F/0.85 lens in Fuji X mount

[Astigmatism]

I noticed this today on Amazon: "Handevision HVIB4085FX IBELUX 40mm f/0.85 High-Speed Lens for Fuji X Digital Cameras".

I know nothing about the lens or the maker, save what it says on the page on Amazon. And of course I'm not promoting it. I just thought it was interesting that there was a lens this fast, and don't think I've seen its equal for our mount.

I did have a single element asphere that was just for one wavelength, for collimating light, so its optical performance would deteriorate rapidly away from the center. It was f/0.67. And I have a paper about a microscope objective design that gave an NA of 0.92 which corresponds to f/0.2, which could be a world record as far as I know. The paper is here:

https://arxiv.org/pdf/1611.02159.pdf

But not anything for mounting on Fuji X cameras.

Just thought it was interesting.

[David01]

That lens you spotted on Amazon sounds really interesting! I'm not surprised that you're intrigued by its speed, which is something you don't see every day in a lens that's compatible with Fuji X cameras.

As far as the lens manufacturer goes and the quality of the lens itself, I don't have much experience with either of those. However, I highly suggest you do some research and read reviews from others who have used it to determine its performance and whether it's worth taking a chance on.

You mentioned that you have experience with fast lenses, including single element asphere and a microscope objective design with an NA of 0.92. That's really impressive! It's always fascinating to learn about other people's experiences with unique lenses and the optical performance they were able to achieve.

[Astigmatism]

I already have the Fuji 50 mm f/1.0, which I like very much. It's a straightforward lens, not one of those that apply filters or odd optical corrections to modify the bokeh for artistic effect. In an ideal rectilinear lens, the bokeh would have uniform illumination and take on the shape of the iris diaphragm, and I think they can only modify that by introducing aberrations (primarily spherical) or vignetting filters. There's no accounting for taste, the heart wants what the heart wants. My personal taste is for minimized aberrations of all types, and my very rare toying with modification away from that only happens in post on long winter evenings. Given that I already own the lens I own, I don't think I'm buying -- but it is interesting! And I'd love to learn about even faster lenses....

[AlfRjw]

I think I read a review of this lens on this site with interesting pics

https://alikgriffin.com/kipon-ibelux-40mm-f0-85-iii-review-sample-photos/

[Astigmatism]

Interesting!

I'm mystified by the statement "A 35mm equivalency would give you something like a 60mm at f1.2, except, it’s still going to be 1.5 stops brighter than an f1.2.". Why does a 35 mm equivalent imply a specific f/ number? This equivalency is simply about focal lengths that would give the same angle of view.

[AlfRjw]

I think it just means that while you are getting a large amount of light because of the f/0,8 , you are going to have some more field in focus than what you would get on a full frame with f/0,8

I’m more inclined in looking at the images which show a lovely focus falloff - but the lens is too expensive for me so it’s all theory