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Image perturbation caused by electronic transformation and processing.

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88
votes
4answers
5k views

What is “ISO” on a digital camera?

What is "ISO" in general, and how is the scale defined? How does the ISO scale for film speed differ from ISO sensitivity as used in digital cameras? Is lower ISO always better?
22
votes
2answers
1k views

What is noise in a digital photograph?

What kinds of effects are present in digital images that are referred to as "noise"? What are the different sources of noise? What causes each type of noise? What are the characteristics of the ...
27
votes
3answers
3k views

Why is the blue channel the noisiest?

It is widely observed that the blue channel in digital cameras is the noisiest. I've certainly noticed that with my camera. Why is this? Is it an artifact of some particular technology (e.g. Bayer ...
21
votes
8answers
2k views

How can I reduce the noise present when taking pictures without lowering my ISO?

I know that high ISOs tend to produce more noise, and some cameras' software can handle that noise better than others, but are there any other settings or conditions tha affect visible noise? I'm ...
4
votes
1answer
619 views

what's the relation between sensor size and image quality (noise, dynamic range)?

I'm reading this description on sensor size: Digital compact cameras have substantially smaller sensors offering a similar number of pixels. As a consequence, the pixels are much smaller, ...
7
votes
2answers
923 views

How to test noise?

I'm just looking for what's the best technique to test for noise on a camera. Like what settings are best? What type of photo is best? What lenses should I test with? Like those sorts of things. ...
18
votes
9answers
14k views

Is it better to shoot with a higher ISO, or use lower ISO and raise the exposure in post-processing?

Suppose there are two photos taken in the following scenario: Scenario 1 - Photo taken using ISO of 3200. Scenario 2 - Photo taken using ISO of 100. Both photos are taken in a medium light ...
11
votes
12answers
788 views

What noise removal tools work best, and why?

Can anyone recommend some good noise removal tools, free and commercial? Should support RAW and JPEG. Are certain tools better than others in particular situations? Do some integrate better with other ...
11
votes
3answers
1k views

Does the order of sharpening and noise reduction matter?

I have been shooting for more than three years, but I never do too much in post-processing. I tend to be strict and keep in mind that PP can only do little to save an otherwise-great photo. I was ...
7
votes
4answers
1k views

Does noise in images depend upon “Megapixels” or “ISO”?

I have a question about image quality. Does noise in an image is depends upon "Megapixels" or on "ISO"?
13
votes
1answer
622 views

Is it really better to shoot at full-stop ISOs?

The second half of this answer says 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 ...
9
votes
4answers
3k views

Astrophotography picture with too much noise. How do I correct this in postprocessing?

This is the Milky Way above Kakadu National Park, Australia, and my first try at astrophotography. Thirty second exposure, f/4.0 at 17mm with ISO 12800 (!!) which in hindsight probably was way too ...
16
votes
5answers
1k views

Might future advances in sensor technology reduce or eliminate noise?

Is there a possibility that future tech advances may reduce or eliminate the noise when using high ISO setting, or is this noise unavoidable and inherent to all digital sensors? If there is a ...
8
votes
2answers
883 views

Why are sensors less sensitive to blue light?

This is a followup question to Why is the blue channel the noisiest?. The simple answer to that question is that sensors are less sensitive to blue, and therefore require more amplification, which ...
4
votes
5answers
392 views

Is this amount of noise expected, or am I doing it wrong?

The picture below is a crop (at 1:1 scale) of a photo I just took. It was taken with a Canon 7D and the 24-105mm F4 lens (RAW, F4, ISO 2500, 1/160s). It looks properly exposed to me, so where is all ...
4
votes
4answers
491 views

What algorithms or example tools are there for denoising of images in Raw format?

I am trying to perform some post-processing of Camera Raw images captrued using my Canon EOS 450-D. I am using PS CS5 and GIMP particulary to remove noise which is present in images. My questions is: ...
7
votes
3answers
657 views

Is Poisson Noise (“Shot Noise”) a significant source of noise for typical photography?

In this answer, @jrista states that even a camera with a perfect, noiseless sensor would still have noise due to "Poisson noise" aka "Photon Shot Noise" - noise caused by the random variations of ...
6
votes
4answers
1k views

How can I tell if two pictures were taken with the same camera without metadata?

Is it possible to identify images (without exif data) and link them to the exact same camera? If so, I'd like some software recommendations to get the job done. I have two photos that I'd like to ...
5
votes
1answer
324 views

How can a newer camera increase ISO while decreasing pixel size?

I am a bit confused as I am considering to upgrade my canon 350D to 600D. The pixel size has reduced from 6.4 microns to 4.3 microns, however, top ISO has increased from 1600 to 6400. How did that ...
5
votes
1answer
274 views

When is high ISO noise not noticeable?

I noticed that sometimes when taking pictures with my D5100, they come out with very little visible noise with ISO 800 and up, for example this picture. It was taken at ISO 1600 if I remember ...
4
votes
2answers
317 views

Is there software for detecting noisy areas in a photograph?

I have been told that this photograph contains noise and is muddy. It is difficult for me to identify noise in a photograph until it is in extremes. Are there any softwares available which detect the ...
3
votes
3answers
342 views

Why is there too much noise in a fog photograph?

I have been told that this photo has terrible noise. I wasn't aware of this fact! :redface: Morning scene, F4.8, Shutter: 1/50, ISO 100, Focal 14.4mm. The fog was dense of course, but still it ...