This is not so much a request for a solution as it is an observation on which I welcome any further insights.
Previously in this forum, it was agreed that Photoshop does not display images as fully sharp except at the pre-defined zooms (e.g. 16.67%, 25%, 33.33% ...) and with Fit to Screen.
However, I just discovered also that if an image has been resized, then Fit to Screen does not display as fully sharp.
For example, if I resize an image from 5616 x 3744 to 6000 x 4000, then Fit to Screen no longer displays the image as fully sharp..
Yet, resized images (or any images) display in Windows Photo Viewer or web browsers as sharp no matter how small or large they are contracted or expanded.
Meanwhile, Windows Picture Viewer and browsers are self-consistent no matter how large or small the image is contracted or expanded.
By the way, another issue, though not regarding Photoshop itself: At least with Windows, for all images whether resized or not, Chrome is slightly less sharp than Windows Picture Viewer, while Internet Explorer is oversharpened. The problem with Internet Explorer is extremely acute especially for images that have been sharpened in Photoshop. Images that are properly and reasonably sharpened in Photoshop display perfectly in Windows Picture Viewer and okay (but a little softer) in Chrome; but in Internet Explorer these images have a ghastly jaggedness.
However, this does not occur in Internet Explorer when the images are set into a slideshow (or other "container" that sizes with the browser window?). For example, if I sharpen an image in Photoshop, then drag the image file icon straight into Internet Explorer, then the display is decidedly unacceptable; but if I put that same image file in a slideshow on my web page, then it looks okay in Internet Explorer.