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originally posted by: silo13
a reply to: StallionDuck
I was uploading - you got me!
I'm not really sure this is going to work either as I have to drop the pixels so low to get it to load into ATS it ruins the pic quality... Ugh.
peace
originally posted by: silo13
a reply to: StallionDuck
Oh! Maybe you can answer something for me.
What do you save your pics size at?
I made a huge mistake a while back with a lot of my pics.
Now I'm saving at the smallest INCH size and LARGEST pixel size.
Is that what you'd advise?
Thanks - pm me if you'd like - I'd like to see your work on FB.
peace
First, begin with how much detail is there actually in the original. This amount of detail varies widely. A halftone screen for an old newspaper may result in less than 200 dpi actual. A modern lens on a quality black 7 white emulsion may be 2800 dpi.
In the old days, (the 1990s) when scanning became widely available, 300 dpi was a good starting point because many, many books and documents did not contain more detail than that, and even today, 300 dpi is a good starting point.
For example, at the Library of Congress we currently print our digital photographs using high quality pigment printers that may claim a resolution of 1200 or 2400 or much, much more. But those are microdots of different color merged to produce the variety of shades of gray or color. Usually the printer driver produces a finished resolution between 240 dpi and 360 dpi.
Second, we need to sort out the term “resolution.” Scanners and cameras contain pixels and “sample” the image at a “sampling rate” depending on the distance between the camera and the image. So when people talk about “resolution” using 300 ppi or 600 ppi or 3000 ppi they are actually using the “sampling rate” of the device. But few devices are 100% efficient.
Common scanners may be only 50% efficient; cameras may be 80 – 95% efficient. Thus the actual resolution achieved at 300 ppi may only be about 200 ppi – higher ppi rates are the result of image processing which may give the appearance of sharper lines but which does not produce additional detail. Many scanners will claim 1200 ppi and produce less than 600 ppi true optical resolution. Federal Agencies Digitization Guidelines Initiative standards (www.digitizationguidelines.gov...) are currently at 80% efficiency for a 2 star, 90% for a 3-star, and 95% for a 4-star outcome. Many of our projects for prints and photographs and rare books are 400 ppi at 3-star levels, although some are much higher.
Third, many people want to enlarge an image. We often try to scan film – particularly 35mm film – at a resolution necessary to provide a final print at 300 dpi. So if you want a common 4�� x 6�� print you need a true resolution of 1200 ppi. Specialized film scanners and high quality camera setups can achieve this. Commonly available consumer flatbed scanners cannot. (If you read the fine print specifications, they will often say something like “true 2400 ISO sampling rate” not ISO “resolution.”)
But once you reach the limits of the device resolution and the detail in the original, then additional enlargement doesn’t help. I think I have a couple of illustrations of this in my most recent blog article about enlargement (go.usa.gov...). I don’t believe you can magnify a newspaper image and find additional detail in a scan with a true resolution above 300 ppi.
Finally, Apple claims that human vision is only capable of resolving 326 ppi (search online for their “Retina display” marketing materials). There is a lot of quibbling about that number but most still claim not more than 450 ppi.
In the end, I doubt that you will see any significant improvement in an image of reflective materials beyond an ISO standard resolution of 400 ppi. I doubt you will find any improved image quality on consumer scanners above an ISO standard resolution beyond 1200 ppi unless you scan 35mm film in a specialized, high quality film scanner.
Two final notes. I believe the costs of higher resolution are vastly underestimated. Scan time will increase significantly with increased resolution. Transfer times increase, processing times increase. The expertise needed increases to get better quality. Storage and multiple backups increase. Consumer hard disk drives are not archival devices. Your children and grandchildren may not be able to retrieve images from a hard disk even 15 years from now. Increased image size means greatly increased cost.
And I believe 300 ppi / 400 ppi is future-proof. At least for reflective materials, I don’t believe we will see greater detail in a 1200ppi scan no matter how improved future equipment is.