There are very significant differences between photo "scanning" and true line scanning. Photo scanning is convenient and sufficient for practical conversion to digital form, but not appropriate for archival work. This assumes we are comparing handheld phones versus a reasonable quality line scanner, and that we are using both with care and practice. The major differences are resolution and distortion. A high quality phone captures a letter-size original at roughly 350ppi. Most line scanners can capture at over 1200ppi. And that is technical resolution, not "effective" resolution. My minimum recommendation for my video work is 600dpi and I don't consider that archival. Phone camera lenses, while extraordinary for their size are vastly inferior to a flatbed scanner, with a wide variety of distortions and resolution deficits across their effective capture area. In simple terms, the center of your photo is much higher quality than the outer edges, and the resulting image is geometrically distorted. With processing and at "photo" sizes, much of this is hidden, but it's there. A flatbed captures a consistent image across its entire surface without any distortion (assuming the object is flat). As an original gets smaller, the difference becomes more significant, not less. While the effective resolution of the camera increases, the distortion introduced by the lens increases as you get closer. And then there's the focus problem. It is very difficult to properly focus a hand-held phone camera with precision. Scanners do not have this problem.
As you push outside flat-bed scanning boundries, this equation can change. Clearly flatbed scanners are not ideal for non-flat objects or items of significant size. In some cases a high-quality photographic image would be preferred. ideally you would use a "large format" camera with high quality lensing, not a phone. I would never recommend a phone camera for anything archival. The idea that a phone can capture a "high quality" image is a subjective fiction perpetrated by phone manufacturers. Sure, "high-quality" in a social media context, but there are very good reasons professionals spend many thousands of dollars on their cameras and lenses.
Of course, if you are simply creating a digital record that is not intended for "archival" preservation, then convenience may trump quality. And that's when phones shine. I am not anti-phone. I use mine constantly for a wide variety of purposes, including professional work, but not because it is equivalent to the proper tools.
Cheers,
tod
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Tod Hopkins
Technical Director
Hillmann & Carr Inc.
Washington DC
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Original Message:
Sent: 10-06-2022 09:15 AM
From: Rene Ballesteros
Subject: Phone Scanning Apps vs Flatbed Scanner
Hello all,
Phone cameras and scanning apps have improved by leaps and bounds. Do they suffice for document and photo scanning? We've pretty successfully used integrated OCR to transcribe text through a telephone based app.
I guess I'm asking for pros and cons of built in scanning features with Google, Microsoft, Adobe and shareware apps. Convenience is great, especially for uploading to a shared drive while doing research. However, a flatbed scanner can give you more reliable perspective versus a human held device. Wondering where the tradeoff point is and if anyone has insight on what future tech can do for digitization projects.
Many thanks,
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René Ballesteros
Community Engagement Officer
Museum of South Texas History
Edinburg, TX
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