Images do not scaled down automatically, or so is my experience.
I've manually resized my images in all my posts. Even though I own a plethora of image editing software, I still stick to this method of resizing.
Open your image in windows photo viewer, use zoom or window resizing to get the size you want, press print screen on your keyboard, open paint, press CTRL + V, drag image corner to canvas corner, crop out the rest by simply resizing the canvas to the photo edge. Save and upload.
Nobody laugh at my neanderthal resizing methods!!  
 
-Adam