“Boke,” often spelled “bokeh,” is a Japanese word for the shapes formed in, and perhaps also broadly the quality of, the out-of-focus areas in a photographed image.
Don’t pronounce this word “bokuh.”
There’s only one “e” sound in Japanese. The same one you find in sake and edimame. To a speaker of US English, it sounds like the e in “felt.”
So “bokay” isn’t exactly right either, although most Americans happily order “sah-kay” at a sushi restaurant. If you listen to a Japanese person pronounce sake, that’s also how they would say the end of boke.
I imagine the “eh” spelling of “bokeh” was intended to help English-speakers see and say this not-quite-soft, not-quite-long, e sound. But this backfired in the form of the “bokuh” pronunciation, which has no provenance, and sounds ugly.
It could be argued that, unlike sake, “bokeh” has become a “westernized” term, so I think it’s okay for English-speakers to arrive at a comfortable pronunciation. I suggest you pronounce it to rhyme with the way you say sake.