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jamaeolus
Joined: 19 Mar 2014 Posts: 2964 Location: Eugene
Expire: 2015-08-20
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Posted: Fri Jul 14, 2023 4:50 am Post subject: Diffraction lenses, any thoughts? |
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jamaeolus wrote:
I read this site regularly and this popped up. Some on here might be interested.
https://theconversation.com/a-new-thin-lensed-telescope-design-could-far-surpass-james-webb-goodbye-mirrors-hello-diffractive-lenses-206055 _________________ photos are moments frozen in time |
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RokkorDoctor
Joined: 27 Nov 2021 Posts: 1405 Location: Kent, UK
Expire: 2025-05-01
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Posted: Fri Jul 14, 2023 8:35 am Post subject: |
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RokkorDoctor wrote:
I think someone got confused as to the difference between Fresnel Diffraction and Fresnel Lenses when describing the original Fresnel lenses as diffraction lenses.
Fresnel lenses use conventional refraction as a way to form an image. Diffraction is a different optics/physics phenomenon.
If you were to make the spacing of the Fresnel rings in a Fresnel lens small enough (approaching the wavelength of light), then you would see diffraction effects appearing.
This sounds simply like a more intelligently constructed Fresnel refraction lens with and additional etched diffraction grating/pattern on the refractive surfaces. Thus it looks like they combine the effects of refraction and diffraction to improve the imaging quality of a Fresnel refractive lens. _________________ Mark
SONY A7S, A7RII + dust-sealed modded Novoflex/Fotodiox/Rayqual MD-NEX adapters
Minolta SR-1, SRT-101/303, XD7/XD11, XGM, X700
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Ricoh GX100
Minolta majority of all Rokkor SR/AR/MC/MD models made
Sigma 14mm/3.5 for SR mount
Tamron SP 60B 300mm/2.8 (Adaptall)
Samyang T-S 24mm/3.5 (Nikon mount, DIY converted to SR mount)
Schneider-Kreuznach PC-Super-Angulon 28mm/2.8 (SR mount)
Bronica PS 35/40/50/65/80/110/135/150/180/200/250mm |
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Lightshow
Joined: 04 Nov 2011 Posts: 3666 Location: Calgary
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Posted: Mon Jul 17, 2023 1:46 am Post subject: |
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Lightshow wrote:
I don't know how stable a Fresnel lens would be in space.
Also I very much doubt it would outperform JWST in mid-IR, the lens would be glowing at those wavelengths, which is why the mirrors are coated in gold. _________________ A Manual Focus Junky...
One photographers junk lens is an artists favorite tool.
My lens list
http://www.flickr.com/photos/lightshow-photography/ |
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kathala
Joined: 13 May 2022 Posts: 141
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Posted: Wed Jul 19, 2023 4:34 pm Post subject: |
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kathala wrote:
This has been done commercially by Canon for twenty-odd years, sometimes quite decently (4oo 4 DO II), sometimes not (all others).
I am staggered that "an astronomer who studies astrobiology" should be "co-leading a team that is developing a new kind of space telescope". No wonder there were so many science sceptics during covid.
I am a professional photographer - maybe I should build my own little nuclear power plant to recharge my cameras, or at least co-lead a team of astrobiologists to build it. _________________ Photography Reference Tables:
drive.google.com/drive/folders/1aJ5F8XM6t5AK4bydthcDoiwhsh5CUx3N
My Art and Books: ChristianSchnalzger.de
My Exploration of Panoramic Photographic Storytelling:
flickr.com/photos/hach_und_ueberhaupt/
The better you look, the more you see (B. E. Ellis) |
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papasito
Joined: 09 Jan 2015 Posts: 1659
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Posted: Wed Jul 19, 2023 5:32 pm Post subject: |
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papasito wrote:
A famous photografer in Spain said that he uses Canon 70-200 IF lens because at f/11 or 16 it has not Diffraction problems at all.
Can be possible? |
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visualopsins
Joined: 05 Mar 2009 Posts: 10956 Location: California
Expire: 2025-04-11
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Posted: Wed Jul 19, 2023 6:59 pm Post subject: |
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visualopsins wrote:
papasito wrote: |
A famous photografer in Spain said that he uses Canon 70-200 IF lens because at f/11 or 16 it has not Diffraction problems at all.
Can be possible? |
For the famous photographer be possible, certainly. Not physically, however, effects can be minimized so as to become invisible when presented. _________________ ☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮ like attracts like! ☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮
Cameras: Sony ILCE-7RM2, Spotmatics II, F, and ESII, Nikon P4
Lenses:
M42 Asahi Optical Co., Takumar 1:4 f=35mm, 1:2 f=58mm (Sonnar), 1:2.4 f=58mm (Heliar), 1:2.2 f=55mm (Gaussian), 1:2.8 f=105mm (Model I), 1:2.8/105 (Model II), 1:5.6/200, Tele-Takumar 1:5.6/200, 1:6.3/300, Macro-Takumar 1:4/50, Auto-Takumar 1:2.3 f=35, 1:1.8 f=55mm, 1:2.2 f=55mm, Super-TAKUMAR 1:3.5/28 (fat), 1:2/35 (Fat), 1:1.4/50 (8-element), Super-Multi-Coated Fisheye-TAKUMAR 1:4/17, Super-Multi-Coated TAKUMAR 1:4.5/20, 1:3.5/24, 1:3.5/28, 1:2/35, 1:3.5/35, 1:1.8/85, 1:1.9/85 1:2.8/105, 1:3.5/135, 1:2.5/135 (II), 1:4/150, 1:4/200, 1:4/300, 1:4.5/500, Super-Multi-Coated Macro-TAKUMAR 1:4/50, 1:4/100, Super-Multi-Coated Bellows-TAKUMAR 1:4/100, SMC TAKUMAR 1:1.4/50, 1:1.8/55
M42 Carl Zeiss Jena Flektogon 2.4/35
Contax Carl Zeiss Vario-Sonnar T* 28-70mm F3.5-4.5
Pentax K-mount SMC PENTAX-A ZOOM 1:3.5 35~105mm, SMC PENTAX ZOOM 1:4 45~125mm
Nikon Micro-NIKKOR-P-C Auto 1:3.5 f=55mm, NIKKOR-P Auto 105mm f/2.5 Pre-AI (Sonnar), Micro-NIKKOR 105mm 1:4 AI, NIKKOR AI-S 35-135mm f/3,5-4,5
Tamron SP 17mm f/3.5 (51B), Tamron SP 17mm f/3.5 (151B), SP 500mm f/8 (55BB), SP 70-210mm f/3.5 (19AH)
Vivitar 100mm 1:2.8 MC 1:1 Macro Telephoto (Kiron)
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kathala
Joined: 13 May 2022 Posts: 141
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Posted: Thu Jul 20, 2023 2:40 pm Post subject: |
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kathala wrote:
papasito wrote: |
A famous photografer in Spain said that he uses Canon 70-200 IF lens because at f/11 or 16 it has not Diffraction problems at all.
Can be possible? |
a) spain has famous photographers?
b) Diffraction in the way YOU describe it is a physical phenomenon and thus not lens dependend. Yes, what he describes is possible - with a 4 MPix camera, and those exist, so yes, possible
c) the "diffraction" phenomenon described by this so-called scientist is of course based on the same principle, but its application is something completely different - it is like the Canon DO lenses (which will ALSO show diffraction at f/11 on a modern hi-res camera, regardless of lens or spaniard using it) _________________ Photography Reference Tables:
drive.google.com/drive/folders/1aJ5F8XM6t5AK4bydthcDoiwhsh5CUx3N
My Art and Books: ChristianSchnalzger.de
My Exploration of Panoramic Photographic Storytelling:
flickr.com/photos/hach_und_ueberhaupt/
The better you look, the more you see (B. E. Ellis) |
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calvin83
Joined: 12 Apr 2009 Posts: 7555 Location: Hong Kong
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Posted: Thu Jul 20, 2023 2:58 pm Post subject: |
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calvin83 wrote:
papasito wrote: |
A famous photografer in Spain said that he uses Canon 70-200 IF lens because at f/11 or 16 it has not Diffraction problems at all.
Can be possible? |
Depend on the print size and viewing distance. _________________ https://lensfever.com/
https://www.instagram.com/_lens_fever/
The best lens is the one you have with you. |
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stevemark
Joined: 29 Apr 2011 Posts: 3930 Location: Switzerland
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Posted: Fri Jul 21, 2023 12:09 pm Post subject: |
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stevemark wrote:
calvin83 wrote: |
papasito wrote: |
A famous photografer in Spain said that he uses Canon 70-200 IF lens because at f/11 or 16 it has not Diffraction problems at all.
Can be possible? |
Depend on the print size and viewing distance. |
The following is based on my my experience with 24 MP FF sensors. Other sensors with lower (12 MP FF) or higher resolution (36 MP and greater) will act differently, of course.
On 24 MP FF, with all lenses I use for professional work, I never hesitate to use f11 if necessary. While the image center - if I'm pixel-peeping! - may have a very slightly higher resolution at f8 (and sometimes also at f5.6, e. g. with Minolta AF 1.4/85mm), this higher resolution is completely irrelevant for large high quality offset printing (e. g. 40x60 cm for calendars).
At f16 the entire images looses some crispness, but aggressive sharpening with a small diameter (e. g. 0.5 px instead of the usual 1 px) will neutralize the effects of diffraction. This works very well if the image is noise-free (ISO 100 or ISO 200); higher ISO may result in unwanted artefacts.
That said, if depth-of-field is an issue, and if the image will be printed at maximal 20x30 cm (e. g. for books), one may use f22 and f32 as well. The resulting increase in depth-of-field is much stronger than the (slightly) diminishing overall sharpness. Again, after re-sizing the original image to the desired size/resolution (e. g. 2000x3000 px for 20x30 cm), some sharpening is recommended.
S _________________ www.artaphot.ch |
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RokkorDoctor
Joined: 27 Nov 2021 Posts: 1405 Location: Kent, UK
Expire: 2025-05-01
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Posted: Fri Jul 21, 2023 12:55 pm Post subject: |
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RokkorDoctor wrote:
Re. the above discussion;
The theoretical discussions re. diffraction-limited resolution usually only consider the the Airy-disk diffraction pattern of a round opening in relation to the circle-of-confusion size. However, in digital photography diffraction-limited sharpness is affected by a number of factors, not just the aperture size:
- aperture size
- aperture shape (e.g. hexagonal, round(ed), star-shaped etc.), which affects the diffraction pattern observed (Airy disk pattern, converging diffraction spikes, diverging diffraction flares etc.)
- The convolution between the particular diffraction pattern and the mathematical complex modulation transfer functions of the anti-aliasing filter & Bayer filter (which themselves are also related to pixel size of the sensor).
E.g. on FF, at f/64 everyone will notice diffraction softening regardless of lens or camera sensor used, but in the "grey" area (say, f/8 to f/16) it depends on the particular lens and filter/sensor combination used. For some combinations of aperture shape and filter/sensor it may become noticeable at f/8, for others not until maybe f/16. And that is assuming an ideal lens without any other lens flaws that may mask the onset of diffraction softening to some extent.
EDIT, incidentally, at a relatively simple level, CD players use a diffraction grating to create a very sharply defined pattern of laser light peaks; depending on the configuration of the photodiodes that read the reflected light different diffraction gratings are used; some players just create a central spike for both data readout and tracking (Phillips CDM transports), others create a pattern of three spikes (one central for reading data, two adjacent for tracking).
The reason I mention this is that this neatly illustrates how diffraction patterns and sensor patterns can interact in terms of readout resolution. _________________ Mark
SONY A7S, A7RII + dust-sealed modded Novoflex/Fotodiox/Rayqual MD-NEX adapters
Minolta SR-1, SRT-101/303, XD7/XD11, XGM, X700
Bronica SQAi
Ricoh GX100
Minolta majority of all Rokkor SR/AR/MC/MD models made
Sigma 14mm/3.5 for SR mount
Tamron SP 60B 300mm/2.8 (Adaptall)
Samyang T-S 24mm/3.5 (Nikon mount, DIY converted to SR mount)
Schneider-Kreuznach PC-Super-Angulon 28mm/2.8 (SR mount)
Bronica PS 35/40/50/65/80/110/135/150/180/200/250mm |
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