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6/13/2025, 3:05:16 AM
I'm looking at taking pics of the milky way on my next mountain hike. I have two questions.
1) 500 rule is depreciated for digital cameras, 200 rule kinda werks, the NFP rule is supposedly the best. NFP asks for the focal length (obviously), the sensor pixel pitch (neat), the aperture (??? but surely the math guys behind the rule know better than me). Let's say a 24mm f1.8 gives me 8.5s of exposure for very slight star trails with the NFP formula. Now, let's say I'll stop down a bit for less coma and shit, and go with f2.8. The formula then gives me 10s of exposure for the same very slight star trails.
Why would the aperture change anything? If I have a 24mm at hand, be it at f1.8 or f11, the exposure time has to be the same for accurate stars. Heck, putting f11 in the calculator gives me 21sec of exposure. It doesn't make sense.
2) Regarding stacking pictures, and considering my camera is ISO-invariant (dual gain starts a ISO 400), am I better off taking, say, 15 pics for 8.5s at ISO 400 (for max dynamic range with less noise), or 15 pics or 8.5s at ISO 1600 or 3200?
One of the point of stacking, is to have the stacking software remove noise between the 15 pics, as it compares them and knows what to remove and what to keep. If so, might as well shoot at higher ISO, no? But then again, I'd get less dynamic range, I suppose.
1) 500 rule is depreciated for digital cameras, 200 rule kinda werks, the NFP rule is supposedly the best. NFP asks for the focal length (obviously), the sensor pixel pitch (neat), the aperture (??? but surely the math guys behind the rule know better than me). Let's say a 24mm f1.8 gives me 8.5s of exposure for very slight star trails with the NFP formula. Now, let's say I'll stop down a bit for less coma and shit, and go with f2.8. The formula then gives me 10s of exposure for the same very slight star trails.
Why would the aperture change anything? If I have a 24mm at hand, be it at f1.8 or f11, the exposure time has to be the same for accurate stars. Heck, putting f11 in the calculator gives me 21sec of exposure. It doesn't make sense.
2) Regarding stacking pictures, and considering my camera is ISO-invariant (dual gain starts a ISO 400), am I better off taking, say, 15 pics for 8.5s at ISO 400 (for max dynamic range with less noise), or 15 pics or 8.5s at ISO 1600 or 3200?
One of the point of stacking, is to have the stacking software remove noise between the 15 pics, as it compares them and knows what to remove and what to keep. If so, might as well shoot at higher ISO, no? But then again, I'd get less dynamic range, I suppose.
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