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Archive 2016 · Front-End Filter Improves Corner Smearing

candreyo
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p.19 #1 · p.19 #1 · Front-End Filter Improves Corner Smearing

Hi Ron,

The ZM 85mm Sonnar is problem free optically, but my copy of the lens has the infamous Zeiss wobble. It's been to Zeiss in Germany twice to fix this, and still it has returned for me. Zeiss charged me over 1000 euros to fix the first time, and I don't want to pay again another charge to get it right.
If I could open it up, I may be able to tighten down whatever keeps comming loose, and fix the wobble. But for the better part of me (and I'm a Opto-Mechanical Deisgn Engineer), I can't seem to open it up.😫
Possibly why this lens was assembled in Germany and not by Cosina Japan, and why it costs so much to fix the first time, I suspect it's a very complicated process with probably some special tools and jigs needed.

rscheffler wrote:
IMO the ZM28 is kind of an odd lens in that it's not a super technical performer. Odd because most often this is not what one expects out of the box from Zeiss, unless it's something like the 50/1.5 Sonnar. It's possible they considered it more of a character/reportage lens and left the technical heavy lifting for the 25?

One would expect the ZM85/2 to be rather problem-free on the Sony cameras... or have you found otherwise? In any case, it's a relatively rare lens and not inexpensive. Having briefly shot with one, I loved its rendering, if not its propensity...Show more →

Dec 26, 2016 at 05:31 AM

candreyo
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p.19 #2 · p.19 #2 · Front-End Filter Improves Corner Smearing

Hi Fred,

Yes, I see a similar improvement with the ZM 28mm lens aswell. 😁
Though, as others have mentioned, the 25mm ZM when it was released had some of the highest MTFs for a lens of that focal length.

I will try and get photos of the 28mm and 18mm ZM soon.

Fred Miranda wrote:
BTW: I checked the full size images. At f/2.8 and infinity distance there is a very big improvement in the corners and mid-zone with the Proxar. Even at f/8, there is a noticeable improvement towards the corners. Very impressive!
I noticed a small hit in contrast in the center area but that can be mitigated in post. The Proxar 1m makes the ZM 25 very strong on the A7RII.

Do you see similar improvement with the ZM 28 + 1.5m PC?

Dec 26, 2016 at 05:40 AM

candreyo
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p.19 #3 · p.19 #3 · Front-End Filter Improves Corner Smearing

Some quick ZM 28mm tests with and without the 1500mm Planoconvex lens:

http://www.andreyophoto.co.uk/Lens-Reviews/Zeiss-28mm-f28-Biogon-ZM/ZM28mm-1500mm-Planoconvex/

I have done a flare test as well, Shooting into the sun.
There is a tad more glaring with the 1500mm Planoconvex lens, whether this is an acceptable trade off, I will let each of you decide.

Again, there seems to be a very small loss in effective focal length, though it is much less then the ZM18mm and 25mm lenses. I'd estimate the 28mm lens with 1500mm Planoconvex becomes maybe a 28.5mm lens.

Dec 26, 2016 at 07:55 AM

HaruhikoT
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p.19 #4 · p.19 #4 · Front-End Filter Improves Corner Smearing

The image at wide open show some halo around the subjects on corner but still having lots of detail. I like this kind of rendition, though perhaps this is not exactly the same as Zeiss originally designed. Astigmatism seems to be very well controlled. Great work

! Thank you.

candreyo wrote:
Some quick ZM 28mm tests with and without the 1500mm Planoconvex lens:

http://www.andreyophoto.co.uk/Lens-Reviews/Zeiss-28mm-f28-Biogon-ZM/ZM28mm-1500mm-Planoconvex/

I have done a flare test as well, Shooting into the sun.
There is a tad more glaring with the 1500mm Planoconvex lens, whether this is an acceptable trade off, I will let each of you decide.

Again, there seems to be a very small loss in effective focal length, though it is much less then the ZM18mm and 25mm lenses. I'd estimate the 28mm lens with 1500mm Planoconvex becomes maybe a 28.5mm lens.

Dec 26, 2016 at 08:57 AM

GMPhotography
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p.19 #5 · p.19 #5 · Front-End Filter Improves Corner Smearing

I'm actually thinking of the ZM 25. Having 12, 18 soon, Zm35 it just gaps better for me.

Dec 26, 2016 at 09:43 AM

candreyo
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p.19 #6 · p.19 #6 · Front-End Filter Improves Corner Smearing

I have added more photos to both the 25mm and 28mm pages.
These were from a park I went to this afternoon, and are as near infinity I can do at the moment.

Dec 26, 2016 at 10:57 AM

Fred Miranda
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p.19 #7 · p.19 #7 · Front-End Filter Improves Corner Smearing

candreyo wrote:
Some quick ZM 28mm tests with and without the 1500mm Planoconvex lens:

http://www.andreyophoto.co.uk/Lens-Reviews/Zeiss-28mm-f28-Biogon-ZM/ZM28mm-1500mm-Planoconvex/

I have done a flare test as well, Shooting into the sun.
There is a tad more glaring with the 1500mm Planoconvex lens, whether this is an acceptable trade off, I will let each of you decide.

Again, there seems to be a very small loss in effective focal length, though it is much less then the ZM18mm and 25mm lenses. I'd estimate the 28mm lens with 1500mm Planoconvex becomes maybe a 28.5mm lens.

candreyo,
I just checked the tests with the houses. (test 1)
Huge improvement at f/2.8. Just as impressive as the ZM 25 samples you posted.

However, at f/8, the corners look worse with PCX filter on. (Only on the left side of the frame).
Something seems to be tilted: Either the lens itself or the 1.5m PC on your filter stack.

Edit: That does not happen with your infinity test (test 2), which looks noticeably better even at f/8 with the PC filter at both corners. I'm not sure what happened with test 1.

Dec 26, 2016 at 12:38 PM

candreyo
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p.19 #8 · p.19 #8 · Front-End Filter Improves Corner Smearing

Hi Fred,

Do you know which one looks off, from top of the page down?
Is it the f8 one with Proxar installed, near infinity, or the flare test one?

I wonder if I had the Proxar mis threaded one instance, causing a tilt off its central axis? I was removing and installing it over and over throughout the day.

Fred Miranda wrote:
candreyo,
I just checked the tests with the houses. (test 1)
Huge improvement at f/2.8. Just as impressive as the ZM 25 samples you posted.

However, at f/8, the corners look worse with PCX filter on. (Only on the left side of the frame).
Something seems to be tilted: Either the lens itself or the 1.5m PC on your filter stack.

PS: That does not happen with your infinity test (test 2), which looks noticeably better even at f/8 with the PC filter at both corners.

Dec 26, 2016 at 12:57 PM

Fred Miranda
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p.19 #9 · p.19 #9 · Front-End Filter Improves Corner Smearing

candreyo wrote:
Hi Fred,

I jjust checked the house ones, and on the ones with the Proxar on, the right side of the images are typically sharper, just as with the left side.
Do you know which one looks off, from top of the page down?

I wonder if I had the Proxar tilted on a shot, as I was removing and installing it over and over?

Here are crops at 1:1

Left crop: Without the filter at f/8
Right crop: With the filter at f8

This only happens on the left side of the frame though.

Without the filter | With the filter

Dec 26, 2016 at 01:03 PM

candreyo
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p.19 #10 · p.19 #10 · Front-End Filter Improves Corner Smearing

Thanks Fred.

I suspect I may have had the Proxar titled slightly somehow.

I'll need to check the filter stack and see if it's off axis at all.

Fred Miranda wrote:
Here are crops at 1:1

Left crop: Without the filter at f/8
Right crop: With the filter at f8

Dec 26, 2016 at 01:07 PM

Fred Miranda
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p.19 #11 · p.19 #11 · Front-End Filter Improves Corner Smearing

candreyo wrote:
Thanks Fred.

I suspect I may have had the Proxar titled slightly somehow.

I'll need to check the filter stack and see if it's off axis at all.

I got the Proxar 1m lens out of its metal casing today and wanted to test with my ZM 28/2.8.

I wonder how you were able to focus at infinity. I can't focus pass 2 meters with the filter attached and I have already removed 2 shims from the lens...Something is odd here.

Dec 26, 2016 at 03:11 PM

GMPhotography
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p.19 #12 · p.19 #12 · Front-End Filter Improves Corner Smearing

Quick question. On the ZM 28 and ZM 25 is there any color smearing going on. I don't think anyone has mentioned it so though I would ask.

Dec 26, 2016 at 05:03 PM

Fred Miranda
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p.19 #13 · p.19 #13 · Front-End Filter Improves Corner Smearing

Fred Miranda wrote:
I got the Proxar 1m lens out of its metal casing today and wanted to test with my ZM 28/2.8.

I wonder how you were able to focus at infinity. I can't focus pass 2 meters with the filter attached and I have already removed 2 shims from the lens...Something is odd here.

Update: I removed 2 more internal shims (total 4) and the lens still can't focus at infinity. (almost though)
There are no shims left to remove and I'm already using my Hawks adapter. The lens without the 1m filter is focusing at infinity at the 1.2 meter mark now.

I tried my other 2 adapters none of them let's me reach infinity focus with the ZM 28/2.8 with all shims removed (4) + Proxar 1m lens... :-(

Dec 26, 2016 at 06:30 PM

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

Hi Fred,

I'm not sure why you aren't able to reach infinity? I only needed to remove 2 shims, and then was able to reach infinity using TAP as the adapter.

Maybe there is a buildup of tolerances in the lens assembly, which the shims are used to calibrate out, and some lenses are more forgiving then others.

It's night here right now, but let me examine my ZM 28mm tommrow and see if there is anything else on the lens that can be adjusted to bring the ability to reach infinity in.

Edit:
I just realised you are trying to use the 1m Proxar on the ZM 28mm..
This may have something to do with it, as I'm using the 1500mm Planoconvex on the ZM 28mm.
The 1m Proxar does work some, but not as good as the 1500mm lens.
When I tested 1500mm vs 1m lenses to find out which worked better on the ZM 28mm, I did so in a city environment, meaning infinity was not checked. Best I could do was distance to my property fence or garage at the time.

This is why I went to the park today, to get some near infinity photos with the the correction lenses on the ZM's, but I didn't think to swap correction lenses (i.e. Put the 1m on the 28mm ZM, and vice versa) as had already determined which worked best for each lens prior.

I will put the 1m Proxar lens on my 28mm ZM tommrow and see if I can reach infinity, and report back.

Cheers,
Candreyo

Fred Miranda wrote:
Update: I removed 2 more internal shims (total 4) and the lens still can't focus at infinity. (almost though)
There are no shims left to remove and I'm already using my Hawks adapter. The lens without the 1m filter is focusing at infinity at the 1.2 meter mark now.

I tried my other 2 adapters none of them let's me reach infinity focus with the ZM 28/2.8 with all shims removed (4) + Proxar 1m lens... :-(

Dec 26, 2016 at 06:37 PM

Fred Miranda
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p.19 #15 · p.19 #15 · Front-End Filter Improves Corner Smearing

candreyo wrote:
Hi Fred,

I'm not sure why you aren't able to reach infinity? I only needed to remove 2 shims, and then was able to reach infinity using TAP as the adapter.

Maybe there is a buildup of tolerances in the lens assembly, which the shims are used to calibrate out, and some lenses are more forgiving then others.

It's night here right now, but let me examine my ZM 28mm tommrow and see if there is anything else on the lens that can be adjusted to bring the ability to reach infinity in.

Edit:
I just realised you are trying to use the 1m Proxar...Show more →

Thanks for checking @candreyo ,
Yes, I realized now why the 1.5m PCX is a better match!.

Overall image

extreme corners of the frame at f/8 (with front filter and without)

Dec 26, 2016 at 07:08 PM

Fred Miranda
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p.19 #16 · p.19 #16 · Front-End Filter Improves Corner Smearing

GMPhotography wrote:
Quick question. On the ZM 28 and ZM 25 is there any color smearing going on. I don't think anyone has mentioned it so though I would ask.

Guy,
Color cast around the edges should not be an issue with the A7RII.

Dec 26, 2016 at 07:35 PM

Fred Miranda
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p.19 #17 · p.19 #17 · Front-End Filter Improves Corner Smearing

DavidBM wrote:
could be; the 28 is sometimes described by Zeiss as a C-Biogon (like the C-Sonnar) which they say can mean either Compact or Classic. So maybe it has some 'classic' rendering that makes up for the lack of technical perfection? Fred has one so maybe he can speak to that!

I have both ZM 28/2.8 and ZM 50/1.5C and the latter is more of a character lens.
The ZM 28 has an incredibly sharp center but as you can see from the sample I posted above, it's capable of great corner resolution (with a front end filter) on the A7RII.
The 28/2 ZF in comparison has a slightly better mid-zone but the very edges never sharpen up like the ZM 28. (not to count it's about 3 times bigger and heavier)

I can see the appeal of the ZM 25/2.8. It has a very impressive MTF when used with the correct sensor stack (perhaps even better than the Batis 25/2), but if you want a 28mm with high micro-contrast, great flare performance and nice sunstar rendering, there are not many solutions out there.

Dec 26, 2016 at 07:43 PM

DavidBM
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p.19 #18 · p.19 #18 · Front-End Filter Improves Corner Smearing

Fred Miranda wrote:
I have both ZM 28/2.8 and ZM 50/1.5C and the latter is more of a character lens.
The ZM 28 has an incredibly sharp center but as you can see from the sample I posted above, it's capable of great corner resolution (with a front end filter) on the A7RII.
The 28/2 ZF in comparison has a slightly better mid-zone but the very edges never sharpen up like the ZM 28. (not to count it's about 3 times bigger and heavier)

I can see the appeal of the ZM 25/2.8. It has a very impressive MTF when used with the correct sensor...Show more →

Yep, I can see that. There's nothing else with 10 blades out there that I know of (and I am a sucker for 10 blade sunstars) and great zeiss contrast. I'm surprised that the extreme corners sharpen up on the ZM28; wouldn't have guessed that from the MTF. Good to know - means that, as a landscape 28, it is tempting after all.....but I had sworn to wait until there's a Lox!!!

Isn't it amazing that there are still gaps that we all care about in 'core' focal lengths. I'm still waiting on a truly great 2/35 and 2.8/28, and I'm prepared to pay a lot (maybe not a Leica Lot). But no dice. And yet we have fantastic solutions at ultra wide lengths, and solutions to burn at short tele!

Dec 26, 2016 at 08:00 PM

DavidBM
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p.19 #19 · p.19 #19 · Front-End Filter Improves Corner Smearing

Fred Miranda wrote:
Thanks for checking @candreyo@ ,
Yes, I realized now why the 1.5m PCX is a better match!.

I tried using TAP with the infinity MF preset and was able to focus at infinity with the 1m Proxar...but to the dot! (and that's without 4 shims)

The results with the Proxar are actually pretty good even with the ZM 28. I can't wait to try the PCX filter on it.

Here are some crops. (Extreme corners)

LEFT: ZM 28/2.8 @f/8 + 1m Proxar
Right: ZM 28/2.8 @f/8 without any front lens.

Both focused at the center of the image (to investigate FC)

PS: I had to lift...Show more →

WOW!

This makes me really tempted by the 28 as well the C Biogon 35: does anyone there know what filter we should use?

Here's why:

The 2/35 Biogon has good or better better MTF than the 2.8/28 stopped down. And yet I agree Fred's samples of the corrected 28 look better than Loxia.

So what was Zeiss doing in generating the correction of Biogon to Loxia? Pure speculation: they wanted a solution that didn't make the lens longer, and didn't make the distortion worse. Perhaps a PCX or other filter is giving better results than the native Loxia correction would, at the slight cost of distortion and focal length change. A cost which, for landscape, I'm happy to pay.

Now since the 2.8 Biogon has somewhat better MTF stopped down than the f2 version, if it can be corrected as much, it ought be both even better than the corrected 28 and the corrected 2/35 (stopped down). In which case....

Dec 26, 2016 at 08:09 PM

rscheffler
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p.19 #20 · p.19 #20 · Front-End Filter Improves Corner Smearing

I'm hoping someone will try a PCX or Proxar on the Voigtlander 35/1.7 (current version)....

Dec 26, 2016 at 09:39 PM

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