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Old May 29, 2004, 1:39 PM   #11
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slipe wrote:
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  • [/*]
  • If you display them at 100% onscreen the 6Mp image is twice as large as the 3Mp image.
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Twice the size means that you have twice the width and twice the height. Which in reality means that the area of the picture is four times as large. Going from 3 MP to 6 MP will not double BOTH dimensions. You need to go 3 MP times 4 to get twice the size.

You sure have double the pixels but your resolution will not double. To double the resolution you need to go from 3 to 12 MP.

Don't forget that pictures are two-dimensional whereas the megapixel figure is one-dimensional.
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Old May 29, 2004, 3:57 PM   #12
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luisr wrote:
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Don't forget that pictures are two-dimensional whereas the megapixel figure is one-dimensional.
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That is likely the root of the smoldering (not quite flaming) going on here - the megapixel figure is a single number, but it is a measure of area. It is the count of the number of "tiles" needed to cover the sensor surface. Given the size of the sensor, it is a measure of the area of each pixel.

What most folks mean by resolution is a linear measure: lpi, ppi, dpi, ...

The relationship between them is a square root (not exponential): with a constant aspect ratio the resolution increases with the square root of the pixel count.
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Old May 30, 2004, 3:09 PM   #13
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Quote:
Twice the size means that you have twice the width and twice the height. Which in reality means that the area of the picture is four times as large. Going from 3 MP to 6 MP will not double BOTH dimensions. You need to go 3 MP times 4 to get twice the size.

You sure have double the pixels but your resolution will not double. To double the resolution you need to go from 3 to 12 MP.

Don't forget that pictures are two-dimensional whereas the megapixel figure is one-dimensional.


You would evidently look at an 8 X 10 and 16 X 20 print side by side and say the 16 X 20 was only twice as large. I can't know what other people are perceiving any more than I can know what they are actually seeing when the say "red" or "blue". But the 16 X 20 looks a lot larger than twice the size to me. You can place four 8 X 10s on the 16 X 20, and that is what it looks like to me.

As BillDrew pointed out, Mp is derived by multiplying the width times the height in pixels to get a two dimensional pixel number for the area.



Quote:
What most folks mean by resolution is a linear measure: lpi, ppi, dpi, ...

The relationship between them is a square root (not exponential): with a constant aspect ratio the resolution increases with the square root of the pixel count.


True. But you have to keep in mind that a resolution of 100 PPI is graphics shorthand for 100 X 100 pixels/sq in. 200 PPI is 4 times the resolution of 100 PPI in the pixel density of an image: 40,000 pixels per square inch compared to 10,000. Graphics are two-dimensional and PPI is just the linear measurement of one side of the square. The other side is assumed because graphics files are always symmetrical in density of height and width. PPI is just a convenient way of expressing density by giving only one side. The true resolution of an image is the pixel density, and you get that by squaring the PPI.

I hate to irritate AMG any more with the tile analogy, but it is appropriate here. If you consider 12" or 18" a standard resolution for a tile without understanding the other X 12" or X 18 inch is assumed you end up with the "resolution" of tiles only increasing with the square root of the actual size. You have to use the second dimension to get the relative size in both cases.
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Old May 31, 2004, 7:34 AM   #14
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this thread is getting out of hand, we really aren't arguing here, we seem to all know what we are talking about, slipe, all I'm saying is that even though me and you, and everyone else who respondedunderstandthe pixel dimensions and what they mean, there are people who don't even know what resolution is, and these people buy cameras, do research, print , try and remove red eye, and it are those people who do not realize the similarity in a 3.2 mp and a 4 mp. A 4mp seems 25 % bigger than a 3.2, and in total area it is, so yippee, we are all happy, but fact still remains that the perception of some is that a 4 mp would have more than 200 pixels more across. The people say " Hey I have 4 megapixel camera, where are my 800,000 extra pixels. The answer is they are there, but the fact still remains that it's about 200 more pixels in width and in height, which is not the expectation. Can we all be friends again now...
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Old May 31, 2004, 2:36 PM   #15
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We've always been friends.

Newbe doesn't mean dumb. Their life experiences tell them that a 24 inch tile is more than double a 12 inch one or a 16 X 20 print is more than double an 8 X 10. If someone wants to point out that double doesn't mean double the sides I have no problem. But couch it in pixels or PPI and intimate they aren't somehow increasing their print size or resolution in direct proportion to the increase in Mp and I will clarify it.
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Old Jun 1, 2004, 1:58 AM   #16
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Hello Everyone,

Thank you all so very much for the help and information. I sure have learned a lot from all of you. The interesting this here is that I did think 4 megapixels was double that of 2 megapixles. I hope that is not considered dumb?

Although I was worried about the "tone" of some of the responses, I have to say that your "professional engaging" sure was a good lesson for me. With everyone explaining their specific knowledge on this subject, I really get it now, and understand it. So good job to youall. The reason I proposed the question in the first placewas for a very simple reason. All the research I have done suggests that scientific research shows that anything over 5 or 6 MP's is only a loss of quality by adding more noise. I just purchased an Olympus C-8080 and was trying to understand where to dial it in within the 5-6MP range for optimum resolution and image quality. Thank you all for taking the time to share your knowledge and help me.

Best Regards,

Kevin
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Old Jun 2, 2004, 1:17 PM   #17
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KSS, here is a visual example that puts things in better perspective, the inner blue box represents a 3.2 megapixel file, behind it in whitewould be a 4 megapixel file and the outer blue is an 8mp file by comparison, so on paper the bigger numbers seem much bigger




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Old Jun 2, 2004, 5:28 PM   #18
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AMG,

Thank you for the great example. I can now see that it is best to shoot in full resolution for best quality. So, with that being said, what are the other resolution settings good for?

Kevin
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Old Jun 2, 2004, 11:10 PM   #19
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The illusion of choice! :roll:

:-):-):lol:
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Old Jun 3, 2004, 7:01 AM   #20
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too funny...illusion of choice. Sounds about right to me, but in reality, if you know you are going to a boat show for example ( don't ask me why I chose boat show, it's early in the morning ) and you know you will only email them and never never crop or print them, then why not take in a lower resolution. This way you can take many more pictures on the card, and you don't waste computer disk space. But I take pics of my kids mostly, so any shot may be printed so I always shoot in full with highest quality setting ( superfine ).
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