[Leica] IMG: Galileo was right

[Howard L Ritter Jr]

That’s a pretty good image for the lens, Peter, and some optimization would make it even more impressive.

In your shot, the relatively small image size of the moons, which are effectively point sources at this FL, suggests that you could capture Jupiter's atmospheric cloud bands if you avoid the overexposure of this image. In photographing the rich but low-contrast detail in the atmosphere, overexposure is your enemy. Underexposure, with enhancement in post-exposure processing, can record nice detail, while overexposure that saturates anything more than a few of the brightest pixels irretrievably obliterates detail. You might try it again at 1/30 and shorter, and play with the result in PS Camera Raw, especially the exposure, contrast, clarity, and dehaze sliders. You might lose the moons at optimal exposure for the atmosphere, but you could do a composite image.

And of course the sweet spot for resolution is somewhere between wide open, where diffraction-limited resolution is best but aberrations can occur, and fully stopped down, where aberrations are negligible but diffraction-limited resolution is worst. If you can find resolution-vs-aperture data for this lens, that might guide you. At f/11, the effective aperture of a 300-mm lens is just over 1 inch, which by the Rayleigh criterion has a resolving power of about 4.5 seconds of arc. (The angular diameter of the Galilean moons is about 1 arcsec, and of Jupiter, currently at opposition, about 45 arcsec.) You might experiment with larger apertures once you’ve found the optimal exposure time at f/11. If your lens goes to f/5.6, you could double your resolution – even if that’s wide open, the aberrations might affect mostly the off-axis portions of the image.

Sorry if I’ve turned a trip to the playground into a regimented chore! If you try any of this, please post. If I ever get clear weather, I’ll put my M240 on my 155-mm f/7 apo refractor and see what I can get.

—howard


> On Jun 17, 2019, at 5:06 AM, Peter Klein via LUG <lug at leica-users.org> wrote:
> 
> <https://www.flickr.com/photos/24844563@N04/48078173256/in/dateposted-public/>
> 
> Jupiter and its four largest moons.  E-M5 on tripod, my $30 bargain-bin 300mm Soligor lens, 1/8 sec at f/11, 100% pixels. One could do better with a telescope, but I thought it would be fun to see what I could get with what I had on hand.  Enjoy!
> 
> --Peter
> 
> 
> 
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