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That photo of the Andromeda galaxy got me thinking about noise reduction
I saw a post on another forum where a guy spent 6 hours stacking exposures of Andromeda and his final image still looked grainy. He said he used ISO 6400 on a Canon 6D and I wonder if dropping the ISO and taking more subs would have helped. Has anyone here found a hard limit on ISO where the noise tradeoff isn't worth it for deep sky shots?
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mark_thomas2mo ago
Dropped ISO to 800 on my 6D and doubled the subs. Night and day difference. The 6D is a ISO-invariant sensor above 800 so you're just adding read noise going higher. Stacking 80 subs at ISO 800 beats 40 at 6400 every time. Try 30 second subs at f/2.8 or faster with ISO 800 and you'll see the noise drop way off.
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the_oscar21d ago
Hold up, 80 subs at ISO 800? That's wild. I mean I get the theory behind it, but actually going out and stacking that many frames just seems like a whole different level of patience. My back hurts just thinking about sitting outside that long. Your mileage may vary obviously, but I've always been a bit skeptical of going that low on ISO for astro. Does the 6D really not pick up any extra noise from that long of an exposure at 800? I've seen some people claim their sensors start to get weird banding at lower ISOs if the sub is too long. Might be worth a try if the results are that clean though.
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