One of the photographers that I'm intrigued by is Michael Wesely ( https://en.wikipedia.org/wiki/Michael_Wesely ) who takes ultra long exposures (a two week long exposure is "short" - his flower photographs are in that range). The museum of modern art was about two years. http://www.amusingplanet.com/2010/08/unusually-long-exposure...

You can see the tracks of the days and the cloud cover in those photographs. Note that the multiple year ones have multiple days going over a single track.

Aside from the extreme reciprocity failure in the film, its "only" about three stops from a one day exposure to a one week exposure... and another two stops to a month, and then another three and a half stops to a year.

Thanks for the reminder on the reciprocity rules! I used to take super-long exposure with my 4x5/10x8 view cameras as well... basically after a few minutes, it doesn't /really/ matter anymore so stop counting in minutes/seconds, more in teacups+newspaper pages :-) I always loved the tonal range you get on way, WAY overexposed film.

Digging up an old page (I am not sure if the film still has that characteristic curve), Provia 100F had some very nice lack of reciprocity failure. http://home.earthlink.net/~kitathome/LunarLight/moonlight_ga... (from http://home.earthlink.net/~kitathome/LunarLight/moonlight_ga... - its an old frames page).

The correction for a 1200 second (20m) exposure on Kodak black and white film was at 12x (for 14400s, 4h). However, the extrapolation for the curve for Provia 100F put the reciprocity failure for 1200s at 2.35 for a 3000 second exposure.

Looking at the methods and results is interesting, though I've gone nearly full digital now.

I've never seen a glass sphere this large - it's almost surreal: https://en.wikipedia.org/wiki/Campbell%E2%80%93Stokes_record...

I keep looking at it, my brain confused why I can't see through what is clearly a transparent object. It doesn't feel like I'm looking through it, though inverted; it feels like I'm seeing a weird depiction of the nature scene around me plastered on its surface.

You might be interested in this:

https://www.treehugger.com/solar-technology/solar-prototype-...

https://cleantechnica.com/2013/12/23/solar-ball-lens-improve...

Not solid glass, though (I don't know what it is, but I imagine there's an upper limit on size of solid glass spheres that can be made)...

I was stationed at a very remote weather station where apparently, in previous years, some of the meteorologists were too lazy to change the sun exposure sheets during the year. Just before the relief voyage came there was a sunny day and they 'recorded' the whole year's data.

That is fascinating and worthy its own submission!

That's ingenious.