MegaPixel Count and Filesize Output

[Bynx]

I have a 7.1 Megapixel S700. The filesize output is 3072 x 2304 pixels. This translates to 42.667 x 32 inches all at 72 dpi.
Could anyone with a different Megapixel count please state the filesize output at maximum Megapixel count for their camera.
Does Megapixel count simply translate to filesize only. The larger the Megapixel the larger the filesize output which allows for larger prints with optimum resolution (300 dpi)?

[Visual Reality]

You are correct...

D80, 10MP, 3872x2592

[David Metsky]

If your output is JPG, then the file size is a result of the JPG compression settings. Number of pixels in the file output isn't going to change, but the information contained in the image will depending on how much compression is used.

If you set compression to 10 (best quality) a 6 MP image would be bigger then a 7.2 MP image which had compression set to 1 (lowest quality). With RAW, your file size match much closer to image resolution.

[Bynx]

I am unable to set the jpeg compression number. To keep things even in my query the jpeg will be at the minimum compression by default. Also for this thread no raw file info is asked for just the default jpeg file size.

Thanks Visual, thats exactly what I wanted to know. Id like to see some more info from different MegaPixel cameras.

[David Metsky]

You're confusing two things: file size, and resolution.

A 10 MP camera (assuming it doesn't have odd dimensions of the CCD) will always have 3872x2592 resolution. It's the definition of resolution. They scale up exactly evenly. 3648 * 2736 = 10036224 (or 10 MP). A 12 MP camera like the A650 takes images that are 4000x3000 = 12000000 (12 MP). This is for P&S cameras with a 4/3 sensor. DSLRs have different dimension sensors 3/2 so their dimensions are like the D80 mentioned by VR.

If you look on the detail pages under Reviews and Info it states the image resolution of all the cameras. Except for a few oddballs they'll all be in that 4/3 ratio for P&S and 3/2 ratio for DSLRs.

File size is a combination of resolution, compression, and file system representation; I don't think it's particularly relevant to your question.

[Ray Schnoor]

I am unable to set the jpeg compression number.
Actually, you have 2 settings for jpeg compression on your camera(fine and normal). While these are not "numbers", they are equivalent to different jpeg compression ratios.

If you go to the reviews page, you can look at the reviews of different megapixel cameras to see what the largest megapixel output dimensions are for the different cameras. While this may be a bit more work on your part, you will get the numbers much faster if you really want them.

While there may be slight differences among like megapixel cameras, they will not be significant. This should be true for all like megapixel P&S cameras and also for all like megapixel dSLR cameras.

If you compare like megapixel P&S cameras to dSLR cameras, though, there will be substantial differences simply for the fact that P&S cameras are normally in a 4:3 width to height ratio while dSLRs are normally in a 3:2 width to height ratio.

Of course 4/3rds dSLR cameras will have a 4:3 width to height ratio.

Ray.

Edit: yeah, what David said.

[Bynx]

Im not interested in the aspect ratio just the pixel count with the resolution being a constant 72dpi with each camera having a higher or lower megapixel rate than mine. While it would be more complete and quicker to just check the reviews Im using this thread to point out the real differences and importance of pixel count. That being the ability to print out larger photos without the need for Genuine Fractal or similar programs. At the same time there is an aspect Im not grasping and hope I will by the time this is done. Thanks for your inputs so far.

[Ray Schnoor]

Im not interested in the aspect ratio just the pixel count with the resolution being a constant 72dpi with each camera having a higher or lower megapixel rate than mine. While it would be more complete and quicker to just check the reviews Im using this thread to point out the real differences and importance of pixel count. That being the ability to print out larger photos without the need for Genuine Fractal or similar programs. At the same time there is an aspect Im not grasping and hope I will by the time this is done. Thanks for your inputs so far.
The resolution of an x MP camera is the same regardless if it is 72 dpi or 300 dpi. The pixel count is still x MP.

Knowing what type of camera P&S or dSLR and the megapixel size of the camera, you can mathematically figure the approximate pixel counts(give or take 20-30 pixels in each direction depending on manufacturer). This variation is really irrelevant when you are talking megapixels.

P&S cameras 4:3 ratio

4MP P&S ~ 2309x1732
6MP P&S ~ 2828x2121
8MP P&S ~ 3266x2449
10MP P&S ~ 3651x2739
12MP P&S ~ 4000x3000

dSLR cameras 3:2 ratio

6MP dSLR ~ 3000x2000
8MP dSLR ~ 3464x2309
10MP dSLR ~ 3873x2582
12MP dSLR ~ 4243x2828

Ray.

[David Metsky]

You've mentioned "real differences and importance of pixel count", presumably for the purpose of printing. Image size in pixels is really all you need for that, and as Ray said, it's just a simple mathematical formula based on whether you are using a 4/3 sensor or a 3/2 sensor.

Keep in mind that at 300 dpi a 6 MP 4/3 image is 9.42" x 7.07" and a 12 MP image is 13.33" x 10". Doubling the MP doesn't increase the printable image size by nearly as much as you might think.

[AlexMonro]

Keep in mind that at 300 dpi a 6 MP 4/3 image is 9.42" x 7.07" and a 12 MP image is 13.33" x 10". Doubling the MP doesn't increase the printable image size by nearly as much as you might think.

Indeed, it's a simple linear / area relation. To double the linear dimensions of a print (at the same Pixels per Inch resolution), you need four times the number of pixels.

However, since large prints are usually viewed from a greater distance than small prints, a lower PPI resolution is often adequate, typically 200 PPI for 11"x14" and 150 PPI for 16"x20" or larger.

[Paradox]

From a photography book in my possession (All these at 72 DPI, sizes in inches):

0.3 Megapixels (640x480) - 8.9x6.7
2 Megapixels (1600x1200) - 22x16
3 Megapixels (2016x1512) - 28x21
5 Megapixels (2592x1944) - 36x27
6 Megapixels (3264x2448) - 45x34
12 Megapixels (4288x2848) - 60x40

[photo-print-reviews]

Yeah, typically a resolution of 4000 x 3000 would be good enough for a 300 dpi print. And a 12MP camera can produce that kind of output images.

[Wesan]

I have a 7.1 Megapixel S700. The filesize output is 3072 x 2304 pixels. This translates to 42.667 x 32 inches all at 72 dpi.
Could anyone with a different Megapixel count please state the filesize output at maximum Megapixel count for their camera.
Does Megapixel count simply translate to filesize only. The larger the Megapixel the larger the filesize output which allows for larger prints with optimum resolution (300 dpi)?

I've thought a little about this now, and I'm getting a bit confused... About printing at a certain dpi - I've noticed that different cameras have different dpi with their resolution. For example, my Canon Powershot S3IS seems to have 180 dpi and a Canon EOS 1D Mk III seems to have 250 dpi. Doesn't this affect the maximum resolution you can get when printing? Can you print at 300 dpi when the image from the camera only has 72, 180 or 250 dpi?

[Bynx]

You cant print out the full size of the picture at 72 dpi. But you can reduce the size of the picture so the dpi increases to 300. For example my camera produces a 72 dpi picture which is 42 x 32 inches. When I reduce the size of the image to 10 x 8 the dpi increases to 300.

[JTL]

I've thought a little about this now, and I'm getting a bit confused... About printing at a certain dpi - I've noticed that different cameras have different dpi with their resolution. For example, my Canon Powershot S3IS seems to have 180 dpi and a Canon EOS 1D Mk III seems to have 250 dpi. Doesn't this affect the maximum resolution you can get when printing? Can you print at 300 dpi when the image from the camera only has 72, 180 or 250 dpi?Here's where you're getting confused...the image from the camera doesn't have any DPI.

[Ray Schnoor]

I've thought a little about this now, and I'm getting a bit confused... About printing at a certain dpi - I've noticed that different cameras have different dpi with their resolution. For example, my Canon Powershot S3IS seems to have 180 dpi and a Canon EOS 1D Mk III seems to have 250 dpi. Doesn't this affect the maximum resolution you can get when printing? Can you print at 300 dpi when the image from the camera only has 72, 180 or 250 dpi?
JTL is correct in that no digital image really has "any" DPI. It does have PPI(pixels/inch) which some people have morphed into DPI(dots/inch) because that is how inkjet printers advertise their quality. This has absolutely nothing to do with a digital image, though, as there are several dots(droplets of ink) for every pixel from a digital image. DPI and PPI really have no correlation at all.

When someone says that their camera has a certain DPI, what they are saying is that their computer software is displaying a digital image at a certain pixel/inch density. This means absolutely nothing until it is printed.

You say that your S3IS "seems to have 180 dpi". It doesn't. Your computer software is displaying it at 180 pixels/inch and just calling a pixel a dot.

If anything, the true pixel/inch value of your S3IS can be calculated by taking the measurements of your image (2816 pixels x 2112 pixels) and divide it by the dimensions of the CCD in the camera (~0.32" x 0.24"). 2816/0.32 = 8800 pixels/inch; 2112/0.24 = 8800 pixels/inch. That means your camera collects your image at a pixel(or dot or whatever you want to call it)/inch density of 8800 pixels/inch.

Now that doesn't mean a whole lot, since no one wants to print anything at 0.32" x 0.24". That is why you enlarge it. They did it with film, they do it with digital images. When you enlarge it, you reduce the pixel density. That is why pixel(or dot) density means absolutely nothing until the image is viewed/printed.

You can print your image at whatever size you want and you will have a different pixel density for each different size you print. You say that your software says your S3IS "seems to have 180 dpi". What you are leaving out is that your software also says that your S3IS image has a size of ~15.6" x 11.7". Does this mean that you can only print at this size. No, and no one ever even considers that. But if your computer says that your image has 180 dpi, that number must be set in stone.

When your computer prints at a size other than the 15.6" x 11.7", it just adjusts the pixel density to fit the size of print you want to make.

I know that this is wordy and very long, but it is not really all that hard to understand.

And, Bynx, yes you can print out the full size image at 72 pixels/inch if you have a printer that can print that large. The point here is that you can print a digital image at whatever pixel density you want. You just have to remember that the smaller pixel density you have, the lower quality of print you are going to get.

Ray.

[Wesan]

Thanks for your repies, Bynx, JTL and Ray Schnoor. The figures I used (180 and 250) I found in the EXIF-data of images from my S3 and one 1D Mk III. This is what the data from my camera looks like:

X Resolution: 180/1
Y Resolution: 180/1
Resolution unit: inches

If that's not about the DPI or PPI, what is it about then? What resolution do the numbers mean? The data is under the Camera item in the EXIF-data.

[Ray Schnoor]

Thanks for your repies, Bynx, JTL and Ray Schnoor. The figures I used (180 and 250) I found in the EXIF-data of images from my S3 and one 1D Mk III. This is what the data from my camera looks like:

X Resolution: 180/1
Y Resolution: 180/1
Resolution unit: inches

If that's not about the DPI or PPI, what is it about then? What resolution do the numbers mean? The data is under the Camera item in the EXIF-data.
My guess is that is is just an arbitrary number that Canon picks to have software use as a starting point when displaying an image. Basically a meaningless number. Not all the data in the EXIF is important.

Ray.

[David Metsky]

Sometimes, numbers are just numbers. They don't mean anything. :)

[Bynx]

Thanks Ray, you are absolutely right. You can print out at 72 dpi but it will be a very course (pixelated) image. If viewed from a distance a 42" x 32" print at 72dpi will look as good as an 10" x 8" viewed close up. But it would be simpler to just use Genuine Fractals and upsample the image to 300 dpi. I thought all cameras output at 72 dpi because that is the optimum for viewing on the monitor. The size doesnt matter until you go to print it out. 300 DPI is optimum printing. This is equivalent to magazine quality prints. 72 dpi is equivalent to newpaper quality. I disagree with your statement David. The numbers always mean something. You just have to know what the numbers represent. Pixels and DPI are confusing and have been from day one. They are often mixed up in context.

[JTL]

JTL is correct in that no digital image really has "any" DPI. It does have PPI(pixels/inch) which some people have morphed into DPI(dots/inch) because that is how inkjet printers advertise their quality. This has absolutely nothing to do with a digital image, though, as there are several dots(droplets of ink) for every pixel from a digital image. DPI and PPI really have no correlation at all.

When someone says that their camera has a certain DPI, what they are saying is that their computer software is displaying a digital image at a certain pixel/inch density. This means absolutely nothing until it is printed.

You say that your S3IS "seems to have 180 dpi". It doesn't. Your computer software is displaying it at 180 pixels/inch and just calling a pixel a dot.

If anything, the true pixel/inch value of your S3IS can be calculated by taking the measurements of your image (2816 pixels x 2112 pixels) and divide it by the dimensions of the CCD in the camera (~0.32" x 0.24"). 2816/0.32 = 8800 pixels/inch; 2112/0.24 = 8800 pixels/inch. That means your camera collects your image at a pixel(or dot or whatever you want to call it)/inch density of 8800 pixels/inch.

Now that doesn't mean a whole lot, since no one wants to print anything at 0.32" x 0.24". That is why you enlarge it. They did it with film, they do it with digital images. When you enlarge it, you reduce the pixel density. That is why pixel(or dot) density means absolutely nothing until the image is viewed/printed.

You can print your image at whatever size you want and you will have a different pixel density for each different size you print. You say that your software says your S3IS "seems to have 180 dpi". What you are leaving out is that your software also says that your S3IS image has a size of ~15.6" x 11.7". Does this mean that you can only print at this size. No, and no one ever even considers that. But if your computer says that your image has 180 dpi, that number must be set in stone.

When your computer prints at a size other than the 15.6" x 11.7", it just adjusts the pixel density to fit the size of print you want to make.

I know that this is wordy and very long, but it is not really all that hard to understand.

And, Bynx, yes you can print out the full size image at 72 pixels/inch if you have a printer that can print that large. The point here is that you can print a digital image at whatever pixel density you want. You just have to remember that the smaller pixel density you have, the lower quality of print you are going to get.

Ray.Thank you Ray. A brilliant explanation.

I thought for half a second about adding an explantion to my comment and I'm glad that I didn't, because your's is a thousand times better and clearer than what I was going to write! :)

[Ray Schnoor]

Thanks. I thought it may have been a little too much rambling. Good to know that someone else understands my thoughts.

Ray.

[David Metsky]

I thought all cameras output at 72 dpi because that is the optimum for viewing on the monitor. The size doesnt matter until you go to print it out. 300 DPI is optimum printing.

Images out of a camera DO NOT HAVE A DPI. It's meaningless to to talk about that, since an image by itself has no way of expressing or representing DPI. An image has pixels. If you camera shoots images that are 4000x3000 pixels, that's the only information that is part of the image. Any concept of DPI, either for screen viewing or printing, is an outside artifact, not intrinsic to the image in any way.

Cameras create images. In this case, software programs represent those images by making arbitrary assumptions about display qualities. This is no more a part of the image then your monitor calibration is part of the image. Again, the concept of DPI related to an on disk image makes no sense; it's a meaningless number.

You can say that if printed at 300 DPI this image will be 8" x 10" in size, but those numbers are merely ways of restating 4000 pixels by 3000 pixels. There's no additional information added.

ETA: Sorry if I got a little excited there. I'm home sick and this is the most interesting part of my day. :(

[Ray Schnoor]

Thank you Ray. A brilliant explanation.
Your reply just makes me thirsty...

http://www.youtube.com/watch?v=2WqO0Q_zNKA

http://www.youtube.com/watch?v=iWqGLVaITsk

http://www.youtube.com/watch?v=MWgSu7qRXEo

http://www.youtube.com/watch?v=t3Ta54L9CLU

http://www.youtube.com/watch?v=t4Isq6qdbJM

http://www.youtube.com/watch?v=5zRbIlcnsAU

http://www.youtube.com/watch?v=_BNQk6jlCfw

Ray.