>There are common misconceptions regarding light gathering in photography. I'll first try and clarify light gathering by lenses as it impacts the choice of lenses for night photography.>Photographers are trained that more light gathering means a faster f-ratio. After all, exposure is directly related to the f-ratio. But f-ratio tells light density in the focal plane, not total light received from the subject. Light gathering from the subject is actually proportional to lens aperture area times exposure time. What this means is that for greater impact with night sky photography, buy the largest aperture lens you can afford. This means the fastest f/ratio in a given focal length. Note, this does not contradict my statement about f/ratio above. For example, a 15 mm f/2.8 lens has an aperture diameter of 15/2.8 = 5.4 mm, an aperture which is smaller than the dark-adapted human eye. A 35 mm f/2.8 lens has an aperture diameter of 35/2.8 = 12.5 mm and collects over 5 times, (12.5/5.4)2 = 5.3, as much light from the subject even though the f-ratios are the same. A 35 mm f/1.4 has an aperture diameter of 35/1.4 = 25.0 mm and collects (25/5.4)2 = 21 times more light than a 15 mm f/2.8 lens. That would be a huge impact in light gathering in night photography when light levels are so low. https://clarkvision.com/articles/characteristics-of-best-cameras-and-lenses-for-nightscape-astro-photography/What the fuck, I mean it's obvious when you think about it purely on an optical and physical standpoint, but somehow it feels like everything I thought I knew was a lie, or rather, an oversimplification. I didn't think the light gathering difference would be so massive even when comparing at the same f stop number for different focal lenghts. It makes me rethink the need for ultra wide angle lenses for simple MW photography. Maybe a 24mm f1.8 or f1.4 is actually a better choice than, I dunno, a 16mm f2, at the cost of doing a stitching if I need to get a better composition.
