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Archive 2016 · Front-End Filter Improves Corner Smearing

MAubrey
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p.14 #1 · p.14 #1 · Front-End Filter Improves Corner Smearing

I know the discussion has shifted to the ZM35, but I've just reread through the earlier pages and was wondering if their was a consensus on what the best option for the Contax G 28mm would be?

Is the G28+PCX1.5m Reversed the ideal?

Dec 17, 2016 at 11:27 AM

candreyo
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p.14 #2 · p.14 #2 · Front-End Filter Improves Corner Smearing

Hi Ceder,

Apologies on the dark video, I hope to get a video done with more light over Christmas break.

With regards to the ZM 28mm 2.8, I have this lens and I have found the best filter to use is a 1500mm Planoconvex from OptoSigma. This sharpens the corners of the lens up tremendously, very similar to the improvements that Haruhiko posted with his modified ZM 35mm and Contax G 28mm lenses.

The process to open them is very similar to what I showed in the video with the ZM 18mm. You need to remove the rear lens retention ring on the lens, then the whole lens block removes from the lower helicoil. On the part that is removed, you will see shims in the same location as was showed on the ZM 18mm. I had to remove 2 shims to achieve infinite focus.

A note to those that use both Leica style rangefinders and Sony A7 cameras. I have tested today that the modifications to the ZM 28mm lens has a negative effect when using Leica M filter stack cameras. There appears to be no free lunch. The corners on my Leica M240 are worse with correction lens on.
So while the ZM 28mm lens can be adjusted with shim removals to get them to focus correctly on the rangefinder, the corners degrade with the planoconvex lens. This is opposite to the results with the correction lenses on with Sony cameras, where you see a noticeable boost in performance.

I've decided to bring my Zeiss 28mm back to how it originally was and use that in my Leica M240 (which I have rangefinder focus frames for) and leave my ZM 25mm Biogon modified with the Proxar lens on it, for dedicated use on my Sony A7Rii.

Equally, my Zeiss ZM 18mm will remain with the Proxar lens on, but I will use the Voigtlander 21mm Ultron in my Leica M240.

I guess this makes senses this would occur like this, as essentially the Proxar lenses are tweaking the incoming light to reduce astigmatism on a given sensor stack. A stack thicker then the Sony sensor like M4/3 would probably need a different correction lens then the Sony sensor would, for any given lens.

ceder wrote:
Many thanks candreyo for posting this!

I have a ZM 28/2.8 that cannot reach infinity on my M9 (@2.8, stopped down @5.6 it is OK), but perhaps removing a shim will help? Same procedure as in the video?

If you do any more videos, I would appreciate more light (the current one is very dark, cannot see).

Anyone tested what filter is best for the ZM 28/2.8? Corners are pretty bad on non-leica cameras...

Ta!

Dec 17, 2016 at 02:02 PM

wfrank
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p.14 #3 · p.14 #3 · Front-End Filter Improves Corner Smearing

MAubrey wrote:
I know the discussion has shifted to the ZM35, but I've just reread through the earlier pages and was wondering if their was a consensus on what the best option for the Contax G 28mm would be?

Is the G28+PCX1.5m Reversed the ideal?

Just found this thread and it looks like there is hope for the Contax G's below 35mm. Was there also a verdict what is best for the G21?

And am I correct that infinity focus is not affected as the G lenses are built to focus beyond anyway?

Thanks for these interesting findings HaruhikoT.

Dec 17, 2016 at 03:12 PM

GMPhotography
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p.14 #4 · p.14 #4 · Front-End Filter Improves Corner Smearing

Fred sent me a email on this for my ZM 35. I just put a order in I think. Waiting to pay for it. I have a TON of step ups and rings so I'll figure that part out

Dec 17, 2016 at 04:31 PM

Fred Miranda
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p.14 #5 · p.14 #5 · Front-End Filter Improves Corner Smearing

HaruhikoT wrote:
Fine day today with brilliant sunlight here in Japan, I went out to shoot with my new gear!
Here are my tested results of A7RII + Pixco LM-E adapter + ZM 1.4/35 + 5m PCX.

All shots are taken at wide open f1.4.
In-camera default jpeg.
5 different subjects focused at 2m, 4m, 6m, 10m and 300m approximately.
Uncropped jpeg files are available on my flickr.
https://www.flickr.com/photos/147672914@N02

Please check and judge by yourself whether this solution is worth or not

https://farm1.staticflickr.com/436/31324460100_149b865048_o_d.jpg
https://farm1.staticflickr.com/400/31324459580_388306dc79_o_d.jpg
https://farm1.staticflickr.com/570/31696925045_ed55bbe480_o_d.jpg
https://farm1.staticflickr.com/275/31696924525_af73d48a16_o_d.jpg
https://farm1.staticflickr.com/405/31696923775_96e11d6d9f_o_d.jpg

Haruhiko

Haruhiko,
This is candy to our eyes! Thanks for the samples and detailed explanation on how to build the filter.
From your corner crops we already know it works great even wide open. Were you able to run a simulation (filter/no filter) that confirms your real world results?

Thanks for this!
Fred

Dec 17, 2016 at 06:05 PM

GMPhotography
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p.14 #6 · p.14 #6 · Front-End Filter Improves Corner Smearing

Looks really good to me, Im in.

Dec 17, 2016 at 06:56 PM

Steve Spencer
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p.14 #7 · p.14 #7 · Front-End Filter Improves Corner Smearing

Fred Miranda wrote:
BTW: I wouldn't be able to get the 5m PCX filter before Jan. 15th. Their american distributer is only 15 miles from my house and he told me that he ordered one (from Japan) and should have it at their location after the 15th for pickup.
Fred,

Where can we get the 5m PCS in North America?

Dec 17, 2016 at 07:13 PM

Fred Miranda
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p.14 #8 · p.14 #8 · Front-End Filter Improves Corner Smearing

Steve Spencer wrote:
Fred,

Where can we get the 5m PCS in North America?

Your can order directly from OptoSigma America distributor.
The contact is Brad. Email him and he will process your order. Their office is only 20min. from my house. (Orange County, CA)

[email protected]

Dec 17, 2016 at 07:54 PM

Steve Spencer
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p.14 #9 · p.14 #9 · Front-End Filter Improves Corner Smearing

Fred Miranda wrote:
Your can order directly from OptoSigma America distributor.
The contact is Brad. Email him and he will process your order. Their office is only 20min. from my house. (Orange County, CA)

[email protected]

Thanks Fred.

Dec 17, 2016 at 08:29 PM

artur5
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p.14 #10 · p.14 #10 · Front-End Filter Improves Corner Smearing

wfrank wrote:
Just found this thread and it looks like there is hope for the Contax G's below 35mm. Was there also a verdict what is best for the G21?
And am I correct that infinity focus is not affected as the G lenses are built to focus beyond anyway?

Thanks for these interesting findings HaruhikoT.
Correct about Contax G lenses focusing beyond infinity. Even using a quite strong 1m. close up lens I had no difficulty reaching infinity with the G28. I think also that MAubrey is right about a PCX 1.5m being the best match for this lens and probably the G21 as well. I used ordinary 1m and 1.4m close-up lenses ( which aren't plano convex but meniscus) and the results were barely acceptable, really far away of what achieved HaruhikoT with a PCX lens

Dec 18, 2016 at 04:45 AM

HaruhikoT
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p.14 #11 · p.14 #11 · Front-End Filter Improves Corner Smearing

MAubrey wrote:
what the best option for the Contax G 28mm would be?
Is the G28+PCX1.5m Reversed the ideal?

Yes.

wfrank wrote:
Was there also a verdict what is best for the G21?
And am I correct that infinity focus is not affected as the G lenses are built to focus beyond anyway?

I use PCX1.5m Reversed for both G21 and G28 and feel satified with them.
Correct. At least my adapter can reach infinity.

Fred Miranda wrote:
Were you able to run a simulation (filter/no filter) that confirms your real world results?

Below shows MTFs using my current sim model.
The lower two unfamilliar graphs represent Through-Focus MTF (focus point vs. contrast).
Without filter, blue lines (mid corner) and green lines (extreme corner) give peak contrast at different focus points from that of purple lines (on-axis).
With PCX 5m, all peaks are in unison.
I think this well represents the improvement of field curvature.
Again please note zeiss datasheet gives very limited information about zm35d so this model is based on some hypothetical values that may not be accurate.


	https://farm1.staticflickr.com/400/31679219056_3c9bca2e6f_o_d.jpg

Dec 18, 2016 at 05:06 AM

rscheffler
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p.14 #12 · p.14 #12 · Front-End Filter Improves Corner Smearing

candreyo wrote:
A note to those that use both Leica style rangefinders and Sony A7 cameras. I have tested today that the modifications to the ZM 28mm lens has a negative effect when using Leica M filter stack cameras. There appears to be no free lunch. The corners on my Leica M240 are worse with correction lens on.
So while the ZM 28mm lens can be adjusted with shim removals to get them to focus correctly on the rangefinder, the corners degrade with the planoconvex lens. This is opposite to the results with the correction lenses on with Sony cameras, where you see...Show more →

Thanks for checking and reporting these details!

Dec 18, 2016 at 10:02 AM

Fred Miranda
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p.14 #13 · p.14 #13 · 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 →

Candreyo,
Were you able to narrow down which PCX lens would work best for the ZM 28/2.8?

According to @HaruhikoT , the G 28/2.8 seems to work best with a 1.5m (reversed) PCX filter. Have you tried this configuration with your ZM 28? They are both Biogon but have different optical designs. I can't find the exit pupil distance (mm) for the ZM.

Dec 18, 2016 at 11:44 AM

Fred Miranda
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p.14 #14 · p.14 #14 · Front-End Filter Improves Corner Smearing

HaruhikoT wrote:
Below shows MTFs using my current sim model.
The lower two unfamilliar graphs represent Through-Focus MTF (focus point vs. contrast).
Without filter, blue lines (mid corner) and green lines (extreme corner) give peak contrast at different focus points from that of purple lines (on-axis).
With PCX 5m, all peaks are in unison.
I think this well represents the improvement of field curvature.
Again please note zeiss datasheet gives very limited information about zm35d so this model is based on some hypothetical values that may not be accurate.

https://farm1.staticflickr.com/400/31679219056_3c9bca2e6f_o_d.jpg

Thanks for the simulation graphs! It's interesting that the MTF is improved everywhere at f/1.4, even in the center!
I guess the only downside would be a little bit more distortion when using the filter.

Dec 18, 2016 at 11:45 AM

candreyo
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p.14 #15 · p.14 #15 · Front-End Filter Improves Corner Smearing

Hi Fred,

I had to do trial and error with the ZM 28mm, as I was unable to program the lens using OSLO due to lack of technical data from Zeiss.

Fred Miranda wrote:
Candreyo,
Were you able to narrow down which PCX lens would work best for the ZM 28/2.8?

According to @HaruhikoT@@ , the G 28/2.8 seems to work best with a 1.5m (reversed) PCX filter. Have you tried this configuration with your ZM 28? They are both Biogon but have different optical designs. I can't find the exit pupil distance (mm) for the ZM.

Dec 18, 2016 at 01:16 PM

BastianK
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p.14 #16 · p.14 #16 · Front-End Filter Improves Corner Smearing

Fred Miranda wrote:
I guess the only downside would be a little bit more distortion when using the filter.
If necessary I will create a correction profile for Lightroom, have done that in the past a few times for lenses where none is available (like Tokina 17mm RMC 3.5).

Dec 18, 2016 at 01:19 PM

ceder
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p.14 #17 · p.14 #17 · Front-End Filter Improves Corner Smearing

Many thanks - I will give it a try! Will just get a spanner first

Dec 18, 2016 at 02:53 PM

Slingers
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p.14 #18 · p.14 #18 · Front-End Filter Improves Corner Smearing

Thanks for this solution. I posted some shots in the FE images thread with the G21 and the opto sigma 1.5m PCX. My method of attaching is a little different. I have a 55-52 step down ring then a Cokin P 52mm adapter which keeps the PCX lens in place. I previously chopped in half a cheap Cokin P holder and when using it on the G21 without problems I could attach an ND and CPL without vignetting.

Dec 18, 2016 at 03:56 PM

Fred Miranda
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p.14 #19 · p.14 #19 · Front-End Filter Improves Corner Smearing

candreyo wrote:
Hi Fred,

I had to do trial and error with the ZM 28mm, as I was unable to program the lens using OSLO due to lack of technical data from Zeiss.

Did you try the 1.5m PCX filter normal or reversed on the ZM 28?
@HaruhikoT@ wrote that it worked best for his G28/2.8 (in reverse orientation) but they probably have different exit pupil distances.

I see from earlier threads that you preferred the 1m Zeiss Proxar for the ZM 28 instead. Is that still the case? If so, how did you attach it to the lens?

Dec 18, 2016 at 04:18 PM

Slalom
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p.14 #20 · p.14 #20 · Front-End Filter Improves Corner Smearing

Slingers wrote:
Thanks for this solution. I posted some shots in the FE images thread with the G21 and the opto sigma 1.5m PCX. My method of attaching is a little different. I have a 55-52 step down ring then a Cokin P 52mm adapter which keeps the PCX lens in place. I previously chopped in half a cheap Cokin P holder and when using it on the G21 without problems I could attach an ND and CPL without vignetting.

Hi with the G21 which Mount are you using and did you have to Hack the rear as for Techart TA-GA3?

Dec 19, 2016 at 07:45 AM

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