megapixels megapixels
03-28-2005 | 05:41 PM
#27
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RE: megapixels megapixels
I would echo the comments on more pixels being good, but for posting to the web, the larger sizes are a waste. After all you simplify the photo to get it to a reasonable size at 72 or 96 dpi on the monitor. Only so many pixels wil fit.
A large issue, and perhaps as important as having enough pixels, is what compression is used. I mention it here, since many lower-end cameras destroy the original digital image when it is compressed to .JPEG.
For those not familiar with the issue, most images are compressed to create a smaller output file. The generic unprocessed "raw" output has defects in it from the imperfect CCD sensor. Compression conveniently covers those problems up, at least to some extent. GIF (pronounced "jif") and .JPEG formats can really make your photos look bad. GIF has very coarse color gradients. JPEG can vary, depending on how much compression is used. Many cameras and software packages are set at one level, and you can't change it. The better ones can be set at anything from 10 to 100%. My own tests show that compression down to as much as 20% (80% compression) of the original is very useful for the web and monitor presentation. Some may be able to use .JPEG at the "maximum detail" (0%) option. This setting would look ordinary to the eye, and if no post-processing correction is to be used, is pretty safe. (Don't re-save again in .JPG, it will get worse!)
However, if your intent is to preserve the maximum detail, perhaps because you want to print it larger, or you are willing to zoom into the details, DON'T use .GIF or .JPEG (.JPG) compression. It will look blocky or fuzzy (depending on software) when you make it "bigger". Keep it in .TIFF (.TIF) format (licensed LZW compression possible) or .PNG if you must compress it at all. PNG is one of the very best "lossy" compression techniques.
PSD format for Photoshop is a special expanded format for processing. Usually the end product will be compressed (gently?) into one of the other formats for those who don't have software to read PSD.
Back to "raw" for a minute, this is not a universal format. Better to turn "raw" files to .TIFF if you want someone else to use them. Some vendors have a .RAW format, which is similar to "raw" but a bit more standard.
I need to learn more about PDF format for text, chart and image data. Whatdayagot? Any advantages there?
A large issue, and perhaps as important as having enough pixels, is what compression is used. I mention it here, since many lower-end cameras destroy the original digital image when it is compressed to .JPEG.
For those not familiar with the issue, most images are compressed to create a smaller output file. The generic unprocessed "raw" output has defects in it from the imperfect CCD sensor. Compression conveniently covers those problems up, at least to some extent. GIF (pronounced "jif") and .JPEG formats can really make your photos look bad. GIF has very coarse color gradients. JPEG can vary, depending on how much compression is used. Many cameras and software packages are set at one level, and you can't change it. The better ones can be set at anything from 10 to 100%. My own tests show that compression down to as much as 20% (80% compression) of the original is very useful for the web and monitor presentation. Some may be able to use .JPEG at the "maximum detail" (0%) option. This setting would look ordinary to the eye, and if no post-processing correction is to be used, is pretty safe. (Don't re-save again in .JPG, it will get worse!)
However, if your intent is to preserve the maximum detail, perhaps because you want to print it larger, or you are willing to zoom into the details, DON'T use .GIF or .JPEG (.JPG) compression. It will look blocky or fuzzy (depending on software) when you make it "bigger". Keep it in .TIFF (.TIF) format (licensed LZW compression possible) or .PNG if you must compress it at all. PNG is one of the very best "lossy" compression techniques.
PSD format for Photoshop is a special expanded format for processing. Usually the end product will be compressed (gently?) into one of the other formats for those who don't have software to read PSD.
Back to "raw" for a minute, this is not a universal format. Better to turn "raw" files to .TIFF if you want someone else to use them. Some vendors have a .RAW format, which is similar to "raw" but a bit more standard.
I need to learn more about PDF format for text, chart and image data. Whatdayagot? Any advantages there?
