In some themes (twenty sixteen) the issue is the media uploader behavior – when adding a custom logo via the Site Identity function in the Customizer, it defaults to Crop Image (after selecting the local file for upload) and THAT cannot be skipped. Even if you spread the crop function, it simply crops at the set max-width anyway.
AND the custom-logo function uploading renames the file.
Here’s my workaround.
add custom CSS >
.custom-logo {
max-width: 500px !important;
width: 300px;
}
with your actual desired values.
Then determine the name given to the file uploaded (and ruined by the crop function). IE> cropped-whatever (should have LOGO label next to it in file view of Library)
Use a separate FTP or file transfer app to locate that directory where your site is hosted. Delete the uploaded ruined image from your host server.
Upload a good version of the image with the same file name (cropped-whatever) to the server.
I hope that makes sense.
THEN, you can edit the custom CSS with the width and max-width value that works best in the various devices view.
THE KEY IS AVOIDING the cropping of your image in the selection & publishing of a crappy small version. It seems like wordpress has decided to NOT fix this by adding a function to the customizer to allow setting logo width and height…. ?? go figure.
And maybe (suggestion) having a way to reset which image is LOGO (as marked in the Media Library) to a different image + PUBLISH image direction from Library would be nice.