Advice in choosing lens for night photography

Normanaus · Dec 9, 2019

Hi,

I am beginner to photography and very interested in taking night sky photos. I have Sony A6000 camera and considering purchasing a wide-angle lens. From the reviews I read and my financial abilities, I narrowed it down to three choices of Rokinon lenses. Can someone help me with choosing a right one?

My understanding is that the larger the aperture , the more light will go in. I also read that longer lens will provide more detail and less noise- so does this mean 21mm f1.4 is a better option? It also has the most features to it.

I also look at specs for each lens (links provided), it seems 12mm f.2 has almost identical features as 21mm f1.4. It is also shorter, which would make it easier to travel with. My primary reason for getting a lens is to shoot night sky, but secondary (and not as critical ) would be to use the lens during everyday travels too. Should I go with that one then? Also I am not sure as to how much difference between f1.4 and f2 there would be - isn't the difference manageable by using higher ISO settings?

The 14mm f2.8 seems like a compromise between the 12 and 21mm, however I read that the wide lens it has will have be a challenge for putting filters on. So it would probably be my least favorite out of the three.

Rokinon 12mm f.2
Rokinon

Rokinon 14mm f2.8
Rokinon

Rokinon 21mm f1.4
Rokinon

Any help, suggestions or ideas on other lenses would be greatly appreciated.

Thank you

Dacaur · Dec 10, 2019

The difference between f1.4 and f2 is that f1.4 let's in twice as much light. Litteraly. twice. as. much. So no, you couldn't manage that with s higher iso.
Each "stop" larger on the aperature doubles the amount of light you let in. So f1.4 let's in twice as much light as f2.0, f2.0 let's in twice as much as f2.8, f2.8 let's in twice as much as f4.0. 1.4 let's in 4 times as much as f2.8, 8 times as much as f4.0, and 16 times as much light as f5.6......
Basically, a 30 second exposure at f2.0 will look the same, brightness wise, as a 15 second exposure at f1.4...

Now, as to your lenses choices, it's not as straightforward as it would seem.
IMO, your budget is the biggest decider here. You have to decide if the benifit if the larger aperature is worth the cost.
First off, Google the "500 rule" for astrophotography.

Once you understand that, you will see that, yes, the 21mm f1.4 let's in twice as much light as the 12mm f2.0, but you can keep the shutter open on the 12mm lense nearly twice as long as you can the 21mm without getting star trails. Of course, the longer exposure will suffer from more noise, but the cost/benifit ratio of that is up to you to decide....

If you also will want to use it for general photography, then the 12mm might be the way to go, as 21mm is likely already covered by your kit lense, as you aren't gaining as much adding a 21mm prime as you are adding a 12mm prime.

photo1x1.com · Dec 10, 2019

Hi there.
There are a few things to consider when photographing the nightsky.
The earth is rotating, so the stars are moving along the night sky. So there are "rules" that you need to understand and follow in order to not get star trails instead of sharp pinpointed stars.
Read up on the 500 rule and the NPF rule. Basically they tell you how long you are able to expose without introducing star trails with a certain focal length. With the 12mm, you will be able to almost double the time of the 21mm. But then again the 21mm will let twice as much light in due to the bigger aperture, so these two are rather similar in this regard.
The 14mm f2.8 however, allows for almost the same amount of time as the 12mm, but has a smaller max opening, only letting half the light in, so that will be the worst in this regard. But it is still very popular among night sky photographers from what I know.

The longer lens won´t have less noise, but more detail because it enlarges the stars.

Another thing to consider is that a wider lens will let you capture more of the nightsky in a single shot, which is really nice, because the milky way can cover the complete sky (depending on the time and the area you live in) Have a look at these examples.

But you could always create a panorama made of multiple shots.

To get an idea of how much difference the various focal lengths make, let me suggest one of my videos. I created it to give people who are thinking about buying a lens some tips. Maybe that helps too.

Derrel · Dec 10, 2019

The 12mm f/2 would be my choice for your aps-c camera.

Normanaus · Dec 11, 2019

Thank you everyone so much for detailed responses!

I googled the 500 rule, so if I was to use 12mm and 21mm lenses it would be:

21 mm
500 / 1.5 (Sony A6000 cropped sensor) x 21 = 16 seconds

12mm
500 / 1.5 x 12 = 28 seconds

Now it was mentioned that the shutter speed can be "longer for 12mm lens without getting a star trail" - so does this mean that keeping shutter for longer time is a good thing? I am a bit confused - 12 mm longer shutter speed = more noise, but captures more image. 21mm shorter shutter speed resulting in smaller image but also less noise. So which one is then better? Would it not then, make more sense to have something that emits more light and produces more detailed images?

Dacaur · Dec 11, 2019

You are right, it's better to get the same light with a shorter shutter time, because a longer shutter shutter time = more noise. I simply mentioned that because, depending on how your camera handles noise, the two lenses can take nearly the same picture, other than field of view, so the larger aperature of the 21mm is less of an advantage than it would seem at first glance, in my opinion...

However, it's not always as simple as more light = the best lens for you. There are other things to consider.
The 12mm lens will capture more of the sky in one shot, by nearly double... This can be good or bad depending on what you are after, as posted above, you can always take multiple pictures and stitch them together, but it would take 3-4 pictures with the 21mm to equal one with the 12mm. But of course, if you do the opposite by cropping the 12mm picture to the 21mm fov, you end up with a lower resolution picture...
Youl likely already have 21mm covered by another zoom lens, however, a prime 21mm will always give better pictures... But still 12mm is probably not a focal length you have covered, and the 12mm would do double duty as a night sky lens, and a landscape lens, on the other hand, 12mm might be TO wide for many situations.....

Helpful, right?
If picking a lens were easy, we wouldn't have such a wide variety to choose from...
Personally, I would go with the 12mm, but only because I already have a 24mm prime.

Lonnie1212 · Dec 11, 2019

Normanaus said:
Hi,

I am beginner to photography and very interested in taking night sky photos. I have Sony A6000 camera and considering purchasing a wide-angle lens. From the reviews I read and my financial abilities, I narrowed it down to three choices of Rokinon lenses. Can someone help me with choosing a right one?

My understanding is that the larger the aperture , the more light will go in. I also read that longer lens will provide more detail and less noise- so does this mean 21mm f1.4 is a better option? It also has the most features to it.

I also look at specs for each lens (links provided), it seems 12mm f.2 has almost identical features as 21mm f1.4. It is also shorter, which would make it easier to travel with. My primary reason for getting a lens is to shoot night sky, but secondary (and not as critical ) would be to use the lens during everyday travels too. Should I go with that one then? Also I am not sure as to how much difference between f1.4 and f2 there would be - isn't the difference manageable by using higher ISO settings?

The 14mm f2.8 seems like a compromise between the 12 and 21mm, however I read that the wide lens it has will have be a challenge for putting filters on. So it would probably be my least favorite out of the three.

Rokinon 12mm f.2
Rokinon

Rokinon 14mm f2.8
Rokinon

Rokinon 21mm f1.4
Rokinon

Any help, suggestions or ideas on other lenses would be greatly appreciated.

Thank you

Lonnie1212 · Dec 11, 2019

Normanaus said:
Hi,

I am beginner to photography and very interested in taking night sky photos. I have Sony A6000 camera and considering purchasing a wide-angle lens. From the reviews I read and my financial abilities, I narrowed it down to three choices of Rokinon lenses. Can someone help me with choosing a right one?

My understanding is that the larger the aperture , the more light will go in. I also read that longer lens will provide more detail and less noise- so does this mean 21mm f1.4 is a better option? It also has the most features to it.

I also look at specs for each lens (links provided), it seems 12mm f.2 has almost identical features as 21mm f1.4. It is also shorter, which would make it easier to travel with. My primary reason for getting a lens is to shoot night sky, but secondary (and not as critical ) would be to use the lens during everyday travels too. Should I go with that one then? Also I am not sure as to how much difference between f1.4 and f2 there would be - isn't the difference manageable by using higher ISO settings?

The 14mm f2.8 seems like a compromise between the 12 and 21mm, however I read that the wide lens it has will have be a challenge for putting filters on. So it would probably be my least favorite out of the three.

Rokinon 12mm f.2
Rokinon

Rokinon 14mm f2.8
Rokinon

Rokinon 21mm f1.4
Rokinon

Any help, suggestions or ideas on other lenses would be greatly appreciated.

Thank you

What size lens do you have on your camera now?

Lonnie1212 · Dec 11, 2019

Normanaus said:
Hi,

I am beginner to photography and very interested in taking night sky photos. I have Sony A6000 camera and considering purchasing a wide-angle lens. From the reviews I read and my financial abilities, I narrowed it down to three choices of Rokinon lenses. Can someone help me with choosing a right one?

My understanding is that the larger the aperture , the more light will go in. I also read that longer lens will provide more detail and less noise- so does this mean 21mm f1.4 is a better option? It also has the most features to it.

I also look at specs for each lens (links provided), it seems 12mm f.2 has almost identical features as 21mm f1.4. It is also shorter, which would make it easier to travel with. My primary reason for getting a lens is to shoot night sky, but secondary (and not as critical ) would be to use the lens during everyday travels too. Should I go with that one then? Also I am not sure as to how much difference between f1.4 and f2 there would be - isn't the difference manageable by using higher ISO settings?

The 14mm f2.8 seems like a compromise between the 12 and 21mm, however I read that the wide lens it has will have be a challenge for putting filters on. So it would probably be my least favorite out of the three.

Rokinon 12mm f.2
Rokinon

Rokinon 14mm f2.8
Rokinon

Rokinon 21mm f1.4
Rokinon

Any help, suggestions or ideas on other lenses would be greatly appreciated.

Thank you

Did your Sony come with the 16-50 lens? If so, many people would be content using that lens for astro photography. Your camera is also known to have excellent low capabilities.

Normanaus · Dec 12, 2019

Thank you Dacaur!
Will need to figure out, what I would prefer - stitching panoramas or taking all in one. This definitely gives me more things to consider.

Lonnie1212
Yes, my camera did come with 16-50 lens. The specs are as follow:

SPECIFICATIONS:
Optics/Lens:
Lens Type: E-mount 16-50mm F3.5-5.6
Lens Mount Type: Sony E-mount lenses
Aperture: f/3.5-5.6
Aperture (Max.): f/3.5-5.6
Aperture (Min.): f/22-36

I tried it out for night photography before, but at the time had no idea what I was doing and whether if it was decent or not. That is what prompted me to read about night lenses.

photo1x1.com · Dec 12, 2019

Normanaus said:
Now it was mentioned that the shutter speed can be "longer for 12mm lens without getting a star trail" - so does this mean that keeping shutter for longer time is a good thing? I am a bit confused - 12 mm longer shutter speed = more noise, but captures more image. 21mm shorter shutter speed resulting in smaller image but also less noise. So which one is then better? Would it not then, make more sense to have something that emits more light and produces more detailed images?

In my experience, doubling the exposure time doesn´t nearly introduce as much noise as doubling the ISO, if that helps with your decision. It depends a lot on the temperatures you are shooting in. High tempertures being worse.