Night Sky/Star/Milky way - f/4 and above

WhiteLight

Senior Member
As its common knowledge that for star photography, the desired aperture would the largest like 1.8 or 2.8
Just wondering how the results would be hampered if using a f/4 or smaller aperture?
Perhaps similar results can be seen if the shutter speed is increased but anything over 60 secs would result in trails..
And on lower end cameras noise would be a huge factor as well..
Thoughts?
 

BackdoorArts

Senior Member
Less light means it takes longer exposure length to get the same effect, and as you've suggested, longer exposure length means you may now have to deal with star movement. Going from f2.8 to f4 is one stop, so if you would shoot at ISO 1600 at f2.8 you could achieve the same exposure at ISO 3200 (one stop faster) at f4 (one stop slower). Want to go to f5.6, just go to ISO 6400. Yes, you are allowing for more noise, so it's always a tradeoff.

As for when you get trails, it all depends on focal length, and at 60 seconds you'll see movement on anything greater than about 10mm. I thought there was a quick and easy way to calculate the maximum exposure time for each focal length without star movement, but I can't seem to remember of find it. There's a calculator here...

How To Calculate Star Trails | Perfect Astronomy
 
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Marcel

Happily retired
Staff member
Super Mod
You could try it and see for yourself. You can experiment with what you have now and see what you can get before you commit to one lens.
 

snaphappy

Senior Member
I played with this when trying to catch the Aurora and I just wasn't very happy with the results. Slower shutter speed made for too much movement and high iso drove me crazy with the noise. Now that I have bright reflective snow on the ground I'll give it a try again but I don't think that is an option for you :)
 

WhiteLight

Senior Member
You could try it and see for yourself. You can experiment with what you have now and see what you can get before you commit to one lens.

I actually did give it a shot with my 35mm prime when I was in Nepal last year but my coordinates and location was quite terrible so couldn't really make things out... :-(
Within the city I don't think I'll be able to see any difference with all the pollution..
But yes, as you noted am thinking this would be quite the deciding factor between the sigma and tokina. So far am sold on the sigma and will mostly go ahead with that if the 2 stop difference can be managed


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WhiteLight

Senior Member
I played with this when trying to catch the Aurora and I just wasn't very happy with the results. Slower shutter speed made for too much movement and high iso drove me crazy with the noise. Now that I have bright reflective snow on the ground I'll give it a try again but I don't think that is an option for you :)

Thanks snap!
What lens and settings did you use? If you remember :)

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WhiteLight

Senior Member
It isn't even 60 secs for crop sensors..
The prevalent rule her is the rule of 600 (or 500) if that makes it easier..
For a full frame is 600 and for crop sensors is 500.
Take 600 or (500) as per your gear, divide by the focal length.
So for crop sensors, a 10mm lens would 33 secs.
For 23mm it world be 14 secs..

So not really a lot of time to keep the shutter pressed !

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BackdoorArts

Senior Member
As a former D7000 user I have to say that I was never thrilled with its high ISO performance, which was one of the main things to drive me to the D600. The new DX sensors have made great strides in that area, which will help you a lot.

With stars, there's nothing that's going to help you more than bright glass. I barely ever use my 28mm f1.8, but it's in my bag just for those days when I want to shoot stars. But as bright as that glass is, it can't fight ambient light. Nothing can fight ambient light outside of wheels and an engine that will take you away. Otherwise all you get is more washout, not more stars.

Now that I'm thinking about it, I really should have dragged my butt out in the days after Hurricane Sandy last year and shot the sky in the 5 1/2 days we were without power (though it may have been cloud covered for a day or two). If you can't get a feel for where the Milky Way is by looking up, you're probably not going to be able to shoot it.
 

WhiteLight

Senior Member
As a former D7000 user I have to say that I was never thrilled with its high ISO performance, which was one of the main things to drive me to the D600. The new DX sensors have made great strides in that area, which will help you a lot.

With stars, there's nothing that's going to help you more than bright glass. I barely ever use my 28mm f1.8, but it's in my bag just for those days when I want to shoot stars. But as bright as that glass is, it can't fight ambient light. Nothing can fight ambient light outside of wheels and an engine that will take you away. Otherwise all you get is more washout, not more stars.

Haha.. True.
The UW has not really been in my scheme of things.. But hey when does anything go according to plan ;-)
I maybe heading somewhere peaceful during Thanksgiving and would like to make use of the time to get a decent lens that wouldn't cost the earth and help in getting some good landscape and night sky photos..
As you would have figured through my older images, I love landscape photography :)

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BackdoorArts

Senior Member
@BackdoorHippie - and I do sense a push from dx to fx too from your message ;-)


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Not a push, necessarily. The D7100's high ISO performance seems to be somewhere around a stop to a stop and a half behind the D600's (i.e. D7100 at ISO3200 is comparable to the D600 at ISO6400). From what I've seen I'd say the D7100 is at least 1-2 stops better than the D7000, so you don't necessarily need to make the jump in format to get noise improvements ... but if you need an excuse, you have one. :)
 

BackdoorArts

Senior Member
That's the Tokina. Others creep in immediately and never give you full frame coverage. That said, it's always possible to use your DX lenses on FX, but you're almost always going to have to crop. You also need to realize that one of the reasons DX glass is cheaper is that it doesn't try and be perfect in those corners you're now utilizing, so expect plenty of CA and distortion on the edges that never get used on the cropped sensor.
 

WhiteLight

Senior Member
That's the Tokina. Others creep in immediately and never give you full frame coverage. That said, it's always possible to use your DX lenses on FX, but you're almost always going to have to crop. You also need to realize that one of the reasons DX glass is cheaper is that it doesn't try and be perfect in those corners you're now utilizing, so expect plenty of CA and distortion on the edges that never get used on the cropped sensor.

Yep.. Tbh I was looking at responses to this as I am on the fence between the sigma 10-20 and tokina 11-16...
I have been infatuated with the sigma for the extra focal reach, but the results from the tokina are making things very difficult :p
It's occasionally good to be spoilt with choices

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Moab Man

Senior Member
Whitelight, I apologize for having not responded to your direct request for input. I wanted to have the time to sit down and write while not rushed. As I write my response there will be little inserts so that newer shooters readers don't get lost.

As you stated up front, the lowest numbered aperture (largest opening) is ideally best to allow the most light you can. However, your question about using f4 is actually more relevant than I knew until two weeks ago (and not for the reason you were asking). As photographers we are all trying to learn and improve our craft. Two weeks ago I attended a seminar on night photography with my daughter. The entire time my daughter kept beating me up to go, "dad you know all this stuff." Which was true, and then I stumbled upon a golden nugget of information relative to aperture. The speaker started to talk about how ideally we want to use the largest aperture we can, but we need to do a little examining of our aperture to figure out what that best aperture is.

At this point he put two pictures shot on the same full frame Canon camera while swapping out lenses. The first lens was a Canon wide angle of professional grade and the second was a considerably cheaper Rokinon wide angle (Sorry I can't tell you the models of any of the equipment as it wasn't important to the lesson or me). He then zoomed into the outer "squared" circle of the two pictures shot at we'll say 1.8 (whatever the widest was for the two lenses). The stars from the Canon lens squared circle area were actually shockingly bad at 100%. Speaking in plain language, the center of the stars were white, but the edges of the stars really suffered from other colors showing up on the edges of the stars that shouldn't have been there. The Rokinon, at the same aperture and 100% zoom had little edge color bleeding into the white of the stars. The presenter was actually quite surprised at the difference when he first noticed and investigated.

The presenter continued to raise the aperture number (smaller opening) and showed us the diminishing edge color bleeding. I do not remember where each came to its ideal star aperture number, but the Rokinon achieved an ideal star in the squared circle at a much lower aperture than his Canon lens did.

To your original question, what are you going do with your pictures? If you are only displaying on a computer then fire away wide open. If you are going to print, and you are shooting wide angle, you want to print big. The compression of a wide angle just doesn't do the print justice unless you go big because you're stuffing too much into a traditional sized picture.


Which now brings me to finally answering your question after all my long windedness, and this is what I am going to do this Friday night on my Milky Way shoot (clouds permitting). Shoot a number of photos starting at a wide open aperture. Then, incrementally tighten up the aperture and shoot again. Of course you will need to play with ISO and exposure time. Once you have these shots sit down and compare the squared circle of your images and see what the stars look like in this area.

Once you know where the aperture sweet spot is for stars on the lens you're shooting then you can start to play with how long of an exposure vs ISO to avoid noise and star trails. However, Milky Way photos are all about the editing and noise reduction. Photoshop has been my tool of choice and I have done really well with it. I have recently started playing with Nik Tools and the noise reduction tools are amazing. Combining the two, Photoshop and Nik Tools, I believe I will be able to push my Milky Way photography to a new level.

As to star trails and avoiding. The wider the angle of lens you're shooting the longer you can expose before trails will start to show. You can also push that a bit by what you will do with it. If you print larger poster sized prints (I do) star trails will readily show up. However, a more traditional sized print will hide it.


I hope this has helped and I have answered your question; even if I didn't answer it for the reason you initially asked.
 

WhiteLight

Senior Member
Thanks [MENTION=11881]Moab Man[/MENTION]
very insightful indeed!
and also a lot more confusion to the mix :D

but definitely points to ponder over..
i will be awaiting your weekend experiments.. and hopefully your results would help me get off the fork in the road :)

thanks again for taking the time out to respond in such detail, the info was something i hadn't really considered
 

Moab Man

Senior Member
Thanks @Moab Man
very insightful indeed!
and also a lot more confusion to the mix :D

but definitely points to ponder over..
i will be awaiting your weekend experiments.. and hopefully your results would help me get off the fork in the road :)

thanks again for taking the time out to respond in such detail, the info was something i hadn't really considered

I know it does add a lot more to the mix for chasing the best we can achieve. And I know for most people this is going way farther than necessary, but I also believe you are one of the likewise obsessive people on here that will take it this far.

Keep in mind, my experimentation this weekend would only apply to the Tokina AT-X116 Pro DX-II 11-16mm f/2.8.

Best wishes on this night photography endeavor. I know I have become obsessed.
 
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WhiteLight

Senior Member
I know it does add a lot more to the mix for chasing the best we can achieve. And I know for most people this is going way farther than necessary, but I also believe you are one of the likewise obsessive people on here that will take it this far.

Keep in mind, my experimentation this weekend would only apply to the Tokina AT-X116 Pro DX-II 11-16mm f/2.8.

Best wishes on this night photography endeavor. I know I have become obsessed.

Hehe.. Totally true..
In fact the Tokina 11-16 is one of the 2 i am really wanting to get.. the first model actually, since i can use it on my D7000 and save a few bucks.. don't think there is any other differences between the 2 versions, is there?
(Btw, i didn't know you got the Tokina 11-16! neat surprise)
The other being the Sigma 10-20.
I have come to the conclusion that the IQ in both is fantastic, so that;s not really a contest there.

Pro's for the Sig - the additional 1mm at the top & the greater focal range
Pro's for the Tok - f/2.8 (especially for the night sky shots) and the fact that this lens would perform as a prime (almost) on Fx.. that is a real bonus..
it works without issues at 15-16mm on fx without much CA or vignetting or loss of quality.. and 16mm is quite wide on Fx..

It would be great if you could shoot 2 images at f/4 & f/2.8 - any settings as long as you happy with the pic, which would be close to the best am sure :)
 

Moab Man

Senior Member
Got the Tokina back at the beginning of summer.

I will shoot f2.8 through to f4.

The pictures from this Tokina have been outstanding so far, but now I will be scrutinizing even harder as I work to improve my game. If you would like am image from the Tokina shooting the Milky Way just to play with and scrutinize I can send you a raw file or two.
 
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