The situation is different. The first letter in "photo" is not the "p" but the "ph". They are one. The "h" is a modifier. In "graphics" there is no modifier on the "g".

TL;DR H as modifier was introduced when translating Greek and they were lacking appropriate letters in Latin.

https://linguistics.stackexchange.com/questions/29625/origin...

https://www.theguardian.com/notesandqueries/query/0,5753,-88... -- last answer by Anastasio de la Luna (and a few other answers there too)

> I'm a phoneticist and a general linguist and "PH" and "F" are, indeed, pronounced the same, and are both represented by /f/ in the International Phonetic Alphabet. Greek Phi was once pronounced as a hard "P" in Ancient Greek. So, Latin inscriptions wrote it as "PH" to show that it's a P sound, but with more air with H. As Greek changed, so did the Greek based English words. In Modern Greek, Phi is pronounced as "F", and no longer like "PH"/a hard P.

..and I forgot: That means that it should have been J-Ph-EG and not JPEG. They created a completely different first letter by ignoring that "ph" is one letter. The J-PEG pronunciation was obtained by using destructive force.