daniel r
10-04-2005, 01:59 PM
Recently I found a lot of discussion here about the issue of HD lenses and their ability to deliver high resolution for 1/3 inch sensor. Particulary, Barry Green in another thread went into specifics -
"Lens size isn't necessarily a limiting factor, but the lens' ability to resolve at a rate of 200 line-pairs-per-millimeter. With 720p the needs are less stringent, but for full 1080 you need almost 200lp/mm........
I'm kinda confused here: how come my relatively cheap compact digital camera (powershot s70) has a resolution of 7MP on a 1/1.8 inch sensor and still is reasonably sharp? 7 megapixels on a 0.55 inch more dense than 2 megapixels of HD on a 0.33 inch.
Barry then went on - "The other limitation is diffraction, because once you get down to where your pixels are 3 microns across, you start running into limitations caused by the size of the wave of light. So you'll likely have a very limited f-stop range within which the image could be resolved; stopping down beyond f/5.6 may introduce diffraction and lower the perceived sharpness. For this reason, the Canon lens is limited to f/9.5, and the Sony has a menu option to force the aperture to go no smaller than f/8 or f/5.6 (your choice)."
This is probably the answer to my question - and my digital camera probably does suffer from that kind of diffractiion.
Does it mean that there is only so much resolution any lens can deliver on a 1/3 inch area and beyond that it is not sharper but to the contrary - less sharp???
This is important because so far the discussion about the "ideal" sensor resolution was SHARPNESS vs LATITUDE.
"Lens size isn't necessarily a limiting factor, but the lens' ability to resolve at a rate of 200 line-pairs-per-millimeter. With 720p the needs are less stringent, but for full 1080 you need almost 200lp/mm........
I'm kinda confused here: how come my relatively cheap compact digital camera (powershot s70) has a resolution of 7MP on a 1/1.8 inch sensor and still is reasonably sharp? 7 megapixels on a 0.55 inch more dense than 2 megapixels of HD on a 0.33 inch.
Barry then went on - "The other limitation is diffraction, because once you get down to where your pixels are 3 microns across, you start running into limitations caused by the size of the wave of light. So you'll likely have a very limited f-stop range within which the image could be resolved; stopping down beyond f/5.6 may introduce diffraction and lower the perceived sharpness. For this reason, the Canon lens is limited to f/9.5, and the Sony has a menu option to force the aperture to go no smaller than f/8 or f/5.6 (your choice)."
This is probably the answer to my question - and my digital camera probably does suffer from that kind of diffractiion.
Does it mean that there is only so much resolution any lens can deliver on a 1/3 inch area and beyond that it is not sharper but to the contrary - less sharp???
This is important because so far the discussion about the "ideal" sensor resolution was SHARPNESS vs LATITUDE.