Image Sizing

When adding a featured image, try this:

1. Open the page or article and edit the text etc.
2. in sidebar [bottom right] click ‘set featured image’-link
3. select the image file you want to use
4. In the sidebar, next to the thumbnal: ‘edit image’
5. click ‘scale image’
6. adjust the size if required
7. if required: crop the image
8. update the post / page

!!IMPORTANT!! check the media settings in your dashboard:

• dashboard > settings > media
• make sure these settings [esp. proportions] match the size of your files.
  This way when uploading media into your medialibrary will keep the correct proportions for your files
• NOTE: EVERY TIME Before uploading a [batch of] mediafile[s] that have different proportions, change the settings, as suggested above.
  This is a bit of a bother, but will save you a lot of frustration

I have done this, edited the media sizes, i have also changed around the sizing of the featured image but it does not work

the images that show on the homepage are set to be width: 750px, and height: auto, but they keep blurring.

for example, the starbucks image is exactly 750px wide, i cropped it in the featured image section, yet it still blurs and zooms itself in for some reason

OMG okay i finally figured it out for anyone who is interested

in functions.php change:

$img .= '<a>ID).'">'.get_the_post_thumbnail($post->ID, 'custom_thumb').'</a>';

to:

$img .= '<a>ID).'">'.get_the_post_thumbnail($post->ID, 'post_thumbnails').'</a>';

since custom_thumb is set to 150, 150 it for some reason sees your featured image as a custom thumb, crops it down to 150X150, and then enlarges and blurs it to your specified measurments

Great that you found the answer.
Thanks for sharing.