I am using the Lightroom export function to create jpegs which are intended for use through a high quality projector and for this I resize (from larger originals) to 1400x1050 pixels.
The use of a projector is new to me so I am trying different amounts of output sharpening to see if there is an optimum set of parameters for this setup. I select Sharpen for Screen and then have the option to select Low, Standard or High.
My question is does the Resolution PPI setting affect the amount of sharpening as well?
I believe that I have seen references that it does, including on a thread on this forum (http://www.luminous-landscape.com/forum/index.php?topic=66916.0
). However when discussing this with other members of my camera club they are adamant that Resolution PPI does not affect the level of sharpening for screen. Which is it?
Apparently, as it is implemented in Lightroom, the PPI setting in Export does change the sharpening that is applied. It is a bit of a black box, and it is not immediately obvious how the sharpening for a display is different from the sharpening for projection. The difference is related to the viewing distance for the projection compared to the viewing distance for a display.
I assume that you could get the best results by calculating how the PPI of the projection at a larger viewing distance translates to a PPI for a normal reading distance or a viewing distance of a display, as follows. If we assume that the projector uses a resized to 1024 pixels wide image, and projects that on a screen size of say 6 feet wide, that would produce a 14.22 PPI image (1024px / 72in = 14.22 PPI). When you view that screen from a 6 feet distance, that is between 3 - 6 times the normal viewing distance of a display, so you use a sharpening PPI of between 3 to 6 x 14.22 PPI, i.e. something between 43 to 85 PPI. Just need to adjust the parameters for your actual projector resolution and viewing distances, and resize the images on output to the projector specifications with the proper calculated PPI setting.