What font to use add text to picture, when there is no white background?

Question

It's like making an internet meme, except it's not about meme.

I am learning English vocabulary, and I think that a meme-like image will help me a lot to memorize the word. It has a picture and a (short) description. However, I'm not sure how to add the text properly. The font using in memes is Impact, but it is used because of the widely distribution of it by Microsoft*, not because of any rationale.

Moreover, the popularity of the font using in meme makes me instantly feel that every picture with a line of text in that font will be a meme, before I even start looking at the picture and reading the text. It could be a little childish to use a meme-like picture in formal context like in a presentation.

Q: So what font should I use to add at the bottom of the picture?
And by the way, how should I choose the size of it?

_{*Vox, The reason every meme uses that one font}

Answer 1

You can use any typeface that pleases your eye except Comic Sans.

The size generally depends on the length of the text object you are applying. If you only put in a few words, use a larger size. If you put in a paragraph of text, use a smaller size. And work to please your eye in this case also.

Impact was used for memes in part because it has a heavy weight (thick lines) that causes the letters to stand out from the image. You will likely want to use a heavy weight also, whatever typeface you choose.