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Lower your resolution = noise reduction...?
Figured this was a rookie question for the tech-heads here, at least in terms of my digital experience, but someone here tell me why, in certain situations, since heavy pixel-density-to-sensor size seems to be a frequent culprit for noise...if cropping isn't a concern, does it not make sense to lower the resolution a tad when you have to bump up the ISO...?.

Just curious. Seems like it would be a natural fix, but what do I know...

Comments (13)

SonyAlphaMale wrote:.

Figured this was a rookie question for the tech-heads here, at leastin terms of my digital experience, but someone here tell me why, incertain situations, since heavy pixel-density-to-sensor size seems tobe a frequent culprit for noise...if cropping isn't a concern, doesit not make sense to lower the resolution a tad when you have to bumpup the ISO...?.

The lower resolution settings are arrived at by just sampling of full resolution (pixels). So no advantage. Nevertheless some cameras do comine data from adjascent pixels at higher ISOs (typically ISO1600+). e.g. Fuji F100fd can thus produce images at ISO1000! at reduced resolution.Best Wishes, Ajayhttp://picasaweb.google.com/ajay0612Thanks for your time...

Comment #1

SonyAlphaMale wrote:.

Figured this was a rookie question for the tech-heads here, at leastin terms of my digital experience, but someone here tell me why, incertain situations, since heavy pixel-density-to-sensor size seems tobe a frequent culprit for noise...if cropping isn't a concern, doesit not make sense to lower the resolution a tad when you have to bumpup the ISO...?.

Just curious. Seems like it would be a natural fix, but what do I know..

No, lowering resolution will not reduce noise in your photo. Typically, when you set your camera to a lower resolution, you reduce the amount of data in your image, and therefore the file size. Your camera accomplishes this in it's firmware. It simply resizes your image to a smaller size. The same number of pixels on your sensor are used no matter what resolution you set. (There are some exceptions to this, depending on the camera you have, but they don't change the answer to your question.).

There is no reason to set a lower resolution unless you need to conserve storage space in your camera's memory..

Your question is a result of confusion as to what causes noise in an image and the meaning of "resolution". I'll try to explain:.

Let's compare two cameras that both have 10 megapixels. Camera A is a point and shoot that has a very small sensor, maybe 1/4th of square centimeter. Camera B is a DSLR that has a sensor that is 4 square centimeters. BOTH these cameras produce images of the SAME resolution: 10MP..

When the light from the scene you are shooting passes through the lens it hits millions of little spots on the sensor that collect light (pixels). In camera A, these 10MP are crammed into a very small space. In camera B the 10MP are on a sensor that is 16 times larger. This means that Camera B also gets 16 time more light falling on it's sensor. Because the sensor is large, the light gathering spots can also be larger and each spot/pixel can gather (roughly) 16 times more light..

The world is full of "noise" ... random energy. The camera sensor also is affected by random energy, much of it coming from the electronics of the camera itself. In camera A, with the small sensor and the smaller light collecting sites/pixels, the noise sometimes "overcomes" the very small amount of "true" energy that comes from the scene you are shooting. In camera B, which gets 16 times as much light, the noise doesn't interfere as much with the energy coming through the lens from the scene you are shooting because it's getting more "true" light. We say that camera B has a better signal/noise ratio and therefore it takes "better" pictures.

Remember, both these cameras have the same "resolution": 10MP..

Now if you are in a really dark situation where there isn't very much light, the small sensor camera image will be full of noise. However, because the large sensor camera is also "struggling" to get enough light to "overcome" the noise, it will also produce a noisey picture, but typically better than the small sensor camera..

Well ... I guess I got carried away ... my explanation was much longer than I had intended ... but ... I hope it helps..

Good luck,.

- Simon.

Http://scpics.smugmug.com/..

Comment #2

SonyAlphaMale wrote:.

Figured this was a rookie question for the tech-heads here, at leastin terms of my digital experience, but someone here tell me why, incertain situations, since heavy pixel-density-to-sensor size seems tobe a frequent culprit for noise...if cropping isn't a concern, doesit not make sense to lower the resolution a tad when you have to bumpup the ISO...?.

Just curious. Seems like it would be a natural fix, but what do I know..

Scphoto's explanation about noise due to sensor size is good (above)..

You could get the same effect you ask about simply by downsampling in photoshop later. Suppose you have a noisy 10MP image and want only a small print; you could resize it to 2.5MP - to keep the maths simple - which would result in a square of four 'small' pixels in the 10MP image being combined into one larger pixel in the 2.5MP image. This will decrease the noise *per pixel* because you have averaged out random fluctuations from four smaller pixels (actually the noise will be halved since it scales as the square root f the number of samples). But, each pixel is 4 times bigger, so although each pixel now has less noise, the random variations from one to the next are more visible to the eye..

So you can choose between more noise in tiny pixels that are less individually visible and less noise in bigger pixels that are more easily visible. In other words, a tie. The real issue is the sensor size which you can't do much about except buy a new camera..

Best wishesMike..

Comment #3

Scphoto wrote:.

No, lowering resolution will not reduce noise in your photo.Typically, when you set your camera to a lower resolution, you reducethe amount of data in your image, and therefore the file size. Yourcamera accomplishes this in it's firmware. It simply resizes yourimage to a smaller size. The same number of pixels on your sensor areused no matter what resolution you set. (There are some exceptions tothis, depending on the camera you have, but they don't change theanswer to your question.).

There is no reason to set a lower resolution unless you need toconserve storage space in your camera's memory..

Your question is a result of confusion as to what causes noise in animage and the meaning of "resolution". I'll try to explain:.

Hi SC,.

No need to patronize. I think my first post indicated that I'm aware of what "resolution" is in terms of sensor size. I appreciate your explanation before the assumption of ignorance on my part, however. That's all I wanted to know..

Thanks,SAM..

Comment #4

SonyAlphaMale wrote:.

Hi SC,.

No need to patronize. I think my first post indicated that I'm awareof what "resolution" is in terms of sensor size. I appreciate yourexplanation before the assumption of ignorance on my part, however.That's all I wanted to know..

SAM -.

I did not mean to "patronize" you. However, I apologize if I offended you by assuming you wanted a detailed explanation regarding how sensor size and resolution effects noise..

Since you posted this in the Beginners Forum, you described your post as a "rookie question" and said "someone here tell me why", I assumed, obviously incorrectly, that a detailed explanation would be helpful. I did not make "the assumption of ignorance" on your part. I felt you were asking a legitimate question and I was trying to be helpful, not patronizing..

Again, I apologize if you feel offended ....

- Simon.

Http://scpics.smugmug.com/..

Comment #5

Very nice input, but let me make a few points:.

Your question is a result of confusion as to what causes noise in animage and the meaning of "resolution". I'll try to explain:.

Good intro.

Camera A, 10 megapixels. 1/4 cm^2Camera B, 10 megapixels. 4 cm^2..

Simple comparison....

In camera A, 10MP are crammed into a very small space.In camera B, 10MP are on a sensor that is 16 times larger.This means that Camera B also gets 16 time more light falling on it'ssensor..

Incorrect! remember the inverse square law. An optical image that is expanded to a larger area will have an intensity much SMALLER hitting each sensor and the SAME intensity covering the sensor. lets say we have and intensity of 4 a.u (arbritrary units) on the first sensor. so thats 4 a.u. times 1/4cm^2. we get an intensity of 1au/cm^2.

Thats 4au/4cm^2, or 1au/cm^2. hmm, no benifit there!.

The sensor is large(er), the light gathering spots canalso be larger.

They CAN be but ARE they??? well lets hope so as that would be stupid if they were not .

And each spot/pixel can gather (roughly) 16 times morelight..

I think you are at least stumbling in the right direction here. Yes the pixel is cabalbe of recieving 16 times as many "light signals", with out example image, that has also increased in size, the distance between each "light signals" is also 16 times greater so each pixel gets the SAME amount of light.

The camera sensoralso is affected by random energy.

True, random energy == noise ;-0.

, much of it coming from theelectronics of the camera itself..

As well as external radiation, electrical and optical.

In camera A, with the small sensorand the smaller light collecting sites/pixels, the noise sometimes"overcomes" the very small amount of "true" energy that comes fromthe scene you are shooting. In camera B, which gets 16 times as muchlight, the noise doesn't interfere as much with the energy comingthrough the lens from the scene you are shooting because it's gettingmore "true" light..

Perhaps we can rethink this...if the energy is the same, why is the bigger sensor better (less noise)?if the energy is greater in the bigger sensor, where does it come from?where does the "false" light go? ;-0.

Well ... I guess I got carried away ... my explanation was muchlonger than I had intended ... but ... I hope it helps..

Of course it helps, but I think needs further discussion!.

So let me restate your original question of interest:what causes noise in an image?I will propose a multiple choice answer?  a) Electronics in the camerab) electrical interperance from outside.

C) optical noise from too many light signals being to close together and the tiny pixels not being able to distinguish between them.

D)signal paths from the pixels crosstalking with nearest neibours. signals being closer and more crosstalk in the smaller sensor.e) all of the abovef) none of the above ..

Comment #6

PhotonFiend wrote:.

Very nice input, but let me make a few points:.

Your question is a result of confusion as to what causes noise in animage and the meaning of "resolution". I'll try to explain:.

Good intro.

Camera A, 10 megapixels. 1/4 cm^2Camera B, 10 megapixels. 4 cm^2..

Simple comparison....

In camera A, 10MP are crammed into a very small space.In camera B, 10MP are on a sensor that is 16 times larger.This means that Camera B also gets 16 time more light falling on it'ssensor..

Incorrect! remember the inverse square law. An optical image thatis expanded to a larger area will have an intensity much SMALLERhitting each sensor and the SAME intensity covering the sensor. letssay we have and intensity of 4 a.u (arbritrary units) on the firstsensor. so thats 4 a.u. times 1/4cm^2. we get an intensity of1au/cm^2.

Thats 4au/4cm^2, or 1au/cm^2. hmm, no benifit there!.

The sensor is large(er), the light gathering spots canalso be larger.

They CAN be but ARE they??? well lets hope so as that would bestupid if they were not .

And each spot/pixel can gather (roughly) 16 times morelight..

I think you are at least stumbling in the right direction here. Yesthe pixel is cabalbe of recieving 16 times as many "light signals",with out example image, that has also increased in size, the distancebetween each "light signals" is also 16 times greater so each pixelgets the SAME amount of light.

PhotonFiend:.

I disagree with your assertion (above) that the same amount of light falls on a small sensor as a large sensor. This is not true when comparing cameras A & B in my example..

You sight the inverse square law of optics. Im the last one to argue with the laws of optics, but the law does NOT apply in my example. You would be correct if the SAME lens was providing the light for both the small sensor and the large sensor, but it is not the same lens because they are different cameras: A vs. B..

The typical point and shoot camera (A in my example) has a very small lens that has limited light gathering ability. My Panasonic TZ3 has a telephoto 280mm lens that is about the size of a plump grape. It does not gather as much light as 280mm lens (the size of a can of beer) on a DSLR (Camera B)..

The small sensor camera (A) uses a small diameter lens to focus a given amount of light on it's tiny sensor. The DSLR (B) uses a much larger lens to focus more light on it's much larger sensor. There are more photons hitting the larger sensor and each photo collecting site (pixel), which is also larger, gets more light..

To be completely correct, the amount of light falling on the sensor (for a given shutter speed and a given scene) is determined by optics of the lens. However, DSLR lenses are designed to take advantage of their larger sensors and therefore deliver more photons per collection site than small sensor cameras. They get a stronger signal (true light) and therefore have a better signal to noise ratio and less noise..

I may have oversimplified the example by not bringing lens optics into the discussion, but what I said is essentially correct: Cameras with bigger sensors gather more light per pixel. This is the way the cameras/sensors we use are designed to work..

You are incorrect in stating that each pixel gets the SAME amount of light (your own capitalized emphasis) in Camera As and Bs sensors. Your statement would be true if DSLRs were designed with the same size lenses as point and shoot cameras (or vice versa), but this is not the case..

- Simon.

Http://scpics.smugmug.com/..

Comment #7

I am not trying to convince you of anything! I simply wanted to point out where I thought your thoughtful explanation could use some more support. when I read it it only posed more question rather than answering the OP about noise. One of them was, what about the lens. you gave no mention about the effect of a lens, which is very important..

This is not true whencomparing cameras A & B in my example..

You give no mention a lens A or B, so it is true for you first example. if I just blow up the size of everything in the p&s camera proportianally by 16x then would it equal a dslr? why or why not?.

You sight the inverse square law of optics. Im the last one toargue with the laws of optics, but the law does NOT apply in myexample..

The inverse square law has nothing to do with optics specifically, but it does apply. what has been failed to be mention is that it applyes to the lens as well. but...inversely I suppose;=0 if you double the diameter of your lens you collect 4x as much light! this Will have a big effect. but more to my point is that WE still have not answered HOW this effects noise in the final image and resolution/noise..

You would be correct if the SAME lens was providing the.

Light for both the small sensor and the large sensor, but it is notthe same lens because they are different cameras: A vs. B..

You assumed this, I did not..

The typical point and shoot camera (A in my example) has a very smalllens that has limited light gathering ability. My Panasonic TZ3 has atelephoto 280mm lens that is about the size of a plump grape. It doesnot gather as much light as 280mm lens (the size of a can of beer) ona DSLR (Camera B)..

So why does this effect noise when as you stated noise is mostly due to the electronics, not the lens or sensor.

The small sensor camera (A) uses a small diameter lens to focus agiven amount of light on it's tiny sensor. The DSLR (B) uses a muchlarger lens to focus more light on it's much larger sensor. There aremore photons hitting the larger sensor and each photo collecting site(pixel), which is also larger, gets more light..

More light on a larger AREA sensor which again seems to me to be balancing each other at least to some extent. you have captured more photons but are they spread out over a larger area? so the flux is the same approximatlly..

To be completely correct, the amount of light falling on the sensor(for a given shutter speed and a given scene) is determined by opticsof the lens. However, DSLR lenses are designed to take advantage oftheir larger sensors and therefore deliver more photons percollection site than small sensor cameras. They get a stronger signal(true light) and therefore have a better signal to noise ratio andless noise..

As you said earlier noise is everywhere and always present, so would you not also capture more noise with that big lens and collect more of it with that big sensor. it does not seem so simply clear why there is less noise in one case vs another...

Comment #8

This has been a very useful thread-discussion on the technicalities of optics!.

To pose a slightly different direction to the techies - If the resolution is lowered it may not affect noise but does in result in lowered IQ? Ie are you not utilising the capabilities of the sensor to it's fullest if you reduce the image size?.

I am using a Canon XSI and it has options to set the file size to L,M,S under the 'Fine' Resolution Setting. Same size options for 'Normal' Resolution setting..

Is it the case that using Fine/Large will result in best IQ, or will using Fine/Small give the same IQ in a smaller file/picture size?.

Thanks for your thoughts!..

Comment #9

SonyAlphaMale wrote:.

...No need to patronize. I think my first post indicated that I'm awareof what "resolution" is in terms of sensor size. I appreciate yourexplanation before the assumption of ignorance on my part, however.That's all I wanted to know..

Mental note to self not to answer questions from this guy ever. That way I won't risk being accused of being patronising for my efforts.

Chris Elliott.

*Nikon* D Eighty + Fifty - Other equipment in Profile.

Http://PlacidoD.Zenfolio.com/..

Comment #10

Sami1978 wrote:.

This has been a very useful thread-discussion on the technicalitiesof optics!.

To pose a slightly different direction to the techies - If theresolution is lowered it may not affect noise but does in result inlowered IQ? Ie are you not utilising the capabilities of the sensorto it's fullest if you reduce the image size?.

I am using a Canon XSI and it has options to set the file size toL,M,S under the 'Fine' Resolution Setting. Same size options for'Normal' Resolution setting..

Is it the case that using Fine/Large will result in best IQ, or willusing Fine/Small give the same IQ in a smaller file/picture size?.

If you want the best possible IQ, then you should use the highest resolution that your camera can produce. In your case, this is Fine/Large. The main reason to use a lower resolution when taking a picture is to conserve memory storage space on your camera's media card. Because memory is relatively cheap, it's just best to buy a bigger card or carry an additional card(s)..

The main exception to the rule of "use the highest resolution" is if you don't need the best resolution for your pictures. For example, if you ONLY make 4"x6" prints or if you ONLY display your photos on the computer, you probably don't need the maximum resolution. However, if you get a shot that you really like and want to print it in a large size (8"x10" or bigger), you will probably regret having used the lower resolution setting..

Typically, the higher the resolution, the bigger the image file you get for your shot, and the more information (data) you have to work with when printing or editing a photo. When you lower the resolution, you are throwing away information that your camera collected at the instant of taking the photo. Once you throw it away, you can't get it back. Photo editing/printing software may be able to approximate what the lost information might have looked like, but this will typically result in reduced image quality..

I hope this helps ....

- Simon.

Http://scpics.smugmug.com/..

Comment #11

Chris Elliott wrote:.

SonyAlphaMale wrote:.

...No need to patronize. I think my first post indicated that I'm awareof what "resolution" is in terms of sensor size. I appreciate yourexplanation before the assumption of ignorance on my part, however.That's all I wanted to know..

Mental note to self not to answer questions from this guy ever. Thatway I won't risk being accused of being patronising for my efforts.

Chris Elliott.

*Nikon* D Eighty + Fifty - Other equipment in Profile.

Http://PlacidoD.Zenfolio.com/.

Mental note to self- remind me never to ask for advice from anyone on the forums going by the name Chris Elliott. He doesn't know how to mind his own business...

Comment #12

Yes, downscaling - means lower overall noise in picture, but I advise topic authour - not stick to in digicam "lower res" shooting mode, because them - mostly for saving card space and-or better speed. and resulted image quality - incomparably to produced on PC' due to lack of DC's IC's "horsepower" in interpolations and-or algorithm-implementations complexity. and even oon PC's, PS - rely mostly on outdated Bicubic algorythm...

Comment #13

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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