There is not a lens that’s going to perform extremely well in the corners wide open . It’s just a acceptable fact but certainly some are better wide open than others. Even 1 stop down is going to be almost near optimum especially with these good optics we are talking about here. Honestly I’m still baffled by the super wides being used for Astro work.how much freaking sky do you need . What’s it really buy you compared to like a 21 than a 14.
Hell im a super wide freak even starting at 12mm but doing Astro work even after 45 years I question that one. Maybe I’m crazy. Lol
I have a 16-35f4 that I’ve been learning with over the last 6 months. For my area I can get in a better composition of hills/mountains, lake, and Milky Way when I’m below 24mm.
Arrover wrote:
I have somewhat decided to order the Sony 20/1.8 but I could use some help comparing it to the Voightlander 21/1.4, specifically in regard to the coma, astigmatism, etc, when wide open (or very close to it). Every time I read a review of the Voightlander, I seem to be swayed away from it because of the corner performance when wide open.
I haven't had a chance to shoot the Sony 20 yet but I love my Voigtlander 21/1.4. While it's true that its astro performance wide open isn't great, things get much better around f/2. See Fred's coma tests here: https://www.fredmiranda.com/forum/topic/1603441/6#14906758
I would have liked to go with the 24GM but I feel like it won't be wide enough for my use. I'm not a huge fan of the filter setups for the Sigma 20mm. I want a lens that is below f2 wide open.
For single-shot milky way I tend to prefer something in the 14-18mm range to showcase its expanse, but I've held on to my 24GM because it is such a phenomenal lens for sucking up light from a dark sky. I find it quite usable for stars wide open and typically shoot panos with it. You can see Fred's coma test for the 24GM here: https://www.fredmiranda.com/forum/topic/1568815/4#14651216
No one asked for it, but I made a quick comparison with my 16-35GM. The 20mm seem to be a bit sharper, particularly in the corners. But the biggest difference to me is how much better color, contrast and chromatic aberation control is. Somewhat surprised how big the difference is. This is not a comprehensive test, but might still be interesting to someone else. This was shot in backlight, which might explain why the difference is so big.
Wide open in center:
Wide open in corner:
Both stopped down to 5.6 in corner:
I also noticed that the 20mm can focus closer in manual focus than AF. According to my measurements I'm able to get about 0.26x magnification in manual focus.
Also field of view seem to match with the 16-35mm zoomed to 19mm, not 20.
Jman13 wrote:
Wow. Is that representative of the 16-35 GM? I figured my Sigma 14-24mm was likely a little better, but if that's typical, it simply destroys it.
Although it has received raving reviews, I've never thought that the 16-35 GM was very sharp towards the edges. I've tested half of dozen copies and the main issue is astigmatism.
It's better at the wide range when stopped down to f/5.6 but I'm pretty sure it does not reach the Sigma 14-24's level of resolution and contrast.
It's a great zoom capable of high resolution across the field but it's not as good as the Sigma. Perhaps more comparable to the 12-24/4G.
The FE 20/1.8 is great from wide open but really comes "alive" at f/4 and smaller. Absolutely outstanding across the field. Only the Sigma zoom is able to keep up with it. I've posted some crops on this thread.
Sooooo I gotta ask as even though I got the sigma 14-24. Which I will keep but want a smaller lens in 20/21 and I was thinking CV 21 1.4 but this Sony may serve me better. Thoughts anyone
GMPhotography wrote:
Sooooo I gotta ask as even though I got the sigma 14-24. Which I will keep but want a smaller lens in 20/21 and I was thinking CV 21 1.4 but this Sony may serve me better. Thoughts anyone
I haven't used the CV 21/1.4, although I do have the 21/3.5,
p.8 #10 · Sony FE 20mm f/1.8 G Versus Other Lenses
Since the first test against the 16-35GM showed such surprisingly big difference in color and contrast, I did another test now, with less challenging lighting (overcast, not the backlighting of the first test). And at least in this lighting the performance is much more similar.
I also realised I screwed up by having a clear filter mounted on the 16-35 GM, which might have made the result worse. It made no difference in this second test, but might make a difference in backlit situations.
So here are some 200% comparisons in this second test:
Wide open in center:
F5.6 in center:
Wide open at edge:
F5.6 at edge:
This second result is much more as I would expect, with the 20mm just slightly sharper, but otherwise quite similar. 16-35 GM might struggle more in backlit situations, but it might also have been caused by the filter.
p.8 #12 · Sony FE 20mm f/1.8 G Versus Other Lenses
None of the zooms mentioned do f1.8. If you need the speed, prime is still the way to go. I am mostly a zoom person but I still plan to get this for Astrophotography.
Bob_S wrote:
I'd rather the 16-35 for the massive advantage in versatility.
Primes make no sense to me when packing for the ultra wide category given the 12-24, Sigma 14-24 & 16-35GM.
p.8 #13 · Sony FE 20mm f/1.8 G Versus Other Lenses
yas887 wrote:
None of the zooms mentioned do f1.8. If you need the speed, prime is still the way to go. I am mostly a zoom person but I still plan to get this for Astrophotography.
Isn't a tracker a better setup that one a one stop faster lens?
A stop isn't really much these days, I'd rather the versatility instead of carrying 4 primes (which still wouldn't cover the focal lengths of a zoom).
p.8 #14 · Sony FE 20mm f/1.8 G Versus Other Lenses
The focal length and framing difference is making it hard to do an accurate comparison. The results certainly look closer but the 20/1.8 still looks noticeable sharper at f1.8 compared to the GM at 2.8. Be interesting to see the comparison with both at f2.8.
arneh wrote:
Since the first test against the 16-35GM showed such surprisingly big difference in color and contrast, I did another test now, with less challenging lighting (overcast, not the backlighting of the first test). And at least in this lighting the performance is much more similar.
I also realised I screwed up by having a clear filter mounted on the 16-35 GM, which might have made the result worse. It made no difference in this second test, but might make a difference in backlit situations.
So here are some 200% comparisons in this second test:
Wide open in center:
https://i.imgur.com/6Z3oHzB.jpg
F5.6 in center:
Wide open at edge:
https://i.imgur.com/LIE0NJJ.jpg
F5.6 at edge:
https://i.imgur.com/nHpbSTV.jpg
This second result is much more as I would expect, with the 20mm just slightly sharper, but otherwise quite similar. 16-35 GM might struggle more in backlit situations, but it might also have been caused by the filter....Show more →
p.8 #15 · Sony FE 20mm f/1.8 G Versus Other Lenses
I have a tracker but never had much success blending a complex foreground with the sky. Using a tracker would blur the foreground. I can take a separate exposure but the blending is almost impossible as the blurred foreground in the tracked photo covers a much bigger area than the foreground in the non tracked photo. There is really no substitute for a fast lens for this type of photography.
Bob_S wrote:
Isn't a tracker a better setup that one a one stop faster lens?
A stop isn't really much these days, I'd rather the versatility instead of carrying 4 primes (which still wouldn't cover the focal lengths of a zoom).
p.8 #16 · Sony FE 20mm f/1.8 G Versus Other Lenses
yas887 wrote:
I have a tracker but never had much success blending a complex foreground with the sky. Using a tracker would blur the foreground. I can take a separate exposure but the blending is almost impossible as the blurred foreground in the tracked photo covers a much bigger area than the foreground in the non tracked photo. There is really no substitute for a fast lens for this type of photography.
I have a tracker too. I have blended images successfully, and it does increase the shooting envelope, but it's a pain. If you are hiking a decent distance, even the smallest trackers are bulky. It's extra work post processing, and it requires batteries and such. I found better success either shooting panos or blending exposures (foreground and sky).
p.8 #17 · Sony FE 20mm f/1.8 G Versus Other Lenses
Any good tutorial or tips you can recommend on blending the foreground with a tracked sky? Everything I found just simply move the foreground in the untracked shot up so it covers the the blurred boundary in the tracked shot. The result looks good but it is also changes the relative position of the stars with the foreground which I try to avoid. It also doesn’t work for complex foreground like trees that stick up into the sky.
nehemiahphoto wrote:
I have a tracker too. I have blended images successfully, and it does increase the shooting envelope, but it's a pain. If you are hiking a decent distance, even the smallest trackers are bulky. It's extra work post processing, and it requires batteries and such. I found better success either shooting panos or blending exposures (foreground and sky).
p.8 #18 · Sony FE 20mm f/1.8 G Versus Other Lenses
Thanks for putting together such nice comparisons We are really spoiled for choices today than even a year ago.
I have the 16-35 GM which is the lens that for the most part swayed me to go to Sony. Also have the CV 21 1.4 which I REALLY love for a landscape lens, and Zeiss milvus 25 1.4 that I used a lot during my nikon days which I still use but a bit less since I got the voigtlander. I love the color and rendering of these voigtlanders for landscapes especially and that sunstar. Pretty much the CV 21 1.4 has become my most used lens for sunrise/sunsets.
Lately I've begun to favor more the 20-25mm focal length for landscapes. I think a lot of the ultra wide shots below 18 are becoming bit less appealing to me and I am going more towards the longer focal length. Guess it's a learning experience one could say.
I definitely have a bad habbit of gas and having lenses in same focal range This plandemic though has made me get out and shoot more toying around with a Sony 24-70 GM and 85 1.8 that I got sorta as a long term loaner from a family member If I didn't have the CV 21 1.4 I probably would've liked the sony 20 1.8 as I LOVED the nikon 20 1.8G lens I had. That was seriously my favorite lenscape lens since it has such nice sunstars.
p.8 #19 · Sony FE 20mm f/1.8 G Versus Other Lenses
yas887 wrote:
Any good tutorial or tips you can recommend on blending the foreground with a tracked sky? Everything I found just simply move the foreground in the untracked shot up so it covers the the blurred boundary in the tracked shot. The result looks good but it is also changes the relative position of the stars with the foreground which I try to avoid. It also doesn’t work for complex foreground like trees that stick up into the sky.
We are really spoiled for choices today than even a year ago. 
This plandemic though has made me get out and shoot more toying around with a Sony 24-70 GM and 85 1.8 that I got sorta as a long term loaner from a family member