Astrophotography & Bright Foregrounds

[0ptics]

Hello,

I've seen a lot of amazing photographers clear star photos and their tutorials about how to edit star photos, reduce noise, 500 rule, equipment, etc.; however, I haven't seen/read any good advice on how to produce star photos with a clear, bright, low noise foreground. For an example, a lot of Michael Shainblum's photos are just mind-blowing and I'd love to produce even a fraction of his artwork!

This is one of my images, I like the composition; however, is photo is extremely noisy, the quality is very poor @ 100%, and the mountain is barely visible!
Womb

1) So my question is how do photographers captures such a clear foreground & sharp+low noise star photos? Do they take a photo right before sunset & not move the tripod until its dark?

2) Are they using the image stacking technique? How many pictures & what settings are recommended generally (eg. ~3-5 pictures? Each one stop +/- different?)

3) Any tutorials (free & paid) that you all would recommended? I plan to purchase Shainblum's, but am open to other photographers!

Oregon and Washington Landscape Photography

Oregon and Washington Landscape Photography

Oregon and Washington Landscape Photography

Oregon and Washington Landscape Photography (Michael Shainblum)

Thank you!
I'd really appreciate the help

 

[0ptics]

Did forget to mention; I'm using the Nikon D7100 & Nikon 17-55mm f/2.8 (sometimes Nikon 12-24mm f/4)

 

[photo1x1.com]

Hi there,
am I wrong, or is your mountain not covered with snow while the others are?
In my experience it has a lot to do with your location. The glow in the linked images may easily be due to to a smaller town nearby, or a city further away.
Image stacking brings down the noise quite a bit - did you try that?
It works really well for the foreground, because you don´t need to align it - but you need to create a mask in photoshop for the foreground only. 5-8 images for stacking seems to be a good compromise. For stacking I don´t bracket the shots, they all have the same exposure.

 

[TCampbell]

Astrophotography images are always aggressively adjusted. Stacking certainly helps but to stack the images all have to be "registered" to each other. Stacking software for astrophotography uses the star positions to align each frame (with the exception being 'planetary' stacking software, but that's another thread.) Anyway, the problem with this is that now that you've aligned the stars, the landscape is no longer aligned due to rotation of the Earth. So ultimately what you need is a decent exposure of your foreground and the stack of the sky and then overlay the foreground onto the combined sky image to create a composite.

I'm always suspicious when I see images that have clouds... but I can see the stars (even the dim stars) shining through the clouds. Stars don't do that so it's always a dead giveaway that the image is stacked and probably stacked via an averaging method.

When I stack I prefer to use a sigma-clipping algorithm. Sigma clipping takes the pixels which would be at the same point in each image and creates a statistical mean (average) for the value of that pixel. But it also looks for frames in which the respective pixel deviates substantially from the mean. If that occurs, the pixel is rejected. You typically need at least 10 frames in the stack for this to work well (more is better.) Due to the way this works... if, for example, an airplane flew through the scene in just one of the frames (and that would create a light path) the sigma clipping method could completely erase the airplane trail - like magic (because you have just one frame with pixels that deviate substantially from the rest of the set.) It does throw away the whole frame... the pixels that don't deviate significantly are retained... only those that deviate are rejected. I did a shot on the Haleakala volcano in Maui ("Science City" where the observatories are located) at night and they were firing the lasers that they use to generate artificial stars (it's used for adaptive optics so ground based telescopes can capture images that rival the Hubble) and very single frame had streaks in it... somewhere. But since no two frames had identical streaks, the sigma clipping method was able to remove the streaks from the final result and what you get is a nice clean image.

Sigma clipping can erase random noise. But it can't erase pattern noise (that noise would show up in the same spot in every frame). "dark frames" can be used to help the computer identify the pattern noise and erase it. But another technique called "dithering" is useful (but this typically requires a go-to telescope mount... not a simple camera tracking head). The technique nudges the mount just a tiny bit (a handful of pixels really) between every frame. The registration process will align all frames based on the positions of stars, but this means that the 'pattern' noise and stuck pixels will now be in a *different* location in each frame and *that* means sigma clipping can even clean up the stuck pixels and pattern noise.

Stacking techniques allow you to improve the signal-to-noise ratio (basically reduce the noise) based on a factor equal to the square root of the number of frames you shoot. So if you shoot 4 identical frames you can improve noise reduction by a factor of 2. But 9 frames can improve it by a factor of 3. 16 frames can improve it by a factor of 4... and so on.

You can check out photographingspace.com for some pretty good tutorials. I also generally recommend the book "Lessons from the Masters" edited by Robert Gendler (each chapter is written by a different "master" - basically the astrophotographer who is typically considered the best at that particular area of astrophotography (because there are many). The chapters cover the techniques not just to capture the data, but also how to process the data.

 

[jsecordphoto]

There's a few methods. Shainblum is using the a7s for a lot of his Astro work which performs very, very well at high ISO. I know for a lot of his panos he'll shoot at iso12,800 and the files with the a7s are still pretty clean at that ISO.

Some people will shoot during blue hour at a lower ISO, then combine that with a Milky Way frame taken a few hours later. That works really well if you take care to blend them cleanly, plus your foreground will be much cleaner shooting at a lower ISO. The thing about that is you pretty much get one composition, unless you're comfortable with compositing.

I tend to shoot my foreground frames at a lower ISO, somewhere between 1600-3200, sometimes up to 8 minutes long, then combine that with a sky frame that's typically about 20" long. The thing I always mention during my workshops is to make sure you make the scene look natural if you combine a very long foreground exposure with a sky frame. One of the biggest mistakes I see is people leaving their foreground WAY too bright compared to the sky, when objects along the horizon are 2-3 stops brighter than the sky...it looks obvious and terrible.

With your camera you'll pretty much need to shoot a longer foreground exposure (or blue hour shot) to combine with your sky exposure because a crop sensor camera, especially an older one, won't perform well at high ISO.

 

[0ptics]

Thank you all for you replies, extremely informative

Image stacking brings down the noise quite a bit - did you try that?
It works really well for the foreground, because you don´t need to align it - but you need to create a mask in photoshop for the foreground only. 5-8 images for stacking seems to be a good compromise. For stacking I don´t bracket the shots, they all have the same exposure.

Correct me if I'm wrong, bracketing is when you take multiple shots of different exposures and then combine it, for example one shot underexposed, one shot "perfectly" exposed, and one shot overexposed, correct? This is HDR, right?

1) So for stacking, I'm taking the same photo composition + same exposure settings, just multiple photos?
2) Do I take one right after another?
3) If more images gives you better noise reduction, I guess why wouldn't you take like 10 photos or more? Compared to say 5-8?

@TCampbell

Awesome in depth summaries of different methods !

1) You mentioned that I should capture a foreground with a decent exposure; I'm assuming I should capture the foreground right after sunset? AND combine it with multiple "stacked" star photos? So 1 well exposed foreground + 5-8 star photos?
2) How & where would I found a "sigma-clipping algorithm," this is all very new to me.

@jsecordphoto

1) Same question as above, but 1 foreground shot @ blue hour (1600-3200 ISO) + multiple "stacked" milky way shots >> combine the two in Photoshop?
2) Man 8 min exposure? I feel like during blue hour, an 8 min shot @ 1600-3200 ISO would be very overexposed! You'd recommend >8 min with the D7100 + 17-55mm f/2.8?
3) Should I do an aperture of f/8-11 or shoot wide open--for the foreground?
4) I'm assuming I shouldn't move my tripod from blue hour and until I've gotten several night star shots? (guess you did mention one composition )
5) Any tutorials on how to combine a blue hour foreground & night star photos? I see a lot of vids on how to stack, but not on combining foreground + background photos.

THANK YOU ALL

 

[sw_]

There's a few methods. Shainblum is using the a7s for a lot of his Astro work which performs very, very well at high ISO. I know for a lot of his panos he'll shoot at iso12,800 and the files with the a7s are still pretty clean at that ISO.

Some people will shoot during blue hour at a lower ISO, then combine that with a Milky Way frame taken a few hours later. That works really well if you take care to blend them cleanly, plus your foreground will be much cleaner shooting at a lower ISO. The thing about that is you pretty much get one composition, unless you're comfortable with compositing.

I tend to shoot my foreground frames at a lower ISO, somewhere between 1600-3200, sometimes up to 8 minutes long, then combine that with a sky frame that's typically about 20" long. The thing I always mention during my workshops is to make sure you make the scene look natural if you combine a very long foreground exposure with a sky frame. One of the biggest mistakes I see is people leaving their foreground WAY too bright compared to the sky, when objects along the horizon are 2-3 stops brighter than the sky...it looks obvious and terrible.

With your camera you'll pretty much need to shoot a longer foreground exposure (or blue hour shot) to combine with your sky exposure because a crop sensor camera, especially an older one, won't perform well at high ISO.

Can't add anymore than that. Great response and advice!

OP: Check lonelyspeck.com for some simple tutorials on blending and stacking.

 

[jsecordphoto]

If you choose to shoot during blue hour for your foreground your ISO will be much lower, and you'll be able to stop down to something like f8, which is why some people will use that method. Obviously your files will be much cleaner shooting at a lower ISO.

When I mentioned doing 5,6,8, etc minute long exposures, that's at night, right before or after taking a sky exposure. Personally I haven't done any blending with blue hour really. I also don't really stack sky exposures because photoshop tends to do a poor job with alignment of the stars.

 

[photo1x1.com]

Thank you all for you replies, extremely informative

Image stacking brings down the noise quite a bit - did you try that?
It works really well for the foreground, because you don´t need to align it - but you need to create a mask in photoshop for the foreground only. 5-8 images for stacking seems to be a good compromise. For stacking I don´t bracket the shots, they all have the same exposure.

Correct me if I'm wrong, bracketing is when you take multiple shots of different exposures and then combine it, for example one shot underexposed, one shot "perfectly" exposed, and one shot overexposed, correct? This is HDR, right?

1) So for stacking, I'm taking the same photo composition + same exposure settings, just multiple photos?
2) Do I take one right after another?
3) If more images gives you better noise reduction, I guess why wouldn't you take like 10 photos or more? Compared to say 5-8?

Correct!
in regard to your last question: the more images you take, the longer it takes to process the files, and to create the files of course. There is some kind of sweet spot that is around 5-8 it seems.
In fact if your goal is the best possible foreground quality, you could use an ultra long exposure for the foreground only, and then take the stack for the sky. But it does look kind of strange to have a foreground image with ISO 100, and a much noisier sky.