How to solve "properly sized images" on lighthouse with ghost?

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• What’s your URL? https://pandia.pro/

• What version of Ghost are you using? latest

• How was Ghost installed and configured? I’m using Ghost Pro

• What Node version, database, OS & browser are you using? Brave (1.48.171 Chromium), MacOS Ventura 13.2

• What errors or information do you see in the console? Nothing

• What steps could someone else take to reproduce the issue you’re having? Scan your website with lighthouse

Hello, I’m having an issue while I was trying to optimize my website speed.

Lighthouse is telling me I could save about 2 seconds by “properly sizing images”, but the code to display images was already good for me, so I tried some new configuration for the loop-grid.hbs, to compare speed, and the default configuration was still the best, here is the the code to display images :

As I said I tried multiple sizes=“” configurations, and no one was better than the actual one. I’m using compressed webp format for my images.
The theme I’m using is “Headline”

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I managed to have better results with this :
sizes=“(max-width: 768px) 150px, (min-width: 768px) 480px, 87.5vw”

but i’m still open to recommandations

btw if you have any solution for this while using the default header, i don’t have access to this code inside my theme folder :