Alley in Pisa, Italy

by Lars Kotthoff

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69

In photography, ISO generally refers to a measure of "Film Speed", which I use including reference to digital sensor sensitivity. In short, the actual letters ISO are a name for the International Organization for Standardization (not, officially, an acronym -- more information here), and in photography it refers to the ISO 12232:2006 standard and other ...


51

Is lower ISO always better? No! For a fixed amount of light coming into the camera, lowering the ISO will not result in a reduction of noise. The only way to reduce noise is to combine lowing the ISO with letting in more light by opening the aperture of leaving the shutter open longer. If the amount of light you can let in is limited (you have hit the ...


32

Nothing Special There is nothing particularly special about ISO 1600, although in some cases ISO settings beyond 1600 have incurred less effective and efficient ways of amplifying the image signal. When you set ISO on a camera, that is simply instructing the camera to change the maximum saturation point of the sensor, from which the signal will be ...


31

From my understanding, higher ISO gives a more grainy photo I'm afraid your understanding is incorrect. High ISO doesn't necessarily give a more grainy photo as there are other factors involved. In some circumstances it can be the case that lowering ISO increases noise. I did an experiment a while back to prove this: What you're seeing is exactly ...


28

Given the current state of the art, the noise in the blue channel is a combination of cascading effects that work together to make the blue "look" the worst. First, with the Bayer pattern setup, there are twice as many green pixels as red or blue ones in the matrix*. This immediately puts the blue and red at a spacial disadvantage as compared to the green ...


24

Regarding the statement: Is lower ISO always better? There seem to be a variety of opinions on this topic, and while they may seem mutually exclusive, I am not certain that is the case. There is no cut and dry "Yes, X ISO setting is always better." I think which is better is very dependent on context...on what it is you are trying to shoot, and what ...


23

Noise is often defined as any deviation from a "pure" signal. The signal is taken to be brightness pattern of the image so any variation in the pixel values that represent the image is noise. These variations arise principally due to: Shot noise. The random way photons are emitted from a lightsource causes random variations in image brightness. The fewer ...


23

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

Keep the camera as cool as possible! High temperature increases the thermal noise in your images. That's why certain astrophotographers actively cool their camera!


22

It is somehow true! For a moment, forget about the live view and consider the case of long exposure. While long exposing, the sensor heats up and this will cause the infamous background noise. So in reality sensor over heating can cause the noise and what happens is that in low light, warmed pixels detect light when there is none. (This last sentence is very ...


21

You can reduce noise without lowering ISO by slightly overexposing your picture, especially if you shoot RAW. From the Expose (to the) Right article at Luminous Landscape: A 12 bit image is capable of recording 4,096 (2^12) discrete tonal values. One would think that therefore each F/Stop of the 5 stop range would be able to record some 850 ...


16

What you are seeing is an image noise -- random fluctuations that affect sensor pixels and cause them to measure value a bit above or bit below light that actually comes to the sensor. The main factor that increases noise is how much is the signal from sensor aplified. There are two things that influence this: Size of sensor pixel: if you have 12 ...


16

Some of the following suggestions will depend on your camera (I have a Nikon so I'm not sure about Canons). Rather than press the shutter button directly, try using a remote shutter release or alternatively there may be a timer function which delays the shutter - this will allow (at least some) vibrations to settle down. Look in your camera manual to see ...


14

ISO is effectively a sensitivity of the sensor, whether it be film or digital. In theory, ISO for a digital camera should be the same as for a film camera. The ISO on film is determined by the grain size of the chemical. What this will mean is that the resolution will be better with a lower ISO film. Also, because a film grain is all or nothing, this will ...


14

A few options for reducing the noise other than lowering the iso or increasing the light: Keep the camera's sensor cool. Take a burst of photos, then average them. Lower the resolution.


13

Well, perhaps you should have gone out after all :) The noise is thermal noise, which will become noticeable as your sensor heats up during a long exposure. In astrophotography, it's quite a common problem. Some ways to reduce such noise: cool sensor down, e.g. by shooting in the cold weather. Note that cold also negatively affects battery life. set the ...


13

1600 is not a magical number, but with today's current technology many DSLR's commonly produce poor results above ISO 1600. On the other hand, you could argue that many still produce fine results at 3200 and 6400 - it depends on the audience and what technology they are familiar with. If you are reading this on a forum with many users of consumer level ...


13

Like many questions about what setting works best: It depends. The native ISO for almost all Canon DLSRs over the last few years has been ISO 100. 'Full stop' intervals, such as ISO 200, ISO 400, ISO 800, etc. increase the analog amplification of the signal readout of the sensor. The 1/3 stops in between those full stops use software adjustments during ...


12

Noise originates due to a number of factors, see: What types of noise can be present in digital photographs? Increasing the number of megapixels keeping everything else constant (sensor size, technology etc.) will increase noise per pixel, but also has the effect of making the noise finer grained which is less objectionable. ISO does not by itself ...


11

In addition to the sensor response discussed by Tall Jeff, most scene illumination (sunlight, incandescent) is deficient in blue light relative to green and red. Fire up this Java blackbody simulator and see that blue is lower than green or red for color temperatures of interest (~5500 K daylight, ~3000 K incandescent). There's another small factor that ...


10

You can measure the noise ratio at different ISO settings in a fairly simple way and use Gimp (Photoshop) to visualise the results. Below are the results with my camera, a Pentax K7. ISO 100 is used as the basis for comparison. The Noise Ratio is a dimensionless number showing the increased noise above that of ISO 100. If you photograph a perfectly ...


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

Assuming all other exposure settings with and without flash are equal, then using flash means you are adding light to the scene. Increased light in the scene means increased light down the lens, which means more light at the sensor. That means you have a higher signal to noise ratio at the sensor, which generally means less noise. Signal to Noise ratio, or ...


9

Because of the pixel density I would say. Your 50D had the highest pixel density in Canon's lineup when it was released, at 4.5MP/cm2. At that density the lens becomes the limiting factor, you need good glass. A few reviews pointed out that the image quality of the 50D wasn't much better than the 40D it was replacing actually, with a density of 3.1 MP/cm2. ...


9

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 ...


9

The difference between sharpness and clarity, is basically that clarity is a sharpness applied with a very large radius, a relatively low amount, and mostly to the midtones. This means that you have to use very much of clarity to get the same sharpening effect as sharpness, which also means that you add a lot of local contrast around details. When the ...


9

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 ...


8

Lightroom 3 is pretty good lately.


8

In general, the camera's manual will tell you the operating temperatures for the camera. Like all pieces of electronics, excessive heat isn't good for it. That said, I've only seen anecdotal evidence of heat adversely affecting image quality. It seems more common for batteries to stop working. As for noise, you're probably going to have this issue in broad ...


8

For instance, sensor noise should be rather consistent if the photos were taken with the same camera, pretty much like firing a handgun and the bullet gets unique marks. Bingo - that's right on the money. There are two aspects research aspects that I'm familiar with when I worked in this area in 2006-2007. The first was the identification of the make ...



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