Why does the moon flare differently on my full-frame Sony than on APS-C?
Asked 1/26/2018
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2 answers
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I switched from an APS-C Sony with a Rokinon 21mm f/1.4 to a full-frame Sony with a Rokinon 24mm f/1.4. Using similar settings (about 15s, f/1.4, ISO 1000), my APS-C moon photos looked normal, but on full frame the moon shows a large bird-like flare/shape instead.
I usually focus on the stars first and then wait for the moon to rise. Is this a focus issue, or is it caused by the lens/sensor change? How can I get a cleaner moon appearance similar to what I had on APS-C?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
2
It might be an effect of "coma" aberration. As I understand, it might be especially bad with fast lenses at large apertures. Here Ken Rockwell talks about coma on his Nikkor 50mm f/1.2 lens, with images and examples.
The solution (partial) is to shoot at smaller f-number, or switch to different lens. In another article Ken suggest that aspherical elements can be introduced to correct coma, as done in Nikkor 58mm f/1.2
Originally by user38691. Source · Licensed CC BY-SA 4.0
user38691
8y ago
0
Generated from our catalog & community — verify before relying on it.
This is most likely a lens/optical issue, not a full-frame sensor problem.
Based on the answers, the main possibilities are:
- Coma or other aberrations from shooting a very fast lens wide open at f/1.4. Bright point sources near the frame can turn into winged or bird-like shapes.
- Flare from smudges or residue on the front or rear element.
- A filter causing extra reflections/flare.
- Simply different flare characteristics between two different lenses.
What to try:
- Clean the front and rear elements carefully.
- Remove any front filter and test again.
- Stop down 2–3 stops (for example to around f/2.8–f/4) and compare; this often reduces coma and flare.
- Move the moon around the frame and see whether the shape changes with position; that points to lens aberration rather than focus.
- If your camera allows it, try crop mode on the full-frame body to see whether using the center of the lens improves things.
Focusing on stars is generally fine, but focus alone usually does not create this kind of dramatic “phoenix” shape. The most likely fix is stopping down, cleaning the optics, removing filters, or using a lens with better wide-open correction.
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AI8y ago
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