I prefer a smaller image size, because I usually post two or three photos at a time in my posts. Some people say my images are too small at 300 x 400 pixels, but you never hear anyone complain about load time.
If you just want to post one or two photos, or a closeup of a bloom, I suggest the settings LIJane used in her recent post. 640 x 480 is a decent sized image, but I am on a laptop, so even photos that big look small to me.
Well for me, a general rule of thumb is to get the picture in the forum/browser screen (with browser screen maximized of course ) without having to scroll left or right. (scrolling left or right to get a full view is not kosher) My pictures are usually a (750x563) pixels at 300 pixels per inch . My screen resolution is at (1024x768) pixels. And so far no ones really complained. This is my typical picture size.
I'm with Marco, as long as I don't have to scroll, I'm happy. I complained the other day that the actual photo John had posted of something came up too small in my database, but I got it straightened out, I didn't mean to imply that ALL your photos linked in too small, J, they're just fine!
Computer monitors, in general, have a 72 pixel per inch display. This means that if your image is 6 inches wide but the resolution is set at 300 dpi, none of that data (beyond 72) is displayed, and you're just making your file size larger. That is, at 6 inches, the photo would look exactly like a 72 dpi photo, but would be up to 4 times larger in file size.
Obviously, that larger file size would come in handy if you expect people to download the image and play with it in an editor or Print it. But most of us only expect people to be looking at our photos on the screen, so I recommend setting your image resolution to 72.
I had thought maybe there was a standard size the forum format may prefer.
I always set images at 72dpi for Internet use. And that is a very good point to remember about file size. It seems some folks prefer smaller images and some bigger. I definitely agree about having to scroll the picture horizontally being undesirable so I'll use around 600 wide.. What are your thoughts for vertical scrolling? I seem to prefer an image where the whole can be seen without scrolling in either direction. But then a vertical format image is smaller and some detail may be hard to see.
So my question now is... To scroll Up and Down or No scroll?