photos – Take away one srcset entry from wp_get_attachment_image

That is the unsuitable strategy. Cellular gadgets are being served the small picture as a result of the default sizes attribute is inaccurate to your makes use of case, not due to the srcset.

If you happen to present an accurate sizes attribute then browsers will select a extra applicable supply. If you happen to take away the 300w model with out altering the sizes attribute the browser will in all probability simply decide the 600w model, which can in all probability nonetheless be blurry. In actual fact, given trendy cellular show resolutions I would wager that it’s selecting the 600w model or increased already, however that is nonetheless too blurry.

The rationale the picture is blurry is as a result of your sizes attribute (which is definitely simply the WordPress default) is telling the browser that on shows smaller than 2664px the picture is displayed at 100vw, i.e. the viewport width, however the picture is definitely displayed at 100vh due to your CSS, which means that the picture is definitely being displayed a lot a lot wider if the show is vertical.

It is advisable inform the browser what width the picture will really be displayed at. In case your photos are 16:9 the the picture goes to be displayed at 1.66 instances the peak of the show (16/9 is 1.66). You possibly can inform the browser this by setting the sizes attribute to calc(100vh * 1.66):

wp_get_attachment_image(
    $attachment->ID,
    'full',
    null,
    array(
        'sizes' => 'calc(100vh * 1.66)',
    )
);

Sadly. as a result of the picture is sized vertically, it isn’t attainable to supply a 100% correct sizes attribute until you already know the facet ratio of the unique picture. If you happen to or your customers are going to make use of a wide range of completely different photos on this slider, then it’s possible you’ll wish to dynamically calculate the ratio:

$picture = wp_get_attachment_image_src( $attachment->ID, 'full' );
$ratio = $src[1] / $src[2];

wp_get_attachment_image(
    $attachment->ID,
    'full',
    null,
    array(
        'sizes' => "max(100vw, calc(100vh * $ratio))",
    )
);

I added max() right here to point that the picture will show at 100vw or calc(100vh * $ratio), whichever is wider. That is to account for the behaviour of object-fit if the unique picture is tall and slender.