i and na adjective

I recently learned about い- adjective and な- adjective. However, I'm not so sure how to form the negative form.

For example,

For い-adjective
If an interesting movie is: おもしろい映画
Then is the negative form "面白くない映画"?

For な-adjective
If a beautiful picture is: きれいな写真
Then how do you say not a beautiful picture?

For い-adjective
If an interesting movie is: おもしろい映画
Then is the negative form "面白くない映画"(make sense)

For な-adjective
If a beautiful picture is: きれいな写真
Then how do you say not a beautiful picture?(きれいではない写真(it makes sense grammatically but not sound natural)

"美しい写真" "美しくない写真" sound more natural in this example.

When the adjective is used not before a noun, but as a predicate of a sentence:

あの映画はおもしろいです That movie is interesting.
あの映画はおもしろくないです。That movie is not interesting.

この写真はきれいです。This picture is beautiful.
この写真はきれいではないです。or　きれいじゃないです。This picture is not beautiful.