Astrophotography - Rokinon 24mm 1.4 vs upcoming Sigma 24mm 1.4 Art (or other ideas)

pigeyejacksn

I am looking to buy a lens for wide angle astrophotography in the next month or two. I am currently looking at the Rokinon 24mm 1.4 due to its stellar reviews and price, but Sigma is coming to market with their 24mm 1.4 Art. I am shooting on FX and want a wide angle lens to capture the Milky Way. The Rokinon is manual focus only, which is absolutely no issue at night in this intended use. That does have its limitations in other uses. The Sigma looks interesting, and supposedly by design should be excellent. In hindsight I wish I'd bought the 14-24 2.8 vs the 16-35 f4, but overall I still love the 16-35. The Nikon 20mm 1.8 is interesting and gives me slightly wider angle than I already have with my 24-70 2.8.

I'm sure there are others on this forum shooting wide angle Milky Way. What are you using and why? I need to stay under $900. Anyone shot with the Rokinon 14mm?

Thanks for the input

funtagraph

Does the Rokinon have a hard stop at infinity? Because the Sigma won't - the focus can be adjusted "beyond infintiy", giving you blurred pictures. I'm no astrophotog, I tried once and this was for sure an issue I was not prepared for.

spraynpray

I'm glad you posted this right now and for what it is worth, I can give you my 2c worth.

I do night sky shooting and as you said, the manual focus is not an issue. I always double check my focus in live view zoomed in 100% and use manual focus even on AF lenses. I would like to start by saying what lens to NOT buy; the Rokinon/Samyang 14mm f2.8. I have it thanks to recommendation by a podcaster/blogger that I previously thought knew what he was talking about. It has tragic coma. As a result of that faux pas, I am selling it and going again.

For me (normally a zoom shooter), a 24mm prime is pretty much only going to be used for night sky work, so my choice is the Rokinon 24/1.4 or to go for a smaller field of view but a far more generally useful focal length of 35mm so I may go for the Sigma 35/1.4 Art.

proudgeek

I shoot with a 17-35, generally at 17mm wide open. At 28 or so seconds, I have to shoot at about ISO 3200.

pigeyejacksn

Thanks. The further I dig, I am starting to lean towards the Nikon 20mm 1.8. I do mostly landscapes, and find myself on camping trips using my gear at the very wide end. The 20mm may have it's advantages for me in that regard as far as cutting weight down.

I am wondering how much of a true advantage 1.4 is over 1.8 in capturing the light. It doesn't seem like much, but on the astrophotography charts for lenses, there is a fairly significant advantage. Does it pan out though?

Anyone using the Nikon? I know it's a fairly new lens, so may not have that much of a following yet I suppose.

Thanks

Ironheart

The difference btwn 1.4 and 1.8 is 2/3rds of a stop, so it will force you to use the next higher ISO. With a 20mm lens on full frame the difference is ISO 1600 vs. ISO 3200 @25 sec, if you are doing milky way shots for example. That can make a big difference in noise, but it all depends on your workflow, tolerance, and preference.

spraynpray

The more you research night sky photography, more complex it gets. You start by cranking ISO up on your body, opening your lens wide and turning everything up to 11 in post then discover that there is a lot, lot more to it. Lens clear aperture, optimum not maximum ISO, the fact that a pixel is only under a star for a short time so a longer expose doesn't result in brighter stars, just streaking stars and the list goes on - especially in post. It is a genre that repays research more than gear acquisition (a bit like macro in that way IMO). Then just when you think you know it all, you find out something new that makes you realise you don't.

proudgeek

^^Nice Spinal Tap reference. I'd love to try the 20 f/1.8. At 17mm, you generally get about 24-28 seconds before you start seeing the earth's rotation. While 20 will lower that to roughly 20-23ish, the extra 1 1/3 stop (is that right) could be enough to offset that. Someone here did the math once that showed me 20mm @ f/1.8 is better than 17mm @ f/2.8.

Golf007sd

The wider the better. Given your price point, I truky believe the 20 1.8 will yield the results you are after. Might want to rent one and test it out before buying.

spraynpray

It's the biggest open aperture diameter that wins.

pigeyejacksn

Good point Ironheart with the math of it. 1.4 to 1.8 doesn't like a lot until you put into perspective. I found a site with a slick exposure calculator for lens comparing and a site detailing lens comparisons.

Calculator:
http://www.lonelyspeck.com/milky-way-exposure-calculator/

Lens Comparisons:
https://docs.google.com/spreadsheet/ccc?key=0AomVJ2lbrwb1dDRGeHJOaVZfYnlFR2ZDTFNlSnk2emc&usp=sharing#gid=2

I'm back to thinking about waiting for the 24mm 1.4 Art Sigma and see how it looks. The 35mm sounds good spraynpray, but for me personally I'd get more use out of the 20mm. My goal is not to regret my purchase, that what I get will give me a long life of use. The Rokinon is cheaper, but for $300 I'd rather have autofocus for other shooting. Question will become how it looks in real life use.

spraynpray

Good point Ironheart with the math of it. 1.4 to 1.8 doesn't like a lot until you put into perspective. I found a site with a slick exposure calculator for lens comparing and a site detailing lens comparisons.

Calculator:
http://www.lonelyspeck.com/milky-way-exposure-calculator/

Lens Comparisons:
https://docs.google.com/spreadsheet/ccc?key=0AomVJ2lbrwb1dDRGeHJOaVZfYnlFR2ZDTFNlSnk2emc&usp=sharing#gid=2

I'm back to thinking about waiting for the 24mm 1.4 Art Sigma and see how it looks. The 35mm sounds good spraynpray, but for me personally I'd get more use out of the 20mm. My goal is not to regret my purchase, that what I get will give me a long life of use. The Rokinon is cheaper, but for $300 I'd rather have autofocus for other shooting. Question will become how it looks in real life use.

The exposure calculator is too simple - there is more to it than that - but the lens comparison is useful.

As you said, at the end of the day if any astro lens is useful to you for other genres, that is good.

sevencrossing

With the clear nights we are having, I would to try my hand at photographing the Milky way

the only lens I own, that would seem to work, is my 50mm f 1.4
your thoughts please

proudgeek

I would think, although YMMV, that 50mm is too long a focal length, even wide open, to get a shot without star trails, particularly along the edges of the image. I could be wrong. If it were me, I'd with a shorter focal length @ f/2.8 if you've got it.

Ironheart

It's a bit narrow FoV, but will otherwise work, full frame? You have a 35 1.8? @proudgeek, you are right, max exposure is 5-10sec, you have to boost the ISO to compensate.

pigeyejacksn

I much agree about the sinplicity of the calculator but it's a good start. Gives me a good grasp at Where to begin and go from there.

It all kills me, I was out at Yosemite, Monument Valley and the north rim of the Grand Canyon on different trips. Both trips of which would have been perfect nights to experiment. No moon, clear skies, beautiful locations. None of it was on my radar back then. I'd love the opportunities again at some point. Hopefully have some fun here on the coast shooting and get familiar. Fortunately I'm close to some fairly sparse population areas.

sevencrossing

I'd with a shorter focal length @ f/2.8 if you've got it.

I have a Nikon 16mm f/2.8D AF Fisheye-
Yes Fx on a D800
my only wide angles are f4 zooms

proudgeek

I have a Nikon 16mm f/2.8D AF Fisheye-
Yes Fx on a D800
my only wide angles are f4 zooms

I'd love to see that. I bet you'd get some interesting results.

Ironheart

You should get at least 20 seconds of exposure with the 16mm. I'm sure it will be fantastic!

spraynpray

@sevencrossing: Have a go with your 16mm f2.8, also your 16-35 f4 may be good, try them both watch for coma in the corners. Bear this in mind: If you are taking snapshots to put on t'internet, you can do all these crazy times that a lot of 'authorities' bang on about BUT, if you do the sums relating your pixel pitch to an average star near the equator (and if you are shooting the milky way, you will be shooting the fast moving stars at the equator), you will find that a pixel is not under a star for very long. That means no matter how long you keep your shutter open, you will not get brighter stars, only streaked stars that appear brighter until you do a decent size print. D800 will likely be approx 4 seconds. This simple fact passes a lot of experts by....

Post processing is where the magic lays. If it is a 'net snap, just shoot a 20-25 second exposure then pass it through lightroom and turn it all up to 11 to get an easy and fun result. But, if you want a 'fine art' quality print, be prepared to spend a lot of time in front of your PC. Try 3200 and 6400 on your D800 and for fun max it out and see what that gets you.

Ironheart

Yes, the exposure times I'm quoting are based on the "300" rule (some use 500 which is even worse). This is similar to the 1 over the focal length rule in that it is a "rule of thumb" and YMMV and all that.

sevencrossing

Many thanks, might head off to the Mendips the next clear night
at the moment its just for my FB page

spraynpray

Oh, and try ETTR'ing too. Any light spoils the stars, so no or up to three days of a new moon are the max. If you want a lit subject, don't use the moon, use a dim torch.

pigeyejacksn

spraynpray or anyone else...what are you using for post on your pictures? I am doing most of my post in Lightroom.

I played a bit with my 16-35mm f4 this weekend before the moon rose on Saturday. It gave me an hour or so on a crystal clear night. I actually got better results than I figured with that lens. Excites me to think what results I'll see with a 1.4 or 1.8. Stars don't seem too perfectly focused. I was using LiveView, but I think it may be the pier I was setup on more than it was the focus. I do need to find a spot without any lights though. Frustrating. They are EVERYWHERE. You don't notice till you look for a clear spot.

proudgeek

This is pretty nice. I'm assuming you shot @ f/4 and 16mm. What was your shutter speed? That may be why you're seeing movement in the stars. At 16mm, you've got a max shutter speed of about :28 before you see movement. Maybe even less at the periphery of the image. Remember, the stars are pretty far away; you're not going to capture tack sharp stars.

pigeyejacksn

Thanks. I will have to check. I believe I was at 16mm/6400/30 seconds/f4. I was experimenting a good bit and will double check. I dropped down to 3200 at one point and was at 15sec at one point.