Thread Subject: Resolution

Dear Sir;
i have only one cofused point , "That same 3.0 megapixel camera might give you a choice in saving JPEG files at the following common resolutions: 2048x1536, 1600x1200, 1280x960 and 640x480", "JPG doesn't remove pixels (which would reduce resolution)", So, 640x480 for example is a lower resolution or simply image size compressed with the same resolution?
Thanks

It's done by binning, before the jpeg process even starts. See this
thread
http://forums.dpreview.com/forums/read.asp?forum=1002&message=31292345
or http://www.ccd.com/ccd103.html
or Google around for something better.

Here's a good camera tutorial site with a nice glossary.
http://www.dpreview.com/learn/?/Glossary/

"Elshaymaa M.E." <engenas_master@yahoo.com> wrote in message <hg7roa$qb4$1@fred.mathworks.com>...
> Dear Sir;
> i have only one cofused point , "That same 3.0 megapixel camera might give you a choice in saving JPEG files at the following common resolutions: 2048x1536, 1600x1200, 1280x960 and 640x480", "JPG doesn't remove pixels (which would reduce resolution)", So, 640x480 for example is a lower resolution or simply image size compressed with the same resolution?
> Thanks

It is a lower resolution. That doesn't mean the JPEG algorithm removed the pixels, though. Something upstream removed them before passing the smaller image to the JPEG encoder. So the two statements you give are entirely consistent.

Dear sir
Thanks in advance for your reply, what was confusing for me in is that "JPEG would not reduce resolution", Am i rght that it does not make extra reduction, i.e. do not remove pixels but reduce the image resolution to one of the 4 stated resolutions to make compression.

Shall i ask a second question
About the USB webcams or digital camera with CCD image sensor, how can its output be converted to a digital form, has it a built-in ADC or the USB connection perform this?

Thanks

Hello,

> About the USB webcams or digital camera with CCD image sensor, how can
> its output be converted to a digital form, has it a built-in ADC or the USB
> connection perform this?

There is an ADC directly behind the sensor of the camera. The digital signal is then converted - de-bayered - into a color image (in RBG or some other color format). As far as I know all webcams will have one ADC, bigger cameras (multi megapixel cameras) may have 2 or 4 of them.


 best regards,

                 Ulf-E. Walter

--
Ulf-E. Walter
------------------///----------------------
Allied Vision Technologies GmbH
Branch Office Ahrensburg / Germany
Klaus-Groth-Strasse 1
22926 Ahrensburg
Germany

ImageAnalyst <imageanalyst@mailinator.com> wrote in message <b9b9dc4b-4be5-405e-84c2-a259b0e6d8bc@v30g2000yqm.googlegroups.com>...
> It's done by binning, before the jpeg process even starts. See this
> thread
> http://forums.dpreview.com/forums/read.asp?forum=1002&message=31292345
> or http://www.ccd.com/ccd103.html
> or Google around for something better.
>
> Here's a good camera tutorial site with a nice glossary.
> http://www.dpreview.com/learn/?/Glossary/



Dear Sir;
Thanks in advance for your reply, really it was wonderful.
Shall i ask a second question please:
About the USB webcams or digital cameras with CCD image sensor, how can its output be converted to a digital form, has it a built-in ADC (where) or the USB connection has a role to perform this?
Thanks

Don't get resolution that refers to the image matrix size confused
with actual real physical spatial resolution. Jpeging an image will
not reduce the matrix size but will reduce the spatial resolution.
You've seen how lower quality parameters will give rise to the well
known block artifacts, which of course will reduce spatial resolution
even though it is not reducing the image array size.

ImageAnalyst <imageanalyst@mailinator.com> wrote in message <d8709043-e141-47a2-a317-e5b3ac381d1f@f20g2000vbl.googlegroups.com>...
> Don't get resolution that refers to the image matrix size confused
> with actual real physical spatial resolution. Jpeging an image will
> not reduce the matrix size but will reduce the spatial resolution.
> You've seen how lower quality parameters will give rise to the well
> known block artifacts, which of course will reduce spatial resolution
> even though it is not reducing the image array size.


Thanks in advance, this is for me so........... good and clear.
Shall i ask another question, i want only to verify that "pixel depth" in an image is related to the number of color levels for that image, not to the image resolution (image matrix nor spatial). Am I right?
Thanks

On Dec 17, 7:00 am, "Elshaymaa M.E."
> Thanks in advance, this is for me so........... good and clear.
> Shall i ask another question, i want only to verify that "pixel depth" in an image is related to the number of color levels for that image, not to the image resolution (image matrix nor spatial). Am I right?
> Thanks
---------------------------------------------------------------
You are correct. Pixel depth or bit depth refers to the intensity
resolution of the image, not the spatial (lateral) resolution.

Dear Sir
I think that there is no relation between pixel depth and image resolution, a binary image can have very high resolution when including very large no. of pixels, while each pivel can have only 1 bit "pixel depth" or 2 levels "2 colors" (black "0", white "1"). Am i right in this example?
Thanks in Advance