slideshow photo compression

i’m working on a photo blog and have discovered a problem when uploading images for the slideshow (featured items) vs. uploading for a blog post. as you can see in these two links, the image is exactly the same image, but the quality when uploaded to the slideshow is horrible because it auto-compresses my file vs. the one in the blog post which doesn’t go through the auto-compression process.

auto-compressed image as featured item

same image uploaded to blog without auto-compression

a HUGE difference in quality and one i’m not ok with being that it’s a blog featuring my photography! is there any way to work around the auto-compression that happens with the slideshow featured items?