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Comment by lostgame | Hacker News Reader

Very misleading title. They are not even talking about the glass.

f/2.5?!

Heh - this is a remarkable feat of intentional engineering; but it’s absolutely useless as a functional camera.

This f2.5 lens is glued to my camera and I take plenty of pictures (not just macro)! https://global.canon/en/c-museum/product/ef271.html

Now that might be a bit unusual choice of lens, but news photographers around the world rely on their zoom lenses that won’t open up more than f2.8.

And for a prime lens in this long focal length, f2.5 is still quite okay, Canon’s EF135mm opens up until 2 that’s only 2/3rd of a stop faster.

Really fast lenses get attention because they are the most expensive, and shallow depth-of-field has been in fashion… I think in part because it gave photographers a way to distinguish themselves from smartphone wielding amateurs. I predict this is on the way out now that portrait mode fakes this look! But a super fast lens is in no way necessary for taking great pictures.

I’m sure there’s plenty of valid criticisms for this project but this one does not convince me :) Personally I wonder more from an ecological point of view, i.e. why use all these resources when there’s plenty of unused lenses on the second hand market. But then again the Open Source aspect is commendable.

What is shocking about the f/2.5 f-stop? That’s a pretty fast lens, especially for something diy.

I second this. For this focal distance, vintage lens tend offer around f/3.5 - f/4. Compared to that, this is pretty impressive for DIY and just two lens elements. Might be more lightweight too, which makes it suitable for street photography.

Everything is a compromise. This optical design manages to be f/2.5 most probably because it does nothing to correct the plenty of aberration and defects it produces. Also f-numbers are deceptive regarding brightness and we should see how much light actually comes out from the other side, i.e. calculating its t-stops.

Also, a manual 165mm lens on full frame? I'm sure it could be great for interesting portraits, but street photography?

If it were actually well-corrected and apochromatic, then a 165mm f/2.5 lens would be fantastic for astrophotography. There's a reason the manual-focus Rokinon 135mm f/2 lens is so popular for that purpose.

And there is a reason why theanual focus Nikon 200 f/2 is, used, at over 2k Euro. Good professional lenses are expensive for a reason. Ehich is the reason why I stick to used ones for DSLRs, those are finally getting cheaper and easily available on the used market now that a lot of people switch to mirrorless and dedicated mirrorless lenses are covering more and more focal length and zoom ranges.

Once you stop caring about image quality, the f-stop of a lens is only fundamentally constrained by the physical diameter and diopter of the lens. I suspect the f/2.5 figure is only being held back by the size of the lens barrel and aperture mechanism.

It's only hard to make a fast lens when you also have a narrow lens barrel or a strict internal quality standards to satisfy. In absence of those, an aperture disc is just a disc that can be drilled, and 50[mm]/3.5 = 12.5mm or 0.5" is a nice round number around the context of a 135 format camera.

> suitable for street photography

Good luck using a 160mm lens for street photography, especially given only the center 10% is somewhat sharp

Vintage lenses are slower but at least you can take good photos with them, it's like comparing a diy car based on a lawnmower and a ford focus

Too long focal length. For street photography in a budget a Nikkor 50 mm f/1.8D is used in excelent condition under 100 bucks. Fast lens, tack sharp, great in low light and small so you do not stand out among the people usibn their phones.

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