Originally posted by biz-engineer .......
There is a lot of confusion around diffraction "limit". There is no such things as diffraction limit, because an image formation is impacted by various contributions, glass, aperture diffraction, digital sensor resolution, pixel level performance.
Oh yes there is
The diffraction limit is a function of the whole imaging medium e.g. smaller photosites or film with smaller grain will have a lower limit of diffraction than larger photosites or grain.
Diffraction happens at every aperture as light passes around the edges of the diaphragm. In optics the effect is known as the Airy disc pattern and describe the best focused spot of light that a perfect lens can make limited by the diffraction of light.
Diffraction limit is the point where the airy disc grows large enough to affect more than a single photosite. This is the meaning of Diffraction Limited
Quote: Diffraction is one of the contributor, its amount varies mainly with lens aperture, but it never 0% nor 100%. Even at f1.0 is diffraction present and become more prominent with higher aperture numbers.
Diffraction is present as you state at all apertures, but the point is at some stage depending on the pixel pitch of the sensor you will have reached the Diffraction Limit at a certain f/stop
Quote: Personally I prefer 100Mpixels with 12bits depth over 50Mpixels with 14bits depth, because displays do no more than 10bits depth
IF all you are doing is looking at a monitor or for that matter a TV then either is fine. Additionally your monitor will probably not be able to display 50 or 100 MP images without downsize interpolation. An 8K UHD monitor (7680 × 4320 pixels) is only 33MP! And while you are talking about bit depth current displays mostly limited to 10bit but 12-bit have been around for a while and one would expect a move to mainstream in the future
Quote: ... and the depth is limited to 8bits for printers.
No it is not. For some time now Mac OS and printer drivers have offered the option of 16 bit printing. Latterly Windows systems have allowed 16 bit through XPS drivers
Quote: Printers aren't limited for resolutions however, as more Mpixels can be printed larger.
Printers are limited for resolution at fine settings of 720ppi or 600 ppi (and possibly 1440 and 1200 ppi). Indeed more MP can be printed larger or more MP can mean printing with a higher resolution than the standard 360 or 300 ppi taking advantage of detail in an image that
may be present but not appreciated at a so called standard res.
Quote: However, if an image is 14bits deep per pixel/per channel, the extra bits over 8bits are lost when printed.
Not really for a couple of reasons:
If you edit your images (12,14 or 16 bit) in Prophoto for instance you should be in 16 bit (PS actually is 15+1 bit) your image will be sent through the printer profile and driver to the printer. At the editing stage it is quite likely that you have used the full 14 or 16 bits to refine your image and that edited image is quite happily sitting within the limits of 8 bit.
Should you really need more than the 8 bit image then you would select that at the printing stage through the print driver. A general consensus seems to be if your image has come from a 14 or 16 bit raw capture that there is very little to be gained most of the time printing in 16 bit. However if you are looking at computer generated images there may be some benefit in certain cases.
Last edited by TonyW; 03-13-2021 at 03:26 PM.