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I am desperately trying to save a psd file as a high res png.

I found some relevant setting when I click Save for Web in photoshop but then I got confused about size vs resolution. I found this explanation:

"Png -8 has less size and low resolution, on the other hand png-24 has more size with high resolution. But these two formats are of less size than normal png file."

I need to crank an image up to 300 px per inch but if I save as png-24 will that do the trick or reduce the size instead of increasing it?

Probably sounds like a silly question for those who know but help would be much appreciated. Thanks.

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    What will this image be used for? – JohnB Jul 31 '14 at 12:07
  • "Probably sounds like a silly question..." It's not a silly question if you don't know the answer ;) – SaturnsEye Jul 31 '14 at 13:43
  • If you are trying to save a hi-res png file at 300 dpi, why use the save for web option? I would just save it normally. The only time you would need 300 dpi is for print, where file size isn't typically a factor. Also, if you are using this for print, you should save as a tif anyway, because png does not support CMYK - the color mode used for print. – Manly Jul 31 '14 at 15:55
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PNG-8 means 8 bits, so 256 colors maximum. PNG-24 means 24 bits, so 16,7 million colors max. Resolution is not an inherent factor of any format, so saying a PNG-8 is "low resolution" does not make sense, it only has low number of colors. You/the image you're saving determine the resolution. It is true though that PNG-24 has a larger file size (i e in kilobytes/megabytes) than a PNG-8 which contains fewer colors.

The DPI setting is just a print setting, you probably don't need to worry about it. Only the number of pixels matter when your destination is digital.

  • Thanks for the answer. So if i want to increase the resolution of a png image for print design, can i just open it in photoshop and save it as png24? – Tina Jul 31 '14 at 12:35
  • Hi. No, hmm, it seems you need to first get a clear grip of the terminology and basic image technology. You can't increase the resolution per se, the image is what it is. Saving in PNG24 is not gonna change anything per se, either, it's just one way to save it. If you saved in PNG-8 it could_decrease_ the quality, but the other way around doesn't happen. You can't increase the inherent resolution of an image by saving it in any format. – Jan 'Saffi' Stekelgunsson Jul 31 '14 at 18:12
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"Resolution" is the amount if points in a pre-defined space.

For example an image saved at 1000x1000 pixels printed at 10x10 inched, would have a resolution of 100dpi.

when you are working with image files (PNG, BMP, JPG etc), they are saved to a pixel heigh and width, the "dpi" is arbitrary as it could be printed at any size.

When you work with PDF / PSD / AI files, you can set up as if you are printing a specific size and dpi, the program then makes that file an appropriate pixel size for the selected output (EG it will create a workspace of 1000 x 1000 pixels if you size it to 10x10" at 100dpi)

(Breathe)

The confusion May be: PNG 8 / 24 is purely a colour depth difference, however this COULD be referred to as "Colour Resolution" as png 24 contains 62,500x the colour information of a png8 file.

  • Thanks for all the help....as you might have guessed i am new to this and its great that i can pick your brains here...eternally grateful T – Tina Aug 1 '14 at 10:08

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