Gene51 wrote:
But you can resize a higher MP image to a smaller screen size, without resampling. If you take an image from a D800 that is 7,360×4,912 and crop it, without resizing, to 1920x1200, it will "fit" a standard WUXGA HD display, which is also 1920x1200 in resolution, with no resampling needed. In this case Adobe's dpi specification is just a metadata tag without meaning or application.
Also, if you send a higher resolution or lower resolution image to a printer, most printer drivers (or raster image processors) will up/down sample the image to fit the image on the paper at the given resolution. A 6 mp image from a NIkon D70 is 6000x4000. At a desired print resolution of 300 ppi, you can print, without resampling, a 20x13.3 image. Without resampling the image, you can print a much larger image, like 60x40, but at a lower printer resolution of 100 ppi, with the print driver or RIP handling the "resizing" without resampling. However, if you need a higher resolution than the image has provided, say 200 ppi, then you have the option to resample the image to 12,000x8,000 px using an image resizing program, or the resizing algorithms in Photoshop, Lightroom or other image editing software, or let the printer driver/RIP resample it - so that you will be able to have enough "pixels" in the image to meet your image resolution requirement. The issue with up-sampling is that software is used to expand the individual "pixel" spacing, and it uses interpolation to take a good guess at what should be placed to fill in the new space between the old pixels. Resizing software NEVER increases resolution, but the better software will increase the edge contrast, or microcontrast, to give the viewer the perception of greater sharpness.
So, though I usually agree with you, Scotty, on this on I don't agree 100% - you can crop to resize to a given pixel count. It doesn't always have to be resampling.
But you can resize a higher MP image to a smaller ... (
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Erm, to pick a rather large nit - you state in the second paragraph "A 6 mp image from a NIkon D70 is 6000x4000. At a desired print resolution of 300 ppi, you can print, without resampling, a 20x13.3 image" - which of course, is incorrect, as are all of the following math samples based on a D70. A 6000x4000 sensor contains 24 million pixels - the antique D70 produces only 3000x2000 pixel images. Maybe the camera reference should have been a D750 or D7100/7200?