Jesse_Wroe’s review published on Letterboxd:
Watched the new blu-ray this time, looks great, much better than what I streamed on Fandor several months ago.
Watching it again proves how hard a time I'm having quantifying and ranking the best gialli. Though it set the format that would be exploited throughout the giallo boom of the 1970s, I still kinda prefer the more overt horror stylings and gratuity of the subsequent rip-offs. But the movie has a unique look, doubtless provided by Academy Award winning DP Vittorio Storaro and Argento's novice, though assured, direction (although, Bertolucci and Coppola definitely used Storaro with much more assuredness).
As a kind of perverse and brutal murder mystery, I like that it feels more of a steeping stone toward a horror film, an antecedent to the slasher. In this sense, it's a close relative to Bava's "Blood and Black Lace."
Despite it's narrative treatment that's definitely superior to the average giallo, there are some moments and a pivotal scene that won't impress the detective skills of the audience. The protagonist Sam reads of the latest murder in the newspaper handed to him by inspector Morosini, yet Sam asks Morosini when it happened. Well, it should say so on the very page Sam is looking at, and Morosini should probably be noticeably irritated by that oversight. Additionally, why did it take so long for Sam to think to contact the artist of the painting that he acquired during the beginning of his amateur investigation? Apart from the fact that this contact creates his absence at a location, which serves as a setup for a scary set piece. And, of course, the information he learns would cut the story short. This is a giallo thing: red herrings, MacGuffins, and a clueless sleuth whom we must follow despite our ability to see beyond his missteps. "Deep Red" is a peculiar example of this, as there's a climax that leaves the audience going "Uh, really? Is the obvious being ignored here, or what?"
Regardless, as pulp entertainment, this giallo is one of the best, for sure.