Craig Stocks
Well-known member
First of all, I'm not trying to do a "which is better" type of comparison, I'm simply trying to understand the differences in the two systems so I can get the most out of each one. I'll be travelling this winter with just the a7rii so I want to play to its strengths.
Note that my a7rii is still on firmware 3.10 which is before the "Star Eater" issue was introduced.
I went out last week to do a star trail shot under a bright waxing gibbous moon and since I'd have plenty of down time I set up both cameras side by side and nearly identical settings. a7rii had a Sony 12-24 zoom @ 12mm and was at ISO 500, 60 seconds @ f/5.6. The IQ3100 had a P1 28mm and was at ISO 400, 60 seconds @ f/5.6. I shot 60 frames with each to stack into star trails. I like the a7rii version better so that one has had more work done on it.
What I noticed is that the IQ3100 version has lots more trails from small stars. I don't know that it necessarily makes a better star trail images, in fact I think I prefer the a7rii version with fewer trails, but it's a difference worth noting.
That led me to wonder about standard night sky images. Since I use both systems I want to understand the differences. I normally do night sky photos with a tracking mount so that's where I started last night before the moon came up. The a7rii had the 12-24 @ 12mm, ISO 1600, 30 seconds @f/4.5. The IQ3100 had the 28mm, ISO 1600, 30 seconds @ f/4.5. Both used the tracking mount. I processed both in Capture One (primarily brightening about 1.8 stops and adjusting white balance). They were then opened in Photoshop where I stack the two frames and transformed the IQ3100 frame so the stars were aligned. This is a crop of the center area of the result.
I'm sure there are other differences but the two that jump out to me are that the IQ3100 shows many more stars but they are all smaller. This is consistent with what I saw in the star trail image. Also there is quite a bit more detail and nuance in the Milky Way in the IQ3100 image. (Also, yes, I know I should have zoomed the Sony to around 17mm for a better match but I didn't think of it at the time. In practice I'll use it at 12mm.)
I then switched to 24mm equivalent lenses and did the same shots only at f/4.0 this time. I also added my a6000 with a 16-70 zoom at 16mm. I also processed and stacked them the same way. The big differences is that (unbeknownst to me) the batteries in my tracking mount gave up in the cold so I only have comparison frames untracked. 30 seconds is a little long for a 24mm eq. focal length but the difference is what's important.
I have noticed in the past that untracked star photos look better than tracked ones, at least until you blow them up. The stars get a little smudged and show up more readily and that seems to be the case here. I still see the difference in the fine details of the Milky Way but note that there is now much less difference in the number and character of the stars, in fact almost no difference at all.
What I don't understand is why. I'd like to explain the difference by the blurring of the stars without tracking minimizing any star-eating tendencies of the a7rii but that should have applied to the original star trail image.
I think in reality I could probably be happy with any one of the photos (except maybe the a6000 because of noise) if that's all I had. I like that the a7rii makes bigger stars and shows more variation in brightness (size) of the stars. I like that the IQ3100 captures more stars, and I can induce the variation in size with my Minimum and Maximum filter application in Photoshop.
I'm curious to get other folks thoughts.
Note that my a7rii is still on firmware 3.10 which is before the "Star Eater" issue was introduced.
I went out last week to do a star trail shot under a bright waxing gibbous moon and since I'd have plenty of down time I set up both cameras side by side and nearly identical settings. a7rii had a Sony 12-24 zoom @ 12mm and was at ISO 500, 60 seconds @ f/5.6. The IQ3100 had a P1 28mm and was at ISO 400, 60 seconds @ f/5.6. I shot 60 frames with each to stack into star trails. I like the a7rii version better so that one has had more work done on it.
What I noticed is that the IQ3100 version has lots more trails from small stars. I don't know that it necessarily makes a better star trail images, in fact I think I prefer the a7rii version with fewer trails, but it's a difference worth noting.
That led me to wonder about standard night sky images. Since I use both systems I want to understand the differences. I normally do night sky photos with a tracking mount so that's where I started last night before the moon came up. The a7rii had the 12-24 @ 12mm, ISO 1600, 30 seconds @f/4.5. The IQ3100 had the 28mm, ISO 1600, 30 seconds @ f/4.5. Both used the tracking mount. I processed both in Capture One (primarily brightening about 1.8 stops and adjusting white balance). They were then opened in Photoshop where I stack the two frames and transformed the IQ3100 frame so the stars were aligned. This is a crop of the center area of the result.
I'm sure there are other differences but the two that jump out to me are that the IQ3100 shows many more stars but they are all smaller. This is consistent with what I saw in the star trail image. Also there is quite a bit more detail and nuance in the Milky Way in the IQ3100 image. (Also, yes, I know I should have zoomed the Sony to around 17mm for a better match but I didn't think of it at the time. In practice I'll use it at 12mm.)
I then switched to 24mm equivalent lenses and did the same shots only at f/4.0 this time. I also added my a6000 with a 16-70 zoom at 16mm. I also processed and stacked them the same way. The big differences is that (unbeknownst to me) the batteries in my tracking mount gave up in the cold so I only have comparison frames untracked. 30 seconds is a little long for a 24mm eq. focal length but the difference is what's important.
I have noticed in the past that untracked star photos look better than tracked ones, at least until you blow them up. The stars get a little smudged and show up more readily and that seems to be the case here. I still see the difference in the fine details of the Milky Way but note that there is now much less difference in the number and character of the stars, in fact almost no difference at all.
What I don't understand is why. I'd like to explain the difference by the blurring of the stars without tracking minimizing any star-eating tendencies of the a7rii but that should have applied to the original star trail image.
I think in reality I could probably be happy with any one of the photos (except maybe the a6000 because of noise) if that's all I had. I like that the a7rii makes bigger stars and shows more variation in brightness (size) of the stars. I like that the IQ3100 captures more stars, and I can induce the variation in size with my Minimum and Maximum filter application in Photoshop.
I'm curious to get other folks thoughts.