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Physics help, I'm confused

Why does noise exist in pictures? How do you get rid of it? What are the advantages and disadvantages of noise removal?
Thanks
You will get very few replies by simply posting homework (or other) questions, for which you can find the answers in your physics textbook without any further reference required.

A good start would be to write what you know about noise already here, and someone may be able to help you determine the relevant pieces of knowledge.
(edited 6 years ago)
Original post by artful_lounger
You will get very few replies by simply posting homework (or other) questions, for which you can find the answers in your physics textbook without any further reference required.

A good start would be to write what you know about noise already here, and someone may be able to help you determine the relevant pieces of knowledge.


Well I understand that noise is unwanted interference and that you can remove it by finding the median of its neighbours, but other than that I'm very confused about the above questions.
Original post by CIEBioloysifh
Well I understand that noise is unwanted interference and that you can remove it by finding the median of its neighbours, but other than that I'm very confused about the above questions.


Well you've already answered one part of the question there anyway, so that's a first step.

For the "why" you need to think to what you know about how digital (or analogue) images are captured and stored.

As for the advantages and disadvantages, you know how it's removed, so you need to think about how or when that could be a bad thing. What is the logical extreme case from this?
Original post by artful_lounger
Well you've already answered one part of the question there anyway, so that's a first step.

For the "why" you need to think to what you know about how digital (or analogue) images are captured and stored.

As for the advantages and disadvantages, you know how it's removed, so you need to think about how or when that could be a bad thing. What is the logical extreme case from this?


All i can think of is bright light when taking a picture as noise and as to why there's an advantage or disadvantage for noise removal, I really don't know, that's why I came here, as a last resort.
Original post by CIEBioloysifh
All i can think of is bright light when taking a picture as noise and as to why there's an advantage or disadvantage for noise removal, I really don't know, that's why I came here, as a last resort.


I would recommend reviewing your notes and coursebooks as appropriate as the first part certainly should be well covered by those.
Original post by artful_lounger
I would recommend reviewing your notes and coursebooks as appropriate as the first part certainly should be well covered by those.



I've scaled the internet, my coursebook and my revision guide as well as my class notes, I can't find where the advantages or disadvantages of noise removal are. I think I might get more insight as to why it exists, but advantages and disadvantages, I haven't a clue. Could you please enlighten me?
Original post by CIEBioloysifh
I've scaled the internet, my coursebook and my revision guide as well as my class notes, I can't find where the advantages or disadvantages of noise removal are. I think I might get more insight as to why it exists, but advantages and disadvantages, I haven't a clue. Could you please enlighten me?


Consider an image made of 4 grayscale squares. What would happen if you applied this noise correction mechanism to it? Is the resulting image more or less accurate? Extrapolate this to an image made of hundreds of thousands of squares (i.e. pixels). How can this affect the accuracy of a typical image?
Original post by artful_lounger
Consider an image made of 4 grayscale squares. What would happen if you applied this noise correction mechanism to it? Is the resulting image more or less accurate? Extrapolate this to an image made of hundreds of thousands of squares (i.e. pixels). How can this affect the accuracy of a typical image?


Ok, so the noise correction mechanism reduces the accuracy as it isn't representitive of that square rather, more similar to those around it. So the accuracy of an image is greatly reduced. But what effect does that have (i.e. how should I word it)? Is it more blurry?

And also, what are the advantages of noise removal?
Original post by CIEBioloysifh
Ok, so the noise correction mechanism reduces the accuracy as it isn't representitive of that square rather, more similar to those around it. So the accuracy of an image is greatly reduced. But what effect does that have (i.e. how should I word it)? Is it more blurry?

And also, what are the advantages of noise removal?


The comments about the accuracy should suffice - it's more precise than saying "It becomes blurrier" (you would be more likely to not gain full marks for that, than pointing out it how it affects the accuracy specifically in terms of the whole vs parts of the image).

The advantages are pretty self explanatory if you find the explanation of what noise is in your notes. In general, you don't wan't noise - noise removal as the name suggests, mitigates noise in an image.

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