Forum Moderators: not2easy
I have had 35m film photographs scanned and burnt to CD at two dpi sizes. The jpeg files are med resolution around 700Kbs each and scanned once at 400 dpi and again at 72 dpi.
Opening these jpeg files up in Photoshop revealed the very poor quality of the 72 dpi files, which makes sense as they only have 72 dots per inch. And no matter how I try to correct the colour, the jpeg files all look washed out. Even in print, the photographs were severely over exposed.
But scanned at 400 dpi the files look perfect as if you are standing in the landscape yourself. Set as computer wallpaper (250kbs) the photographs also looked like high-grade quality prints. I am using Professional NPH film, which gives even better colour for the computer wallpaper than off the shelf Fuji film.
But what I am not sure about is monitor dpi resolution. I have read on photographic forums that anything over, I think 96 dpi, can’t be seen on a monitor. So why do scanned negatives at 400 dpi look so much better than 72 dpi on a computer screen? All I have read about 72 dpi has me confused or is that because I live downunder?
Rod
While it is true that your monitor (on average, depending on the resolution) will not be able to identify anything over about 96dpi, photos scanned in at 72 dpi are of a lower quality. Think about what 72 dpi means. You only have 72 dots in that inch of which to change each pixles hue, saturation, sharpness, etc. Even if the resolution is not visible, the control that a higher dpi gives you automatically creates a higher quality. To the naked eye however, the quality difference would be virtually invisible between 300 and 400 dpi. Hence the print industry standard of 300dpi if the press will be printing a 141 lpi screen. A lot of print shops accept 150 dpi. The quality difference between 150 and 300 is somewhat noticable, yet some feel it's a trivial sacrifice for faster print-time and smaller files. Needless to say, while you won't be able to see the resolution of a 400 dpi photo, you sure as heck will be able to see the quality on-screen, but you shouldn't need anything more than 300 dpi. Now remember that we're talking about scans here. If we were talking about a digital picture taken out of a camera, that would be a whole new discusion, being the photo is only 72 dpi, but the image size itself starts at a large size. Most of the times like 27"X41" or larger. This would give you a total of 5,738,688 pixles to work with. So even though there is only 72 dpi, the surface area contains more pixles than a 4X6 print of 72 dpi, which has only 124,416 pixles total.. So if you scanned your 4X6 in at 72 dpi, you end up with just over a hundered thousand pixels to contrast eachother and make the image a whole.
Sorry if you didn't get that, kind-of hard for me to explain, as I just got here at 4 a.m. and I am still waking up. I know what I am trying to say... lol I hope this helps :0)
-- Zak
Monitor is 1024 x 768 then picture should be greater than or equal to 1024 x 768
Monitor is 800 x 600 then picture should be greater than or equal to 800 x 600
If you are scanning a poster, you may only need to scan at 30 dpi to end up with this number of pixels or if you are scanning a postage stamp, you may need 400-600 dpi to end with this number of pixels.
When you exceed the width and/or height the computer will either stretch or scale the picture to fit based on the users settings.
Rod
