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Archive 2016 · Front-End Filter Improves Corner Smearing

Fred Miranda
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p.83 #1 · p.83 #1 · Front-End Filter Improves Corner Smearing

sebboh wrote:
here's my infinity test of the cv 35/1.7 + 5m optosigma filter on the a9 against the same lens on the a9 with no filter and on my kolari UT a7 with no filter:
http://c1.staticflickr.com/5/4414/36940529750_58fa5030e2_o.jpg
full sized

seems like the pcx gives a 2-3 stop improvement in the corners over the stock a9, but the lens is as good at f/4 on the UT as it ever gets on the a9 even with the pcx filter.

Thanks for posting the test. The results are a bit disappointing to me. I am now wondering if the CV 35 will beat my Loxia 35 at f/8. I will find out on Friday.

Sep 20, 2017 at 12:10 AM

BastianK
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p.83 #2 · p.83 #2 · Front-End Filter Improves Corner Smearing

Fred Miranda wrote:
Thanks for posting the test. The results are a bit disappointing to me. I am now wondering if the CV 35 will beat my Loxia 35 at f/8. I will find out on Friday.

It's a draw at f/8.

Contrast may be oh so slightly higher on the Loxia, but I preferred a lens that is usable at f/1.7 (see https://www.flickr.com/photos/bastian_k/37327400185).

Sep 20, 2017 at 12:43 AM

genji
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p.83 #3 · p.83 #3 · Front-End Filter Improves Corner Smearing

KlausJH wrote:
What an amazing thread, now on page #83. Thanks to all contributors!
Here are my experiences:
I bought the ZM25 again. It was a great lens on my old NEX-5N but useless on the A7R. Now, with the PCX 2500 it is as good as it gets. OptoSigma is now very fast, at least from their European website. The SLB-50-5000PM arrived 7 days after the order, the SLB-50-2500PM came 10 days later.
I was not very happy with the step-up/step-down ring solution and found finally an optometrist with a CNC machine. He reduced the diameter of the lens to fit in an old...Show more →

Many thanks for this tip. I spoke to my optometrist today and he can arrange for the diameter of my SLB-50-1500PM to be reduced to fit in a UV filter ring.

Sep 20, 2017 at 01:31 AM

sebboh
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p.83 #4 · p.83 #4 · Front-End Filter Improves Corner Smearing

Fred Miranda wrote:
Thanks for posting the test. The results are a bit disappointing to me. I am now wondering if the CV 35 will beat my Loxia 35 at f/8. I will find out on Friday.

performance will actually look better if you focus a bit before infinity i suspect. my guess is that the pcx filter isn't quite fully correcting the field curvature.

Sep 20, 2017 at 01:38 AM

DavidBM
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p.83 #5 · p.83 #5 · Front-End Filter Improves Corner Smearing

genji wrote:
Many thanks for this tip. I spoke to my optometrist today and he can arrange for the diameter of my SLB-50-1500PM to be reduced to fit in a UV filter ring.

Whoah! This transforms my sense of how Heath-Robinson the front filter solution is! Maybe a ZM 2.8/25 may be in the future of my hiking kit. I know people have done this but my optometrist giggled. Maybe I need to switch. Who is yours, Jonathan?

Sep 20, 2017 at 01:57 AM

pavgfromparis
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p.83 #6 · p.83 #6 · Front-End Filter Improves Corner Smearing

genji wrote:
Many thanks for this tip. I spoke to my optometrist today and he can arrange for the diameter of my SLB-50-1500PM to be reduced to fit in a UV filter ring.

It is still possible to make a customized coating directly on the anti-reflex SLB, so you wont need anymore any UV filter ring. (and we could arrange your diameter issue)

Its is not something that we do as standard , but as the SLB product line dont need a lot ressources to be modified, we can decrease the unitary price for custom products with only some parts (2-3 are enough to have a 30% discount).

Maybe if you can explain what specification you are looking for, one of our engineer could create a fully customized lens for you, photographers.

You can write an email to Ali ( [email protected] ) I'm sure that he can help you.

Paul from OptoSigma Europe

Sep 20, 2017 at 03:32 AM

KlausJH
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p.83 #7 · p.83 #7 · Front-End Filter Improves Corner Smearing

Sep 20, 2017 at 03:36 AM

genji
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p.83 #8 · p.83 #8 · Front-End Filter Improves Corner Smearing

DavidBM wrote:
Whoah! This transforms my sense of how Heath-Robinson the front filter solution is! Maybe a ZM 2.8/25 may be in the future of my hiking kit. I know people have done this but my optometrist giggled. Maybe I need to switch. Who is yours, Jonathan?

Mark Falkenstein (Abel, Robson & Falkenstein) at Forestville. There are optometrists galore in Newtown so the fact that I'm willing to traipse out to Forestville indicates how highly I regard him.

I needed to have new distance varifocals so I took my A7RII bodies, one with the Biogon G 28/2.8, the other with the Yashinon DX 45/1.4 frankenlens (because I knew he'd get a kick out of seeing it). I explained the front-end filter solution and he got it immediately. His practice used to have a CNC machine so he was familiar with what needed to be done and said he would arrange with one of his suppliers to have it done for me.

He also measured me up for a pair of bifocals that will allow me to use the A7RII comfortably at waist level (the distance varifocals don't quite cut it).

However, the message from Paul from OptoSigma Europe is also intriguing except that I suspect OptoSigma Europe might only sell to customers within the European Union (given the extent to which OptoSigma supports its local distributors).

Sep 20, 2017 at 06:55 AM

pavgfromparis
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p.83 #9 · p.83 #9 · Front-End Filter Improves Corner Smearing

Actually, you're partially right : OptoSigma is a brand from the 'Sigma Koki' japanese group. We produce everything in Japan, and we sells via local distributors, or directly via our Website. But as our American, and Asian version of the website is still under development (release in late October for USA, and later for Asia), for now, only Europeans can pay online by card and benefits small shipments.

But as we are not a reseller brand, but an hard producer, each of our 3 branches (located in Japan, California, and France) is able to design new products. So if you need a custom design, we can make it in Europe, send the specs to Japanese guys and ask American guys to care the billing & shipment. Its a bit complicated for now but we are working hard to benefits everyone the european "lab".

I have been enjoying reading your tests for some time, so I can take care of your requests and make a phone call to the US staff when your product concept is ready.

Edited on Sep 20, 2017 at 10:23 AM · View previous versions

Sep 20, 2017 at 07:55 AM

Fred Miranda
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p.83 #10 · p.83 #10 · Front-End Filter Improves Corner Smearing

BastianK wrote:
It's a draw at f/8.

Contrast may be oh so slightly higher on the Loxia, but I preferred a lens that is usable at f/1.7 (see https://www.flickr.com/photos/bastian_k/37327400185).

Lovely Bastian.
Do you remember Haruhiko posted simulation charts for this lens using a 5m front-lens?

Sep 20, 2017 at 09:16 AM

Fred Miranda
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p.83 #11 · p.83 #11 · Front-End Filter Improves Corner Smearing

sebboh wrote:
performance will actually look better if you focus a bit before infinity i suspect. my guess is that the pcx filter isn't quite fully correcting the field curvature.

I don't think the PCX filter would completely correct FC. Even native lenses (Loxia 21, 35) have moderate FC. I will test focusing a different distances when I get it. Thanks!

Sep 20, 2017 at 09:19 AM

sebboh
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p.83 #12 · p.83 #12 · Front-End Filter Improves Corner Smearing

Fred Miranda wrote:
I don't think the PCX filter would completely correct FC. Even native lenses (Loxia 21, 35) have moderate FC. I will test focusing a different distances when I get it. Thanks!

yeah, those are compromises that i'm not sure the reason for (size constraints or allowing for different stack thicknesses?). neither the vc nor the zm seem to have any real FC on my kolari UT or the m9.

Sep 20, 2017 at 10:35 AM

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p.83 #13 · p.83 #13 · Front-End Filter Improves Corner Smearing

Maknof wrote:
Someone tried a filter in CV 28/2?
Suggestion? Infinity focus?

It was discussed earlier in the thread but I don't think anyone tried it. From what HaruhikoT wrote:

HaruhikoT wrote:
As hiepphotog wrote, I also think focal length and exit pupil distance of the primary lens should define optimal focal length of the P-C filter.

At perfect lens, focal length = exit pupil distance.
My simulation results will be accurate in this condition.

Assuming a "perfect lens" the main variable would be the focal length. I'm thinking of picking up the plano-convex filters for the Contax G21 and G28 and putting them on the VC 21/1.8 and VC 28/2 to see if they will improve the edge performance. But its a bit of an investment without some confirmation that these should work.

Sep 20, 2017 at 10:41 AM

GMPhotography
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p.83 #14 · p.83 #14 · Front-End Filter Improves Corner Smearing

The CV 28mm F2 does not have any shims for adjustment( I tore one down). It will have to come from the adapter. I gave up on it since i did not have a adapter to get me infinity

Sep 20, 2017 at 11:19 AM

GMPhotography
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p.83 #15 · p.83 #15 · Front-End Filter Improves Corner Smearing

CV 35mm I have on hand with the filter looks really good. Will update the Big Bronco three. I have a surprise too.

Sep 20, 2017 at 11:20 AM

Makten
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p.83 #16 · p.83 #16 · Front-End Filter Improves Corner Smearing

sychan wrote:
Assuming a "perfect lens" the main variable would be the focal length.

I'm only guessing out of curiosity, but wouldn't a "perfect lens" then be a 100% symmetrical lens?

Sep 20, 2017 at 12:29 PM

Fred Miranda
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p.83 #17 · p.83 #17 · Front-End Filter Improves Corner Smearing

Makten wrote:
I'm only guessing out of curiosity, but wouldn't a "perfect lens" then be a 100% symmetrical lens?

There are not many of those, but some of the Biogons seems kind of close.

---------

On the Loxia 35/2 FC, it's really awkward. I can barely see it at close distance, but at ~2-4 meters it's kind of flat from the borders to 1/3 in, and then makes a sudden "dome" jump to further distance in the middle. You can clearly see the background being much sharper in dead middle at that distance, even stopped down to f/4 or so.
I even...Show more →

Same for Loxia 21/2.8. FC less apparent at closer distances.

I find the Loxia 35/2 FC awkward as well. Corners need to be focused further than center way BUT after F/4, they look better when the image if focused at center!...That's not the behavior of the Loxia 21 where the corners look perfect at hard stop and remain great as we stop down the lens...On my Loxia 35, I can get perfect infinity focus, (best center, mid and corners) by positioning the focusing ring right at the middle of the infinity symbol's first circle.

Sep 20, 2017 at 12:38 PM

BastianK
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p.83 #18 · p.83 #18 · Front-End Filter Improves Corner Smearing

Fred Miranda wrote:
Lovely Bastian.
Do you remember Haruhiko posted simulation charts for this lens using a 5m front-lens?
To my knowledge he never did because of missing lens data.
But he managed to create a pretty much perfect simulation of the ZM 35mm 1.4 which exactly matches what I was seeing (midzone dip, worse midzone dip with 5m filter).

Sep 20, 2017 at 12:42 PM

Fred Miranda
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p.83 #19 · p.83 #19 · Front-End Filter Improves Corner Smearing

BastianK wrote:
To my knowledge he never did because of missing lens data.
But he managed to create a pretty much perfect simulation of the ZM 35mm 1.4 which exactly matches what I was seeing (midzone dip, worse midzone dip with 5m filter).

Perhaps we could send him a picture like this (link) showing the CV 35/1.7 Ultron, so he can estimate the exit pupil diameter and perhaps confirm that 5m is the best PCX for this lens.

https://www.fredmiranda.com/forum/topic/1453834/2#13757285

Update: I got my 35/1.7 today and did that.

Sep 20, 2017 at 12:45 PM

jhinkey
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p.83 #20 · p.83 #20 · Front-End Filter Improves Corner Smearing

Well, now for me it's a decision between the 35/1.4 Zeiss+5m or 35/1.7 CV + 5m.
I like the Zeiss mechanics and the faster aperture, but the CV is significantly smaller and lighter and cheaper.

Sep 21, 2017 at 06:18 PM

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