[Theme: Hatch] Change default size of featured image in a post?

Realizing now after all that, that my images are getting cropped and coming out blurry. For instance, with a 335×500 image, I tweaked the dimensions for single-thumbnail as suggested above, but it’s still not working. I’m so confused now as I’ve ended up with the problem that started this thread. Initially I just wanted to include portrait size so the images wouldn’t load at full size but were in proportion to page layout without getting cropped off or being fuzzy. Did I miss something?

WordPress makes imported images blurry by default when it re-sizes them – it’s one of it’s cool features.

Actually that was wrong about wordpress Hatch blurry images
Check out:
https://codex.www.ads-software.com/Function_Reference/add_image_size

Where is says:

“Notes
Using the ‘false’ setting will fail to produce a new image in the upload directory if one of the image dimensions of the uploaded image are equal to the new image size.”

I have found that uploading an image at exactly the size (width or height) you want to use it results in no image being saved at that size, and the wrong-size image will be used instead, resulting in a blurry appearance.

Therefore upload images that are slightly too large and let WordPress resize them for you.

This seems stupid, but it also seems to work with Hatch Theme, and Twentytwelve.