snapsy Offline Upload & Sell: On
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jimmy462 wrote:
Hi Snapsy,
I truly enjoy that second image...nice play of foreground visibility vs. starry sky...
It'll be interesting to see where a favorable balance of ISO, aperture and shutter speed will work in extreme-low-light situations. Learning the camera's sensor behaviors at various ISO settings will clearly take some in-the-field testing.
I bring this up because of your settings for that second image...15 sec @ 12,800 ISO (you don't state f/stop). Bumping up the ISO in an attempt to freeze the wave action we get...
8 sec @ 25,600
4 sec @ 51,200
2 sec @ 102,400
1 sec @ 204,800
.5 sec @ 409,600
...and, clearly, one would be pushing ISO to quite the extreme to try and do so.
Comparing your shoreline image settings (I'm assuming f/4) with the similar shoreline framing at 1/25 sec, ISO 40,000, f/1,4, in this video it's clear that your scene was at least 3-to-4-stops stops darker. (See video at 3:36 mark for how shots were done). Low light video test of a7S from Philip Bloom...
...Show more →
Thanks Jimmy. I used a 15 second exposure because that's the shortest exposure which avoids stair trails @ 24mm. The aperture was f/5, which is necessary to get some extra corner sharpness on the 24-70 f/4 FE (24mm is its weakest focal length and it would actually sharpen up even more beyond f/5). The exposure was ETTR by about 1 1/2 stops, which the DR of the scene permitted and so it allowed me to use a higher ISO at the same absolute exposure (same f/stop and shutter) to get a further reduction in shadow noise in that scene.
One thing I noticed is that the A7s has pretty significant hot pixels even at the modest long exposures I used. This was first reported here. I didn't use long-exposure NR because it's not available for the fully-electronic shutter mode I used for the above images (since LENR would require closing the shutter to take the dark frame). I'm using the fully-electronic shutter to avoid the amp noise/glow that occurs on the A7s at ultra low exposures (I compared that here) - I haven't tested whether LENR would remove the amp glow as effectively as the electronic shutter does.
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