Understanding scanning resolution

[Lol999]

Hope someone can clear this up for me:er: I've read the posted threads but am sometimes a bit thick:mrgreen: From my last thread it's obvious I need a new scanner. The pictures I posted up were scanned at 300dpi and as I understand it this is the maximum resolution the eye can differentiate.
So, let's say I scan a 7x5 inch print on a scanner that has a resolution of 1200 x 2400. I'm going to end up with a massive scan, probably bigger than A4. What value has this in terms of usability and the resolution beyond which the eye can apprecciate? I use Paintshop Pro 8 for my TWAIN interface and post scanning cropping etc. Any pointers?

Lol

 

[airgunr]

Ok, first off I'm no expert on this by any means....

That being said. This is how I understand it. If you are planning on printing out your pictures you should scan at a resolution of 300dpi. Any higher and you are really wasting data space. I would only scan higher if I planned on working on the file extensively before printing it.

If you are only planning on posting the picture on a web site or on a forum like this then the optimal scan rate is 72dpi. That will display just fine as this is the optimum resolution for computer monitors and also makes the files small enough for efficient transfer/display times.

I have a Nikon Coolscan (which I am still learning to use...) When I scan I first select the output size I want, say 8x10. Then I select the resolution/dpi, ex: 300dpi if I'm planning on printing it, 72dpi if I just want to post to the forum. Then I position the crop I want on the screen, it never is exactly the full negative size for some reason. From there I adjust the levels, curves, hue, saturation, contrast, etc. Then I scan the picture.

HTH

HTH

 

[markc]

There is no set number. At all depends on what your planned output size. There is no dpi to a digital file, only physical. A digital file will be in pixels, like 3000px X 9000px. At 100dpi, it will make a print 30" X 90". At 300dpi, 10" X 30". Same for scanning.

When scanning, I'd almost always pick the highest optical resolution of the scanner. That way I'd have a lot of options for what I could do with it. If I knew I was only going to use it for the web, I might go lower based on the pixel size I wanted, but usually would still scan high, do my manipulations, and then reduce it in PS.

Realistically, I know most people don't approach this the same way I do. I'd say for the average person, still pick the highest optical if you are planning on printing, but if for the web, pick the resolution that will give you the desired pixel X pixel size you are looking for.

This is a good primer: http://www.bobatkins.com/photography/digital/digital_image_resizing.html

 

[Lol999]

Thanks for the input fellas, the primer link looks pretty useful. Now, to save up for a decent scanner...........

 

[airgunr]

Mark,

Thanks for the followup and link. It certainly helps expand my knowlage as well. ;^D

 

[Don Simon]

Only slightly off-topic this; I'm about to have a bunch of prints made and want to scan them, and was wondering whether I should go for matt or glossy prints? When I've scanned, edited and printed them I'll probably print some onto glossy and some onto satin (which tbh I prefer), but I was wondering whether it makes any difference to the quality of the scan (i.e. how much detail is picked up, how much noise etc) if the original print is matt or glossy? Thanks in advance, oh and happy new year!

 

[Rob]

IMO glossy usually scans better as the matte effect reflects the light slightly differently and will show up as less sharp.

 

[markc]

Whichever you go with, you definitely want to stay away from any sort of surface texture. Like Rob, I've usually had better luck with glossy.

 

[Don Simon]

Great, thanks for the info there guys!