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Archive 2016 · Front-End Filter Improves Corner Smearing

  
 
Fred Miranda
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p.59 #1 · p.59 #1 · Front-End Filter Improves Corner Smearing


polylepis wrote:
I combed back through the thread and found pictures of the multi-colored rear shims on the ZM35 under the chrome bayonet. Removing the bayonet on my ZM25, there were no shims there at all! I had been manipulating the internal, small brass shims to try for infinity with the +1 diopter without success. Is there another location for the shims you mentioned that I can't find?


The ZM 18, 25 and 28 have internal shims and a few of them must be removed in order to achieve infinity using a PCX lens.

Here is a quick video showing how to do it:
https://www.fredmiranda.com/forum/topic/1453834/11#13839430



Mar 03, 2017 at 10:45 PM
GMPhotography
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p.59 #2 · p.59 #2 · Front-End Filter Improves Corner Smearing


Yes there are shims in the rear element plus if you pull the lens from the casing there are front shims as well. I have a combination of both areas removed. I posted this awhile back in the thread.

Just remember the front shims have a notch in them to remove away from a tab inside. You need a spanner wrench to remove the big nut around the rear element. Each lens maybe slightly different so you have to do trial and error until you can hit infinity at the hard stop. It sounds complicated but it's rear not. Just don't touch anything else but the rear element removal, the shroud around it and just the shims. There are no screws or anything you need to touch so don't. Lol

Fred was posting at the same time. The video is pretty accurate for the front shims the rear ones are obvious to see

ZM 25

Edited on Mar 03, 2017 at 10:57 PM · View previous versions



Mar 03, 2017 at 10:52 PM
teeraash
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p.59 #3 · p.59 #3 · Front-End Filter Improves Corner Smearing


http://Screenshot 2017-03-04 10.48.36.jpg by Teera Ashakul, on Flickr


From the diagram above, the curve side should be facing the camera. If it is facing subject then it is reversed. I don't know how this lens is oriented on my camera. Just choose the one that is sharper and has more contrast. It is even more difficult to identify the curve side once you grounded it. Perhaps I should try Fred's method or navmannz's rocking method to identify it.



Mar 03, 2017 at 10:54 PM
Fred Miranda
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p.59 #4 · p.59 #4 · Front-End Filter Improves Corner Smearing


HaruhikoT wrote:
Hi John, Rob and Fred,

Regarding that 35mm + PCX 5m, orientation of the corrective lens made no visible difference in my simulated MTFs. No difference in infinity focus position, too.
Something that my simulation doesn't take into account may cause John's experimental results but I'm not sure.
Curious about how does the difference looks like. Comparison images would be appreciated.

Haruhiko


I will test this out over the weekend and post the results.



Mar 03, 2017 at 11:14 PM
polylepis
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p.59 #5 · p.59 #5 · Front-End Filter Improves Corner Smearing


GMPhotography wrote:
Yes there are shims in the rear element plus if you pull the lens from the casing there are front shims as well. I have a combination of both areas removed. I posted this awhile back in the thread.

Just remember the front shims have a notch in them to remove away from a tab inside. You need a spanner wrench to remove the big nut around the rear element. Each lens maybe slightly different so you have to do trial and error until you can hit infinity at the hard stop. It sounds complicated but it's rear not. Just
...Show more

Yes, the front shims or "internal shims" (notched) shown in the video did allow me to get to infinity with a PCX front lens. But Guy, I just can't locate the other set of shims you mention that let you adjust for the Hoya +1. Where exactly are they? Not under the chrome bayonet 'cause I looked. Does it entail removing the front lens element for access?



Mar 03, 2017 at 11:23 PM
GMPhotography
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p.59 #6 · p.59 #6 · Front-End Filter Improves Corner Smearing


It's funny it's a lens element that unscrews it's the very rear of the lens it's about 3/4 of a inch long. Look real carefully you will see the break and those are the shims. I missed it at first blush myself. Take the shroud off but it's the element at the very last one towards the rear. Hint if you took the rear cap off and placed it on a table that's the element. I think there are 4 shims there they are smaller than the front. Size of a nickel let's say


Mar 03, 2017 at 11:51 PM
polylepis
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p.59 #7 · p.59 #7 · Front-End Filter Improves Corner Smearing


Found it! (after multiple blushes) Thanks so much. Did you use some padded pliers to remove that element?
I'll do this tomorrow and post pictures.



Mar 04, 2017 at 12:04 AM
robgo2
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p.59 #8 · p.59 #8 · Front-End Filter Improves Corner Smearing


Fred Miranda wrote:
You can't shave the front metal section of the adapter. That thickness is needed to securely mount the adapter in place and making it thinner will create mounting issues. (it may get wobbly)

It's not easy to make an adapter thinner. You need to remove the front end metal and shave the area where it sits on. Ask your shop if that's is possible for them to do that.


Fred,

They tried but could not get the screws loose. Those babies are really locked tight. I did not realize that removing such a small depth would cause a significant laxity in the mount. Fortunately, all that I lost in the process was a cheap adapter.

Rob


Edited on Mar 04, 2017 at 12:15 AM · View previous versions



Mar 04, 2017 at 12:08 AM
GMPhotography
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p.59 #9 · p.59 #9 · Front-End Filter Improves Corner Smearing


polylepis wrote:
Found it! (after multiple blushes) Thanks so much. Did you use some padded pliers to remove that element?
I'll do this tomorrow and post pictures.


No just by hand. It's on a little tight but hand pressure should do it.



Mar 04, 2017 at 12:15 AM
artur5
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p.59 #10 · p.59 #10 · Front-End Filter Improves Corner Smearing


Fred Miranda wrote:
You can't shave the front metal section of the adapter. That thickness is needed to securely mount the adapter in place and making it thinner will create mounting issues. (it may get wobbly)
It's not easy to make an adapter thinner. You need to remove the front end metal and shave the area where it sits on. Ask your shop if that's is possible for them to do that.


That depends a lot on how the adapter is built. There're ways to retighten the fit after shaving the front plate, if we don't exceed 0.2-0.3mm. On some models, it can be done enlarging those wedges made in the cams of the adapter that press the rear of the lens against the camera mount. Other adapters employ a leaf spring system to perform the same task. The springs allow for some leeway in the thickness of the front plate before the lens starts to wobble. The best brands have more margin than cheapish units with weaker springs.
In order to use it with a front filter modded Zeiss M lens, I bought recently a Pixco adapter that uses the leaf spring system. I grinded it about 0.2-0.25mm. and there's no difference in the lens fit after the mod. No wobble at all.
Of course, instead of modifying the adapter, it's better to remove lens shims but sometimes this is very difficult or impossible.



Edited on Mar 04, 2017 at 12:42 PM · View previous versions



Mar 04, 2017 at 05:27 AM
Samuli Vahonen
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p.59 #11 · p.59 #11 · Front-End Filter Improves Corner Smearing


As the OptoSigma delivery times are so long, I needed other way to participate this thread Local store had used ZM25, so I exchanged it to 150-500 lens, which I never used (gigantic size and AF didn't work with A7 and was crappy with 5DmkII).

Copy paste from my wiki page (if it does not show up properly here, check from the wiki):
https://vahonen.info/secure/wiki/index.php/Sony_A7_-_Thick_filter_stack_issues#Carl_Zeiss_Biogon_T.2A_2.8.2F25_ZM





Carl Zeiss Biogon T* 2.8/25 ZM
25mm Biogon has so steep ray angle to sensor that it does not work even with thin filter stack modified cameras. Therefore only possible way to use the lens is using front filter method.

Filter stack
1. ZM25 lens
2. 46mm - 55mm step up ring
3. Empty (=glass removed) Contax 55mm UV filter
4. Proxar 1.0m lens
5. Leica Elpro 3 retention ring

Image: Top view
Image: Side view

Shim removal
Image #1

Image #2

1. Remove ring from rear of the lens indicated by blue arrow in image #1
2. Lift the rear outer part of the lens (image #2 top left corner)
3. Remove shims - top of the image #2, make sure you rotate the "holes" in rings so that they can go over the skrew
4. Reverse the process

My shims were 0.71mm total thickness, and them removed lens focuses little over infinity with 1.0m Proxar. With the shims it did focus ~1.5m distance or less.

On forum some people needed additional shims removed. See Guy's posts p59 #2 and p59 #6. Personally I would not touch these as they are having effect to how rear lens group positions compared to front lens group => this is not just focus adjustment. This is done by removing rear protection ring (image #1 red arrow), and then removing the shims. According to Guy it should come off by rotating it by hand - mine doesn't rotate by hand, something stronger would be needed to open it.

Vignetting
With the above mentioned filter stack there is almost no mechanical vignetting. However it seems that with this setup it's impossible to use any filters. Below are four pictures shoot at f/8, shooting 0.5m focus and infinity focus.

First two are with filter stack explained above in chapter "Filter stack":
Infinity:

0.5m:


Next two are with additional 55mm - 82mm step up ring, which is needed if I want to use polarizer- or ND-filter with the lens. As can be seen there is mechanical vignettin already at 0.5m focus distance, and at infinity it gets really bad:
Infinity:

0.5m:


Image quality
Like seen in many examples in forum the infinity performance is very good with this solution.


However boke issues are NOT fully fixed by Proxar f=1m filter. The corners get weirdly in focus and there are remains of astigmatism. This can be caused either by Proxar just not being good for for this purpose, or we should not use edges of proxar filter - or the mechanical vignetting is causing the boke issues (not astigmatism). One possibility is that close focus distances require different correction - I asked this from HaruhikoT and he said simulation should be valid for all distances (on lenses not having floating elements).

This should not be understood wrong; lens is useful and better than many other lenses - boke just does not reach same quality which can be seen from slides shoot with this lens. I'll put here detailed examples IF the final conclusion is that front filter can only help @ infinity. Here are some random shots linked to show the remaining issues on boke :

Field curvature in top corners (f/2.8)
Field curvature makes right side of the island much more defined
At minimum focus distance it was hard to detect, or not at all visible

Conclusion and next steps
Image quality @ infinity is OK with Proxar f=1m filter. One of the best lenses I have seen at this focal length @ f/5.6. However as I use filters (polarizer or ND) when shooting landscapes this solution is not going to work very well. Boke has issues and need to test if other front filter solutions or front filter + Kolari combination provides solution.

TODO:

  1. DONE: Order Hoya +1 HMC lens, but in larger sizes (58mm and 67mm) to avoid the mechanical vignetting.
  2. Test Hoya +1 filter for boke and vignetting
  3. Experiment with OptoSigma Plano Convex lenses (1500mm reversed? or 3000mm with A7 Kolari modified cameras)




Mar 04, 2017 at 07:13 AM
GMPhotography
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p.59 #12 · p.59 #12 · Front-End Filter Improves Corner Smearing


I'm wondering if your ELPro retaining ring is too thick. I have 46-55 and a thin empty 55 with retaining ring built in it . I'll get a link to that up. I actually think I can add a CPL with it. I just don't have anything in 55 to try. I'll take a shot of my setup and I'm going to count how many shims are removed as well, I hit infinity right at the hard stop with a Fotosy adapter. I have my Hawk on my ZM 35 and another Fotosy on my ZM 85. These cheap adapters from Amazon are actually quite nice. So all three lenses have a adapter so I don't have to carry the Zeiss M rear caps with me. So everything is FE caps. Love this. I hate caps to begin with.


Mar 04, 2017 at 08:10 AM
artur5
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p.59 #13 · p.59 #13 · Front-End Filter Improves Corner Smearing


Great post, Samuli. A perfect tutorial for people wanting to use the ZM25 with a Front filter.
Now I wish I hadn't taken the trouble to grind my adapter because, if all these shims stacked are 0.71mm, according to theory that's enough for reaching infinity with a +1 front element and any adapter that focuses normally up to infinity or a bit past it.
I believe that the most convenient setup for using the ZM25 without additional filters is what Guy did: get a 46mm +1 Hoya HMC close up filter..Remove the glass from the mount (it's too thick and vignettes a bit with a 25mm lens). Relocate the glass to an empty ring from another 46mm. filter (UV or similar. Those come in thin mounts that won't vignette.). If possible, use a filter with a retaining ring system, as they're easy to remove and reinstall.
This way you can use the original hood on the lens. Step-up rings will not allow that, except maybe a 46-49



Mar 04, 2017 at 08:50 AM
GMPhotography
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p.59 #14 · p.59 #14 · Front-End Filter Improves Corner Smearing


I need to retest my Hoya versus the Proxar as I found my Proxar off center so I may do that tomorrow. They are very close though. I'm heading into my office now maybe I can summarize both options. The Hoya I'm able to use the hood the Proxar I can't . I took the Hoya to NY to shoot and it did well. I'm back to painting my perimeter wall around my house. Love paint sprayers they are therapeutic. Lol

Waiting for sun so I'll run in and take some quick shots of my setups



Mar 04, 2017 at 09:09 AM
GMPhotography
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p.59 #15 · p.59 #15 · Front-End Filter Improves Corner Smearing


Okay first things first Shims. . Taken out of the front 2 Gold and 1 Bronze. I believe I have a silver in the front. On the rear i took out the Bronze left the rest in there. ZM 25







Mar 04, 2017 at 09:27 AM
GMPhotography
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p.59 #16 · p.59 #16 · Front-End Filter Improves Corner Smearing


Proxar +1 here is my setup. A 46-55 Fotiox normal size than a Slim 55mm from amazon. Getting link

https://www.amazon.com/gp/product/B00HW71ZYE/ref=oh_aui_detailpage_o09_s01?ie=UTF8&psc=1

This has a built in retaining ring. So break the glass with a hammer use needle nose pliers pull all the glass out remove the rear retaining ring, it just pays out. Your left with a 55mm that has a built in retaining ring, so Put proxar on 46-55 than center and put this slim ring on and it will hold the Proxar down. Thats it and you still have plenty of thread for a filter or a step up for filters. I need a 55mm filter to try

















Mar 04, 2017 at 09:35 AM
GMPhotography
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p.59 #17 · p.59 #17 · Front-End Filter Improves Corner Smearing


Hoya +1 just needed a basic 46mm UV with retaining ring. I used a Tiffen UV 46mm

https://www.amazon.com/gp/product/B00004ZCJE/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1



Mar 04, 2017 at 09:38 AM
GMPhotography
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p.59 #18 · p.59 #18 · Front-End Filter Improves Corner Smearing


Way OFF topic. Check this out a Really Right Stuff B-H 25 head and a RRS Micro clamp

http://www.reallyrightstuff.com/BH-25-Ballhead?custcol19=2

https://www.bhphotovideo.com/c/product/1301208-REG/really_right_stuff_multi_clamp_no_adapters_versatile_clamp_for_mounting.html

Plus I got a table pod

https://www.bhphotovideo.com/c/product/1317756-REG/really_right_stuff_13720_tfa_01_ultra_pocket_pod.html







Mar 04, 2017 at 09:46 AM
Sr.Cordeiro
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p.59 #19 · p.59 #19 · Front-End Filter Improves Corner Smearing


I have a Voigtlander Ultron 28mm f/2 that I would really like to use on my X-Pro2 for the manual shooting experience, but in the end it all comes to the final images and the blured corners constantly make me hesitate on using the lens more. Did anyone found a good (and preferably cheap) screw lens for this Voigtlander?

(PS: Didn't check this thread for a while, and man, how this have grow, 59 pages!)



Mar 04, 2017 at 09:55 AM
polylepis
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p.59 #20 · p.59 #20 · Front-End Filter Improves Corner Smearing


Effusive thanks Samuli for addressing most of my basic questions about modding the ZM25. It is just so helpful to have this information collected in one place. 24-28 is my preferred FL for landscapes and an excellent, compact lens has been elusive for use on the Sonys. The many knowledgeable contributors on this thread have really moved this discussion forward. Hats off to everyone!


Mar 04, 2017 at 10:56 AM
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