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 ...


21

While there may be truth to the principle that noise adds the illusion of detail, in this example I think you are misinterpreting what you are looking at. If I remove all the noise in its lower part, it will not look natural (from my point of view) This is mostly because no noise-reduction algorithm can perfectly remove all noise and retain all detail. ...


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 ...


12

Firstly had you lowered the ISO whilst staying at 30s f/4 you wouldn't have ended up with any less noise. There's probably nothing you could have done to prevent the noise, I presume f/4.0 was the maximum aperture and if you went any longer than 30 seconds you would get star trails. You might even get less noise if you raise the ISO but that's another story. ...


12

The key difference between the two is that one works on a post-digitized image, where as the other works on the pre-digitized analog signal. Whenever you work with an analog signal, you have the ability to be more precise and accurate, and can eliminate noise before it is "burned into" a digitized image. Thats most certainly not to say that applying noise ...


12

You can only preview noise reduction in RT when you zoom image to 100%, even in latest version. Many other tools have same limitations for previewing, they are marked with small "1:1" label near their names.


11

When I have extremely noisy images, I do two things: Use a 3rd party noise reduction plugin - in my case I use Topaz DeNoise - it, and others, have free trials - so you could give them a try if you want to experiment. These denoise plugins have sliders that will reduce noise, which softens the image, but you also have control over detail (you can decrease ...


11

The technique used by Cortex Camera is called Median Blending. Astrophotographers have been using this concept for years to combine multiple photos of dim objects in the night sky to reduce the noise and increase contrast and color. It is often referred to as image stacking in which hundreds of images of the same piece of sky are overlaid and the values for ...


11

The long exposure Noise Reduction takes a "dark frame" after the real shot, and then uses the noise pattern from that image to reduce the noise generated by the sensor. That's why the exposure takes twice as long as this NR were disabled. Long time exposure can increase the sensor temperature, and increased temperature also means more noise. So you should ...


10

No Canon dSLR has built in image stabilization. Canon offers it in select lenses, known as 'IS' lenses. So, no, neither offer image stabilization. All Canon cameras also offer noise reduction, and of course, it can be applied (or not in the case of RAW) on the computer after the fact as well. Does it matter? Noise reduction matters, because all cameras ...


9

There has been an improvement between the 40D and 650D, but not that great. Certainly less than a stop. You'll get a far far greater improvement in image quality by getting more light onto the sensor. There are a number of ways to achieve this: Depending on what lens you're currently using you may be able to get a three stop improvement by switching to a ...


8

Noise is random, it causes gray values to fluctuate from one pixel to the next. This is then random information present at the smallest scale in the picture. If you remove it, then it gives the illusion of the image having become less sharp, as the gray values are not changing as fast on the smallest scale anymore. This doesn't mean that removing the noise ...


7

Active D-Lighting Active D-Lighting isn't necessary at all. It works by doing two things: slightly underexposing (by 1/3 to 2/3 stop) and applying some adjustments to raise the shadows back up It isn't needed if you shoot RAW as you can underexpose and raise the shadows in post It is only relevant if you are shooting high dynamic range scenes with bright ...


7

The thing that creates noise is not enough light. You can think of your image has having a constant amount of noise (this is a big inaccurate over simplification, but it helps understand the issue), when you are photographing something nice and bright the sensor captures a lot of data and it completely overpowers the noise. On the other hand if you are ...


7

It is poorly written. Indicated Green Background refers to the list below where lenses models with stabilization are highlighted with a green background like the AF-S 16-35mm in the wide-angle section:


6

First, I must say that for a start, this is a great photo. Noise is a problem but your photo still looks great. Now I suggest you have a look to the software DeepSkyStacker, its website and documentation. They have a great page that explains the theory behind the software. Basically, you combine multiple similar shots to reduce the noise. You can also ...


6

Whenever you see a truly breathtaking image, you can be sure that it's the culmination of doing a whole lot of things really, really well. In the examples you indicated, we're looking at images scaled to a size much smaller than the files produced by your camera, which suggests that at least some of the impact you're perceiving in the photos you're trying ...


6

This is normal considering the high ISO you are using on that camera. If you look at samples for each ISO with the Canon 7D, yours show more noise than the ISO 1600, similar to the ISO 3200 crop. Notice that I only shot full-stop ISO which is important with Canon DSLRs because the gain to obtain the 1/3 stops in between is applied in software by the ...


6

This is not only possible, but is in fact the way that some noise cancellation modes already work. Long exposure noise reduction (or LENR) will automatically take a dark frame of the same exposure length after a long exposure image capture. It then uses this dark frame for noise cancellation. More detail on LENR is covered in this question.


5

High ISO performance has greatly improved over the last few years but if you scrape the bottom of the barrel you wont see much improvement! While test results for the T4i are not out yet, if you compare the T3i to the 40D at DXO lab, their scores is almost identical (54 vs 64) and looking at the low-light scores in particular, you will see 793 vs 703, ...


5

There is a way to do this in Photoshop (I'm using CS5 Extended) Shoot multiple exposures. In Photoshop, go to File > Scripts > Load Files into Stack. Click Browse and select the exposures to be used in the Stack and check Attempt to Automatically Align Source Images and Create Smart Object after Loading Layers. This will create a single Smart Object from ...


5

Except for dark frame subtraction, which helps get rid of (non-random) pattern noise,no noise reduction is done at the pre-demosaiced level. There are simply too many variables that come between the raw sensel data and a rendered image. However, there are a couple of demosaicing algorithms (LMMSE and IGV) that are optimized to deal with noisy data, and many ...


5

darktable has a "raw denoise" module that does noise reduction before the demosaic step. In practice, it is rarely better than the other modules that work on the demosaiced image. Most noise reduction options in raw development software work between the demosaic step and the sharpening.


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

Generally, the best performance is on your camera's native ISO. This is usually ISO 100, but not always - some Fuji cameras use ISO 200 (go figure..). Check your manual. For decently lit subjects (gizmos on a table, not the Milky Way) and exposures in low single digit seconds sensor heat should not be an issue. I would worry more about camera shake - even ...


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


4

Adding some info to Akram's answer. You could use try some of the filters from G'mic (a "plugin pack" for the Gimp which has a lot more filters than just noise removal ones). Here's its website and download page. For a tutorial: Noise reduction with G'Mic . An excerpt: Anisotropic Smoothing is the best solution for pure noise reduction, it can be found ...


4

One thing you can do is to convert to black and white and use the noise for effect. I believe that sensors (and I confess I forget why) have twice as many green sensors as as red or blue, when converting to B*W only use the green channel and you when you reduce the noise using your favourites editing software (I use light-room and it is very effective) ...


4

Photos taken with digital cameras will, for the most part, show some amount of noise when inspecting them at 100%. The tripod and lenses won't affect the noise because the noise comes from the sensor, something that remains constant regardless of which lens or tripod you shoot with. Generally, you can lower the apparent noise by reducing the ISO but proper ...


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