55

It would be wrong to think that increasing ISO results in no "physical" change in the camera at all. The problem with ISO is that people often call it sensitivity. That is really a misnomer...sensitivity is a fixed attribute of any given sensor, and it cannot be changed. Sensitivity is really more synonymous with the quantum efficiency of the photodiodes, ...


30

So I first shoot with ISO 1600 and shutter speed set to 1/125 second and then I shoot with ISO 3200 and shutter speed set to 1/250 second. The amount of light should be identical and indeed both shots look properly exposed and exposed the same way. The amount of light is not identical. You let twice as much light into the camera at 1/125 second than at 1/...


26

Noise is a fact of life when it comes to astrophotography, with the exception being stacked deep sky photos taken on a tracking mount (more in a moment). Your photo is actually very low noise, in the grand scheme of wide field, single-frame astrophotography shots that I have seen...but it also lacks saturation. I think it really comes down to a matter of ...


26

It's very important to realize that it is not the high ISO setting itself that results in noisy image, it's that fact that using a high ISO setting means you capture very little light. Light is made up of photons which are randomly emitted by a lightsource. When the light levels are low or the exposure time very short then the number of photons you get will ...


22

Cost. Every price raise results in fewer sales. Size. Cooling has to fit somewhere, those handgrips are already full of batteries... Weight. There's a reason P&S are popular and not lugging around a brick is one of them =) Battery Life. Cooling costs energy, lost energy means fewer shots in each battery pack. Minor Improvement: only shots pushing ...


22

A few things you can do to improve your results. Use ISO 5000 or 6400. The way Canon DSLRs handle the ISO settings between the full-stop settings (100, 200, 400, 800, etc.) means ISO 5000 is cleaner than ISO 4000 and even ISO 2000 on most Canon cameras. The +1/3 stop settings (ISO 125, 250, 500, 1000, 2000, 4000, etc.) should be avoided if noise is a ...


14

I think you might be confusing a few issues here. The terms "Base ISO" or "native ISO" are often used to refer to the unamplified sensitivity of the camera. In addition to this digital camera sensors have built in amplifiers to amplify a weak signal (such as you get in low light) before it is digitised in order to reduce read noise and increase signal to ...


14

The base ISO of all Canon cameras is ISO 100. This is the ISO with the lowest gain, without any in-camera magickry to achieve the setting (like ISO 50, which mucks with the actual exposure settings behind the scenes). There is a lot of conjecture and misunderstanding about Canon's ISO settings because they use a "real/push/pull" model for ISO settings, ...


11

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 ...


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

The last two are really the same thing and works due to the fact that in most cases noise is just as likely to push the value of a pixel up as it is to pull the value down. Let's say the 'true' value of a given pixel is 100 (out of 255). Take 10 images of the same scene in noisy conditions and you might record the following values: 104, 99, 98, 100, 101, ...


10

Image noise in a properly operating DSLR will be affected by shutter speed, but not in the linear relationship the question implies. In decreasing order of impact, image noise is a factor of: - Amplification applied to the sensor cells (higher ISO increases noise) - Thermal noise (hotter sensor is noisier) - Duration of exposure (longer the capture, more ...


10

Technically speaking, increasing ISO does not actually "increase noise". When you increase the ISO setting, you are actually just instructing the camera to change what level of charge represents "maximum saturation" (the point at which a pixel should reach its maximum numeric value, which in the case of a 14-bit sensor is 16384.) The primary cause of noise ...


10

Reduce it, yes. For example, the Canon 5D Mark III is 2/3 stops better than the Canon 5D in high ISO performance, although their sensors are the same size, because it is seven years newer. Of course, past performance is not necessarily indicative of future results, but I see no reason for incremental gains not to continue to be made. Eliminating it ...


9

For some sort of photography high ISO is very important. At some point the picture quality does not matter as much as having at least taken a photo, even if it is very noisy. News journalists or street photographers, who want to capture the moment do not have the time to light up the scene. Therefore they accept the noise to get the shot. High ISO is also ...


8

It boils down to power, and lack of market demand. There are specialty cooled-sensor cameras out there. They're generally just used for astrophotography. The cooler that is used in almost all cooled cameras is what is called a thermoelectric cooler, commonly colloquially called a "Peltier" or "Seebeck cooler". Generally, you will need a fairly chunky ...


8

When you change the ISO value to a higher, you really change the amplification in the chip. Let's look at one single pixel first. During exposure the pixel receives a number of photons, which generate (let's say) 100 mV, and the chip's noise gives 10 mV. You have a signal-to-noise ratio of 10:1. Now, you need to expose half the time, and therefore you ...


8

I'm not even going to try to supplant jrista's very informative and well written answer. He covers the bases of the physics in the camera's imaging pipeline very well. I would like to add an observation that may shed some light on the relationship between stars and noise. If all the stars in the universe were equally bright as viewed from the surface of the ...


8

I believe it may be a flaw in your testing. Raising ISO should not be getting you a higher signal to noise ratio (or usable dynamic range). You are raising the noise floor, without any corresponding increase in dynamic range at the bright end. Thus you should be left with overall lower dynamic range. It would not be possible to go the other way. Is it ...


7

This question is probably best answered in two parts. Part1: You may need to increase the ISO to combat noise. This sounds counter intuitive due to common misconceptions regarding noise. Noise is principally caused by lack of light. Lightsources emit photons randomly, the more photons you collect, the more the randomness averages out, leaving a smooth ...


7

The bigger the pixels, the less noise there is. This is a matter of physics. More light gets accumulated in each pixel and so it take more noise to appear significant. The 600D and 7D have APS-C sensors which are small and have a high megapixels count. This makes their pixels comparatively smaller than the 5D Mark II which has a larger sensor and hence ...


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 already happened! On film, or early digital, high ISO meant 400, on latest full frame cameras it means 6400. Problem is that each time it happens, 'High ISO' gets redefined to be even higher, or in another words, high ISO always means "so high that current tech makes it noisy". As noted by Tony, there are eventually, physical limitations as to how far it ...


7

ISOs lower than 100 on the A7 are not "real" in the sense that they don't lower the gain on the sensor, they just instruct the camera to increase exposure time as if the sensitivity was lower. The net result of this is reduced highlight headroom. If you shoot RAW there is nothing really to be gained from any ISO setting less than 100.


6

As with many such things, which is best has some level of opinion and which looks best to an individual. I think Noise Ninja products consistently produce some of the best results. Prior to Lightroom I used it within Bibble, and found it to be simply mouth dropping good. However, I have found Lightroom 3 to have nearly as good results, bringing it, to me, ...


6

Noise is the difference between what the sensor measures and what it should have measured. If you take a photo with the lens cap on (or with some other means of completely blocking any light from entering the lens), you'd expect to get a frame where every pixel is entirely black. In reality, you'll get an image where the pixels vary slightly from one to the ...


6

Beyond the sensationalist title, I think what you are asking is simply - Are my results typical? To which I'd answer, yes your results are typical and expected. I don't often try to shoot in the woods, in November, right before sunset, handheld, but if I did - I would be well aware that I am pushing the capabilities of my equipment no matter if I have a f/...


6

Yes Here comes the definition of Circuitry, from whatdigitalcamera.com CCD and CMOS sensors differ in terms of their construction. CCDs collect the charge at each photosite, and transfer it from the sensor through a light-shielded vertical array of pixels before it is converted to a signal and amplified. CMOS sensors convert charge to voltage and ...


5

Temperature In silicon there is an effect called thermal noise (Johnson noise). This is basically electrons been torn loose from the substrate and adding to the electrons being knocked loose by photons. These electrons are then considered part of the "signal" from the sensor, creating noise. This kind of noise is Gaussian distributed and have a mean value ...


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