TIF LZW compression and 24-bit PNG compression are both lossless. Lossless compression means we get exactly the same data back out of the file as we put into the file, as expected, no change whatsoever.Image Data Compression is of two types, lossless or lossy. However, image tonal values can be more forgiving in casual viewing, until it becomes excessive. Lossy compression cannot be used in like Quicken, Excel or Word or backup software, because we insist that every byte compressed come back out exactly as it went into the file. Lossy compression can make small changes in the data values. It must be uncompressed for use, but lossless compression comes back out exactly as it went in. Still, saving JPG as High Quality JPG is very adequate for viewing or printing, but the lossless files are much better ways to archive it.ĭata is often compressed to smaller size for storage in the file (very radically smaller for JPG). 24-bit PNG is lossless for photos, and TIF with LZW compression is lossless too, but neither is near as small as JPG, because JPG takes liberties with the data in order to be smaller. Expressing Image Size in bytes of File Size is useless to describe how the image might be used, because images get variably compressed smaller for storage.ĭata and File size is dimensioned in bytes, for example, 12 megabytes (but JPG is compressed smaller, not lossless).Ģ4-bit RGB photo data is always 3 bytes per pixel (when uncompressed for use). Image size is always dimensioned in pixels, for example 6000x4000 pixels, or 24 megapixels. If uncompressed, the data is three bytes per pixel. The larger it is, the better the image quality. But the smaller it is, the worse the image quality. The last '× 3' is for 3 bytes of RGB color information per pixel for 24-bit color (3 RGB values per pixel, which is one 8-bit byte for each RGB value, which totals 24-bit color).īut the compressed file will be smaller (maybe 10% of that size for JPG), selected by our choice for JPG Quality. The memory cost for the initial default 8x10 inch color image is:ģ000 x 2400 pixels x 3 = 21.6 million bytes = 20.6 megabytes. The printer or the print lab will simply discard the excess, but too many fewer pixels can seriously limit the resolution and sharpness of the printed copy.Ĭropping Aspect Ratio to fit the paper size is an important concern too.Īnd there is a larger dpi calculator that knows about scanning, printing, and enlargement. More pixels will work too (but slow to upload, essentially wasted effort). See a printing guideline for the resolution needed for several common purposes. It's generally about what our eye is capable of seeing, but varies with the media. More than 300 dpi really can't help photo prints, but less than 200 dpi can suffer less image quality. But planning image size to have sufficient pixels to be somewhere around 240 to 300 pixels per inch is a very good thing for printing, called 'photo quality'. But this dpi number does NOT need to be exact, 10% or 15% variation won't have great effect. Printing photos at 250 or 300 dpi is considered very desirable and optimum. Photos are preferably done on a photo quality printer and photo paper.įile size is shown at The Four Sizes of a Digital Image below

To do that, scan and print just have to be the same dpi number, but 300 dpi will be a great number for a high quality print. TIP: If you both scan and then print at the same dpi, it will print a copy at the same original size.Meaning, if you want to print 8×10 inches at 300 dpi, then you need 2400×3000 pixels. Printing: It also calculates the required image size (pixels) to print this image size (inches or mm) on paper at the dpi resolution.ģ000×2400 pixels printed at 300 dpi will print (3000 pixels / 300 dpi)×(2400 pixels / 300 dpi) = 10x8 inches on paper.The calculator shows that if you scan a 6×4 inch print at 100 dpi, it will create a 600×400 pixel image, and the monitor will show it at that same 600×400 pixel size. Video monitors: Video does not use dpi, but scanners do.Your scanner program probably shows you the same information. Scanning: It calculates the scanned output image size created if the area is scanned at the dpi resolution.This little calculator has these purposes: (or there's another fancier calculator)

Hi res image convert