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Archive 2015 · Kolari Mod's Improvements: A Summary of Tests

JimBuchanan
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p.8 #1 · Kolari Mod's Improvements: A Summary of Tests

hiepphotog wrote:
FWIW, I checked the Batis 25 on Lloyd's comparison between the stock and modded cam. Without saying too much, personally, I wouldn't worry too much about the degradation with native lenses.

From my experience, I agree. I suppose one has to pay money to read Lloyd's observations.

24-25mm is my sweet spot for a wide angle. I hoped the ZM25 would work on Sony, and it is workable on a Kolari mod. The Leica Elmar 24/3.8 needs no/little back-off focusing at infinity on the Kolari a7. Better yet.

But the Batis 25 is even better on the a7Kolari, as it beats both of the above in the extreme corners in terms of sharpness and vignetting.

If I focus for center frame at wide open and move magnifier to a corner, I would need to focus out toward infinity to gain sharpness. This implies an umbrella field of curvature inward. This is in contrast to the typical M mount rangefinder lens on a Sony camera, where the umbrella has been hit with wind and the edges point out toward infinity.

I look forward to understanding if the extreme edges actually improve on a stock a7 camera over an a7Kolari, but The improvements in vignetting and corner sharpness are very welcome.

Nov 23, 2015 at 11:26 PM

hiepphotog
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p.8 #2 · Kolari Mod's Improvements: A Summary of Tests

JimBuchanan wrote:
From my experience, I agree. I suppose one has to pay money to read Lloyd's observations.

24-25mm is my sweet spot for a wide angle. I hoped the ZM25 would work on Sony, and it is workable on a Kolari mod. The Leica Elmar 24/3.8 needs no/little back-off focusing at infinity on the Kolari a7. Better yet.

But the Batis 25 is even better on the a7Kolari, as it beats both of the above in the extreme corners in terms of sharpness and vignetting.

If I focus for center frame at wide open and move magnifier to a corner, I would need to...Show more →

Jim, am I reading it right? The Batis 25 actually beats the Elmar 24 (I assume you mean both at WO?) on your A7Kolari. That is very interesting. I don't have the Elmar any more, but I remember it's pretty close to perfect at WO (well f/5.6 does give a bit more contrast boost at the corners), at least no double image or sign of astigmatism.

Nov 24, 2015 at 01:03 AM

JimBuchanan
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p.8 #3 · Kolari Mod's Improvements: A Summary of Tests

Yes, the Elmar 24 performs well on my a7mod at WO. As you say, f/5.6 tightens things up a bit.

And backing off infinity only a small amount will sharpen the corners a very small amount. However, this implies the field of curvature extends out away from the sensor as most other rangefinder lenses. My testing the Elmar stopped here, but I wonder about closer up performance, as in those scenes where center focus is on a closer object and the distant edges start to sharpen up due to the field of curvature bending out toward infinity. In the end, I settled on the Batis 25, because it does have floating elements for closer image quality.

My testing occurred at different times of day and different weather conditions, but the Batis at WO had noticeable brighter corners than the Elmar. The Elmar was pretty much at its optimum at f/5.6, but the best corners of the Batis needed also f/5.6 and sometimes f/8. That's what I always liked about later Leica lenses, 2 stops down and your at optimum.

So, the difference here is something of the reverse condition. The thick cover glass makes plane of focus bend out in the corners of the typical symmetrical RF lens. The a7modded cameras will bring that out curve back a bit depending on the lens. Here, if the Batis 25 indeed has a flat field on a stock a7 camera, then the modded camera will also bring the plane of focus in a bit. However, stopping down really takes care of the corner sharpness on a modded camera.

Nov 24, 2015 at 10:00 AM

hiepphotog
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p.8 #4 · Kolari Mod's Improvements: A Summary of Tests

JimBuchanan wrote:
Yes, the Elmar 24 performs well on my a7mod at WO. As you say, f/5.6 tightens things up a bit.

And backing off infinity only a small amount will sharpen the corners a very small amount. However, this implies the field of curvature extends out away from the sensor as most other rangefinder lenses. My testing the Elmar stopped here, but I wonder about closer up performance, as in those scenes where center focus is on a closer object and the distant edges start to sharpen up due to the field of curvature bending out toward infinity. In the end,...Show more →
Thank you for sharing. I think this would alleviate some of the concerns about using native wide on a modded cam. Your observation on field curvature is consistent with my thinking on this subject as well.

How easy is it for you to balance the inward curvature? I have done enough shooting with a 15mm to know that outward curvature can be a pain at time. Luckily I finally figure out a trick to balance both the center and corners, foreground and background.

Nov 24, 2015 at 10:16 AM

JimBuchanan
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p.8 #5 · Kolari Mod's Improvements: A Summary of Tests

hiepphotog wrote:
Thank you for sharing. I think this would alleviate some of the concerns about using native wide on a modded cam. Your observation on field curvature is consistent with my thinking on this subject as well.

How easy is it for you to balance the inward curvature? I have done enough shooting with a 15mm to know that outward curvature can be a pain at time. Luckily I finally figure out a trick to balance both the center and corners, foreground and background.

I gave up trying to balance the inward curvature, as it is relatively slight. One thing making it a challenge is the lack of a hard infinity stop. I really miss that. Anyway, I focus for infinity and stop down a bit but never past f/8.

Nov 25, 2015 at 09:57 AM

brendans
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p.8 #6 · Kolari Mod's Improvements: A Summary of Tests

hiepphotog wrote:
Luckily I finally figure out a trick to balance both the center and corners, foreground and background.

Just curious Hiep, what technique did you find that worked best?

Nov 25, 2015 at 10:57 AM

hiepphotog
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p.8 #7 · Kolari Mod's Improvements: A Summary of Tests

brendans wrote:
Just curious Hiep, what technique did you find that worked best?

Brendans, it does depend on the lens, since this is about maximizing depth of focus. You need to have a distance scale on your lens for this (so Contax G would be next to impossible).

For an outward field curvature (like we have with our RF lenses), you need to know the distance of the closest element in your corners (i.e. your lower left or right corners). You can find this distance by focusing into the corner at WO until it's at its sharpest; the distance should be exactly in the middle of your DOF scale. And you would be surprised as how thin that DOF (even on my 15 and f/5.6) is. Now backtrack your focus (i.e. focus toward infinity) until that distance is at the aperture mark two stops above your current aperture; that is, if you're shooting at f/11, set it at f/5.6. This balance the sharpness between both the center and corners. And you can just use a global sharpening scheme to bring the whole frame up to your standard. If you want a sharper corner, go with 1 stop instead of two.

It's easier to understand with a visual guide, so if you need one, let me know. So with this technique, I know the corresponding aperture I need to set for a given distance to my corners. For example, I would use f/11 if I have an element in the corners about 2 ft away. On the other hand, at 7ft distance, I found f/8 is adequate. With this technique, I can take a evenly sharp front to back picture at f/5.6 without creeping into the diffraction zone in many situations.

Nov 25, 2015 at 05:46 PM

beetlephoto
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p.8 #8 · Kolari Mod's Improvements: A Summary of Tests

Hello,

I know the ZM 35/1.4 has been tested twice here with the A7sM (f/1.4, f/4 and f/8), and A7rM (f/8 I think), but I'm trying to asses how this lens would perform on an A7rm at all apertures (I'm interested in the wide apertures).

I'm currently using the Nokton 35/1.2 on my A7rM, but considering the ZM 35/1.4.

Icing on the cake would be a test with the second iteration of the A7rM sensor stack (which I have)

Thanks!

Edited on Nov 15, 2016 at 10:18 AM · View previous versions

Nov 30, 2015 at 04:53 AM

RustyBug
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p.8 #9 · Kolari Mod's Improvements: A Summary of Tests

Seems like a whole lot of modification away from OEM to still be heavily reliant on hyperfocal and stopped down techniques. Seems like those old school techniques would still be prevalent for use with stock and new glass designed specifically for the the OEM.

No specific examples, but I'm getting a vibe that folks are comparing apples to oranges a bit. Trade off one issue for another, but then that's okay because we can offset / compensate ... yet, we didn't allow for the offset / compensate techniques in the original OEM application.

The comment at needing two cameras @ one stock / one modded ... well, I get that folks want to use their fav glass. But, I'm not convinced that the mod is the all around savior. It seems more like a workaround for preferring to use a tool that was never designed to be used with it (or that has inherent design tradeoffs) ... which is fine for "alt use", but I'm thinking that affords a "different" rather than necessarily "better" result.

Seems like yet another exercise in choose your poison(s) ... moreover than the answer for all @ a rising tide floats all boats. I'd still be curious to how the mod compares to simply replacing the AA filter with OEM dimensioned cover glass (and using the OEM application designed lenses, i.e. Batis, etc.)

JimBuchanan wrote:
But the Batis 25 is even better on the a7Kolari, as it beats both of the above in the extreme corners in terms of sharpness and vignetting.

If Jim is going with the Batis ... glass rules.

Nov 30, 2015 at 08:20 AM

hiepphotog
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p.8 #10 · Kolari Mod's Improvements: A Summary of Tests

beetlephoto wrote:
Hello,

I know the ZM 35/1.4 has been tested twice here with the A7sM (f/1.4, f/4 and f/8), and A7rM (f/8 I think), but I'm trying to asses how this lens would perform on an A7rm at all apertures (I'm interested in the wide apertures).

I'm currently using the Nokton 35/1.2 on my A7rM, but considering the ZM 35/1.4.

Cherry on the cake would be a test with the second iteration of the A7rM sensor stack (which I have)

Thanks!

Bettlephoto, before I bought my ZM 35/1.4, I asked Gregg (Greggf) to send me a WO shot of the ZM 35/1.4 on his A7R.Mod. It's pretty much what you see on other modded A7. And we have tested on the A7R.Mod, A7S.Mod, and A7RII.Mod

. I can send you a full-res JPEG at WO. Just PM me where to.

By the way, Rich (naturephoto) told me that the lens has some magenta color cast on the A7R.Mod.

---------------------------------------------

RustyBug wrote:
Seems like a whole lot of modification away from OEM to still be heavily reliant on hyperfocal and stopped down techniques. Seems like those old school techniques would still be prevalent for use with stock and new glass designed specifically for the the OEM.

No specific examples, but I'm getting a vibe that folks are comparing apples to oranges a bit. Trade off one issue for another, but then that's okay because we can offset / compensate ... yet, we didn't allow for the offset / compensate techniques in the original OEM application.

The comment at needing two cameras @ one stock...Show more →

Rusty, the mod would completely eliminate the induced field curvature on some lenses (check my tests for the lenses that I didn't post corner focus) or largely reduce that FC that you can get sharp image at its peak aperture (f/5.6 or f/8). Furthermore, like I said before, the reduction in field curvature is real that the mere act of removing of an AA filter would not have the same effect.

The ZM 15 is more of a special case, borderline at usable. However, this lens has the highest central to about 2/3 resolution 15mm out there (beats the ZF/ZE 15). Stopping down would remedy that edge. The corners, however, remain okay to me. The WATE 16 is better at the corner portions, going past the long edge. But even the WATE at f/8, its center can't match the WO center of the ZM. With all that said, I have seen corners from the Canon 16-35/2.8 II, 16-35/4, and the new 11-24/4. They all have weaker corners than the ZM. Don't know about the Nikon 14-24 since I heard its corners still remain the best of all UWA. The WATE might be as good.

With all that said, if Zeiss comes out with a Loxia 15/2.8 that is similar sized to the ZM and they fix that field curvature, and more important, the astigmatism of the original ZM 15, I would drop everything to get

. For now, the ZM 15 is still the highest performing 15 to me. The size and weight are just icing on the cake.

Edited on Dec 04, 2015 at 07:49 PM · View previous versions

Nov 30, 2015 at 10:00 AM

RustyBug
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p.8 #11 · Kolari Mod's Improvements: A Summary of Tests

hiepphotog wrote:
The ZM 15 is more of a special case, borderline at usable. However, this lens has the highest central to about 2/3 resolution 15mm out there (beats the ZF/ZE 15).

I guess that's really my point that when you understand the strengths and weakness of the optical projection attributes ... the series of optical properties that are diametrically opposed can become an exercise in push / pull. The lens design that produces great corners in Zone C relinquishes some of Zone A and vice verse (or you start playing with distortion induced designs in Zone B).

Jockeying around the sensor to better accommodate Zone C on a lens that is by design to be excellent in Zone A at the expense of Zone C seems a bit folly to me. Rather than modifying the sensor, just use a lens that is designed to get better corners, if corners are your concern. Sure, that means you might give up some of that uber-excellence in the 2/3 Zone A / B to mere excellence.

The tenets of this can be seen readily in (not RF, I realize) comparing the (legacy) Oly's vs. the Nikon's. Oly's tend to be more even across the frame, Nikon's tend to be "sharper" in the center. The design properties that advantage one, inherently disadvantage the other ... i.e. pick your poison. I just think that folks are trying to make a silk purse of a sow's ear. If you want a lens that produces better corners ... ummm, buy a lens that is designed to produce better corners. If you want one that is uber-sharp in the centric areas, then mount up the one that is uber-centric designed.

If we were shooting 24x24, then those (uber sharp) 2/3 of 24x36 would make perfect sense. But, if you are looking for 24x36 corners, you are really looking at (sorta) 36x36 (just cropped vertically), so get a lens that covers 36x36 better than one that is designed to be concentrated to 24x24.

Trying to have it be "uber" both ways at the same time by jockeying the stack thickness to offset the lens design ... well, imo that's just a bit of dreamin'. Kickin' the AA filter to the curb to improve sharpness, that's a different matter.

hiepphotog wrote:

For now, the ZM 15 is still the highest performing 15 to me.

In Zone A, Zone B or Zone C ?

Nov 30, 2015 at 11:14 AM

hiepphotog
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p.8 #12 · Kolari Mod's Improvements: A Summary of Tests

RustyBug wrote:
I guess that's really my point that when you understand the strengths and weakness of the optical projection attributes ... the series of optical properties that are diametrically opposed can become an exercise in push / pull. The lens design that produces great corners in Zone C relinquishes some of Zone A and vice verse (or you start playing with distortion induced designs in Zone B).

Jockeying around the sensor to better accommodate Zone C on a lens that is by design to be excellent in Zone A at the expense of Zone C seems a bit folly to me....Show more →

Well, but without the mod, I can even use the lens at WO. Without the mod, even at f/11 and f/16, smearing still occurs even with extensive playing with hyperfocal. The key here is the much more reduction in field curvature, which is the whole point of this mod. It's reduced to the point users can manage it or, most of the times, don't have to even think about it. Yes, it is about sharpness, but it's not because it simply enhances the sharpness (or more false details like many would view it

) like an AA filter would.

And a weak lens will remain a weak lens after the mod, no matter what

Nov 30, 2015 at 11:49 AM

RustyBug
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p.8 #13 · Kolari Mod's Improvements: A Summary of Tests

hiepphotog wrote:
The key here is the much more reduction in field curvature, which is the whole point of this mod. It's reduced to the point users can manage it or, most of the times, don't have to even think about it. Yes, it is about sharpness, but it's not because it simply enhances the sharpness (or more false details like many would view it

) like an AA filter would.

Just to be clear ... the mod does include removing the AA filter?
(My understanding is that the mod does include the removal of the AA filter, so I'm not quite sure why the comment about false detail from AA removal.)

Field curvature. Ummm, isn't that a product of the optical projection. Do you mean angle of incidence and / or angle of refraction?

From what I can tell there are two variables being applied simultaneously by the mod:
1) Removal of the AA filter, and
2) Change in the angle of incidence / refraction trigonometry

Until we see those changes being applied singularly, we won't know how much of one versus the other is responsible for the gains. From what I'm seeing, I can't help but wonder how much of that is due to 1) vs. 2)

I mean, by the time we get out to the corners, we are "fanning out" our vector angles progressively more than in Zones A & B. Pushing those "fanned out" angles through an intentional diffraction screen ... well, that just strikes me as a prime candidate for producing additional smearing. Nixing that culprit seems to me to be the first order of business ... one which can be accommodated and still retain OEM geometry for those lenses being designed for OEM geometry.

Until we get a simple cover glass replacement of the AA filter to compare against the thinner stack -AA, it'll will be a theoretical guessing game of sorts. But, I'm still thinking that the removal of the AA filter component of the mod is the primary gain, and the angle changes are the culprit for the color shifts moreover than the sharpness itself.

And a weak lens will remain a weak lens after the mod, no matter what

And a lens designed to be even across Zones A, B, C will be even across Zones A, B, C. You're definition of weak must be followed by the question of "weaker at what". Better balanced across the zones may mean less in Zone A, but a lens that is weak in Zone C remains weak in Zone C after the mod as well. The optical projection design has remained unchanged ... you're only mitigating the additional interferences with the optical projection, not changing the lens design for weighted projections into Zones A, B, C.

I can argue all day long that my Nikon is sharper in Zone A than my Oly. Does that make my Oly a weak lens?

The wider you go, the tougher it gets ... choose your poison(s).

Nov 30, 2015 at 12:06 PM

hiepphotog
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p.8 #14 · Kolari Mod's Improvements: A Summary of Tests

Nov 30, 2015 at 02:24 PM

Steve Spencer
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p.8 #15 · Kolari Mod's Improvements: A Summary of Tests

RustyBug wrote:
Just to be clear ... the mod does include removing the AA filter?
(My understanding is that the mod does include the removal of the AA filter, so I'm not quite sure why the comment about false detail from AA removal.)

Field curvature. Ummm, isn't that a product of the optical projection. Do you mean angle of incidence and / or angle of refraction?

From what I can tell there are two variables being applied simultaneously by the mod:
1) Removal of the AA filter, and
2) Change in the angle of incidence / refraction trigonometry

Until we see those changes...Show more →

Hi Rusty,

What the thicker sensor glass does is not cause general field curvature, but field curvature just in the tangential orientation. This causes astigmatism and when astigmatism is bad enough it looks smeared. If you read toothwalker's description of astigmatism here:

http://toothwalker.org/optics/astigmatism.html

You can see how if you take a lens that is an anastigmat and you introduce field curvature in just one orientation (i.e., the tangential orientation in this case with the change in sensor cover) it will cause astigmatism. When you understand that this is the problem you also see why performance in the centre is unaffected by the thicker glass and that performance generally gets progressively worse as you move toward the corners. Now exactly where in the frame the worst astigmatism will occur is also dependent on the sagittal field curvature, but introducing curvature in the tangential orientation is not going to be a good thing in almost all cases. So the general rule is that thicker or thinner cover glass than a lens was designed for (i.e., thicker or thinner cover glass than when it would have the curvature that would make it an anastigmat) will decrease performance increasing astigmatism and that increase in astigmatism will be worse at wide apertures and if the lens has a short exit pupil because those two factors will make the tangential field curvature more extreme.

Now thicker or thinner cover glass will always introduce field curvature in the tangential orientation (but not the sagittal) and the extent of that curvature will be affected by how wide the aperture is and how short the exit pupil is, but to know the exact effect one needs to know the exact curves in the sagittal and tangential orientation. Most lenses are more or less anastigmats so the above diagrams give a clear general picture of how lenses are effected, but each lens varies to some extent from being a perfect anastigmat so effects will be lens dependent as well. So we can know in general what lenses will tend to do with the thicker or thinner cover glass, but we won't know about a specific lens until we see its actual performance. That is why the work that Hiep, K-H, Ron, and others have done has been so helpful. I hope this makes the issue clearer.

Nov 30, 2015 at 03:40 PM

hiepphotog
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p.8 #16 · Kolari Mod's Improvements: A Summary of Tests

Steve Spencer wrote:
Hi Rusty,

What the thicker sensor glass does is not cause general field curvature, but field curvature just in the tangential orientation. This causes astigmatism and when astigmatism is bad enough it looks smeared. If you read toothwalker's description of astigmatism here:

http://toothwalker.org/optics/astigmatism.html

You can see how if you take a lens that is an anastigmat and you introduce field curvature in just one orientation (i.e., the tangential orientation in this case with the change in sensor cover) it will cause astigmatism. When you understand that this is the problem you also see why performance in the centre is unaffected by the...Show more →

Steve,

It does change field curvature. This is what I have observed while testing lenses on the stock vs. mod cam. On the stock, when I focus on the corner to get sharp corner, I need to back focus by a significant amount. On the modded, with some lenses, you don't even need to do that, or only by a much smaller amount. For example, a stock camera might need a focus point at 2ft to get that corners sharp, while the mod might need a little back focus from infinity mark. Therefore, you can focus stack a rangefinder lens on a stock camera to get a perfectly sharp picture. Unfortunately, focus stack is not always possible and it's a PITA.

Then comes the issue of astigmatism. So when you focus on the sharpest corner for both stock and mod, the stock still looks fuzzier. I remember there was a thread by Ken Walsh (kwalsh) asking about a way to improve astigmatism. There is pretty much no shooting technique that can do that.

Nov 30, 2015 at 05:14 PM

Steve Spencer
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p.8 #17 · Kolari Mod's Improvements: A Summary of Tests

hiepphotog wrote:
Steve,

It does change field curvature. This is what I have observed while testing lenses on the stock vs. mod cam. On the stock, when I focus on the corner to get sharp corner, I need to back focus by a significant amount. On the modded, with some lenses, you don't even need to do that, or only by a much smaller amount. For example, a stock camera might need a focus point at 2ft to get that corners sharp, while the mod might need a little back focus from infinity mark. Therefore, you can focus stack a rangefinder lens on...Show more →

Hiep,

If you read Toothwalker's article in the link you will see that astigmatism and field curvature are intricately related. What the cover glass does is change field curvature but only in the tangential orientation. Now depending on the exact nature of the field curvature in the sagittal orientation this can create a pattern for the lens that is field curvature in both orientations. This happens if the cover glass field curvature change in tangential field curvature more or less matches the unaffected field curvature in the sagittal direction. In this unusual case the cover glass actually may reduce astigmatism and increase field curvature. For the typical anastigmat, however, the cover glass increase astigmatism rather than field curvature. But as I said above the exact pattern of sagittal and tangential curvature (after the cover glass has been taken into account) will vary from lens to lens and that means we need to see the performance of each lens.

Also when I say that the cover glass affects tangential curvature and does not affect sagittal curvature that is a bit of a simplification. The more precise statement is probably the cover glass can have a large effect on tangential curvature and only a mild effect on sagittal curvature. But such precision isn't really necessary. The major point is that in general the thick cover glass causes astigmatism by affecting the tangential curvature much more than the sagittal curvature, but each lenses individual lens' properties of curvature in both the sagittal and tangential orientation need to be taken into account so each lens' performance should be examined individually.

Nov 30, 2015 at 05:42 PM

hiepphotog
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p.8 #18 · Kolari Mod's Improvements: A Summary of Tests

Nov 30, 2015 at 05:49 PM

hiepphotog
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p.8 #19 · Kolari Mod's Improvements: A Summary of Tests

Steve Spencer wrote:
Hiep,

If you read Toothwalker's article in the link you will see that astigmatism and field curvature are intricately related. What the cover glass does is change field curvature but only in the tangential orientation. Now depending on the exact nature of the field curvature in the sagittal orientation this can create a pattern for the lens that is field curvature in both orientations. This happens if the cover glass field curvature change in tangential field curvature more or less matches the unaffected field curvature in the sagittal direction. In this unusual case the cover glass actually may reduce astigmatism...Show more →

Astigmatism, in toothwalker's article, can be seen as a subset of field curvature, because not all field curvature phenomena would result in astigmatism, but all astigmatic events are caused by the drop of one curve due to field curvature.

With that said, astigmatism alone can't explain why refocusing in the corners would give you a much sharper result at a certain focus point. Again, you can't reduce astigmatism by simply doing focus stacking.

Nov 30, 2015 at 06:00 PM

Steve Spencer
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p.8 #20 · Kolari Mod's Improvements: A Summary of Tests

hiepphotog wrote:
Astigmatism, in toothwalker's article, can be seen as a subset of field curvature, because not all field curvature phenomena would result in astigmatism, but all astigmatic events are caused by the drop of one curve due to field curvature.

With that said, astigmatism alone can't explain why refocusing in the corners would give you a much sharper result at a certain focus point. Again, you can't reduce astigmatism by simply doing focus stacking.

Totally agree and I think we agree on everything as far as I can see. I was just trying to point out that the cover glass will affect tangential field curvature a lot more than sagittal field curvature and that means that depending on exactly how these curvatures manifest themselves with the designed cover glass you can get either astigmatism or field curvature or in rare cases better performance in a particular lens. I do think astigmatism will be the most common primary results, however, because most lenses are designed more or less to be anastigmats. Regardless, I think we totally agree that each lens needs to be tested on its own to see what is going to happen with the change in the cover glass.

Nov 30, 2015 at 06:08 PM

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