i use a black background on my screen, because my eyes can’t stand looking at white. it’s too bright for my poor vision. i noticed when trying a white background that it can wash out the full color of the sunset pics. that may be why some appear to be dark. they don’t appear dark to me with a black background on my computer display.
i use windows accessibility option for high contrast to switch my screen from white to black. unfortunately the high contrast option does not display all pages properly. sometimes it hides text or even whole pictures on some sites. using a black background is the only way i can look at a computer screen for any length of time without my eyes getting stessed.
anyways, if some of the pics appear too dark it could be because a white background washes out the actual picture colors, especially the darker ones after it is dark. i like the pictures to look as it appeared to me at the time. i could brighten them but that is not the desire or how it looked at the time. real is the deal.
one more little tid bit. the pics are as taken. no color changes at all. resized them smaller for upload. but made no other adjustments. it was really that good, with rich purples all around. the water was awesome too.