It's two mites and mildew. The small black dots are the chasmothecium of powdery mildew, and you can clearly see the fungus' strands. Therefore, the translucent dots are most likely the fruiting bodies of powdery mildew. I don't know what the magnification is. In the top 1/8th of the picture, the leaf has already been consumed by mildew and looks very different from the rest.
See more here.
In fact, from that same page, this is exactly what you're looking at here at a different magnification, in the first post:
See more here.
In fact, from that same page, this is exactly what you're looking at here at a different magnification, in the first post:
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