View previous topic :: View next topic |
Author |
Message |
iangreenhalgh1
Joined: 18 Mar 2011 Posts: 15679
Expire: 2014-01-07
|
Posted: Fri Mar 06, 2015 2:54 pm Post subject: How to calculate sensor spatial resolution? |
|
|
iangreenhalgh1 wrote:
Hi folks
I'm trying to work out, in line pairs per mm the spatial resolution of a sensor.
This sensor produces images 4000 pixels wide and is 7.6mm wide.
4000 pixels/2 gives us line pairs, correct? That would be 2000lp.
Therefore, to get lp per mm, we would divide 2000 by 7.6, correct?
2000/7.6 = 263
So is the correct answer 263lp/mm?
Seems awfully high to me. _________________ I don't care who designed it, who made it or what country it comes from - I just enjoy using it! |
|
Back to top |
|
|
calvin83
Joined: 12 Apr 2009 Posts: 7557 Location: Hong Kong
|
Posted: Fri Mar 06, 2015 3:25 pm Post subject: |
|
|
calvin83 wrote:
I think so.
http://photo.blogoverflow.com/2012/06/the-realities-of-resolution/ _________________ https://lensfever.com/
https://www.instagram.com/_lens_fever/
The best lens is the one you have with you. |
|
Back to top |
|
|
Ray Parkhurst
Joined: 04 Jul 2011 Posts: 504 Location: Santa Clara, CA, USA
|
Posted: Fri Mar 06, 2015 3:38 pm Post subject: Re: How to calculate sensor spatial resolution? |
|
|
Ray Parkhurst wrote:
iangreenhalgh1 wrote: |
Hi folks
I'm trying to work out, in line pairs per mm the spatial resolution of a sensor.
This sensor produces images 4000 pixels wide and is 7.6mm wide.
4000 pixels/2 gives us line pairs, correct? That would be 2000lp.
Therefore, to get lp per mm, we would divide 2000 by 7.6, correct?
2000/7.6 = 263
So is the correct answer 263lp/mm?
Seems awfully high to me. |
Yes, your calculation is correct. The sensor you're describing has a 1.9um pixel pitch, which is pretty small, hence the high calculated resolution.
Note however that the actual resolution is less if the sensor has an anti aliasing filter. Typically this cuts resolution by 50% or more, sometimes 100%. Plus the demosaicing algorithms don't produce sharp images at pixel level so the algorithm itself limits resolution. Don't expect to be able to clearly see 263 line pairs on a test pattern with the sensor, it just won't happen. |
|
Back to top |
|
|
Ray Parkhurst
Joined: 04 Jul 2011 Posts: 504 Location: Santa Clara, CA, USA
|
Posted: Fri Mar 06, 2015 3:46 pm Post subject: |
|
|
Ray Parkhurst wrote:
That is an excellent article. Thanks for posting the link, I had not seen it before. |
|
Back to top |
|
|
dan_
Joined: 05 Dec 2012 Posts: 1058 Location: Romania
Expire: 2016-12-19
|
Posted: Fri Mar 06, 2015 4:41 pm Post subject: |
|
|
dan_ wrote:
That resolution also only refers to vertical/horizontal lines/mm. For diagonals you should expect it to be less. |
|
Back to top |
|
|
visualopsins
Joined: 05 Mar 2009 Posts: 11010 Location: California
Expire: 2025-04-11
|
Posted: Fri Mar 06, 2015 4:50 pm Post subject: |
|
|
visualopsins wrote:
Thanks Ian & Calvin83 _________________ ☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮☮ 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)
|
|
Back to top |
|
|
kds315*
Joined: 12 Mar 2008 Posts: 16651 Location: Weinheim, Germany
Expire: 2021-03-09
|
Posted: Fri Mar 06, 2015 6:36 pm Post subject: |
|
|
kds315* wrote:
I had about 100lppm in memory as the max working resolution of a camera, seems to be correct from that article.
Well there still are lenses that outresolve that... not for long as sensor development seem to move faster than
lens development ... _________________ Klaus - Admin
"S'il vient a point, me souviendra" [Thomas Bohier (1460-1523)]
http://www.macrolenses.de for macro and special lens info
http://www.pbase.com/kds315/uv_photos for UV Images and lens/filter info
https://www.flickr.com/photos/kds315/albums my albums using various lenses
http://photographyoftheinvisibleworld.blogspot.com/ my UV BLOG
http://www.travelmeetsfood.com/blog Food + Travel BLOG
https://galeriafotografia.com Architecture + Drone photography
Currently most FAV lens(es):
X80QF f3.2/80mm
Hypergon f11/26mm
ELCAN UV f5.6/52mm
Zeiss UV-Planar f4/60mm
Zeiss UV-Planar f2/62mm
Lomo Уфар-12 f2.5/41mm
Lomo Зуфар-2 f4.0/350mm
Lomo ZIKAR-1A f1.2/100mm
Nikon UV Nikkor f4.5/105mm
Zeiss UV-Sonnar f4.3/105mm
CERCO UV-VIS-NIR f1.8/45mm
CERCO UV-VIS-NIR f4.1/94mm
CERCO UV-VIS-NIR f2.8/100mm
Steinheil Quarzobjektiv f1.8/50mm
Pentax Quartz Takumar f3.5/85mm
Carl Zeiss Jena UV-Objektiv f4/60mm
NYE OPTICAL Lyman-Alpha II f1.1/90mm
NYE OPTICAL Lyman-Alpha I f2.8/200mm
COASTAL OPTICS f4/60mm UV-VIS-IR Apo
COASTAL OPTICS f4.5/105mm UV-Micro-Apo
Pentax Ultra-Achromatic Takumar f4.5/85mm
Pentax Ultra-Achromatic Takumar f5.6/300mm
Rodenstock UV-Rodagon f5.6/60mm + 105mm + 150mm
|
|
Back to top |
|
|
iangreenhalgh1
Joined: 18 Mar 2011 Posts: 15679
Expire: 2014-01-07
|
Posted: Fri Mar 06, 2015 7:03 pm Post subject: |
|
|
iangreenhalgh1 wrote:
Cheers guys. The sensor in question is that of my Pentax Q7 which has no AA filter.
I was trying to work out what a lens would have to resolve to be able to outresolve the sensor. _________________ I don't care who designed it, who made it or what country it comes from - I just enjoy using it! |
|
Back to top |
|
|
Ray Parkhurst
Joined: 04 Jul 2011 Posts: 504 Location: Santa Clara, CA, USA
|
Posted: Fri Mar 06, 2015 7:53 pm Post subject: |
|
|
Ray Parkhurst wrote:
kds315* wrote: |
I had about 100lppm in memory as the max working resolution of a camera, seems to be correct from that article.
Well there still are lenses that outresolve that... not for long as sensor development seem to move faster than
lens development ... |
Klaus...none of the cameras discussed have CCD sensors with the kind of resolution Ian is working with. If you do the same type of analysis, using lenses designed to have large diffraction-limited apertures, you'll find that the 100lp/mm moves into the 180-200lp territory.
iangreenhalgh1 wrote: |
Cheers guys. The sensor in question is that of my Pentax Q7 which has no AA filter.
I was trying to work out what a lens would have to resolve to be able to outresolve the sensor. |
I prefer looking at the problem from the pixel pitch / Airy disk perspective. So what you need is a lens that is diffraction-limited at f/2.8 or larger to out-resolve your sensor. This is the DLA for 1.9um pixel pitch. In practice you won't see much degradation at probably f/3.3 or even f/4 depending on the quality of the Pentax demosaicing algorithm. The DLA is the point at which no visible degradation occurs because the the first null of the Airy disk falls on the center of the adjacent pixels (Rayleigh limit). You have to go further to see degradation. |
|
Back to top |
|
|
iangreenhalgh1
Joined: 18 Mar 2011 Posts: 15679
Expire: 2014-01-07
|
Posted: Fri Mar 06, 2015 9:00 pm Post subject: |
|
|
iangreenhalgh1 wrote:
Cheers Ray. Not sure I understand fully, but it's something to mull over.
This shot was one that got me thinking about the resolution. It was taken with a Computar 1.3/8.5mm lens wide open. Notice the hairs in front of the girl's face and how the lens has resolved them, so it must be a pretty sharp little lens.
_________________ I don't care who designed it, who made it or what country it comes from - I just enjoy using it! |
|
Back to top |
|
|
Ray Parkhurst
Joined: 04 Jul 2011 Posts: 504 Location: Santa Clara, CA, USA
|
Posted: Fri Mar 06, 2015 9:46 pm Post subject: |
|
|
Ray Parkhurst wrote:
iangreenhalgh1 wrote: |
Cheers Ray. Not sure I understand fully, but it's something to mull over.
This shot was one that got me thinking about the resolution. It was taken with a Computar 1.3/8.5mm lens wide open. Notice the hairs in front of the girl's face and how the lens has resolved them, so it must be a pretty sharp little lens.
|
Ian...is this a 100% crop or is it a downsized full-sensor image? It appears to be a crop because it is an odd size, 1500x999. If so, then the resolution does seem very good.
Note that there is little advantage from lens perspective to shoot wide open vs stopping down to the DLA (in spite of what the resolution article says) especially for sensors without AA filters. So what I'm saying is that you will get essentially the same performance shooting at f/1.3, f/2, f/2.8, or possibly even f/3.3 from system resolution perspective. You'll get shallower DOF at f/1.3, but the parts of the image that are in critical focus will have about the same sharpness up to f/2.8 or possibly f/3.3. Unless you're trying for shallow DOF, it is usually better to stop-down to the camera DLA. I learned this empirically after having the AA filter removed from my T2i, and found that I could easily excite false colors if the aperture was wider than the DLA. Also, the lens itself is probably sharper at f/2.8 than it is at f/1.3 due to aberrations, so the final image may actually be sharper. |
|
Back to top |
|
|
MartinCrabtree
Joined: 10 Jan 2015 Posts: 121
|
Posted: Fri Mar 06, 2015 10:45 pm Post subject: |
|
|
MartinCrabtree wrote:
Well then thanks for confirming I'm not overthinking this whole photography thing. |
|
Back to top |
|
|
iangreenhalgh1
Joined: 18 Mar 2011 Posts: 15679
Expire: 2014-01-07
|
Posted: Fri Mar 06, 2015 11:16 pm Post subject: |
|
|
iangreenhalgh1 wrote:
Hi Ray
It's a 4000x3000 RAW image downsized then saved as an 80% JPEG, no other processing.
It was shot on a dark train at ISO 3200, f1.2, just to see if it worked. _________________ I don't care who designed it, who made it or what country it comes from - I just enjoy using it! |
|
Back to top |
|
|
|
|
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
|