20 - 24mm lens for nightscapes-astro imaging

Capt_SpauldingCapt_Spaulding Posts: 383Member
Friends, I posted a related request sometime back but couldn't find it :( so I apologize for posting a new thread. The question is this. I'm interested in a wide, fast(ish) prime for nightscapes and astro imaging. Both Nikon and Sigma make primes in 20 and 24mm that are priced identically. The Sigma Arts are wider at 1.4, while this is the Nikon 1.8. Both are in the $700-800 range. Both get decent reviews, but I suspect both are somewhat plagued by coma. Any thoughts? Mnay thanks in advance for your expertise.

Comments

  • spraynprayspraynpray Posts: 5,827Moderator
    For sure the 20's are disappointing. I tried them and they had tangential and sagittal astigmatism levels that were too bad. I have the 24-35 Art which is f2 and good for aberrations - better than the primes. My dream is to get the 14/1.8 Art to pair with my D850 but that will have to wait. Until then, I am loving the 24-35 f2 which all the tests described as three primes in one.
    Always learning.
  • BetelgeuseBetelgeuse Posts: 39Member
    After a fair amount of research, I settled on the Rokinon 14mm F/2.8. It's corrected for Low Coma, low flare and ghosting, and low CA. The linked Lonely Speak article was the body of information that helped me pop on this lens. It's very good, and I do recommend it. https://lonelyspeck.com/rokinon-14mm-f2-8-review/
  • spraynprayspraynpray Posts: 5,827Moderator
    I tried that lens and rejected it for terrible aberrations. I increasingly find a disparity between reviews and reality. Thankfully, good camera shops have a return policy that allows me to try a lens before I settle with it.

    Another advantage of the 24-35 Art is that it is pretty handy for landscapes too.
    Always learning.
  • BetelgeuseBetelgeuse Posts: 39Member
    edited June 10
    Maybe you had a bad copy, I don't know, but that lens is widely popular for astro. CA usually manifests in fringes of color and astigmatism aberrations causing stretched out stars in the corner of the photo. The linked photo I took with the Rokinon 14mm F/2,8.

    Notice how the stars in the corners are still pinpoints of light and not stretched out. That's pretty good. Bad CA is very noticeable.

    Milky Way On The Canal">
    Post edited by Betelgeuse on
  • spraynprayspraynpray Posts: 5,827Moderator
    edited June 10
    We may have different expectations Betelgeuse. Firstly, you will not see significant aberrations at that image size. Secondly, your shutter speed is excessive (30 seconds) which means when you look closely all your stars are slotting. I always aim to print large which shows all the flaws. I see you shoot with a D750 so you could have taken that shot at ISO 3200 and 14 seconds and got the same result without slotting. If you want to avoid that, you are looking at using a tracking head and either blurring the foreground or creating a composite image.

    That is what I see on facebook all the time, people cooing over others night shots which I know would not hold up to printing large or even viewing large on a monitor.

    14mm is such a wide angle that it is pretty much impossible to take a shot that does not have the astronomical equator in it so the stars will be moving quickest there (and lets face it that is where the good stuff is) and so you just can't go over the 200 rule unless you are happy with looking at the images small.

    All IMHO.
    Post edited by spraynpray on
    Always learning.
  • BetelgeuseBetelgeuse Posts: 39Member
    edited June 10
    I experiment with different settings when taking these types of shots. My settings in this one photo have nothing to do with the Rokinon 14mm F/2.8 performance, but rather my performance, so I think you're deflecting there a bit. When taking these types of photos, I vary my exposure time, and ISO settings with varying results. I was using the 500 rule which says I could go up to 36 seconds. Why do they call them rules when there's the 600, 500, 400, 300, and 200 rule, and if you use the "rule" people call you out for using it?

    I don't use Facebook as it's a social media site dedicated to making you and your information the product.

    Star trailing in a photo is a factor of time and movement, and doesn't reflect the characteristics of a particular lens's traits such as CA.

    On this particular shoot I didn't get to shoot for long as I was on the Hood Canal in the winter and almost as soon as I get into position, the fog started rolling up the canal shockingly fast. Bad timing on my part, I should have been there earlier, so I could do more, but it was hard to find a spot that wasn't posted.
    Post edited by Betelgeuse on
  • spraynprayspraynpray Posts: 5,827Moderator
    My point was that it is hard to determine the extent of aberrations when the stars are not round due to keeping the shutter open too long. I don't understand what you mean by 'deflecting'.
    Always learning.
  • BetelgeuseBetelgeuse Posts: 39Member
    I just meant that you were focused on my setting rather than what the lens is capable of, but I didn't get that you were saying it would be hard to differentiate between trails and CA.
    The shortest photo from that shoot I have at 3200 is 20 seconds. It is slightly better on the edges, but it has fog moving in, which obscures a 1/4 of the sky just above the trees, and that is why I didn't use it.

    The closest exposure I have to 14 seconds is one at ISO 1600 and 16 seconds. I cropped the upper left 1/9th quadrant of that photo, and here is a link pasted so you can see the full size.

    https://flic.kr/p/26JcFhz
  • BetelgeuseBetelgeuse Posts: 39Member
    Here is the same photo not cropped.
    https://flic.kr/p/271hi1J
  • spraynprayspraynpray Posts: 5,827Moderator
    Looks good in those low res uploads, did you upload it 6000 x 4000?
    Always learning.
  • BetelgeuseBetelgeuse Posts: 39Member
    edited June 11
    Do you control the 6000x4000 setting on flickr? I don't have a premium account, and I haven't ran across that option.

    I do believe in Lightroom that I exported to full size, but as a jpg.

    I did notice I can zoom in more on the cropped flickr link vs the none cropped flickr link, so it seems their site is reducing the full size, and probably the crop, too.
    Post edited by Betelgeuse on
  • BetelgeuseBetelgeuse Posts: 39Member
    I went back to Flickr, the only options I see for size when uploading is "default" and "small", it's set to default.

    I checked the exports from Lightroom, the full is 6016x4016, and the crop naturally is less, 2173x1449.
  • spraynprayspraynpray Posts: 5,827Moderator
    Yes, in Lightroom, you don't resize at all then the jpeg comes out full size 6016 x 4016. You can upload whatever size you like to Flickr and people usually limit the image size if they keep a lot on Flickr so not to use all the capacity up, or if the image falls apart under close scrutiny like 99% of macro shots do.
    Always learning.
  • BetelgeuseBetelgeuse Posts: 39Member
    edited June 11
    That's what I thought. I always upload smaller sizes, but not to save space, but rather to prevent people from snatching my images in full usable size. The two last photos I did export in full size, so you could get a closer look.
    Post edited by Betelgeuse on
  • spraynprayspraynpray Posts: 5,827Moderator
    You can disable downloads and still upload full res for critical viewing purposes. They are not mutually exclusive.
    Always learning.
  • BetelgeuseBetelgeuse Posts: 39Member
    edited June 12
    I have downloads disabled, but I took the further step as I had read computer savvy people could still take photos that display large.
    Post edited by Betelgeuse on
  • WestEndFotoWestEndFoto Posts: 2,701Member
    Try zooming in and taking a screen shot. Short of hacking your account, that is the most that they can do.
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