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Front-End Filter Improves Corner Smearing
  
 
artur5
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p.5 #1 · p.5 #1 · Front-End Filter Improves Corner Smearing


I was using the simplified formula f3 = (f1*f2)/(f1+f2). So, you're surely right about 0.2mm. instead of 0.3 and also a good point about the G lenses being more friendly. The question is how we deal with this issue with M lenses. Grinding is a possibity, yes. I did in the past with different adapters to Canon EOS but frankly is quite a PITA, specially if you have to grind several tenths of mm. and not easy to achieve an even thickness all around the ring without the right tools and skills. Besides, I wouldn't be willing to try that on a expensive Techart adapter. Best thing is IMHO a Sony-E to M adapter with user adjustable infinity.
Sorry if I may sound negative, HaruhikoT. I appreciate a lot your contribution to this matter. It's only that I want badly this solution to work right, so I'm playing a bit the role of devil's advocate.



Oct 10, 2016 at 05:09 PM
EDBR
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p.5 #2 · p.5 #2 · Front-End Filter Improves Corner Smearing


Mr HaruhikoT

Sorry but took the freedom to launch a link of this to two other forums,
1. Sony alpha rumors: http://www.sonyalphaforum.com/topic/6129-regarding-smearing-of-legacy-wide-angle-lenses-on-a7-series-the-front-end-filter-solution-by-mr-haruhikot/
2. Philip Reeve: http://phillipreeve.net/blog/user-guide-ultra-wideangle-lenses-sony-alpha-7-series/#comment-31565

When you’re talking about the 5m I presume you`re talking about this filter SLB-50-500PM ?
Must say that the 6m seems to be discontinued.
Do other company’s provide these lenses as well ?
Europe ?

Must say that the MTF-performances look amazing !



Oct 11, 2016 at 05:20 PM
TheEmrys
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p.5 #3 · p.5 #3 · Front-End Filter Improves Corner Smearing


This could be really interesting for anyone using a Speedbooster/Lens Turbo. I may have to get one and try it out on my XT2, MB SB, and Minolta MD 35-70/3.5. If it gets a decently sharp corners, it could be an elegant solution. But man, that is a lot of light bending.


Oct 11, 2016 at 06:25 PM
Nanh
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p.5 #4 · p.5 #4 · Front-End Filter Improves Corner Smearing


You shouldn't mistake the mtf for the real performance of the combination. The simulation is based on a perfect lens, so without the filters the MTF should be just flat lines at 100%. What the graph shows is just the degradation caused by the coverglass and filter combination. Any aberration of the original lens is likely compounded. The addon filter would never make the lens better than it was originally designed.

EDBR wrote:
Mr HaruhikoT

Sorry but took the freedom to launch a link of this to two other forums,
1. Sony alpha rumors: http://www.sonyalphaforum.com/topic/6129-regarding-smearing-of-legacy-wide-angle-lenses-on-a7-series-the-front-end-filter-solution-by-mr-haruhikot/
2. Philip Reeve: http://phillipreeve.net/blog/user-guide-ultra-wideangle-lenses-sony-alpha-7-series/#comment-31565

When you’re talking about the 5m I presume you`re talking about this filter SLB-50-500PM ?
Must say that the 6m seems to be discontinued.
Do other company’s provide these lenses as well ?
Europe ?

Must say that the MTF-performances look amazing !




Oct 12, 2016 at 01:07 AM
HaruhikoT
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p.5 #5 · p.5 #5 · Front-End Filter Improves Corner Smearing



EDBR wrote
When you’re talking about the 5m I presume you`re talking about this filter SLB-50-500PM ?

No, SLB-50-500PM has FL=500mm that is too shoot. SLB-50-5000PM (FL=5000mm=5m) should be optimal for G45.

And thank you Nanh, That's also my point.
MTFs in the graph just represent how well the PCX would compensate aberrations added by sensor stack, not represent whole lens system's MTF.

Simulation is just simulation, there is no guarantee until tested.
At least for G21 and G28, I tested and results look similar to the simulation in my eyes.

I would appreciate your contribution in testing any unproved combination of lens and front-end filter.

Haruhiko



Oct 12, 2016 at 03:08 AM
candreyo
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p.5 #6 · p.5 #6 · Front-End Filter Improves Corner Smearing


Greetings,

I've registered with this forum just so I could post on this thread!

I'm an opto-mechanical design engineer who works with Lasers, and a passionate photography enthusiast on the side.
I have almost a full set of Zeiss ZM lenses, and am willing to take a stab at this to try and see if I can program some of the Zeiss ZM lenses, and find which PCX lenses may work the best.
I have a 1500mm PCX lens being mailed to me from Laser 2000 (UK distributor for Optosigma).
My main goal is the Zeiss 25mm and 28mm lenses, as these perform the worst for me on the Sony A7 cameras.

I have downloaded the OSLO software, and have gotten a copy of the Zeiss Contax G datasheets. I've been trying to wade my way through it, and decided to try and simulate the 28mm Biogon G lens in the software, so I get a hang on how it works.

Unfortunately, after following Haruhiko T's wonderful guide here and using the values from Zeiss's website, I still haven't been able to get the Contax G 28mm to compute correctly.
I would like to use this Contax G 28mm lens as a baseline for me developing a Zeiss 28mm ZM lens simulation. I understand they are different computations, but need to start somewhere.

Haruhiko T,

Would you mind sharing the exact contents of the *.len file you use to simulate the 28mm biogon here? That way I can see where I'm going wrong?

Equally, once my 1500mm PCX lens arrives, I'll let everyone know here how it fares on the Zeiss 25mm and 28mm ZM lenses. I also own a copy of the Zeiss 35mm 1.4 Distagon ZM lens, and shall place the 1500mm PCX on it to see how it fares also.

Hoping we can find a cure for the Zeiss ZM WA RF lenses also! This thread and its research have really perked my interest.

Also, I may have a solution for the Zeiss ZM lenses when used on Sony A7, that may loose the ability to reach infinity with the PCX installed.
I have had about half my Zeiss ZM lenses disassembled in the past, adjusting their rangefinder focusing ability. The reason I did this was, many of them I bought used off ebay, and when I used them on my Leica M240, their focus was off (some too near, others too far). I have other Voigtlander and Leica lenses that have always worked fine with my M240, but have had problems with the Zeiss ZM range. Anyhow, often whats needed to simply correct the lenses so they focus properly, is installing or removing internal shims inside the lens. The shims are accessible my usually removing the rear lens retaining ring with a two pronged adjustable lens spanner.

The way Zeiss seems to adjust the lenses on their ZM line for accurate rangefinder focusing, is very similar to how the Soviet M39 Jupiter 3, 8, 11..etc. are adjusted. i.e., open the lens and add/ or remove shims. The Soviet Jupiter lenses themselves are post war clones of pre-war Zeiss lenses anyways, so it appears not much has changed in about 70+ years!

If by adding the PCX lenses to the Zeiss ZM WA lenses like the 25mm biogon, result in the lens not able to reach infinity anymore, its possible the lens could be adjusted internally with an appropriate shim to enable it to reach infinity.

This would definitely have a knock-on affect to the rangefinder focusing system, so if you plan to dual use these lenses with both a Leica body and a Sony body, this is probably bot the best option. However, for those that purely may use these lenses on a Sony body and don't care about the lens being accurate rangefinder wise, this might be a plausible solution?


Best Regards,

Candreyo



Oct 12, 2016 at 06:43 PM
HaruhikoT
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p.5 #7 · p.5 #7 · Front-End Filter Improves Corner Smearing


candreyo wrote:
Greetings,

I've registered with this forum just so I could post on this thread!

I'm an opto-mechanical design engineer who works with Lasers, and a passionate photography enthusiast on the side.
I have almost a full set of Zeiss ZM lenses, and am willing to take a stab at this to try and see if I can program some of the Zeiss ZM lenses, and find which PCX lenses may work the best.
I have a 1500mm PCX lens being mailed to me from Laser 2000 (UK distributor for Optosigma).
My main goal is the Zeiss 25mm and 28mm lenses, as these perform the worst
...Show more

Wow you have great lens collection! I envy you .
Looking forward to see your test results.

This is G28's len file just exported from my simulation environment. I hope this may help you.
https://drive.google.com/file/d/0B1BhTESBmBxoTzBQUXVyMV9LSU0/view?usp=sharing

Thank you,
Haruhiko



Oct 13, 2016 at 03:28 AM
beetlephoto
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p.5 #8 · p.5 #8 · Front-End Filter Improves Corner Smearing


Subscribed, this is a great topic, thanks!!!


Oct 13, 2016 at 11:54 AM
candreyo
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p.5 #9 · p.5 #9 · Front-End Filter Improves Corner Smearing


Thank you so much for this, download it and its working fine for me now.
I work with a few laser physicist who know a lot about optics and ray tracing. I'm going to show them this software and gather any input they may have. I've explained to one of them what we're trying to do, and he understand it on a physics level, so hopefully he will be able to guide me in programming up a 28mm Zeiss ZM simulation. I have a caliper and will try to extract the dimensions from the lens as best I can, but of course this will not be as accurate as if Zeiss were to release the actual data about these lenses to us.

My hope is that I can model a best effort simulation of the Zeiss 28mm ZM, to narrow estimate what may be the best PCX to use within a lens or two, then order those lenses and see what happens!

I do wish I had a full compliment of PCX lenses, I could just trial and error across the entire Zeiss ZM line and figure out what works best.

FYI for those located in the United Kingdom, Laser 2000 charges approx. 59,00GBP for each PCX lens. I was able to order the other parts needed (step up rings and filer) for less then 5.00GBP off a popular auction site.

All the best,

Candreyo



Oct 13, 2016 at 05:33 PM
Brandon Dube
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p.5 #10 · p.5 #10 · Front-End Filter Improves Corner Smearing


candreyo wrote:
Thank you so much for this, download it and its working fine for me now.
I work with a few laser physicist who know a lot about optics and ray tracing. I'm going to show them this software and gather any input they may have. I've explained to one of them what we're trying to do, and he understand it on a physics level, so hopefully he will be able to guide me in programming up a 28mm Zeiss ZM simulation. I have a caliper and will try to extract the dimensions from the lens as best I can, but of
...Show more

OSLO is a fine software. Dave Shafer is a very highly regarded lens designer and I believe it is his software of choice to this day. Be aware that you absolutely may not use OSLO edu for commercial purposes, the same going for my Code V student license.

In terms of modeling the ZM 28mm, it is also not possible to model that lens in optical design software without knowing its exact parameters. I believe OSLO edu is still limited to 6 surfaces, so the best you can do is a thin lens with a displaced aperture stop to get the correct exit pupil location, then add a thick meniscus lens right on top of the image in front of the coverglass to simulate some of the field curvature.

If you require guidance, I can assist provided these efforts remain noncommercial.



Oct 14, 2016 at 12:00 AM
 

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candreyo
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p.5 #11 · p.5 #11 · Front-End Filter Improves Corner Smearing


Hello Brandon,

Many thanks for your input on this, I appreciate it.
No, I have no intentions of using the software commerically, Im merely trying to use it to model some of the Zeiss ZM lenses I own, to help me narrow done which PCX filters may work.

I wish I had about $900.00 of disposible income, I could buy a near complete set of PCX lenses and see what actually works without simulating it.

Unfortunately, I only have enough money set asisde at the moment for 2-3 PCX lenses, so I would like to use the software to help me narrow down which PCX lenses may work best for the 25mm and 28mm Zeiss Biogon ZM's.

I have created a 28mm ZM profile, using Haruhiko T's 28G lens template, and you are right. Without knowing the exact specifications of the lens, its very difficult to try and model it. i have been using a caliper to try and estimate the various dimensions I need, and have not had any luck getting the lens file to compute properly.

My goal ultimately is to find which PCX lenses work best with the Zeiss 25 and 28mm ZM, lenses, then let the community know this, so that anyone who may own these type of lenses can get the correct PCX lens that addresses the corner smearing issue the best.

Im going to have another go this evening trying to further program a Zeiss 28mm ZM lens file, but if I continue to run into issues, I may post what code I have here and ask for some guidance.

Best Regards,
Candreyo



Oct 14, 2016 at 01:01 PM
Brandon Dube
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p.5 #12 · p.5 #12 · Front-End Filter Improves Corner Smearing


candreyo wrote:
Hello Brandon,

Many thanks for your input on this, I appreciate it.
No, I have no intentions of using the software commerically, Im merely trying to use it to model some of the Zeiss ZM lenses I own, to help me narrow done which PCX filters may work.

I wish I had about $900.00 of disposible income, I could buy a near complete set of PCX lenses and see what actually works without simulating it.

Unfortunately, I only have enough money set asisde at the moment for 2-3 PCX lenses, so I would like to use the software to help me narrow down which
...Show more

The only thing that matters in a perfect lens model is the chief ray angle and amount of vignetting. You cannot simulate the vignetting with a perfect lens as only one surface, but it is possible to do with dummy surfaces. I don't think you have enough surfaces in OSLO edu for that, but I may be wrong.

To find the thickness between the stop and the perfect lens you can use thin lens imaging. 1/s' = 1/s + 1/f, f~=28.5. If the exit pupil is at, say, 35mm we would have 1/-6.5 = 1/x + 1/28.5, x=-5.293. Sign is very important here.

I do not know the commands for OSLO, as it is not a program I am very familiar with. I can provide a .seq file from Code V if OSLO can convert those, based on a lens module equivalent to a thin lens.

What I would need from you is:

(a) the exit pupil distance of the lenses you are interested in
(b) how far in front of the exit pupil you want the lens.

FWIW, if you can put a 1.2m meniscus lens with negative radii right on top of the entrance/exit pupil, you can attain performance that is diffraction limited across the entire frame in the sagittal ray fan, and limited by lateral color in the tangential plane.

If you put it 1" in front of that, you cannot do as good a correction but still do ok. The ideal lens is a 4.4m EFL meniscus lens with negative radii. The performance is limited by coma at f/2.8; at f/5.6 you are essentially diffraction limited in the sagittal fan, and the tangential plane has an MTF at 50lp/mm of 0.45 in the full-field.

Get back to me with the exact(ish) distance from the pupil to the filter, and where the pupil is and I can do a more exact simulation. If you have the Seidel aberration coefficients for the lens, I can also add that to the thin lens model equivalent.

All the best,
Brandon



Oct 14, 2016 at 10:50 PM
TheEmrys
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p.5 #13 · p.5 #13 · Front-End Filter Improves Corner Smearing


I could see further testing being something for a kickstarter campaign. I would contribute.


Oct 14, 2016 at 11:37 PM
DavidBM
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p.5 #14 · p.5 #14 · Front-End Filter Improves Corner Smearing


TheEmrys wrote:
I could see further testing being something for a kickstarter campaign. I would contribute.


I think once a kickstarter campaign starts, then you wpb;d need to shell out three grand or so for a commercial OSLO license. Which is not unreasonable. I think it really requires someone to decide that there is a niche market for testing and simulating the lenses people are most likely to want to use, and then putting in bulk orders for the lenses and hoping that there is a decent markup.

Males most commercial sense for lenses like the ZM 1.4/35 where the required correction probably comes from a meniscus lens which is special order.



Oct 15, 2016 at 01:59 AM
Brandon Dube
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p.5 #15 · p.5 #15 · Front-End Filter Improves Corner Smearing


DavidBM wrote:
I think once a kickstarter campaign starts, then you wpb;d need to shell out three grand or so for a commercial OSLO license. Which is not unreasonable. I think it really requires someone to decide that there is a niche market for testing and simulating the lenses people are most likely to want to use, and then putting in bulk orders for the lenses and hoping that there is a decent markup.

Males most commercial sense for lenses like the ZM 1.4/35 where the required correction probably comes from a meniscus lens which is special order.


Code V is quite expensive, but a commercial license for a short amount of time is cheaper than a license of OSLO. If there was sufficient interest, there is no reason I couldn't design a suite of correctors in Code V. and let the license go after a month or two. A company like e.g. metabones may be interested in doing the mechanical bits and handling the business side of things.



Oct 15, 2016 at 04:20 AM
DavidBM
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p.5 #16 · p.5 #16 · Front-End Filter Improves Corner Smearing


Brandon Dube wrote:
Code V is quite expensive, but a commercial license for a short amount of time is cheaper than a license of OSLO. If there was sufficient interest, there is no reason I couldn't design a suite of correctors in Code V. and let the license go after a month or two. A company like e.g. metabones may be interested in doing the mechanical bits and handling the business side of things.


That would be a great outcome. Someone like them could also arrange to have high spec coatings on the surfaces, which the intended market would want. You really interested? How would you guague interest? Maybe from the ks campaign. But you'd need to know if someone like MB was interested in principle first...



Oct 15, 2016 at 05:03 AM
HaruhikoT
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p.5 #17 · p.5 #17 · Front-End Filter Improves Corner Smearing


Hi,
Today it's fine autumn weather here, so I tested G21/G28 again, with the new setup.

Previous test condition was:
G21+PCX1.5m Forward(curved surface faces to object)
G28+PCX2.0m Forward

My latest simulation tells PCX1.3m is the best for both G21/G28, but I only have 1.5m.
Simulation also tells Reversed 1.5m has similar effect to 1.3m.

So today's setup is:
G21+PCX1.5m Reversed(curved surface faces to primary lens)
G28+PCX1.5m Reversed

Results are even better. Especially at f4 and f5.6, they are ultra sharp and the micro-contrast looks great.
I'm so impressed. I love contax G biogon!

Stock A7+G21+PCX1.5m Reversed @F4

Center 100% crop

Mid 100% crop

Corner 100% crop


You can download unresized test samples including wide open. Please check my flickr.
https://www.flickr.com/photos/[email protected]

Haruhiko



Oct 15, 2016 at 05:51 AM
Brandon Dube
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p.5 #18 · p.5 #18 · Front-End Filter Improves Corner Smearing


DavidBM wrote:
That would be a great outcome. Someone like them could also arrange to have high spec coatings on the surfaces, which the intended market would want. You really interested? How would you guague interest? Maybe from the ks campaign. But you'd need to know if someone like MB was interested in principle first...


An optics education is quite expensive. This would not be a time consuming project, and the income from a commercialized variant could go towards my debt. I can contact Metabones and see if they are interested in the idea, if they are and will pay a sufficient fee for the design of the filters there is no reason to do a KS/GFM, etc.

Coatings do not really have a design cost associated with them, most of the aberrations caused by the filter are field curvature and astigmatism related, which are aberrations combated by a meniscus lens. The best coatings for a meniscus lens for a given common glass type are already well known.



Oct 15, 2016 at 04:03 PM
realVivek
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p.5 #19 · p.5 #19 · Front-End Filter Improves Corner Smearing


Haruhiko, Thanks for the latest experiments with reversed PCX lens!


Oct 15, 2016 at 09:21 PM
DavidBM
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p.5 #20 · p.5 #20 · Front-End Filter Improves Corner Smearing


Brandon Dube wrote:
An optics education is quite expensive. This would not be a time consuming project, and the income from a commercialized variant could go towards my debt. I can contact Metabones and see if they are interested in the idea, if they are and will pay a sufficient fee for the design of the filters there is no reason to do a KS/GFM, etc.

Coatings do not really have a design cost associated with them, most of the aberrations caused by the filter are field curvature and astigmatism related, which are aberrations combated by a meniscus lens. The best coatings for
...Show more

Sure that was my point: in a purely commercial sense MB (or someone else) could just trivially arrange to have the glass coated. Whereas if we individually buy pieces we get them as they come, it not being financially rational to send off one piece for coating if the way it comes is not what you want (though it might be). I wasn't imagining there was any design issue.

Go for it Brandon! I'll be up for a piece or two to mitigate your student debt...



Oct 15, 2016 at 09:35 PM
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