The folder image, 1560px wide, is just as sharp as the slide image. The slide image is 2500px wide, but it isn't tack sharp to begin with. The smaller details are slightly blurry. Open the slide image in your browser raw, i.e., not being displayed on an album page, and I think you'll see the same thing.

Start with an original in which everything is in focus. In this case, I suspect that the original is no better than the slide image.

You might also let the jAlbum scaling do a bit of sharpening, maybe 25%, or even more. There are no faces in your photos, and that's where sharpening tends to make things worse, not better. But for railroad pics, it might help.

BTW, there's no sense setting jAlbum for 100% JPEG Quality. There's a reason for the warning triangle you're seeing there. Past about 80%, you will not be able to detect any improvement, but the file sizes get huge. Just a waste of bandwidth.

You're scaling the images to 1200px, but the folder image is 1560px wide. So, the browser is trying to make it larger than it really is, which will make it blurry. Leave everything at 2500px.

Using larger bounds simply cannot produce a less-sharp image. Make sure you're refreshing your browser cache.

Attach or post a link to the original image, Jeff has already said he suspects it is not tack sharp.
If you have another image that is tack sharp try using that image instead.

Laza - I think we're dealing with a combination of two things, here.

The first is the fact that, to the human eye, an image shown in 1200px looks subjectively sharper than one shown in 1500px, even though objectively they are equally sharp.

But the other factor is that folderimage.jpg seems to be generated with a fixed JPEG Quality, unlike the slide images, and it appears to be defaulting to 80%. That, of course, should be more than good enough - I doubt that in a double-blind test, anyone can tell the difference between and 80% image and a 90% image.

For those following this from the peanut gallery, if you start with a sufficiently large image (over 1240px wide), set the image bounds to 1240x1240, set the JPEG Quality to 80%, and set the Tiger maximum page width to 1240px, you end up with a slide image and a folder theme image that are identical.

ETA: I take it back. It's more convoluted than that. The folder image doesn't appear to be using things like the sharpness setting, the smoothing method, and so on. It's almost impossible to do a controlled test to reveal what's happening "under the hood."

But folderimage.jpg doesn't get regenerated if you change, for example, just the JPEG Quality. You have to delete the existing one from the output first (or delete the entire local album). Even a Force Remake doesn't take care of it.

In my skins, this happens automagically.

So, I'm not sure what Tiger is doing.