40

Stars don't show up voluntarily on a photo. You need to tweak them a bit using photo editing tools on a computer. Best if you use RAW file format, and RAW-processing software to do this. JPEGs can be tweaked to show more stars, but with a lot less working room and result being of lesser quality. The likely JPEG image you get with the exposure settings you ...


32

To achieve what you're thinking of you would have to know what the noise was. If you knew what the noise was then you could just remove that to get clean images.


22

Can I get the same result by coping a raw ( same exposure ) file many times and stacking to reduce noise as I would if I used many separate exposures? No. If you stack copies of the same image, you'll amplify the noise right along with the signal. Stacking images to reduce noise is an averaging process. It's like a science experiment: you don't measure ...


20

I'd like preface my answer with a note that a tripod is not only useful in conjunction with ND filters — it also improves the results from image stacking as well. By fixing the position of the camera, the tripod eliminates changes in perspective, which can occur through minor motion while hand-held shooting a sequence for image stacking. Aside from fixing ...


19

Image stacking works to reduce noise because the noise is random — or at least, ideally so — while the stars are (famously) constant. That means that (once you've corrected for rotation) the stars will be in every photo. But noise — at least, the kinds of noise that this can correct for — is already random fluctuations... maybe there in one image, and not ...


14

Everyone talks about shortest focal length and lower aperture when shooting Milky Way, and this guy does it with f5 How is that possible? It is possible to shoot at f/5 because he is also shooting at ISO12800. A single image at that ISO would be extremely noisy, but stacking 100 images at that ISO allows the random noise from each image to be averaged out. ...


13

You cannot. Removing noise via photo stacking works on the principle that the noise in your images is random, and appears in different places of the image between exposures. When you stack multiple exposures on top of each other, a common method to remove this random noise is called median blending. During this process, software will evaluate the same pixel ...


13

Well, with regards to your (1)... You could carry a light tripod (or beanbag or any other way of stabilizing a camera) and use only a single ND filter instead of several stacked filters. With regard to (2), yes you could do that, but stacking a sequence of discrete single images will give you a result that contains several discrete non- or less-blurred ...


10

Simple answer to your main question is: The Dynamic-range of the sensors of current digital camera is not yet a match for the dynamic range of human eye's sensor (aka retina). Detailed answer of "how to bring it up" will bring all the techniques on the table. The majors are: Widest possible aperture on lens, if possible f/1.8 or f/1.4 Widest angle: To ...


9

Here is the process I use: cd ~/directory_with_raw_files ufraw-batch --out-type=tif --out-depth=8 --wb=camera --exposure=0.33 --black-point=auto *.NEF Of course, you will process CR2 files instead of NEF. I usually open just the first raw file to find acceptable parameters for ufraw-batch, such as exposure. Then install the stacking package: sudo apt-...


8

There are possibly several options available. From a cursory search, native Mac applications include: Nebulosity Keith's Image Stacker PixInsight (cross-platform) Starry Landscape Stacker If none of the Mac native applications do what you want, you're probably going to have to consider somehow running Windows programs. Your question rules out running ...


8

What you're asking about is generally called star-eating. From an algorithm point of view, in an astrophotograph, how can software determine what is signal (that is, stars) vs. what is noise? A simple method would be to just call anything below a certain intensity level as noise, and cut it all off below that level. In essence, that's the same as throwing ...


7

I didn't have enough "reputation" to address some of these answers as comments. AJ Henderson is wrong, 30 1s exposures will (for the most part) be identical to 1 30s exposure. If it shows up in a 30s exposure, then stacking 30 1s exposures will also show it. I am actually the author of the article that Trengot linked (thanks!). In fact, unless you are ...


7

Imagemagick cannot be used to compose 30 images in one step. The documentation states: Image Composition is the process of merging two (and only two) images in a variety of ways. The following simple bash script creates a black 100x100 image (temp.png) and compose all the test_*.jpg images (assuming all of them are 100x100) one by one to this image. ...


6

There is no substitute for per-image SNR (Signal to Noise Ratio). A half-second exposure following the 600 rule won't be enough. You have to factor in read noise as well as photon shot noise. Photon shot noise can be delt with via stacking, but read noise...read noise diminishes detail and in the deeper shadows, can eliminate it entirely. With half-second ...


6

This is not a definitive answer to my own question, but it's too long for a comment. I implemented the idea of using the RMS Laplacian. The idea is that if the brightness of the image is represented by an array of pixels a[i,j], then at any point (i,j), we have the discrete approximation to the Laplacian L=a[i-1,j]+a[i+1,j]+a[i,j-1]+a[i,j+1]-4a[i,j]. This ...


6

For me the main advantage is... Joy. I enjoy a lot more taking photos, people places, products, rather than editing the images, especially on automated tasks, like stacking photos. Of course, there are some parts enjoyable, like tweaking the final result. But, overall, I prefer not having a ton of shots to review. Taking a long exposure image on site gives ...


5

Even I had experienced similar problems while shooting night sky photos and later stacking them together although not as apparent of a moire pattern as you have. after a bit of troubleshooting, I found out that by disabling Lens Correction before stacking the photos and applying it after stacking eliminates the problem. A side note would be that I used ...


5

I'm guessing this has to do with two overlays that were very slightly misaligned from each other such that the small variations in each image due to the Bayer matrix become apparent. If so, this is a rare case where working in raw is actually hurting. Put another way, the raw data has some regular high frequency content due to the Bayer matrix. Normally ...


5

You are achieving somewhat long shutter speeds of 2 seconds. But the problem is the result of this is that the moving objects are not captured for long enough in the same position to get the desired effect. What might work best is to stack images. You could capture shorter frames of the cars moving, maybe 1/15th of a second for example, multiple times, then ...


5

In Nikon DLSRs, including the D7000, there is image-processing software that removes noise and hot pixels, and this software has come to be known as "the star eater" because it interprets isolated bright pixels as noise and removes them or averages them into the background. Isolated bright pixels, of course, are kind of what you want to see when you're ...


5

When you set the opacity of a layer 50%, what you get is 50% of that layer, and 50% of all the layers underneath it combined. For this reason you should set the bottom layer to 100%, then layer above that to 50%. Now you have a perfect balance of the two layers. The layer above that should be set to 33%, meaning your image is one-third that layer and two ...


5

Fundamentally you're capturing the same amount of light in either case so the results should be the same. Practically, there are 2 differences between stacking 30 one second exposures and shooting one 30 second exposure. The first is the light lost between each one second exposure after the shutter closes before it reopens for the next exposure. This can ...


5

Long Exposure Noise Reduction takes a dark frame of the same duration to subtract the noise from the image. That's why there is a long delay; a 30-second exposure plus a 30-second dark frame plus processing time plus the time to write the image to the memory card. There will be obvious gaps in the star trails. If the gaps are minor, they can be corrected in ...


5

Based on the color swapping in the result, I would guess the blue values are being summed into the red result and vice versa. I've made sillier mistakes...


5

Yes, I have done it in CS5 and CS6 with the following: File > Scripts > Load Files into Stack Select all layers and use Edit > Auto Align to align them Layer > Smart Objects > Convert to Smart Object Layer > Smart Objects > Stack Mode and choose Median


5

It doesn't really work that way. But even if it did, it would depend on the way you stack the images. Do you add them together? Do you average them? Use some other even more complex method? Stacking multiple images only reduces the influence of photon noise, often called shot noise. Shot noise is caused by the random nature of light. Simplistically put, ...


5

As others have pointed out, what you describe is not possible. If you could randomize the noise, it would mean that you can already detect what is noise and what is not. Then you could just as easily remove the noise and keep just the signal. But you do not know what the noise is and what is actually signal, that's why people stack photos - that actually &...


5

Stacking more images reduces noise to signal ratio, but don't add resolution or details. In order to enhance resolution, my advice is to use a prime lense, instead of a zoom one. Even if it has less focal length. In my personal experience, I get more details with a 80mm prime than with a 55-250mm at 200mm


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