Hacker News new | past | comments | ask | show | jobs | submit login

I'm not a photographer, is a '163mm f/2.5' lens supposed to be in focus only in the middle, or is that an artefact of it being a budget DIY model?

Also, I think the source link might be better: https://www.pixelsandprisms.com/3d-printed-lens/ (more photos, no ads to block, and not sure what OP adds).




> is that an artefact of it being a budget DIY model

This one. I believe all lenses are blurry in the corners to some extent, but it's not usually that bad.


Legend has it that some of the disposable cameras had curved film planes to, uh, take advantage of the abundant spherical aberration and astigmatism. I'm sure this lens need something like that too.


Isn't that the expected depth of field you'd get from f/2.5?


No. The "depth of field" for a lens parallel to the sensor is a space between two planes, so you'd expect it to be clear all the way across the image but blur closer and further from the sensor (up and down the image). This blurs out to all the sides, it's due to spherical abberation from inappropriate glass (more suited to telescopes where only the center of the image circle matters).


That's what I'm asking, without even being certain if it's f/x or y mm that affects that.


Amongst other things, the f number affects the depth of field (how much of the image is in focus.

A low number (f/1.6 is fairly low. f22 is fairly high) means that only the object you focused on will be sharp and anything nearer or further away will become blurry. This is great for portaits for example as it draws attention to the person.

(f is the aperture and also affects the amount of light. You can shoot with a lower shutter speed if you have a wide aperture/low f number)

The "mm" number is the amount you're zoomed in. Wide is a low number, telephoto from a distance is a high number.

But blur can come from other things. Cheap lenses, unsteady hands or moving subjects. Depth of field is just one type of blur.




Join us for AI Startup School this June 16-17 in San Francisco!

Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact

Search: