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Ultracheap wide angle lens for UV?


nfoto

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25mm on M43 is equivalent to 50mm on full-frame, so "normal", not "wide". I can not find anywhere if it covers larger sensors, but if this lens is triplet, I highly doubt it.
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Agree Alex, but quoting the seller's advert here.

 

Assessed from the attached pictures of the eBay post, I don't think the image quality is that high, however that being said, might be a fun lens to experiment with.

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Yes, but Igor's eBay add title is somewhat misleading, although he "rectifies" the "wide angle" statement further down in the description.
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Well, hello, guys. I was wondering when someone on here would catch wind of my most recent developments (I've been very busy, lately, which is why I have also been "MIA" for quite a long time). :D

 

To answer some of the questions brought up, in this thread:

 

1. "25mm on M43 is equivalent to 50mm on full-frame, so 'normal', not 'wide.'"

 

Yes, both is correct. The actual lens is 25mm focal length. But becomes 50mm on a crop sensor with a 2x crop-factor.

 

2. "Yes, but Igor's eBay add title is somewhat misleading, although he 'rectifies' the 'wide angle' statement further down in the description."

 

Not misleading at all, given that the native focal length of the lens is indeed 25mm. And then depending on which camera it is adapted to, one would then do some simple multiplication. (Ex: On an APS-C sensor, 1.5 x 25mm = 37.5mm. On a Micro-4/3 sensor, 2 x 25mm = 50mm, and so on).

 

To say that I am "misleading" with stating that it is a wide-angle lens (because it is a wide-angle lens), would be like saying that every other lens ever made with the same native focal length is also misleading people. But it's not misleading people. Thousands upon thousands of 25mm focal-lengths lenses, old and new, have "wide angle" stamped on them, within the range of such focal lengths. That they become a different focal length on a non-35mm film/sensor plane is not "misleading." It is consequential and purely circumstantial. Just as it would be purely consequential - in a reverse circumstance - if a lens would suddenly become even wider (if adapted to a larger-format film/sensor plane).

 

The point is, natively, it is a 25mm focal-length lens. That makes it technically a wide-angle lens. (I'd say that any lens with a native focal length of 35mm or below would constitute "wide-angle" territory. But ... "tomayto-tomahto", I suppose. Heheh.)

 

(Although, as you've rightfully pointed out, I made sure in the associated details of the ad that any prospective buyer understands how non-35mm film or sensor planes can modify the resulting focal length, depending on which camera the lens is adapted to).

 

Also, it should be noted that my actual ad title states: "Wider than Kyoei Kuribayashi 35mm", in case which it is. Therefore, no deception. ;)

 

3. "I can not find anywhere if it covers larger sensors, but if this lens is triplet, I highly doubt it."

 

This particular design will not adequately cover a FF sensor. Your hunch is correct. It will cover up to an APS-C frame (Nikon DX, Pentax APS-C, Sony NEX, etc), per my tests/measurements.

 

However, I am in current experimentation with another design that will cover a FF sensor ... but the developmental stages are still early to be conclusive. Also, I've noticed that some triplets will in fact adequately cover a FF sensor, but at the expense of even more pronounced edge-softness. On the other hand, I've been able to (at least with some partial success, as it stands) to significantly "sharpen up" a greater expanse of the image frame by using a smaller iris for the optical build (Ex: F/9, instead of F/6). More to come, as I continue to test.

 

4. " Assessed from the attached pictures of the eBay post, I don't think the image quality is that high, however that being said, might be a fun lens to experiment with. "

 

That's true. I mentioned in the ad details that the prospective buyer should not expect thousands-of-dollars performance with this build. Not even hundreds-of-dollars performance. The whole idea is to offer a UV-capable lens that is 1. budget-minded, 2. finally breaks through the previous 35mm focal-length "wide-angle" UV-lens available arsenal by offering a 25mm focal-length design, 3. effectively allows one to reach ever-so-closer to the much-sough after "UV landscape", and 4. does this with an "everything-in-focus" (3 meters to infinity) panfocal build that spares one of having to re-focus each time before shooting.

 

In short, the goal was to come up with a "simple and convenient" UV-capable lens that can shoot UV-landscapes (or rather, semi-landscapes) at a moment's notice (after taking the camera immediately out of the bag), with no set-up time. Essentially, the UV-photographer's equivalent to a "body-cap" lens for general fun. Except that the image quality is certainly better than a pinhole camera, that much I can vouch for. And still marginally better than the majority of crappy and primitive two or three-element optical builds. B)

 

(Plus, it transmits UV quite deeply, with no significant image anomalies ... aside from reduced edge-sharpness and lower contrast than more complex optical formulas).

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If used on a 24 x 36 sensor, how much corner-clipping is there? How much actual usable frame is there? Would the usable FOV be significantly more than my Asahi 35 (which does cover the entire frame?)

 

Is there a Sony or M42 mount version?

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If used on a 24 x 36 sensor, how much corner-clipping is there? How much actual usable frame is there? Would the usable FOV be significantly more than my Asahi 35 (which does cover the entire frame?)

 

Is there a Sony or M42 mount version?

 

I will try to go back and take some test shots on a FF camera, then report back. I do not own a FF digital body, myself. Only 35mm film cameras. So, I would have to either borrow someone else's FF digital body to obtain immediate web-publishable samples, or alternatively, take film shots on one of my own 35mm film bodies which I own.

 

The latter seems more feasible at the moment. Thus, I will report back as soon as I get the chance to test again.

 

As for adapting this lens to APS-C platforms (Sony NEX, Fuji-X, etc), I am in the prototyping phase of developing such mounting options.

 

Why, just the other day, I was sent a PM from an interested and potential buyer on Ebay, who was inquiring if I can supply this optical build through a Fuji-X mount.

 

My response was:

 

<<< I am planning to extend my prototyping research into other mounts, yes. Although I would have to gain access to a Fuji mirrorless system, in order to TRULY be confident that I have reached correct infinity focus. (Accounting for the published FFD - "Flange Focal Distance" - of any camera system is not always straightforward enough to guarantee that I would design a properly-calibrated lens without DIRECT hands-on testing on the actual camera in question).

 

Granted, given that the FFD of the Sony NEX is only 0.3mm larger than the Fuji-X System (18mm versus 17.7mm, respectively), then I suppose that once I finish prototyping this lens for the Sony NEX system (which I do have access to), then the 0.3mm difference in FFD would be negligible ... or, at the very most, would require only the slightest of re-calibration in order to make this optical build viable for the Fuji-X platform.

 

Thus, I believe this is indeed feasible, and I hope to release such subsequent mounts by the turning of the year (aimed for the start of the early Spring of 2016). >>>

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I should also mention, that I did start initial testing on a similar optical build that can cover an FF sensor, but the native focal length on this lens is 27mm. Thus, I am not certain this would even be a worthwhile pursuit, given that there are already a number of 28mm pre-set lenses out there that can transmit ample UV and cover a FF sensor, and are based on a fully-functional focusing helicoid build.

 

But then again, a 27mm everything-in-focus pancake UV-lens can still be an attractive and fun accessory, for on-the-fly UV-landscapes on a FF digital body, no?

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Igor, you might add the filter thread?

 

A 52mm filter thread is already built into my currently-selling models for M-4/3 cameras.

 

Here, read the ad (if you have time, of course). Ebay item: 272007217970

 

(Note that I am not trying to be a solicitor. In fact, I immensely dislike random and/or unprovoked solicitation, unless someone asks me first for information.)

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2. "Yes, but Igor's eBay add title is somewhat misleading, although he 'rectifies' the 'wide angle' statement further down in the description."

 

Not misleading at all, given that the native focal length of the lens is indeed 25mm. And then depending on which camera it is adapted to, one would then do some simple multiplication. (Ex: On an APS-C sensor, 1.5 x 25mm = 37.5mm. On a Micro-4/3 sensor, 2 x 25mm = 50mm, and so on).

 

To say that I am "misleading" with stating that it is a wide-angle lens (because it is a wide-angle lens), would be like saying that every other lens ever made with the same native focal length is also misleading people. But it's not misleading people. Thousands upon thousands of 25mm focal-lengths lenses, old and new, have "wide angle" stamped on them, within the range of such focal lengths. That they become a different focal length on a non-35mm film/sensor plane is not "misleading." It is consequential and purely circumstantial. Just as it would be purely consequential - in a reverse circumstance - if a lens would suddenly become even wider (if adapted to a larger-format film/sensor plane).

 

The point is, natively, it is a 25mm focal-length lens. That makes it technically a wide-angle lens. (I'd say that any lens with a native focal length of 35mm or below would constitute "wide-angle" territory. But ... "tomayto-tomahto", I suppose. Heheh.)

 

(Although, as you've rightfully pointed out, I made sure in the associated details of the ad that any prospective buyer understands how non-35mm film or sensor planes can modify the resulting focal length, depending on which camera the lens is adapted to).

 

Despite all the nonsence written on Wikipedia and many other places on internet, the definition of wide angle lens has nothing to do with the focal lenght of the lens, but with its angle of view that is based on useable image circle.

 

Wide angle lens s the lens that covers 60° or more angle of view. Period.

 

Thus, my 60mm Hypergon that covers 135° angle of view is ultra-wide, despite being 60mm in focal length.

 

While even 6mm lens designed for 1/2" sensor will be few degrees short of wide angle.

 

Since you advertise your 25mm lens for M43 cameras, its angle of view (diagonal) is no more than 46°.

Only if it covers APS-C sensor, and prodices useable image from corner to corner, it can be classified as wide angle lens.

 

25mm lenses with "wide-angle" stamped on them are based on 135mm film format. Just like 55mm wide angle lenses for medium format. But have you seen 25mm lenses designed for 8mm film format with a "wide angle" stamp?

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4. " Assessed from the attached pictures of the eBay post, I don't think the image quality is that high, however that being said, might be a fun lens to experiment with. "

 

That's true. I mentioned in the ad details that the prospective buyer should not expect thousands-of-dollars performance with this build. Not even hundreds-of-dollars performance. The whole idea is to offer a UV-capable lens that is 1. budget-minded, 2. finally breaks through the previous 35mm focal-length "wide-angle" UV-lens available arsenal by offering a 25mm focal-length design, 3. effectively allows one to reach ever-so-closer to the much-sough after "UV landscape", and 4. does this with an "everything-in-focus" (3 meters to infinity) panfocal build that spares one of having to re-focus each time before shooting.

 

3.5/20 and 4/25 Zuiko lenses for half-frame Pen cameras from film era are cheap, very sharp in UV and fully cover APS-C sensor. I would rather recommend one of them.

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Despite all the nonsence written on Wikipedia and many other places on internet, the definition of wide angle lens has nothing to do with the focal lenght of the lens, but with its angle of view that is based on useable image circle.

 

Wide angle lens s the lens that covers 60° or more angle of view. Period.

 

Thus, my 60mm Hypergon that covers 135° angle of view is ultra-wide, despite being 60mm in focal length.

 

While even 6mm lens designed for 1/2" sensor will be few degrees short of wide angle.

 

Excellent points. Which is why I also noted in my ad that I am not a "guru" or an "expert" in such matters. Only that I am trying to supply a "wider" UV-capable lens, than the currently popular 35mm F/3.5 UV-capable (accidental) lenses out there.

 

That you have clarified this, of course, is a much welcome addition. Thank you, Alex!

 

Only if it covers APS-C sensor, and prodices useable image from corner to corner, it can be classified as wide angle lens.

 

25mm lenses with "wide-angle" stamped on them are based on 135mm film format. Just like 55mm wide angle lenses for medium format. But have you seen 25mm lenses designed for 8mm film format with a "wide angle" stamp?

 

Yes. This lens does cover the APS-C sensor. And the images remain quite usable. (In fact, this lens's image circle is even slightly larger than digital APS-C. It can cover up to a 30mm x 17mm frame without any edge-clipping).

 

No, I haven't seen much smaller-format lenses in the 25mm focal-length stamped with "wide-angle" stamped on. But those are much smaller-format lenses (such as CCTV / cine lenses, for instance). Whereas, my lens is not a smaller-format lens. It has a native image-circle that more than adequately fits for APS-C sensors (with some room to spare, in fact). Which is precisely why I said above - "native 25mm focal length" (emphasis on the word *native*, as in for the system it was originally designed for). Thus, you are essentially saying the very same things that I just explained, albeit with more greater and knowledgeable detail, of course. Thanks!

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3.5/20 and 4/25 Zuiko lenses for half-frame Pen cameras from film era are cheap, very sharp in UV and fully cover APS-C sensor. I would rather recommend one of them.

 

Oh, I would too. But that's comparing the proverbial apples and oranges, because these lenses have nothing to do with the stated goals of my own design.

 

(See my four points, again, below, in case you missed them in my prior comments):

 

1. budget-minded, 2. finally breaks through the previous 35mm focal-length "wide-angle" UV-lens available arsenal by offering a 25mm focal-length design, 3. effectively allows one to reach ever-so-closer to the much-sough after "UV landscape", and 4. does this with an "everything-in-focus" (3 meters to infinity) panfocal build that spares one of having to re-focus each time before shooting.

 

Not to mention, the "pancake" (almost body-cap-like profile) of this build goal.

 

(I crossed out #2 and #3, when in contrast to your other viable solutions ... albeit less-available and often more costly.)

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Also, how deeply do the 3.5/20 and 4/25 Zuiko transmit in UV? How about focus shift?

 

My 25mm F/6 displays virtually no focus-shift, when switching from VIS to UV, and it appears to transmit as low as 330-340 nanometers (estimated, based on Steve Smeed's, narrow-bandpass "Sparticle" testing ideas).

 

Even so, this is not a competition for other lenses. Not my concern, nor my goal. My own project stands on its own offering. If someone is interested in the other options, then by all means ... I am not holding them back. :D

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Half frame covers APS-C. And you can close the aperture on Zuiko lenses to F11-F16 and have "everything in focus". 25mm lens sells for about 60-70 USD these days.

 

And now to clarify why I said that your title is misleading.

 

You sell 25mm lens for M43 cameras and call it wide angle. 25mm for M43 is not wide angle. So either say its actual coverage and field of view (and say it can be used on other cameras), or do not call it wide angle.

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And now to clarify why I said that your title is misleading.

 

You sell 25mm lens for M43 cameras and call it wide angle. 25mm for M43 is not wide angle. So either say its actual coverage and field of view (and say it can be used on other cameras), or do not call it wide angle.

 

I stated in the title that it is "wider than the Kyoei / Kuribayashi 35mm." That is not "misleading." (Key word on *wider*).

 

Secondly, I also very clearly (and intently) made sure in my ad literature that all prospective buyers be aware of the 2x crop-sensor effects. Thus, I did responsibly express those facts (and quite transparently, I should say).

 

So, where is the "misleading?" The title is accurate (it is *wider* than the Kyoei 35mm, even on a 2x crop-sensor, since the Kyoei 35mm then becomes a 70mm lens), and my ad literature is also transparent.

 

Is there any reason for the lingering accusatory tone? I ask this with respect, by the way.

 

Half frame covers APS-C. And you can close the aperture on Zuiko lenses to F11-F16 and have "everything in focus". 25mm lens sells for about 60-70 USD these days.

 

That's a great thing. I will see if I can obtain some copies of my own, and also to do some test comparisons. But this in no way discourages me to desist from my own goals, and ongoing developments. It is a "free market", after all. Right? :D

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... and say it can be used on other cameras.

 

I did mention this. This is also in my ad ("in the stages of prototyping for other mounts, including for 1.5x crop-factor APS-C cameras such as for Nikon, Pentax, etc.")

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And you can close the aperture on Zuiko lenses to F11-F16 and have "everything in focus."

 

So, F/11-F/16 for "everything-in-focus" for your Zuiko examples, versus a lens that can keep everything in focus at F/6. More apples to oranges, I think?

 

(BTW: F/16 ... the start of diffraction region, no? Whereas F/6 is far from it. Or am I mistaken here?)

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You do understand that all 25mm lenses will have the same depth of focus if closed down to the same aperture setting. If only Zuikos had F/6 setting.
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You do understand that all 25mm lenses will have the same depth of focus if closed down to the same aperture setting. If only Zuikos had F/6 setting.

 

If that's the case, then why is it that no other lens which I currently own can obtain everything-in-focus DOF at F/6 (except for my Pentax-110 18mm F/2.8 Panfocus), but the 25mm F/6 lens that I am selling within my ad can actually do this?

 

If your statement holds true for "all 25mm lenses", then why are there also a few panfocus lenses (with comparable focal lengths) but with as fast of apertures as F/2.8?

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If that's the case, then why is it that no other lens which I currently own can obtain everything-in-focus DOF at F/6 (except for my Pentax-110 18mm F/2.8 Panfocus), but the 25mm F/6 lens that I am selling within my ad can actually do this?

 

Please be so kind and post 100% unsharpened crops showing both near and far objects within the same picture so we all can appreciate what you claim.

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Show me a panfocal 25mm F/2.8 lens.

 

I am not talking about a panfocal 25mm F/2.8. I am talking about a panfocal 18mm F/2.8 and my panfocal 25mm F/6.

 

(I have a few other 18mm prime lenses that cannot get "everything in focus" at F/2.8, nor can any of my other 25mm prime lenses get "everything in focus" at F/6).

 

Thus, clearly, differences in optical formulas exist to account for these variables. I do not know what these precise optical variables are (since I am not an optics expert, you are), but I certainly can say from my own experiences that it is not true that "all 25mm lenses will have the same depth of focus if closed down to the same aperture setting.") If that were the case, then my 25mm F/6 should not have worked the way it does.

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Please be so kind and post 100% unsharpened crops showing both near and far objects within the same picture so we all can appreciate what you claim.

 

I would be happy to do so, once I have access to doing more tests. (I am not in a position to do it at this moment).

 

I also have a different 25mm prime lens, which I can compare with my three-element fixed-focus 25mm F/6 lens. We shall see if stopping down to F/6 on my other 25mm prime lens will "get everything into focus." :D

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