If you head over to the review of the shiny new Viltrox AF 35mm f/1.7 Air, you'll see that we liked it rather a lot, awarding it a highly respectable four-and-a-half stars and our coveted 'recommended' badge to boot. But there's one thing that really gets my goat: that f/1.7 aperture.
What gives with these unnatural fractions of an f-stop? I know where I am with an f/1.8 lens, just as I know the score with an f/1.4 or f/2 or f/2.8 lens, because they follow the longstanding accepted convention of dealing with f-stops in full or third stops.
Yes, I get that f/1.8 isn't on the full f-stop scale either, being 1/3-stop faster than an f/2 lens and 2/3-stop slower than an f/1.4 lens, both of which are true full-f-stop lenses (see our f-stop explainer for the reason why 1.4 is considered a 'whole' number when it comes to the weird maths behind apertures!). But f/1.8 lenses have been around since the dawn of photography, pretty much.
So f/1.7 is marginally faster than an f/1.8 lens, such as Nikon's own Z 35mm f/1.8 S, but it feels like that 0.1 f-stop difference is there for the sake of it. A kind of f-stop arms race to be just a little bit better than the competition, but without providing any real material benefit to the photographer.
So f/1.7 is actually a half-f-stop, and sure, you can set your camera to use half-stop rather than third-stop increments, but nobody ever does.
I don't mean to single Viltrox out here – many other lens makers have produced lenses with the same ever-so-slightly wider maximum aperture, not least of which is Nikon itself, with the Nikon Z DX 24mm f/1.7.
And don't get me started on 27mm lenses. The classic wide prime focal lengths from the dawn of time are 24mm, 28mm and 35mm, always have been, always should be. Still, we rated the Viltrox AF 27mm f/1.2 Pro and TTArtisan AF 27mm f/2.8 pretty highly too.
Maybe I'm just stuck in my ways?
