WordPress changing my images size

Hello.

I usually post long images on my blog (dimensions can be 600×10000) and it wasn’t a problem when I was using WordPress.com. But ever since I switch to www.remarpro.com, every time I upload a long image, its dimensions are automatically changed to something way smaller (like 113×2520) and that makes my images unreadable. I tried changing the dimensions manually to fit the originals, but its just streching the image out and pixelates it.

How do I fix this problem?

The page I need help with: [log in to see the link]