Moon photos

Jul 29, 2012
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Walrus and Alan,

Well done, guys.
a025.gif
 
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Jul 21, 2010
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It's a Super Blue Moon tonight, next one will be in a decade. R7 + RF 100-500mm. It's cloudy here this evening, unfortunately, with some haze in front of it.
Tungsten WB on that one? :p

From my driveway this evening...

2023 Super Blue Moon.jpg
EOS R3, EF 600mm f/4L IS USM + 2xIII, 1/320 s, f/8, ISO 100
 
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Jul 21, 2010
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Man, it was a joke; you would probably have written f7.1 and you forgot the dot, and I joked about f71 suffering from diffraction. Take it easy :)
Man, apparently you missed the point that @AlanF was making about his missing the point. 71 instead of 7.1. Seventy-one instead of seven point one. "Missed the point." Rimshot. Bah-dum-bum. As in, 'missing the decimal point'...or dot as you call it...a period by any other name. As in he got the joke and was making one of his own. Take it easy. ;)
 
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AlanF

Desperately seeking birds
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Aug 16, 2012
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We can use the size of these images to calculate the focal length of the lenses. The moon has a diameter of 3474.8 km. Last night, it was 357344 km away. The diameter of the image on my R7 sensor is 1470px, corresponding to 4.71 mm. The focal length of my RF 100-500mm fully extended is (357344/3474.8)x4.71 mm = 484 mm

The focal length of @jabird56's 100-400mm II is 394mm.
 
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Jul 21, 2010
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We can use the size of these images to calculate the focal length of the lenses. The moon has a diameter of 3474.8 km. Last night, it was 357344 km away. The diameter of the image on my R7 sensor is 1470px, corresponding to 4.71 mm. The focal length of my RF 100-500mm fully extended is (357344/3474.8)x4.71 mm = 484 mm

The focal length of @jabird56's 100-400mm II is 394mm.
Mine is 1907 pixels on the original (the image I posted was downsampled), with a 6.0 µm pixel meaning a focal length of 1177mm.

At that distance, not much of the 'loss' is due to focus breathing (as would be the case with a close subject, since focal length is specified at infinity focus). Rather, it's Canon's rounding of both the focal length and aperture (up and down, respectively) for the lens name vs. the actual optical formula. In my case, 600 mm / 4 = 150 mm for the entrance pupil. In a telephoto design, that’s typically right at the front element, which for this lens measures 142 mm. So the 600/4 is really approximately a 589/4.14.
 
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