What should I hand over for a banner or poster print?
A banner or a poster needs the file at the size of that piece, not a story crop, with the plate clear of the edge where the type will sit. A feed screenshot does not get there: it pixelates in print.
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Ask the printer for the width and height of the piece before the shoot. The miss in the sierra is sending the Instagram jpg and having the plate land on the banner fold. If the banner is in the uses, that version goes in its own file, larger than the social one, with room for the type.