Nikon D200 noise

Nikonzoom · August 3, 2009

Hi;
I own a Nikon D200 and love the camera very much.
I have only recently begun to experiment with night photography, and did some tests to find what kind of noise I can expect.

I took some shots with the lens cap on. Used RAW format.
Adobe Photoshop 7 to import files, and did not alter anything.

At ISO 400, a shot of about 30 seconds showed several (maybe 4 or 5) dots of red, blue, or white that were about 4x3 pixels, with brightness reducing towards the edges.

At ISO 400 at 5 seconds, I only saw one or two red or white dots (same size).

At ISO 100, I saw absolutely nothing in a 30 second shot.

Is this all normal?

I would expect that noise would increase as ISO is increased, and with time.
So it seems that I should always be doing any night shots at ISO 100.

Thanks for your advice

FW

Qarik · August 3, 2009

Nikonzoom wrote:

Hi;
I own a Nikon D200 and love the camera very much.
I have only recently begun to experiment with night photography, and did some tests to find what kind of noise I can expect.

I took some shots with the lens cap on. Used RAW format.
Adobe Photoshop 7 to import files, and did not alter anything.

At ISO 400, a shot of about 30 seconds showed several (maybe 4 or 5) dots of red, blue, or white that were about 4x3 pixels, with brightness reducing towards the edges.

At ISO 400 at 5 seconds, I only saw one or two red or white dots (same size).

At ISO 100, I saw absolutely nothing in a 30 second shot.

Is this all normal?

I would expect that noise would increase as ISO is increased, and with time.
So it seems that I should always be doing any night shots at ISO 100.

Thanks for your advice

FW

That is a unreasonable way to judge noise behavior in a camera as well as an unreasonable way of thinking about night time photography. You should simply go out and shoot a bunch at different iso's and see what works best for you.

Nikonzoom · August 3, 2009

Qarik wrote:

That is a unreasonable way to judge noise behavior in a camera as well as an unreasonable way of thinking about night time photography. You should simply go out and shoot a bunch at different iso's and see what works best for you.

Right. Thanks

FW

Qarik · August 3, 2009

Nikonzoom wrote:

Right. Thanks

FW

You state" I would expect that noise would increase as ISO is increased, and with time" you are correct. The pixels you see at iso 400 are probably random alpha particles/waves hitting your sensor whcih don't show up at iso 100 due to decreased activation threshold.

From that you conclude that shooting at iso 100 is the way to go for night time shots? Absolutely not.

You need to shoot at what ever iso will get you the shot. It maybe iso 100
if you have tripod and the subject is stationary. It maybe iso 800 if you are handholding and the subject is not static. Then throw into the mix what your aceptable noise threshold is for the shot. That's an aethestic judgment.

ziggy53 · August 3, 2009

Qarik wrote:

... The pixels you see at iso 400 are probably random alpha particles/waves hitting your sensor whcih don't show up at iso 100 due to decreased activation threshold. ...

Nothing radioactive causes that sort of imager noise. It is simply the combination of amplifiers employed to boost the sensitivity of the sensor, just like audio noise with a low signal when it is boosted.

It takes specialized sensors to be sensitive to ionizing radiation like alpha particles, beta particles or gamma/x-rays. (Alpha radiation is actually somewhat difficult to detect just because it takes so little to stop it.)

Nikonzoom · August 4, 2009

ziggy53 wrote:

Nothing radioactive causes that sort of imager noise. It is simply the combination of amplifiers employed to boost the sensitivity of the sensor, just like audio noise with a low signal when it is boosted.

It takes specialized sensors to be sensitive to ionizing radiation like alpha particles, beta particles or gamma/x-rays. (Alpha radiation is actually somewhat difficult to detect just because it takes so little to stop it.)

Maybe he was referring to photons.
It seemed to me that the dots I saw were in about the same place on the image each time, so I thought perhaps "bad pixels" on the CCD. But in PS, I can see that they are not just one pixel.
Whatever the cause, I was just curious about it. It is certainly not going to bother any night photography I do.

FW

ziggy53 · August 4, 2009

Nikonzoom wrote:

Maybe he was referring to photons.
It seemed to me that the dots I saw were in about the same place on the image each time, so I thought perhaps "bad pixels" on the CCD. But in PS, I can see that they are not just one pixel.
Whatever the cause, I was just curious about it. It is certainly not going to bother any night photography I do.

FW

In long exposure photography both hot/stuck pixels as well as high ISO noise may come into play.

The truth is that the individual photosites, commonly referred to as "pixels", are not created exactly equal in sensitivity or quality. The differences are affected by manufacturing tolerances relating to both substrate thicknesses and substrate purity (amongst other things).

Most dSLRs have "long-exposure noise reduction", which is an automation of a process known as "dark frame subtraction". Basically, buy shooting a dark frame just after the image exposure, of the same duration, the hot pixels are accumulated into the dark frame (which has no real image information, just the hot pixels) and then that is inverted and composited onto the image allowing the hot pixels to be effectively neutralized. The problem is that the process requires the same duration for the dark frame as for the taking exposure, doubling the time required and causing the camera to appear to lock up until the dark frame has finished.

Some astro photographers will take a single dark frame and do their own subtraction later on in post-processing, which makes sense if you are doing any quantity of images.

Information here:

http://en.wikipedia.org/wiki/Dark_frame_subtraction

The manual process:

http://www.anandtech.com/digitalcameras/showdoc.aspx?i=2351&p=2

Qarik · August 4, 2009

in fact any piece of silcion with a P/N junction can be effected by alpha particle/wave which can be generated from common solder for example. (just to clarify I have been working in the silcon industry for 15 years and even have worthless masters in the field!). But upon rethinking it, an alpaha wave/partcle occurence is rare enough that is unlikely to be reproducible in the 30 sec time frames described.

It's probably random tiny ground/voltage bounces in the sensor that trip the reduced (increased iso) threshold input level of indivdiual sensor bits. SInce the cap is on..I don't expect it is a photon.

mmroden · August 4, 2009

I remember...
Back in the day, those types of spots could be seen on some pretty high-end scientific imaging devices. The manufacturers used to always assure us that they were 'gamma rays' or some other such things. The chances of a gamma ray or high-energy particle interacting with an imaging device designed to capture visible light are vanishingly small; more likely, the particle just keeps going. It can happen, but not with the frequency you're seeing.

As detectors got better, those random spots disappeared. We jokingly asked the manufacturers if this meant that the background radiation of the universe was decreasing; they had to sheepishly admit that they'd been a bit misleading.

Qarik · August 4, 2009

mmroden wrote:

Back in the day, those types of spots could be seen on some pretty high-end scientific imaging devices. The manufacturers used to always assure us that they were 'gamma rays' or some other such things. The chances of a gamma ray or high-energy particle interacting with an imaging device designed to capture visible light are vanishingly small; more likely, the particle just keeps going. It can happen, but not with the frequency you're seeing.

As detectors got better, those random spots disappeared. We jokingly asked the manufacturers if this meant that the background radiation of the universe was decreasing; they had to sheepishly admit that they'd been a bit misleading.

copied from wiki! Nikon zoom..did you notice any unusual sunspot activity during the day you did this exp?

<img src="https://us.v-cdn.net/6029383/emoji/eek7.gif" border="0" alt="" >

URL="http://en.wikipedia.org/w/index.php?title=Soft_error&action=edit&section=3"][COLOR=#0000ff]edit[/COLOR][/URL Alpha Particles from Package Decay

Soft errors became widely known with the introduction of dynamic RAM in the 1970s. In these early devices, chip packaging materials contained small amounts of radioactive contaminants. Very low decay rates are needed to avoid excess soft errors, and chip companies have occasionally suffered problems with contamination ever since. It is extremely hard to maintain the material purity needed. Controlling alpha particle emission rates for critical packaging materials to less than a level of 0.001 counts per hour per cm2 (cph/cm2) is required for reliable performance of most circuits. For comparison, the count rate of a typical shoe's sole is between 0.1 and 10 cph/cm2.
Package radioactive decay usually causes a soft error by alpha particle emission. The positively charged alpha particle travels through the semiconductor and disturbs the distribution of electrons there. If the disturbance is large enough, a digital signal can change from a 0 to a 1 or vice versa. In combinational logic, this effect is transient, perhaps lasting a fraction of a nanosecond, and this has led to the challenge of soft errors in combinational logic mostly going unnoticed. In sequential logic such as latches and RAM, even this transient upset can become stored for an indefinite time, to be read out later. Thus, designers are usually much more aware of the problem in storage circuits.

URL="http://en.wikipedia.org/w/index.php?title=Soft_error&action=edit&section=4"][COLOR=#0000ff]edit[/COLOR][/URL Cosmic rays creating energetic neutrons and protons

Once the electronics industry had determined how to control package contaminants, it became clear that other causes were also at work. James F. Ziegler led a program of work at IBM which culminated in the publication of a number of papers (Ziegler and Lanford, 1979) demonstrating that cosmic rays also could cause soft errors. Indeed, in modern devices, cosmic rays may be the predominant cause. Although the primary particle of the cosmic ray does not generally reach the Earth's surface it creates a shower of energetic secondary particles. At the Earth's surface approximately 95% of the particles capable of causing soft errors are energetic neutrons with the remainder composed of protons and pions (Ziegler, 1996).[1] This flux of energetic neutrons is typically referred to as "cosmic rays" in the soft error literature. Neutrons are uncharged and cannot disturb a circuit on their own, but undergo neutron capture by the nucleus of an atom in a chip. This process may result in the production of charged secondaries, such as alpha particles and oxygen nuclei, which can then cause soft errors.
Cosmic ray flux depends on altitude. For the common reference location of 40.7N, 74W at 0 meters (sea level in New York City, NY, USA) the flux is approximately 14 neutrons / cm2/hour. Burying a system in a cave reduces the rate of cosmic-ray induced soft errors to a negligible level. In the lower levels of the atmosphere, the flux increases by a factor of about 2.2 for every 1000 m (1.3 for every 1000 ft) increase in altitude above sea level. Computers operated on top of mountains experience an order of magnitude higher rate of soft errors compared to sea level. The rate of upsets in aircraft may be more than 300 times the sea level upset rate. This is in contrast to package decay induced soft errors, which do not change with location. A model of the energetic neutron flux is presented in (Gordon & Goldhagen, 2004).[2]. An online calculator for this model is available at www.seutest.com.
The average rate of cosmic-ray soft errors is inversely proportional to sunspot activity. That is, the average number of cosmic-ray soft errors decreases during the active portion of the sunspot cycle and increases during the quiet portion. This counterintuitive result occurs for two reasons. The sun does not generally produce cosmic ray particles with energy above 1 GeV that are capable of penetrating to the Earth's upper atmosphere and creating particle showers, so the changes in the solar flux do not directly influence the number of errors. Further, the increase in the solar flux during an active sun period does have the effect of reshaping the Earth's magnetic field providing some additional shielding against higher energy cosmic rays, resulting in a decrease in the number of particles creating showers. The effect is fairly small in any case resulting in a +/- 7% modulation of the energetic neutron flux in New York City. Other locations are similarly affected.
Energetic neutrons produced by cosmic rays may lose most of their kinetic energy and reach thermal equilibrium with their surroundings as they are scattered by materials. The resulting neutrons are simply referred to as thermal neutrons and have an average kinetic energy of about 25 millielectron-volts at 25°C. Thermal neutrons are also produced by environmental radiation sources such as the decay of naturally occurring uranium or thorium. The thermal neutron flux from sources other than cosmic-ray showers may still be noticeable in an underground location and an important contributor to soft errors for some circuits.

Nikon D200 noise

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