> I’m also a sucker for 35mm in medium format so you can see photo content around the glorious sprocket holes.

Have you seen Ted Orland's holga photos? https://www.anseladams.com/products/tree-in-snowstorm-yosemi... and https://www.anseladams.com/products/dawn-at-mono-lake-in-win...

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I personally like 4x6 (a 5x7 is a bit more awkward and 8x10 is right out). One of my favorite things was when Polaroid peel apart film was available - I'd do a transfer to a watercolor post card in the field and put a stamp on it and send it. One of a kind photograph - while you could take another photograph there, you could never make the same print of it since it was a destructive process.

(Also neat being in the field and letting a young child do it from being under the hood to pulling out the film and transferring it to a post card or having the print as it is properly developed)