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72

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 ...


55

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 ...


41

The ISO function on most digital cameras amplifies the analog signal prior to readout and digitization, which itself is a source of noise. If you just apply the correction digitally you amplify the read/quantisation noise as well as the signal. Increasing ISO in camera to account for lack of light actually reduces the overall noise seen the image. Here's ...


41

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, ...


36

There are two reasons why an ISO is not made part of the 'normal' range: It is considered a non-trivial drop in quality and you do not want users complaining about its performance. In other words, if the quality difference between ISO 12800 and 6400 is stronger than the one from 3200 to 6400. Note that there may be more changes than simply more noise, ...


36

Hardware ISO control exists to amplify the signal before readout to maximise the signal to noise ratio. Without read noise you wouldn't need ISO if you had a high precision ADC as you could simply shoot everything at the native sensitivity, and if the image was too dark just apply digital gain (multiply the pixel values). It's easy to demonstrate this ...


34

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 ...


33

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

I think Film vs Digital article by Roger N. Clark answers exactly this question. Let me quote the chart from its summary: The main point is that digital sensors have fixed resolutions and variable sensitivity, while films have fixed sensitivity and varied resolution. Overall, at high ISO (> 400) most of the modern sensors provide higher resolution, and to ...


27

In general, photos at lower ISOs will have less noise. This means that they compress better (remember that RAW files have lossless compression) and so, on average, you'll be able to fit more images onto the card. The other important thing to remember is that the number shown is only an estimate - how many images actually fit depends on what you take photos ...


27

The mountain and the valley obviously are static -- even more from that distance. The clouds, however, move. If you chose a low ISO value, e.g., in the range of 50 to 100, the exposure time might be enough to get washy/faded/blurred clouds. If I calculated it correctly, an ISO value of 100 with the other settings (exluding shutter speed) staying the same ...


26

Basically all "expanded" means is that this is not part of the standard recommended range. Often the expanded ISOs are implemented in software rather than hardware (which is bad) With ISO 50 you might be getting an overexposed ISO 80 (the native, unamplified ISO) so could end up with less dynamic range. This is done by metering for ISO 50 but actually ...


25

I think "several fluorescent fixtures that I use to light my studio" is the key here. I'm guessing that the very high ISOs are accompanied by very short shutter speeds. Fluorescent lights cycle, and there are color variations within the cycle. Repeat your test with incandescent light or sunlight (or a strobe with high-speed sync). See Do fluorescent ...


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 ...


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

1~2 and 3. On CCDs, the amplifier is effectively in the corner of the sensor, but on CMOS, there is an amplifier built into each photosite, dispersed throughout the sensor. See here. As mentioned in one thing I recently discovered, most DSLRs have an amplifier before the ADC (Analog-to-Digital Conversion). They tend to max at 800 or 1600 ISO and are all ...


22

I am also very skeptical about this article. If that was true, then opening the aperture past a certain point should not make any difference in the defocusing ability of the lens. I tried a small experiment: these are pictures of a couple of street lights close to my home. I set everything to manual and used the exact same settings for all the pictures: ...


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 ...


20

The size of the grains in the film varies depending on the film sensetivity. The more sensetive the film, the larger the grains. Digital noise is always the size of a pixel, regardless of the ISO setting. Film grain is color neutral, as it consist mostly of luminance differences. Digital noise consists of both luminance and color differences, and is most ...


20

ISO is very useful as it helps overcome read noise by amplifying a weak analogue signal prior to digitization (which adds a more or less constant amount of noise) thus giving a better signal to noise ratio. That's all raising the ISO does, amplify the signal. It does not make the picture noisier because it only amplifies what's already there. See this ...


20

Lets try this as a very different explanation: Imagine that you have been asked to record a piano recital at the local school. It will occur in the auditorium, and it will be full of parents and friends to hear the work of the pianists. You are not a studio technician, but are doing this as a favor to a friend. You bring your laptop, and you have an old ...


18

What does exposure compensation do? Although I agree with the technical aspects of the other answers, I still prefer to explain "exposure compensation" in lay terms as a way to impose a disagreement with the camera opinion about the shot. :o) Every time you point your camera to a scene, it tries to calculate how much light should hit the sensor in order to ...


18

Shooting manual mode doesn't make you a better photographer, understanding what all the settings effectively do will. Your camera has three basic settings: Aperture: Use this to control depth of field (DoF). This is usually the most important setting to most photographers, as it influences both subject matter and composition. You're not going to be taking ...


18

Camera sensors (see this article for an overview) consist of a very large number of individual sensor elements, each of which can be regarded as a bucket that collects photons. These buckets have a maximum number of photons they can capture before they become full, which is called being saturated (this is when the highlights clip). This maximum capacity is ...


16

Generally speaking, increasing ISO will not really improve the quality of your shots. Higher ISO means more noise in most cases, which can drown out details. The story is a little more complicated than that, however. To put it simply...if you can't get a shot at the lowest ISO, increase it. Getting a shot at all is certainly "higher quality" than missing a ...


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 ...


15

That would really depend on what kind of effect you are going for, and which format you shoot. Some can't stand the more apparent grain that comes with higher speed film, but I think it adds character. Then there is development and printing, etc. I personally find B&W ISO 400 film to suit my taste though, mostly T-Max or Tri-X with a side of Ilford HP5 ...


15

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 ...



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