Author Topic: Showing pictures at optimum sharpest scaled resolution (not quite full screen)  (Read 470 times)

Offline ybp

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While I'm here after reporting my previous feature request (possible bug?) I also have another super important request, the absence of which has negatively impacted my ability to quickly assess the quality of images during the culling process.

Right now you can view full screen, super fast, the best way to cull clearly, correct? Yes, except for when I'm using a 4K or higher resolution monitor.

In those cases I have noticed that when the resolution of the original image is close to but not exactly twice as large as the 4K resolution, (either slightly less than twice as large or sightly more than twice as large), that the full screen image is actually lower quality than if the image were simply scaled down to exactly twice as small as the original image, due to smoothing/interpolation in order to get the image scaled to the full screen size.

If the original image is a random multiple of the display resolution, like 2.5x or 1.7x, etc., then the full screen display is best. But if the original width or height is something like 1.9x or 2.1x larger than the screen resolution, then I can tell a distinct loss of quality when viewing the image full screen in Photo Mechanic versus looking at the image scaled to 50%.

So my question is, could Photo Mechanic have a feature added that will do "smart full screen" display that will show the images at full screen preview unless the original is very close to being 2x larger than the screen width or height, and in that case it would just scale the image to exactly 50%, making a preview that is a more accurate assessment of the original sharpness?

Of course, this would leave a tiny border or possibly crop a tiny bit of the edge depending on the original resolution ratio, but this would be a small price to pay for getting a more accurate instant view of the photo's actual sharpness.

Note that just zooming in with the letter Z is NOT an option, as I have to get through 2000 photos within 15-20 minutes sometimes, and picking the sharpest image is very critical. Not all images are the same resolution either, so I can't just set the zoom to 50% ahead of time.

Even better, this would make Photo Mechanic go even faster when culling, since for almost all interpolation methods 50% scaling is less computationally intensive, more accurate, as well as sharper than scaling to some odd ratio in order to fit the exact screen size of the monitor.

Thanks!
« Last Edit: February 15, 2019, 11:55:47 AM by ybp »

Offline Kirk Baker

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In your Preview preferences, do you have "Enlarge photos to fit previews and slideshows" turned on (checkbox is checked) ?

I advise turning it off and see if that improves things for you.  Also make sure that High DPI Display Quality is set to "Best (uses more memory)"

If neither of these settings changes makes an improvement you could turn on sharpening.

-Kirk

Offline ybp

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Thank you for the suggestions. That checkbox helps a lot when I'm working with photos bigger than the screen resolution combined with photos smaller than the screen resolution.

I hadn't thought about the issue of photos that are less than the screen resolution, but you are right! The issue of scaling reducing apparent image sharpness becomes FAR worse for images if they are scaled up to the full size of the preview window.

I tried sharpening as you suggested in this morning, and although it does seem to hide the issue I am seeing, sharpening isn't an option due to slowness and I am also concerned that it will inhibit my ability to do my job of culling which requires me to assess images as they are.

I have basically worked out my own solution to this problem by using the 50% zoom view to cull the images. But then in those cases, when I run into an image that is much smaller than the screen size, it would be nice to have a checkbox that was the "inverse" of the checkbox you mentioned, so that it would not zoom out images that are already smaller than the preview window.


FYI, for clarity, this is what I was thinking of previously, which I still think would be extremely nice:

Smart Preview Scaling Options Descriptions (for achieving highest speed scaling quality while avoiding unlucky scaling ratios close to 50% or 100%, without needing to do sharpening or use a higher and slower level of scaling quality)

Let

imageToScreenRatio = max(Img.width/Screen.width, Img.height/Screen.height)

Then

if (imageToScreenRatio > 2.1)
    then zoom "Z" will scale to 100% or other selected zoom ratio, and non-zoom will scale to the exact preview window size

else if (imageToScreenRatio > 1.9)
    then zoom "Z" will scale to 100% or other selected zoom ratio, and non-zoom will scale to either the exact preview window size (default) or to 50% (if new "Prefer sharper/faster scaling near 50% and 100%" option is checked)

else if (imageToScreenRatio > 1.1)
    then zoom "Z" will scale to 100% or other selected zoom ratio, and non-zoom will scale to the exact preview window size

else if (imageToScreen Ratio > 1)
     then zoom "Z" will scale to 100% or other selected zoom ratio, and non-zoom will scale to either the exact preview window size (default) or to 100% (if new "Prefer sharper/faster scaling near 50% and 100%" option is checked)

else if (imageToScreenRatio > .9)
    then zoom "Z" will scale to 100% or other selected zoom ratio, and non-zoom will scale to either the exact preview window size (default) or to 100% (if either the existing "Enlarge photos to fit previews and slideshows" option is unchecked, or the new "Prefer sharper/faster scaling near 50% and 100%" is checked).

else
    then zoom "Z" will scale to 100% or other selected zoom ratio, and non-zoom will scale to either the exact preview window size (default) or to 100% (if existing "Enlarge photos to fit previews and slideshows" option is unchecked)


In fact, maybe it would be better not to have this option as some strange checkbox hidden away in the options, but rather as just a toggle key.

Thinking about possibilities… maybe the whole pseudocode thing about is actually missing the point! Maybe the toggle key could really just be a way of changing the scaling with one simple key press from whatever it is to the nearest level of mathematically optimal sharpening. For example, 50% scaling is much more mathematically optimum than 51% or 53% or 47%, and so pushing the toggle key for an image close to 50% would simply rescale it to 50%. And once the toggle key is pushed it would continue to show photos at their optimal scaling level until it was pushed again. What about that?