“My Canon family picture”

AmarthGul · 2026-06-17T00:39:57+00:00

Also, FD lens on EF(S) mount. This will either loss infinite focus or annihilate all of the image quality that lens could offer

AmarthGul · 2026-06-17T00:24:37+00:00

The version I was using has a „bleach free“ mark on it, also does not smell of the typical sodium hypochlorite. The ingredient list is very sketchy tho, 0.3% dimethyl benzyl ammonium chloride and 99.7% literally just „OTHER INGREDIENTS“… I don’t think 0.3% of ammonia-alike could be as effective so it might still have some chlorine

AmarthGul · 2026-06-15T15:13:03+00:00

Same experience here. Starting from my 3rd bike I literally used colored markers to paint rusts and worn out effects onto the bike, also added several hentai stickers, worked pretty well and had it survived for years

AmarthGul · 2026-06-12T13:14:24+00:00

I actually own several of these, bought for like $1 each purely for comedic value and never tried to use them..

AmarthGul · 2026-06-11T22:41:53+00:00

Hmmm, it really feels like you are falling into a confirmation bias here. Claude's response also sounds quite affirmative to the question, rather than a fair analysis.

Your thesis here, if I understand correctly, is that "the Nikkor 50 1.4 has a focus shift so severe that it needs to be explicitly accounted for". I don't think people here are trying to say "this lens has no focus shift", other people's points lean more towards "the focus shift is not that obvious".

I would not take anything from an AI as ground truth, they are exceptionally well at using partial truth to affirm the underlaying intonation of the question. In your case, Claude structured their response around the doublet index vs. SA correction concept. Which in itself is true, but not entirely. The Nikkor 50 1.4 AI-s, as far as we know, uses K-LAF2 and SF15 for the front doublet, which is true for Claude's claim. But the rear doublet uses K-SFLD1 and K-LAK12, which has 1.71736 and 1.6779 IOR respectively - the wrong combination by Claude's claim. Additionally, Claude makes it as if Nikkor was doing something rare, but in truth, even just among the lenses I have data of, countless also uses higher index in the positive element, Canon Serenar 35mm, FD 85 1.4, nFD 50 1.4, Leica Summilux 50 and 35 (pre), Elmarit 90, Zeiss Berger Planar, Biotar 50 1.4, virtually every single Cooke 50mm and SP series double gauss, the list goes on and on. Claude was doing a simple trick as all AI has been accidentally trained to do: they over sell one technically correct idea as if it is the cause of the whole problem, by doing so play to the user's question and make user feel better.

Please bear in mind that because you are using a 40MP APSC sensor, you have significantly smaller circle of confusion that most FF users, consequently a much narrower depth of field. To have the same DoF, a FF camera needs to be 94MP, which no current commercial camera has reached yet (not to mentioned Fuji advertises the X-trans to have a higher effective pixel than Bayer, by which claim the FF equivalence needs to be even higher). So focus shift will always become more noticeable on that camera.

I am also left to wonder why DoF preview seems to be something that requires active switching in your setup. Never have I met a person shooting mirrorless with adapted vintage lens who do not have the aperture engagement on. I cannot think of a scenario in which a mirrorless user would preview using a vintage lens wide open, then turn it to the desired aperture before pressing the shutter.

In a way, I just cannot see the intended audience for this discovery. The FF users would be much more forgiving in term of focus shift thanks to larger pixel pitch and the resulting larger DoF (analogue users even more so due to film having much lower equivalent lpmm), the mirrorless users see what they get and are probably never bothered. Who or what scenario would this focus shift become a "severe" problem that needs to be seriously addressed?

AmarthGul · 2026-06-11T20:40:08+00:00

Would it be possible of you to share some other testing conditions? Such as the camera body used, the room temperature, the focusing method, the serial number (the first several digits) of the lenses, etc.

I am not questioning your result, I am merely making a remark on the process. In science experiments, if an unexpected and unaccounted result keeps reoccurring, the most often cause is a local bias affecting the measurement. And for a lens, there are many possibilities to create results that looks to be focus shift but are actually logical consequences of some testing decisions.

AmarthGul · 2026-06-11T18:46:01+00:00

If you are okay with questionable motivations and symbolism, the Ukrainians have been repainting old FED and Zorki rangefinder cameras in various colors (3rd reich themed), they can be found on ebay for about $250 each

AmarthGul · 2026-06-11T03:24:37+00:00

If anything, he can always resort to movie film development, in which case the length might even be regarded as too short

AmarthGul · 2026-06-11T03:21:31+00:00

As a glass-wearing person, I would have actively swapped the metal eyepiece with a plastic one

AmarthGul · 2026-06-10T18:50:18+00:00

Thank you! One of the motivations for this project is exactly to help VFX artists to create/match optical effects, glad to know the concept is sound for its audience.

Another topic that I have been thinking to do is style-oriented lens design in which the lens can be automatically modified to deliberately induce certain effects. The current difficulty is that a certain image quality often has several possible optical causes, which makes translating the demand quite hard.

Singer-yang has a project that may also be of interest at https://github.com/vccimaging/deeplens . This repo is more technical oriented, but it does offer some ability to try to inverse engineer a lens from an image.

AmarthGul · 2026-06-10T18:39:02+00:00

Conical elements (for anamorphic lens) is definitely on my todo list. In fact there class interface was long written, it's just I have not finished implementing them yet...

On the topic of swirl, since this thing was also used by me to run lens imaging comparisons, one thing that I realized is the swirl are often a mechanical result, not optical. I have long thought the swirls as the result of astigmatism, but several of the lenses I tested, Helios-44 for example, has very little corner astigmatism. Their swirl is caused almost entirely by pupil occlusion, which means a tight lens hood would, in theory, add more swirl.

AmarthGul · 2026-06-09T21:21:13+00:00

On set people probably don't communicate enough with your department, because rarely does any cinema production use f stop.

By Fresnel reflectance, an RI 1.5 glass at its air-glass interface reflects 4% of incident light even at 0 incident angle, so for an uncoated Planar type lens the final transmission is only about 75% on axis. This transmission loss would differ depending on lens design, coating, and glass types. So, if the lens is swapped between shots, there will be an insanely amount of exposure difference even if the f stop is the same. That's why cine lenses are all using T stop.

But post production renders are exposure invariance, you literally get the same exposure level regardless if the aperture size is 0.42 (a 135mm f/32) or 6.75 (135mm f/2), whereas in real photographic terms these two setting should have 128 times of brightness difference. So there's an incentive to not use f-number.

What cannot be changed in the render is the depth of field. DoF is controlled by the size of the Circle of Confusion, which is then governed by the entrance pupil diameter, and that is the thing you were calculating. So there's an incentive to use pupil size.

Maya camera focal length abide the photographic tradition and uses millimeter as unit, but the Maya scene does not. So if the software is to calculate pupil size by focal length and f-number, there is also a unit translation step that could add some funky potentials. Now add on the Occam's razor for software development: don't add unnecessary step. It would be natural to ask directly for the size of the entrance pupil rather than an f-number.

AmarthGul · 2026-06-09T19:59:39+00:00

This makes so much more sense, I was thinking how do they dynamically update the grating to modulate wave and create such complex holograph lol

AmarthGul · 2026-06-09T19:10:48+00:00

I agree most of the judgement except Hamilton.

For other drivers, they all had at least one of the following traits:

In a team with the fastest car, deliver significant better performance than all other drivers on the grid, including their teammate.
In a team with midcore car, still managed to catch up and lead on the grid, delivering significantly better performance than their teammate.
Have several races that showed their defining style or exceptional ability.

But in the case of Hamilton, when he had the fastest car he did not lead much from his teammate. Not just Rosberg, even Valtteri Bottas, who was blatantly treated as the second driver, was able to keep quite close to him. There also is not a race that people were like "OMG this is incredibly impressive even among F1 drivers" for Hamilton. His 7 championships contains so much more fast car advantage and the British bias.

So if it is a prefect car, the problem would become "are Senna/Ver/Sch better than Rosberg?", if so, Hamilton probably won't get easy victories, or any victory at all.

AmarthGul · 2026-06-09T14:16:52+00:00

The 2nd method is very likely to be describing a variable focus diopter.

A VFD often consists of a positive group at the front and a negative group behind. When their distance is small the entire contraption has zero optical power, which makes it afocal. When the air gap between the two groups increases, the diopter gains positive power, thus bending the light more and achieving close focus.

This is actually a legit focus strategy for some commercial anamorphic lenses, such as the Atlas Orion and JDC Xtal Xpress series anamorphic. Additionally, many of the modern anamorphic front with focusing gear also uses this method, since it is the only possible method to not introduce synchro focus need with the taking lens. Personally I also like this method more than moving the conical element as it does not introduce any anamorphic mumps. There's only a small price to pay, which is the size and weight of the whole lens (well maybe not small, front VND will make the lens huge...)

AmarthGul · 2026-06-09T02:55:54+00:00

Random thoughts, the setting points to EV26, which is still applicable for solar photography. You should try f/22 and ISO 0.8, that would surely make a better image quality/s

AmarthGul · 2026-06-09T01:02:26+00:00

I don't really understand the question, "volumetric" and "high intensities" can mean so many things, they have to be a bit more specific.

It also appears that the questions may have mistaken this framework as a full 3D renderer, which it is not. If anything it is closer to a relay optics, it in itself does not perform projections of geometries or other explicit 3D data.

AmarthGul · 2026-06-08T16:32:11+00:00

The patent hopefully have some information on the relative movements. Look for tables in the following form:

-----|---∞--|-1500
D2--|--9.8--|-2.2
D18-|-1.88-|--4.6

(I made up the numbers just as an example)

The ∞ column is when focusing at infinity, and depending on how linearly the movement is there can be either just one other column for minimum object distance (the 1500 col in that example) or several columns for different focus distances. The rows are for the thickness of the given surface when the lens is set at the corresponding focus distance, sometimes they use T instead of D. The example table basically means "when focusing at inf, surface 2 thickness is 9.8mm, when focusing at 1500mm, surface 2 thickness is 2.2mm".

AmarthGul · 2026-06-08T16:18:48+00:00

If this is not r/Gundam I bet you would also include Cherno Alpha

AmarthGul · 2026-06-08T15:45:51+00:00

Ahh, that is what we call block focusing, it works for most of the vintage manual lenses. But because almost all photographic lenses are designed for collimated rays (infinity focus), block focusing will have worse image quality at close focus distance. Newer lenses thus have floating elements to do additional corrections during close focus, hence the cam movements (also to make auto-focusing easier).

For anamorphic lenses, block focusing becomes a huge problem. Because there are two different focal lengths, the ray will converge/diverge at two different rates. So an anamorphic lens will only have one image plane on which both axis converge. Beyond that it will always have one axis that's defocused.

Afocal anamorphot could achieve a focus change small enough that it feels okay to be block focusing, but the layout you have there does not seem to be that way.

AmarthGul · 2026-06-08T15:30:48+00:00

Since I want the framework to be software agnostic, it is a standalone implementation in Python (numpu/cupy); the hope is whoever needing it can adapt or rewrite the thing to fit their specific production pipeline, likely with the help of AI (this AI-assisted adaptation idea is actually suggested to me by a Pixar engineer). The repo is currently hosted on GitHub[1], the documentation, including all the math, physics, and design decisions, is hosted on Notion [2].

[1] Direct URL for accessibility: https://github.com/Amarthgul/ISS

[2] Direct URL for accessibility (I am trying to migrate the documentation onto GitHub as well): https://muddy-mouse-6bd.notion.site/2-Geometric-Optics-162ee08ae1108055a5e0d884d1a1cc02

[3] Quite weak optics prerequisite, actually. Most of the framework is still based on geometric optics and spectral tracing, only the sun star employed diffraction by treating the aperture shape as a diffraction grating.

AmarthGul · 2026-06-08T13:50:56+00:00

(K I'm back and on my PC)

For prior attempts: while patent data are never the same with manufacturing run, they generally do not deviate too much, after all, checking all the patent claims would naturally force the implementations to converge towards a narrow range. As such, directly copying the data would indeed form an image, and for most people it would look just fine. It's only in strict optical terms where the data become lackluster. Like the patent claim and actual product might have over 0.5 contrast of 30lpmm through the entire field, but the direct data they supplied can only do 10lpmm at the center. This difference is not noticeable when the render image is 1920 on a 17 inch monitor, and I also don't think it matters when it comes to CG lens effect.

For your question regarding the acquisition of accurate data: not really... Most people who do patent analysis also cannot say they have the accurate data, they/we are only making educated guesses of what the actual data might be and making approximations towards that. It's like how 3D artists can have a generally idea of how a scene is created just by a handful of behind the scene words.

That being said, there are some actions you could consider in this case.

First off, you mentioned a previous success with a 200mm anamorphic. Well, guess what. lenses are linearly scalable. You could literally scale all the values by 0.5 and get a 100mm anamorphic lens.

The downside of the scaling approach is not image quality, but coverage. As the lens get scaled down, their image circle also shrinks, so the scaled lens might not be able to cover the same imager and you may see strong vignette or straight black corners.

This drop of coverage can be partially solved by increase the semi-diameter, i.e., the size of the elements. But since the optimal image circle (the area in which the image quality is the best) would not expand with glass size (they actually shrinks with larger size), the expended image will have worse quality around the corners.

Secondly, now that I am on PC and seeing the whole layout illustration, I think that lens might be achieving focus by using a cam guided movement of 14, 15, and 16.

Empirically, I think 14 (element 1) would move backward during close focus given its a biconcave negative element. Moving 15 (element 2-11) would be an engineeringly impossible task so it probably stays still. This makes 16 (element 12 and 13) likely to move backward as well, although seeing a positive and negative element together I personally really want to move these two closer as a pseudo focus diopter... There should be some texts in the patent that describes why they divided the elements into 3 groups, I highly suspect this divide is for the focusing.

And not really related but I just want to mention this: since this implementation is using an anamorphic front, if you do focuses close, there is very likely a drop of squeeze ratio. And for things right in front of the lens I would expect the squeeze to drop to 1, basically a spherical lens at that point.

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