Hot answers tagged noise
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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Is it better to shoot with a higher ISO, or use lower ISO and raise the exposure in post-processing?
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 ...
19
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 ...
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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 ...
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 ...
13
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 ...
13
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 ...
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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 ...
12
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 ...
12
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 ...
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
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 ...
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. ...
8
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 ...
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
I can't see any obvious noise in the photo at this resolution. I can see some JPEG artifacts (sections where the subtle differences in shade look like blocks rather than a gradual transition). Some people get confused between "noise" and "artifacting", and refer to both as "noise".
Actual noise exists in almost all digital photos to some extent. Cameras ...
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 ...
7
HTP will increase noise as it underexposes the image in order to avoid possibly clipping the highlights. Noise reduction will obviously reduce noise, but at the expense of fine details.
All other in camera processing may reveal noise, but not create it. If you are concerned about noise then I would highly recommend shooting Raw and taking full control over ...
7
All other things being equal, bigger pixels give a better performance. In the real world though, all other things are extremely rarely equal.
However, given both are latest full-frame models, one would guess the 5D Mark III does better (which I just reviewed it here and you can see full-resolution samples at all ISO sensitivities) in terms of high ISO. Keep ...
7
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 ...
6
The sharpness seems reasonable for that lens at f/4. Noise can make an image look less sharp, but you could sharpen it a little in post.
As for the noise, it's most likely the result of underexposing the image. Underexposing an ISO100 will lead to more noise than using a higher ISO! If that weren't the case there'd be little point in having ISO settings.
...
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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 ...
6
the long exposure times needed will cause things to move during the exposure if there's only the slightest breeze or tremor (if you're shooting indoors on a wooden floor, you stepping away from the camera after setting the exposure timer can be enough).
That causes perceived unsharpness, but in reality it's motion blur.
Noise you'll always have with digital ...
6
Simple answer is YES!
Noise is an undesirable artifact, and many operations can enhance its appearance, not just sharpening. Tweaking curves, adjusting contrast, working exposure, etc. can all have some impact on the noise that is present in an image...although sharpening tends to have the greatest impact. It is important to handle the bulk of your noise ...
6
Noise is like death and taxes, it is unavoidable.
Even the most expensive cameras produce noise and, although, it may only be visible at 100%. The base ISO, usually between 100 and 200 is almost noise-free, but you will still see noise in images, particularly in shadow areas.
What strikes me as odd about your request is that 100% scale can give you very ...
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