How many different interchangeable lenses do you have?

Started 3 months ago | Polls thread
OP ProfHankD Veteran Member • Posts: 7,860
Birds Eye lenses

petrochemist wrote:

ProfHankD wrote:

fferreres wrote:

Is the outermost a french press?

That's the one everybody misidentifies... often as being a NSFW device.

Not quite everyone - I have a Kaidon 360 which is much the same. I was thinking you can't get much wider than that

The Kaidon 360 does avoid the glass tube, but is a lot more fragile.

Honestly, the Spiratone is the best built, smartest design, and was historically first. The main plus being that in it, the mirror position is adjustable through a pretty large range of distances. However, IQ is challenged by the need of all of these to focus on the mirror (i.e., you need depth of field to cover the mirror depth, which is hard to do because it's close up) and, in the Spiratone and Egg, you get flare from the glass cylinder. My first homemade ones used a very similar construction except the glass cylinder was instead thin plastic from a soda bottle and the mirror was a "1/2-chrome" DecorLite lightbulb, which is a surprisingly accurate spherical mirror -- it worked great.

The later version was something I created for my cameras as computing systems course way back in 2015:

It's a simple 3D-printed frame (Thingiverse Thing 1188289 ) using a "Holiday Glass Ornament" filled with sand to help stabilize the device. You do block a few degrees with the printed clear support, but that's not the big problem: the big issue is that the reflective surface is not of optical quality, but is rather distorted. That was actually a feature for the course project, which had my students implement the calibrated transformation into a cylindrical projection inside the PowerShot ELPH115IS camera using CHDK. Here's what the calibration target looked like as seen by the camera:

Their software had to find the dots (including the red one) and use those coordinates to create a mapping table. The mapping was then implemented using Bresenham's algorithm to interpolate without using any multiplies or divides... because those Canons are just a dual-core 80MHz ARM inside and the frame buffer is awkwardly 12-bits per pixel with the wrong endianness (a downside of Canon reusing much of the same guts for decades).

I think I still have at least a couple of these birds-eye stands, but not with the ornaments intact. One in my lab got broken at some point such that one day I found it was cracked with a little pile of leaked sand around it.

 ProfHankD's gear list:ProfHankD's gear list
Canon PowerShot SX530 Olympus TG-860 Sony a7R II Canon EOS 5D Mark IV Sony a6500 +30 more
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