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Pixel Size for Uploads
Old 03-04-2005, 12:46 AM   #1 (permalink)
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First off, I hope im placing this in the right section. Please move if needed. Im confused when it says files should be 600 pixels on the long side. Is this related to the file size? I want to post fles and at the same time follow the rules of the site, but a little confused how to tell what size the file is and how to change it. Example: I place a negative or print on the scanner, select the area i want to scan, it says that it is around 1.2 meg. When i save it as a jpeg, it is 226 kb. does that mean my photo is 226 pixels? Keep in mind while reading this, im not the most computer savvy person around. Oh, another question. I can scan in true color - (16 million colors), 256 optomized pallet and 256 color web pallet. I have read a few things saying i need to be using jpeg files. I have a problem in that i can only save as a jpeg using 16 million colors. the web pallet only give me the option of using bmp, tif, gif, pcx, png, pdf, htm, and rtf files. Should i use the web pallet and save in a diff format? If so, any recommendations on what format i should save the file as? I did a test scan using the tif file and web pallet but the file is real grainy not sure if that is just the colors or the way it was saved. Any help with this is greatly appreciated.
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Re: Pixel Size for Uploads
Old 03-04-2005, 01:08 AM   #2 (permalink)
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Basically pixels are a relative measure of height. For GG, it is best to keep the height of the photo at no greater than 550 pixels high and that way in almost all browsers on 1024x768 or greater it will be fully visible with out scrolling. In Photo shop, do a File | Save for web and then use the Image Size adjustment tab to set the height to 550 and it will automatically resize the image and adjust the width appropriately. Then save it. The Save for Web will also set the right dpi (usually 72). By the way, save it as JPEG as that is the standard for the web.
Cheers,
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Re: Pixel Size for Uploads
Old 03-04-2005, 05:45 AM   #3 (permalink)
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Short for Picture Element, a pixel is a single point in a graphic image. Graphics monitors display pictures by dividing the display screen into thousands (or millions) of pixels, arranged in rows and columns. The pixels are so close together that they appear connected.
The number of bits used to represent each pixel determines how many colors or shades of gray can be displayed. For example, in 8-bit color mode, the color monitor uses 8 bits for each pixel, making it possible to display 2 to the 8th power (256) different colors or shades of gray.

On color monitors, each pixel is actually composed of three dots -- a red, a blue, and a green one. Ideally, the three dots should all converge at the same point, but all monitors have some convergence error that can make color pixels appear fuzzy.

The quality of a display system largely depends on its resolution, how many pixels it can display, and how many bits are used to represent each pixel. VGA systems display 640 by 480, or about 300,000 pixels. In contrast, SVGA systems display 800 by 600, or 480,000 pixels. True Color systems use 24 bits per pixel, allowing them to display more than 16 million different colors


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I cheated I looked it up HEHE webopedia
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Re: Pixel Size for Uploads
Old 03-04-2005, 08:29 AM   #4 (permalink)
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Love that shot Marty!

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Re: Pixel Size for Uploads
Old 03-04-2005, 03:27 PM   #5 (permalink)
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The total number of pixels in an image has only a loose association with the file size. It's even looser when you're talking about a JPG file, since you can change the file size up or down, depending on how much compression you use. GG doesn't specify a file size limit (as some other sites do), but rather an image size limit, which is expressed as maximum pixels on the longest side.

Yes, you should scan in "true color," or 16 million colors, and save the file as a JPG. (Don't use TIF or BMP, since they will product HUGE files because they don't use any compression. Don't use GIF because it is mainly for spot colors in graphics, not the continuous range of colors in a photo. Don't use the others because I say so. [img]/ubbthreads/images/graemlins/smile.gif[/img] )

If there is a way for you to set your scan size to a certain number of pixels, that's ideal. Simply select the area to scan, lock the proportions (also known as "constrain proportions" or "preserve aspect ratio"), then change the largest dimension to 600 pixels and allow the other dimension to change accordingly. In this case, it doesn't matter what dpi you set, but you can use 72 if you must set something.

If you cannot set the scan size to a specific number of pixels, you're going to have to break out the calculator. In this case, you can change only the dpi, so we're going to have to calculate the dpi needed to produce a 600 pixel image. Take the longest dimension, expressed in pixels, and divide it by 600. Stick the result in memory. Take the default number of dpi showing and divide it by the result in memory. Round to the nearest whole number and enter that number as the dpi for the scan. Example: Let's say you're scanning a photo, and the part you want to include is 1168 x 2186 pixels at 300 dpi. We need to make the 2186 pixel side 600 pixels, so we divide 2186 by 600, to yield 3.6433333. Stick that in memory. Next, divide 300 (the original dpi) by the 3.6433333 in memory, and you get 82.34+. Change the 300 dpi to 82 dpi, and your scan will come out at 600 pixels on the longest side. (Why it works, if you care: The longest side is 2186/300 = 7.2866667 inches long. 7.2866667 inches x 82 dots per inch = 597.5 total dots, or pixels.)

Once you get a 600x??? pixel image, save it as a JPG file, using about a 7 or 8 quality (also called "high quality"), and make sure it has the ".jpg" ending on the file name. Hope this helps. --Randy
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Re: Pixel Size for Uploads
Old 03-04-2005, 05:19 PM   #6 (permalink)
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It doesnt look like i can set the pixel when scanning, only the resolution and the output width and height which does seem to make necessary changes - i change height, it updates the width ect. I can set the resolution from 75 to 2400 dpi. The default is 200. I am using an HP Scanjet 5470c with HP precisionscan pro software which was the software that came with the scanner.

I did find the save to web part in photoshop. Im still learning that as i havent had it very long. Using photoshop cs. will be looking at the post production forum to learn more about using PS. Appreciate all the help on this subject.

I have a lot better understanding of what pixel and resolution is after reading all the posts here. thanks again.
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