Meepzorp,
Yes, pictures are very dark on my desk-top and tablet. I often find that pictures that look
fine on my computer don’t always look the same on the web-page. I’m not sure why.
Yes, there are many programs that can adjust and correct pictures, but you can’t beat making them right in the first place.
Dark coins are always difficult to photograph. Try using a mid-grey plain background. Also, to avoid the shadow of the coin merging with the coin itself, try placing the coin on a small object to lift it above the background. Try using a supplementary light as described above. There is
plenty of advice on
Forum.
You have correctly written the code to give a 500x500 pixel display. The pictures themselves can be any size and the web-page will make them fit the 500x500 box. However, if the height and width of the picture itself are different (you have one 460x420 for example) then the image will be stretched unequally on the web-page and you will end up with oval looking coins. Just make the picture height and width the same, say in this case 420x420.
Peter