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Canis lupus familiaris [Domestic Dog]

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#1 OlDoinyo

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Posted 29 November 2014 - 20:36

Attached Image: Canis lupus familiaris j small ex DSC00013.jpg

Converted Sony A900, Goema/Makowsky 500mm mirror optic, Baader U2 filter; 1/2 second @ f/8 and ISO 800; display intent GBR.

The depicted specimen (named Jacques) is a mixture of border collie and other indeterminate ancestry.

The identity of the colored objects at lower right is uncertain; they are not flowers. The greenish shadowing in the fur may represent an actual wavelength dependency, or it could be an artifact. The nose does exhibit a faint reddish tinge, perhaps due to preferential absorption of shorter wavelengths by skin pigment; alternatively, this may be a scattering phenomenon.

The mirror objective, which is the only glassless optic in the photographer's possession, exhibits an apparent tint gradient from lower right to upper left. The cause of this is not known.

#2 nfoto

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Posted 30 November 2014 - 09:08

Presumably I have the same (or a close relative) of your glassless lens (a contradiction in terms yet true). I have never got any useful UV imagery out of it despite the alluring optical design (can you speak of optics when there are none?). UV response wasn't great and sharpness even worse.

My suspicion is that the oblique angle of incidence of light onto the sensor plane causes issues with the microlenses of digital cameras. The design is old (50's if memory serves).

#3 OlDoinyo

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Posted 30 November 2014 - 18:30

(I realize that I stray a bit off topic here, and beg the reader's indulgence.)

Anton Kutter invented the Schiefspiegler telecope in 1953; Helmut Makowsky patented the camera objective based on it in 1968. The actual products seem to have been sold in the early-to-mid 1970s; I remember reading a piece in Popular Science about it back in the day, and lusting after it ever since, though I could never find it. The idea of a long telephoto based on an off-axis reflecting design seemed logical to me then, and still does; all of us know how limiting it is to have a secondary mirror in the primary light path, the default design for all those cheap fixed-aperture Maksutov-Gregorian telephotos which have given mirror lenses an evil reputation, and fostered the notion that the only possible good telephoto lens is a giant refractor design like all those baseball bats that sports photographers put on their cameras. It sounded like a dream come true, and the official hype promised as much: coma below diffraction limits, diffraction-limited sharpness, etc.

Yeah, right.

It may be that Helmut Makowsky actually constructed a prototype which performed on this level. By all accounts from then until now, however, the production runs were something else: numerous reviewers have noted poor build quality, clumsy controls, and a generally "improvised" feel, as well as image quality no better than the above-mentioned cheap lenses (the Makowsky was not cheap when new.) This is doubtless why the product and the design died a hasty death. The example I have appeared to have been used hard in the past, and then neglected; I had to clean spiderwebs out of the interior as best I could, without touching the mirrors. Someone epoxied the focusing lever back in place, doubtless because it stripped out. So yes, getting a professional-quality image with this optic is a challenge, and attempting non-UV photography with it is all but pointless. It may also be that the product is fragile and prone to mirror misalignment under heavy use. The light-angle thing is usually more of an issue with wide-angle lenses, not long telephotos; it would surprise me if that is a problem here; and I do not see how a microlens issue could degrade sharpness. As to the UV spectral response, I do not have the means to test that directly; but for pete's sake, how could something that is just a box with two front-surface mirrors and some air impede UV response?

Edited by OlDoinyo, 30 November 2014 - 18:39.


#4 nfoto

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Posted 30 November 2014 - 19:21

UV is impacted by mirror coatings to name one example.

It is true the ray bundle exiting the lens is near collimated for such a long lens, but for this particular design, it also enters the camera at an oblique angle. I suspect this somehow is related to the quite disappointing field performance.

#5 OlDoinyo

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Posted 13 December 2014 - 04:21

A postscript:

Looking down the bore of the Makowski reveals that the secondary mirror is dead-center with respect to the camera's optical axis:

Attached Image: Katoptaron-boresight.jpg

Therefore there can be no oblique incidence angle at the focal plane; a simple Herschelian geometry with a flat secondary would have been thus, but evidently the Schiefspiegler is a bit different.
What is inclined about 20 degrees from the incoming light axis, however, is the filter mount (a silly design omission which could easily have been corrected.) As the Baader filter is partly dichroic and therefore possibly angle-sensitive, one wonders at the implications.

Interestingly, Vitastra markets a Schiefspiegler kit which is touted as being usable for telephoto as well as astronomical use:

http://www.vitastra....uper-telephoto/

I don't know of anyone who actually has one of these, so I can say no more.

Edited by OlDoinyo, 13 December 2014 - 04:32.


#6 nfoto

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Posted 13 December 2014 - 15:38

My Baader is either rear-mounted or in-camera, and the UV performance of this 500 lens is appalling for lack of a better word.

#7 OlDoinyo

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Posted 13 December 2014 - 17:13

UV performance of this 500 lens is appalling

The image quality in the visible is no better, as far as I can see: the optical quality of a children's toy telescope (other than the lack of flare.) So frustrating, given what could have been. But it is still useful for some limited purposes.
Perhaps Dr Schmitt or someone will report on the Vitastra some day...

#8 Alex H

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Posted 13 December 2014 - 17:33

I shot this picture with my Katoptaron - http://www.holovacho...19156#h52219156
At 1/13 sec I think the image quality is not much worse than the pictures I shot using Canon 500mm L lens (manual focus nFD) and solar filter.

#9 OlDoinyo

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Posted 13 December 2014 - 22:20

That's nicely done. But in all fairness, image quality away from the center of the frame is difficult to judge with this subject matter. It is also possible some individual production pieces were better than others.

#10 Alex H

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Posted 14 December 2014 - 07:43

View PostOlDoinyo, on 13 December 2014 - 22:20, said:

It is also possible some individual production pieces were better than others.

Does this characterise the lens or the photographer?

#11 nfoto

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Posted 14 December 2014 - 11:15

I surmise he had the lens in mind....

#12 OlDoinyo

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Posted 14 December 2014 - 13:33

Surmise correct. I certainly meant no insult to anyone and apologize if such was perceived.

#13 Andrea B.

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Posted 15 December 2014 - 15:48

I think Alex was making a subtle joke. "-)

I've never shot with a mirror lens, so it is always interesting to see such fotos.
Andrea G. Blum
Often found hanging out with flowers & bees.

#14 nfoto

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Posted 15 December 2014 - 20:28

To paraphrase, the Makovski is 'all mirrors no smoke'. Unless one gets the lens directly from the designer himself, which is a devoted cigar smoker. My sample of this 500 reeked accordingly.

#15 OlDoinyo

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Posted 16 December 2014 - 21:58

Considering the extraordinary rarity and obscurity of this piece of equipment, I am amazed that at least three persons on this forum possess one.

#16 nfoto

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Posted 16 December 2014 - 22:32

We indeed appear to be 'special' ;)

#17 Alex H

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Posted 17 December 2014 - 07:16

View PostOlDoinyo, on 16 December 2014 - 21:58, said:

Considering the extraordinary rarity and obscurity of this piece of equipment, I am amazed that at least three persons on this forum possess one.

I have never specifically paid any attention to the number of these lenses being sold on eBay, but over past few years I noticed a few, just by accident. Mostly sold in Europe.

#18 renaud

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Posted 27 February 2015 - 17:02

I happen to own a variant of this lens, the LDM-1. It has a third knob (labelled CORR) besides the focus and aperture controls. Turning the knob tilts the rear mirror (it even comes with a laminated handwritten table with correction values for various focusing distances).

Attached Image: P1000133.jpg

I think this is supposed to correct astigmatism (I remember reading this although I can't find the documentation anymore). I assume that other lenses of the same design with a fixed mirror will suffer from this defect outside their optimal focusing range.

#19 enricosavazzi

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Posted 02 August 2020 - 17:29

View Postrenaud, on 27 February 2015 - 17:02, said:

I happen to own a variant of this lens, the LDM-1. It has a third knob (labelled CORR) besides the focus and aperture controls. Turning the knob tilts the rear mirror (it even comes with a laminated handwritten table with correction values for various focusing distances).
I think this is supposed to correct astigmatism (I remember reading this although I can't find the documentation anymore). I assume that other lenses of the same design with a fixed mirror will suffer from this defect outside their optimal focusing range.
If I remember correctly, early production runs had a manual adjustment control like your specimen, while the last series before production ended had an internal mechanical coupling between focus and mirror inclination. Whichever way, the adjustment is critical to correct the strong aberrations that otherwise arise if the inclination of the mirrors is incorrect for a given focus distance. According to a piece I read years ago, the designer strongly resisted modifying the original lens design to add this coupling, until forced to by plummeting sales. By that time, it was too late to gain a sufficient market foothold.

Edited by enricosavazzi, 02 August 2020 - 17:30.

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#20 dabateman

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Posted 03 August 2020 - 23:32

Enrico this thread is a blast from the past. Over 5 years ago. I hope they weren't patiently waiting for a response.