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Old 05-28-2021, 09:13 PM   #1
RandomTroll
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What is the minimum resolution to scan documents?


I used to use the scanners at the local U, but they're off-limits to civilians due to the coronavirus. Some have suggested that I use my 'smart'phone. I have an un-smartphone. Its 640x480 camera makes unreadable images. I also will soon need a bluetooth device to control an automated gate. Thus I want to buy a cheap 'smart'phone but not for making phone calls (remember those?) or browsing the Internet, just pictures and bluetooth. How low a resolution will allow me to scan my tax returns (for example) legibly? I won't get a SIM for it.
 
Old 05-28-2021, 09:24 PM   #2
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Based on my experience, for viewing on a computer, 300 dpi is the bare minimum. For printing, 600 dpi is the bare minimum.

If you have a decent digital camera, you might consider using it as an alternative.
 
Old 05-29-2021, 12:54 AM   #3
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I've never liked using my phone for such (unless in a pinch, and some with the pun,) but fortunately I'm surrounded by thrift stores, many of which have stacks of old scanners.

Phones do have some apps making it easy with (e.g:) autocrop to the page* you're scanning...

Searching: f-droid phone scanner

...may find a few?

Last edited by jamison20000e; 05-29-2021 at 12:55 AM.
 
Old 05-29-2021, 01:32 AM   #4
RandomTroll
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Quote:
Originally Posted by frankbell View Post
Based on my experience, for viewing on a computer, 300 dpi is the bare minimum. For printing, 600 dpi is the bare minimum.
Are cameras specified in dpi?

Quote:
Originally Posted by frankbell View Post
If you have a decent digital camera, you might consider using it as an alternative.
I have a Kodak Brownie.

Quote:
Originally Posted by jamison20000e View Post
I've never liked using my phone for such (unless in a pinch, and some with the pun,) but fortunately I'm surrounded by thrift stores, many of which have stacks of old scanners.
I don't want one around. Others have told me they have good luck using their phones. I have another use for the phone.
 
Old 05-29-2021, 04:14 AM   #5
ferrari
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I imagine any contemporary low-end smart phone would have cameras offering far better than 640x480 pixels. For example, even the Pixel 4A device offers a camera of 12.2MP. Free scanning apps for Android phones and iPhones are available to download, although I usually just use the Notes app for my iPhone when in this situation.
 
Old 05-29-2021, 07:33 AM   #6
boughtonp
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The resolution of cameras on any recent mobile device shouldn't be an issue, but I wouldn't buy one for use as a scanner.

A quick search shows there are portable scanners for around $50, which might be a preferable option.


Quote:
Originally Posted by RandomTroll View Post
Are cameras specified in dpi?
No, because cameras don't use dots or inches. They are generally specified in megapixels - which is the width multiplied by height.

(However, one 12MP camera is not necessarily the same as another 12MP camera - there are other factors involved in the quality of the image.)

Your camera produces 640x480 images = 307,200 pixels = 0.3 MP. Such an image can be printed at 300 pixels per inch, and it will occupy 2.1x1.6 inches.

To produce a legible image you just need enough pixels that the image can fill the page with the pixels being small enough to not be individually noticeable.

A photo of something 12 inches long turned into a 640px long image would produce approx 50 pixels per inch, which doesn't produce good text.


Last edited by boughtonp; 05-29-2021 at 07:41 AM.
 
Old 05-29-2021, 07:48 AM   #7
rtmistler
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I don't know if your thinking cheap, small, or both.

I bought a multifunction printer, scanner machine for about $170. Yes it's like the size of a small countertop microwave but it allows me to print and scan from my phone. Gets great resolution. It's in the corner on the floor, out of the way. Shooting for the lowest resolution just because you have so narrowly limited your options seems more work. Taking a photo also depends on you stability holding the camera, and aim.

The one I have is WiFi so it doesn't need a computer, just an outlet and a WiFi signal.

I honestly looked up scanners alone and they're still $150 and up.

Last edited by rtmistler; 05-29-2021 at 07:56 AM.
 
Old 05-29-2021, 09:23 AM   #8
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https://www.worldwildlife.org/initiatives/forests
HP Deskjet 3755 inkjet printer:
Quote:
boasts 'world's smallest all-in-one' design. Reclaim your cluttered workspace with the new HP Deskjet 3755 inkjet, a wireless all-in-one that can print, copy and scan from computers and mobile devices.Jun 1, 2016
but let's not go backwards.
Could take the ink cartridge out, reseal the ink port with tape and paper and use for years?

Last edited by jamison20000e; 05-29-2021 at 09:25 AM. Reason: clarification
 
Old 05-29-2021, 09:33 AM   #9
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Quote:
Originally Posted by rtmistler View Post
I don't know if your thinking cheap, small, or both.
I want cheap and portable. Multiple uses tipped me. A few times a year I want to take a photo, not often enough to buy a camera; a few times a year I want to scan a document, not often enough to put up with the clutter of a scanner; now I need a Bluetooth device that can run an Android app that I can carry in my pickup conveniently. A 'phone' (har!) can do all 3, enough uses to tip me to spending $20-$30 for a 'smart'phone. I guessed that the most-difficult task of those 3 is scanning a document. I see them as cheap as $15 on the Bay of e, with resolutions quoted in MP. I'd hate to buy one that didn't work well enough.
 
Old 05-29-2021, 10:27 AM   #10
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You can buy a brand new 20-some dollar smartphone anywhere nowadays, prepay comes to mind or a search?
 
Old 05-29-2021, 06:33 PM   #11
colorpurple21859
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for text 300 for pictures 300 to 600 depending on the picture.
 
Old 05-29-2021, 09:00 PM   #12
ferrari
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Quote:
Originally Posted by colorpurple21859 View Post
for text 300 for pictures 300 to 600 depending on the picture.
You're quoting DPI, but the OP wants to make sure that some candidate low-end mobile phone with a camera will satisfy his requirements. Of course he will need to maximise the quality by having the document of interest fill the frame for best results.

Here is one of many discussions around this...
https://www.ortery.com/what-is-dpi/

There is a chart which shows that a 6MP (3008x2000) camera will take a 10"x8" subject (=document) effectively at 300DPI (ie 3000 pixels over the 10" captured --->300DPI lengthwise, and about 250DPI widthwise). A ~12MP camera would be ideal for this purpose IMHO (assuming an actual scanner is out of the question). I mentioned that Notes can do this if using an iPhone. It allows one to select the captured area of interest which can then be saved or emailed etc.

For Android users, similar apps exist, but here's a way to do it with Google Drive...
https://support.google.com/drive/ans...DAndroid&hl=en

Last edited by ferrari; 05-29-2021 at 09:03 PM.
 
Old 05-30-2021, 12:52 AM   #13
RandomTroll
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Originally Posted by jamison20000e View Post
You can buy a brand new 20-some dollar smartphone anywhere nowadays
$30 is the cheapest I've found. I don't need new so am looking at used

Quote:
Originally Posted by ferrari View Post
I mentioned that Notes can do this if using an iPhone. It allows one to select the captured area of interest which can then be saved or emailed etc.
Thanks. Have you done this yourself?
 
Old 05-30-2021, 01:24 AM   #14
ferrari
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Quote:
Originally Posted by RandomTroll View Post
$30 is the cheapest I've found. I don't need new so am looking at used



Thanks. Have you done this yourself?
Yes, I have used my iPhone to capture a document when the need arose (as I mentioned in post #5).
 
Old 05-30-2021, 09:29 AM   #15
jamison20000e
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Simply look up document scanner or the like in an app store. Be free: https://www.pine64.org/pinephone/
 
  


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