website where you can buy these filters and it look’s like they are sold out already, due to the succes of your statements I presume…
Anyone an idea where we can buy these kind of glases in Europe ?

And thanks for this new fresh approach !!!!

Thanks for any reply.



Oct 09, 2016 at 09:10 AM
HaruhikoT
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p.4 #14 · p.4 #14 · Front-End Filter Improves Corner Smearing


Makten wrote:
Very interesting solution!

But... Wouldn't this screw up the ability to focus at infinity? I mean, a positive lens (albeit much stronger) is often used for closeups, and with one of those mounted, you can't focus to infinity.


Yes, this solution is essentially equal to close-up filter having very small Diopter.
It changes focus point slightly closer, so if you use adapter having no room to beyond infinity, maybe you can't reach infinity.
I think some cheap M-FE adapters have enough margin to solve this issue.



Oct 09, 2016 at 11:08 AM
HaruhikoT
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p.4 #15 · p.4 #15 · Front-End Filter Improves Corner Smearing


EDBR wrote:
1. Mr HaruhikoT, do you have an idea if the filter from the A7R2 has the same thickness ?

2. Other approach, do you think it’s possible to set this kind of correction glas in the adapter, between lens and A7 body ?
Tried this out once with my 14mm Samyang + a filter to reduce light pollution, but it changed completely my 14mm (regarding focus and induced some astigmatisme)

3. Would the use of these filters give me better results for the Contax G 35mm ( at < f8), what would be the filter to use


1. I believe all A7 series have optically-same sensor stack thickness, otherwise they would have compatibility issue with their genuine FE lenses.

2. The approach between lens and A7 body, there is possibility, but currently I don't have any good idea.

3. For G 35mm and also G 45mm, this solution will greatly work. Simulation tells 6m PCX is optimal. I will post details another day.

Haruhiko



Oct 09, 2016 at 11:22 AM
HaruhikoT
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p.4 #16 · p.4 #16 · Front-End Filter Improves Corner Smearing


Here are G35 and G45 results.

For G35 6m is, For G45 5m is the best.
Simulation also tells MTF has small difference between PCX 5m and 6m, so practically you can share same filter for those two lenses.

https://farm9.staticflickr.com/8620/30143563591_87ace96103_z_d.jpg

https://farm6.staticflickr.com/5631/30143563401_f706f2ea88_z_d.jpg



Edited on Oct 10, 2016 at 07:37 AM · View previous versions



Oct 10, 2016 at 12:08 AM
EDBR
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p.4 #17 · p.4 #17 · Front-End Filter Improves Corner Smearing


Yes, nice thanks Mr. Haruhiko it seems definitely the way to go. Don't have to make changes of the sensor-filter which could, maybe, induce problems with lenses like the Loxia 21mm or the 18mm Batis.
Presume these lenses are corrected and take in account the filter on the A7 series...?
An y idea about this, would these lenses be "de-corrected" ?



Oct 10, 2016 at 06:05 AM
HaruhikoT
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p.4 #18 · p.4 #18 · Front-End Filter Improves Corner Smearing


EDBR wrote:
Yes, nice thanks Mr. Haruhiko it seems definitely the way to go. Don't have to make changes of the sensor-filter which could, maybe, induce problems with lenses like the Loxia 21mm or the 18mm Batis.
Presume these lenses are corrected and take in account the filter on the A7 series...?
An y idea about this, would these lenses be "de-corrected" ?


At least Loxia lenses, Zeiss officially explained they took A7's sensor stack thickness into account.
So their Batis series must be the same.

http://www.mattgrum.com/fm/image37.jpg
Source: http://www.verybiglobo.com/photokina-2014-zeiss-loxia-story/

Modifying sensor stack thickness may reduce performance of those specially optimized latest lenses.
But I don't know how much the reduction is and it is really problematic or not.



Oct 10, 2016 at 07:29 AM
artur5
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p.4 #19 · p.4 #19 · Front-End Filter Improves Corner Smearing


What I’m foreseeing as a potential source of trouble is the infinity question. For instance, an additional front element of 5mtr. changes the focal of a Zeiss G 45/2 into a 44.7mm. lens. We’d need to reduce 0.3mm, the distance to the focal plane in order to reach infinity.
Most cheap adapters are 0.1 - 0.2mm. thinner than required, but it takes a very sloppy Sony-E to M adapter to be at least 0.3mm out of specifications. That rules out the Techart TAP or other good quality brands, except if the ring has the possibility of fine tuning infinity ( I believe the last version of the Hawks with helical has this feature ? )
Adjusting the infinity hard stop of the lens itself could be another solution but, depending on the construction, sometimes this is very difficult or not possible at all. Besides, it wouldn’t be useful for people trying to use that lens on different cameras.



Oct 10, 2016 at 08:36 AM
HaruhikoT
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p.4 #20 · p.4 #20 · Front-End Filter Improves Corner Smearing


artur5 wrote:
What I’m foreseeing as a potential source of trouble is the infinity question. For instance, an additional front element of 5mtr. changes the focal of a Zeiss G 45/2 into a 44.7mm. lens. We’d need to reduce 0.3mm, the distance to the focal plane in order to reach infinity.
Most cheap adapters are 0.1 - 0.2mm. thinner than required, but it takes a very sloppy Sony-E to M adapter to be at least 0.3mm out of specifications. That rules out the Techart TAP or other good quality brands, except if the ring has the possibility of fine tuning infinity (
...Show more

You are right this is possible issue for Leica M lenses + TAP or good quality adapters.
One possible (but wild ) solution is, to disassemble the adapter and grind its mount plate.
I don't have TAP but my techart contax G adapter have 1mm+ thick mount plate, so grinding it 0.3mm is maybe possible.

For Contax G lenses, sinse these are native AF lenses and as I look at mine, not only ContaxG-E adapters but also helicoids of these lenses themselves have enough margin. So I'm not worry about G lenses.
And just nitpicking but G45 + PCX 5m changes its FL only 0.2mm, because 2 lenses combined focal length is obtained from not only each lens' focal length but also distance between each lens's principal plane.



Oct 10, 2016 at 09:58 AM
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