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12-11-2017, 09:29 AM   #16
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This could be an option slightly above your budget: Samyang 8mm F3.5 UMC Fish-eye CS II Lens Reviews - Samyang Lenses - Pentax Lens Review Database

The fish eye effect should not be an issue here.

Seb

12-11-2017, 01:08 PM   #17
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Option 1: A fast wideangle prime lens (<24mm) like the Samyang 14mm f2.8 (FF lens) or16mm f2 (Apsc lens), both can be found used on B&H, though they're both a bit over $200: Used Digital Camera SLR Interchangeable Lenses | B&H Photo Video

Option 2: A constant aperture zoom like the Tamron 17-50mm f2.8 Tamron 17-50mm F/2.8 Aspherical DI II SP IF LD XR (A16) K Mount Autofocus Lens For Pentax APS-C Sensor DSLRS {67} at KEH Camera Store), would also be a good option.

---------- Post added 12-11-17 at 01:14 PM ----------

Another good option is to check out the marketplace here in the forums, good chance you can find a good quality fast W/A prime/constant aperture zoom that's around you're budget.
12-11-2017, 01:18 PM   #18
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A lot of good advice, I want to add that don't be too busy with the camera and forget to enjoy the Northern Lights ... It is breathtakingly magnificent!!!

Based on my limited experience:
Practice before hand as much as possible: focus the lens to infinity during daytime, manual focus if possible, use a tape or something to lock the focus ring in place, so you won't have to fiddle with it at night.
Depends on the activity and strength of the light, it can be moving/changing shape very very quickly or some what slowly... they are unpredictable.
Look for interesting foreground composition ahead of time. Scout your locations.
Be quick to react, if the lights are changing shape very rapidly, and you have the camera set to, let's say, 15 second exposure, then the outcome will probably not be so desirable...

If this is a rare chance/vacation, I would almost suggest to set the camera on interval shooting (you can end up with a timelapse video too) while you sit and enjoy the scene...
Good luck!
12-11-2017, 04:45 PM   #19
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Not a lot of good advice at all, it is clear that nobody here understands the principle of 'clear aperture' and how important it is with faint light sources...

For example, someone recommending an 8mm f3.5 lens... You may as well use your cell phone as this has a 8mm/3.5 =2.29mm diameter aperture opening...

The human eye has about 6mm/7mm aperture opening.

I have the Samyang 14mm f2.8 and it only has a 5mm aperture opening which is why it doesn't suck in much faint light, I need to use astro tracer and stack exposures, for example a total of 12 minutes to get a decent Milky Way photograph...

A K1 with a 35mm f1.4 or 24mm f1.4 is the way to go or use APSC but this is an advantage of full frame, i.e. you can use longer focal length lenses to suck in more light for the same field of view.

Or use a Pentax-M 50mm f1.7... great for astro and cheap. But you have the DA40... my favourite astro lens and the Samyang never gets used any more.

12-11-2017, 05:35 PM   #20
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QuoteOriginally posted by nocturnal Quote
faint light sources...
Would you consider the Northern Light as faint light sources though?
I have seen some strong activity right beside a full moon and it matches the full moon's brightness without problem! The milkway can't do that... it won't be visible at all in that case.
Of course I only had one chance to photograph the Northern Lights (with Samyang 14 f/2.8) so I can't compare results, would be interesting to know how much a bigger 'clear aperture' improves the photo during this kind of scenario though...
12-11-2017, 05:38 PM   #21
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QuoteOriginally posted by nocturnal Quote
Not a lot of good advice at all, it is clear that nobody here understands the principle of 'clear aperture' and how important it is with faint light sources...

For example, someone recommending an 8mm f3.5 lens... You may as well use your cell phone as this has a 8mm/3.5 =2.29mm diameter aperture opening...

The human eye has about 6mm/7mm aperture opening.

I have the Samyang 14mm f2.8 and it only has a 5mm aperture opening which is why it doesn't suck in much faint light, I need to use astro tracer and stack exposures, for example a total of 12 minutes to get a decent Milky Way photograph...

A K1 with a 35mm f1.4 or 24mm f1.4 is the way to go or use APSC but this is an advantage of full frame, i.e. you can use longer focal length lenses to suck in more light for the same field of view.

Or use a Pentax-M 50mm f1.7... great for astro and cheap. But you have the DA40... my favourite astro lens and the Samyang never gets used any more.
The concept of clear aperture is very important to astrophotography but it really only applies to point light sources*.

For a diffuse object (an aurora, blank wall lit by moonlight, or a blank wall lit by sunlight), only the relative aperture matters. That's why a standalone light meter can be used to measure exposure. And if the light meter says to use f/4 then that exposure will be correct whether it's a 8mm lens or an 800 mm lens. If 30 seconds @ f/4 creates decent aurora exposure, it will be the same decent exposure at any focal length.


You are right that longer focal length lenses do suck in more light but then they spread all that extra light further across the sensor. A tiny 10 pixel x 10 pixel blob (100 pixels total) in an 8 mm lens image will become a huge 1000 pixel x 1000 pixel blob (1 million pixels total) if you use an 800 mm lens at the same aperture. Yes, the 800 mm lens sucked in 10,000X more light but in then spread it over 10,000 X more pixels. So the effect cancels out for diffuse objects.

But the stars and other point objects are different. Their brightness will be a function of clear aperture. A star will be a 1 pixel dot in the 8mm lens image and it will still be a 1 pixel dot in the 800 mm lens image but now that dot will be 10,000X brighter because of the clear aperture effect.

(*NOTE: the clear aperture effect operates to a lesser extent with thin-line objects like meteor tracks. A meteor track in an 800 mm lens image will be 100X brigher than the same track in an 8 mm image.)

Last edited by photoptimist; 12-11-2017 at 05:48 PM. Reason: typos
12-11-2017, 06:19 PM - 2 Likes   #22
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QuoteOriginally posted by nocturnal Quote
Not a lot of good advice at all, it is clear that nobody here understands the principle of 'clear aperture' and how important it is with faint light sources...
I dare to have a different point of view on this (the understanding part) and I'd suggest you try to be less judgmental and open to broaden your repertoire of concepts. If fully agree on
QuoteOriginally posted by nocturnal Quote
A K1 with a 35mm f1.4 or 24mm f1.4 is the way to go or use APSC but this is an advantage of full frame, i.e. you can use longer focal length lenses to suck in more light for the same field of view.
... given you use the same relative input-referred aperture, or 'f-stop'. For telephoto lenses btw., the absolute aperture size is most often determined by the front element size, so as a rule of thumb, you can use the lenses diameter to judge the light gathering abilities irrespective of the sensor format. But a new full-frame camera doesn't fit the original poster's budget at all anyway, nor is it required for taking beautiful pictures.

Now back to the original poster's question: The goal is to photograph the Aurora borealis, which happens to be neither very faint on reasonably good days, nor is it a collection of point sources (stars) with a lot of black in between, nor do all the beautiful structures tend to fit the field-of-view of a 24mm lens on APS-C in the Yukon territory, nor is it static enough to stitch together multiple exposures. Therefore, the 'clear aperture' criterion in not 'the one to rule them all'. Being a moving and shape-shifting 'subject', it has to fit into the frame at once for a single exposure, leaving ultra-wide lenses as the only practical option. Luckily, being a spatially continuous phenomenon, even with the smaller absolute aperture diameter - in contrast to point sources like stars - the tiny open aperture of an ultra-wide lens will record light from an inverse-proportionally larger spherical angle of view on each sensor site, bringing us back from astro-photography to the same principles as for daylight photography: Two exposures exposed at the same relative aperture (f-stop), from two lenses of different focal lengths, other parameters unchanged, will be equally bright, just showing different fields of view.

So I find most of the advice above very relevant: Bring an ultra-wide lens with f/2.8 or better if you can, consider selling it later to reclaim a significant portion of the price to stay within budget, optionally add something like a really inexpensive but good 50/1.7 (otherwise use the 40/2.8) for the 'narrow' view shots and practice before you leave. Some moon-lit clouds under windy conditions can be similar in brightness to the Aurora borealis and do move as well as change shape. For examples on all of this, see the samples already linked above.

Last edited by JensE; 12-11-2017 at 06:46 PM.
12-12-2017, 05:02 AM   #23
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QuoteOriginally posted by bassek Quote
This could be an option slightly above your budget: Samyang 8mm F3.5
I have that lens and use it occationally for northern lights photography. Northern lights photography is a genre of landscape photography. Ultra wild angles may suit certain landscapes but its to wide for most situations, including northern lights. Northern light photos without an interessting foreground is boring.

QuoteOriginally posted by nocturnal Quote
For example, someone recommending an 8mm f3.5 lens... You may as well use your cell phone as this has a 8mm/3.5 =2.29mm diameter aperture opening...
Not true. Mobile phone cameras have a much narrower field of view. Any subject movement are amplified by the narrower field of view. An ultra wide angle 8mm f/3,5 can handle a lot longer exposures of northern lights compared to a normal angle 8mm f/3,5. Light intensity per sensor area will be equal, but with a lot more sensor area on one of them, this will gather a lot more light and thus give less image noise per area or per image. The combination of larger sensor area and longer exposures gives a lot cleaner images for the large sensor option.

12-12-2017, 06:49 AM   #24
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QuoteOriginally posted by Simen1 Quote
I have that lens and use it occationally for northern lights photography. Northern lights photography is a genre of landscape photography. Ultra wild angles may suit certain landscapes but its to wide for most situations, including northern lights. Northern light photos without an interessting foreground is boring.
At least you are up north (further than me) so you would know. Sometimes my SigmaEX15-30 is not wide enough. Another issue is the amount of street lighting in my area.
If I would be somewhere dark I assumed I would want to go ultrawide. I'll try my DA21 next time.

Seb

PS: We are all entitled to our own opinions. And I assume many of the commentators are more experienced than me. Which is just fine.
12-12-2017, 10:48 AM   #25
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QuoteOriginally posted by czhao1009 Quote
A lot of good advice, I want to add that don't be too busy with the camera and forget to enjoy the Northern Lights ... It is breathtakingly magnificent!
Thanks for that excellent advice. If I get one half-way decent photo, that will be icing on the cake, but it's more important that I see them at all - there is certainly no guarantee that I will. It's exciting to be in snow at all now that I live in Coastal California so I'll focus more on that.

I am more confused than ever but I've received some good tips. My initial thought was that I would try different lenses and it still seems like that's what I'll do. Once I'm there I'll scope out the photo possibilities and decide which one goes on my camera first.
12-12-2017, 12:27 PM - 2 Likes   #26
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QuoteOriginally posted by nocturnal Quote
Not a lot of good advice at all, it is clear that nobody here understands the principle of 'clear aperture' and how important it is with faint light sources...

For example, someone recommending an 8mm f3.5 lens... You may as well use your cell phone as this has a 8mm/3.5 =2.29mm diameter aperture opening...

The human eye has about 6mm/7mm aperture opening.

I have the Samyang 14mm f2.8 and it only has a 5mm aperture opening which is why it doesn't suck in much faint light, I need to use astro tracer and stack exposures, for example a total of 12 minutes to get a decent Milky Way photograph...

A K1 with a 35mm f1.4 or 24mm f1.4 is the way to go or use APSC but this is an advantage of full frame, i.e. you can use longer focal length lenses to suck in more light for the same field of view.

Or use a Pentax-M 50mm f1.7... great for astro and cheap. But you have the DA40... my favourite astro lens and the Samyang never gets used any more.
Taking photos of the northern lights is not astrophotography.

Would a K1 with a 31 Limited work? Sure! It's not as wide as I'd want overall, but it'll definitely do.

Will a K-30 with a 20-40 Limited work too? Yup, sure will... this is from my front yard last winter at 20mm.



The 10-20 will give him a wider field of view however... again, my front yard but earlier this year.




We're talking exposures of 6 to 20 SECONDS, not minutes. When the northern lights are out bright enough to warrant photography, they're really not all that faint. I am lucky enough to be able to see the Milky Way at my house at night, and the auroras are several orders of magnitude brighter. I do wish I had faster wide lenses however, so I could drop my ISO's down to 800 or even 400 more consistently. I'll very eagerly waiting the announced DA*11-18 f2.8 for just that reason. Until then, I'll use what I have...


Some other advice: Dress warmly, especially your feet as you'll most likely be standing on ice and snow at -20*F for a while as the skies usually won't get really clear until its very cold out. Keep spare batteries in an inside pocket. Be comfortable with your tripod and working with it in the dark.
12-12-2017, 03:54 PM - 2 Likes   #27
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Wide angle lenses works well for auroras; you'll want a large part of the sky in the picture. Lenses don't need to be very fast although it helps. >This is shot with the K-3 and the DA* 16-50/2.8 at F:4. 16mm

12-12-2017, 04:18 PM   #28
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QuoteOriginally posted by Pål Jensen Quote
Wide angle lenses works well for auroras; you'll want a large part of the sky in the picture. Lenses don't need to be very fast although it helps. >This is shot with the K-3 and the DA* 16-50/2.8 at F:4. 16mm
Excellent Image!

What's also interesting is that a lower-right crop of this image (such as what 28 mm on APS-C might deliver) would also be a stunning image. And even a 50mm on APS-C (in portrait orientation) could have gotten a great picture.

Auroras might lend themselves to UWA lenses but other focal lengths can get great shots through suitable framing.
12-13-2017, 03:53 AM - 1 Like   #29
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I don't have an FF digital camera but this is shot on film with the LX and the 31 Limited at F:4. 200ISO


.
12-13-2017, 03:45 PM   #30
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Didn't mean to offend my fellow Pentaxians and I have back-tracked at full speed in reverse! 😥 But at least some good discussion and points were learnt all around. 😀

Some great aurorae photos here, I just got the 20-40 Ltd (cracking lens!) and great to see it used for aurorae. I love the colours from the LX/FA31 on 200 film. The aurorae here are much more faint, only sometimes faintly visible away in the distance and hence my original thinking. If I knew the targeted aurorae were as bright as the moon I wouldn't have thought so.

I'd love to try my HD DA15 f4 for aurorae over the Samyang 14mm but I better get on a flight to Iceland.
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