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. ...


14

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.


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

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 ...


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 ...


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.


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 ...


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

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 ...


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

Noise reduction is very computationally expensive process. When you zoomed in it only processes a small part of the image, but when you zoomed out the algorithm would have to process the whole file and then re-scale it, which takes a great deal of time even on modern hardware.


4

If you open the image with any editor, you can see in the histogram (below) that it only uses (in a significant proportion) 12 of the 255 available brightness levels. This means that it only has 12 shades to represent the image that it captured. Switching to the logarithmic histogram, you can see that actually there is more, but the most significant part, ...


4

JPEG doesn't retain 100% of the data. What you're calling "noise" in the jpeg might be what's usually called compression artifacts, or jpeg artifacts. If they're showing up when you save as a jpeg made with the maximum quality setting, the only fix is to save in a lossless format (tiff and png are popular). I save everything in a lossless format, usually ...


4

Theoretically the mean of 10 one-second exposures should give the same amount of noise as one ten-second exposure. The results in practice differ mainly on account of thermal noise. The longer the sensor is active during an exposure the warmer it gets which results in an increase in dark current noise. Multiple short exposures allow the sensor to cool in ...


4

You are correct that there is no free lunch. Software NR works by looking for sharp edges and trying to identify what is detail and what is noise, but at a very fine level, they can't be distinguished. What you will normally see with light NR is a reduction in fine detail, but gross detail is maintained. The more you turn up NR, the more gross the detail ...


4

You can also use an median blending (create image stack and apply the "Median" stack mode) File > Scripts > Load Files into Stack Select all layers and use Edit > Auto Align to align them (if necessary) Layer > Smart Objects > Convert to Smart Object Layer > Smart Objects > Stack Mode and choose Median Discussion of this and other methods here: Does ...


4

Demosaicing and noise reduction should be done simultaneously. It's best to use the DCRaw program to extract the raw pixel data and then to tackle the problem of reconstructing the image from first principles instead of using the standard algorithms which won't yield the best possible reconstruction of the image. In such a first principle treatment, you ...


4

Many previews in image editing applications are just that - previews. To get an exact view of what many effects and settings applied to an image will look like you should export the image with the changes applied. Since this can be rather tedious and cumbersome, previews allow us to see an approximation. Many noise reduction tools, including RawTherapee, ...


4

It sounds like you want to use an alternate noise reduction algorithm integrated into Lightroom's RAW conversion, as an alternate for or addition to the built-in noise reduction. I don't think there are any plugins that work that way. Everything I can find uses Lightroom's external editing functionality — which sends a processed TIFF or JPEG to the other ...


4

There's an old saying about photography: Gear doesn't matter. While true, it is only part of the fuller truth: Gear doesn't matter... until it does. What that means is that better gear won't make anyone a better photographer. If the photographer is not applying the proper technique, skill, and knowledge when using lesser gear then better gear will not ...


4

Even the same exact camera will not demonstrate the same "exact" noise characteristics on successive shots. But techniques such as "dark frame subtraction" or other noise reduction processes that measure unexposed areas of the sensor and other characteristics of the noise generated by the camera's circuitry will be "close enough for government work." Image ...


4

In my limited experience (back when Astrostack was the hot item, and using video captured at 640x480 with a webcam -- call it 1998 or so), stacking more frames will decrease the appearance of noise by averaging it away, but won't increase detail beyond about double the actual pixel resolution of the image (you only get that much because the image wanders a ...


Only top voted, non community-wiki answers of a minimum length are eligible