Solargraphy simulation with pinhole cameras

[Guillermo Luijk]

DIY pinhole film cameras are used to obtain ultra long exposure solargraphs, drawing the Sun trajectories in the sky. The most common camera format is a cylinder (beer can), but I have made the calculations on how an alternative half cylinder (semi can) would perform, and I find a lot of advantages in the half cylinder:

• Easier to get a wide FOV with quality because of a less critical angle of incidence over the film
• Each film axis only represents one angular coordinate (X ⭢ Azimuth and Y ⭢ Elevation) while the beer can mixes up Azimuth and Elevation in the Y axis
• It doesn't distort the curves near the extreme angles (Azimuths close to 90º/270º) which the beer can camera turns to 0 losing the Elevation information

Solargraph by Gianluca Belgrado


Studied cameras


Sun trajectory projections of each camera, including analemmas


Check of calculations vs real beer can (actually PVC tube) solargraph


The article here (Engllish translation available top right): https://www.overfitting.net/2022/04/simulacion-de-solarigrafias-con-r.html

Regards

[kers]

good subject!
Indeed pinhole makes a perfect wide angle lens- up tu 180º undistorted!
It surprised me when i made one; but it is never sharp and i mostly don't like the way it is unsharp...
nevertheless it is as spectacular as simple.

[gebseng]

Hi Guillermo,

Back in 2007, a student of mine, Andreas Zingerle, tried the "half-can" pinhole camera. You can see the results here:https://gebseng.com/media_archeology/student_works/2007/Andreas%20Zingerle%20-%20Solargrafica/neoanalog_pinhole%20andreas%20zingerle.pdf

best, geb

[Guillermo Luijk]

Cool Geb. I took a look at the PDF and I think it only shows full cylindric cameras, is that correct?

I just found another photographer, Steve Riegel, who built a half can camera. I'm a bit surprised on how few people use it vs the beer can, when it has advantages. Here we can see non-distorted analemmas thanks to the half can camera:



And the camera he built:


Regards

[ced]

Where would/was the pinhole on this half tube?

[Guillermo Luijk]

Where would/was the pinhole on this half tube?

I guess in the upper half of the tube, to get more field of view over the horizon where the analemmas get formed, and with the camera slightly pointed over the horizon (which then projects a bit curved).

I have come across with an idea to improve the effective FOV. The physical dimensions of the pinhole make impossible to achieve a FOV=180º. What if some polished melted plastic/adhesive material is located surrounding the pinhole to save ray paths thanks to diffraction that would otherwise get lost? the camera FOV would be increased:

http://guillermoluijk.com/misc/estenopoplus.png

Regards

[Guillermo Luijk]

A nicer simulation of the concept:



Regards

[Guillermo Luijk]

Closer to a real implementation with microscopy coverslips and Superglue (same refraction index as glass: ~1.5):



The adhesive fills the pinhole at the same time that sticks the coverslips.

Regards