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The Question(s)

I need to know how to do my own research when evaluating various overhead scanners against each other at various prices and evaluating various cameras against each other at various prices. I also need to understand how to evaluate an overhead scanner versus a camera (i.e. on a tripod, facing downward).

For illustration purposes only, I will give an example to clarify what I am referring to by overhead scanner: see this link.

By the term evaluate, I mean that I need to know what technical specifications to look for, in the cameras, and in the overhead scanners, and how they will affect the quality of the output. This information will help me to avoid (for example) having to make an Amazon purchase, see that the quality is insufficient, and then return the item.

If needed, I plan on telephoning the technical support of the manufacturer of the overhead scanner or camera, to ask about the technical specifications.

The remainder of this posting describes the purpose of my upcoming purchase (of either an overhead scanner or a [camera + tripod]), and the research that I have done so far.

As described in the scanner research section below, all I know about overhead scanners, is the vague idea that the more megapixels the better.

For cameras, I have the vague idea that it is partly about specifying the parameters correctly, and (perhaps) partly about using more expensive lenses.

As (also) discussed below, since I will necessarily be scaling the images to fit them into pdf pages, considerations may become tricky/problematic.


My Purpose

When I self-study a Math textbook, I keep my problem solutions in a pdf file that I do not print out. I also keep a separate pdf file that summarizes the chapter. This summary file includes my clarifications, my list of theorems or worked examples, the occasional diagram from the book, and the back-of-the-chapter pages of exercises, for reference.

All of the pages that I photograph or scan will go in the chapter summary pdf file, which I will print to paper.

Unfortunately, since the images will have to be framed in the page, I will probably have to scale the images, which will necessarily degrade the quality of the image.

My old camera has a mechanical on-off switch that often malfunctions. However, I will almost never be needing photographs or scans for anything other than the above Math documentation. If I can accomplish my Math goals via an overhead scanner, then I can keep the old camera for the once-every-5-years photograph that I may need to take.

Also, I subscribe to the Games World of Puzzles magazine, and I like to work the puzzles without actually writing in the magazine itself. Instead, I like to scan the page, save the image to my PC, and then print out the page image when I feel like attacking that particular puzzle.

For magazines and Math books combined, I expect to photograph or scan about 5-10 pages per week.


My research on Cameras

I recently posted a question concerning compensating for low light conditions. See this link.

Following up on suggestions from that posting, I experimented with my old Kodak EasyShare P712. I repositioned the four 60 watt lamps, set the iso to 100, the aperture to F8.0, and the shutter to 1/100 second. There was noticeable improvement. However, even though only I will be seeing the notebook, the images still are too fuzzy/grainy.

The P712 specifically instructs me to press the shutter half-way down, wait for the green light to indicate good focus and exposure, and then press the shutter all the way down. I did this, from about 18 inches away.

As juhist mentioned in the previous posting, I suspect that the problem is the camera itself. Beyond that, the (old) camera's malfunctioning on-off switch compels me to make a new purchase, anyway.

I also found this article on How could I get scanner-like images with a camera. The article is fairly old, so I suspect that the overhead scanner versus camera comparison is no longer valid. The article suggests that when using a camera, it is simply a matter of experimenting with the right parameters.


My research on Overhead Scanners

I purchased, experimented with, and then returned an 8mp $99 overhead scanner. The pictures were simply too grainy. I did not attempt to position the lamps around the overhead scanner. However, if need be, I can certainly do that each time.

Then, I experimented with my 7 year old brothers MFC-L2700DW (flatbed) printer/scanner/copier. I cut out a magazine page, manually placed it on the scanning bed, closed the scanning lid, and then chose the copy option on the printer. The printer created a reasonably clear crisp copy.

Then, keeping the magazine page in place, I ran 6 scans against the page. I varied the dpi to 300, 600, and 1200, and the output format to both jpeg and png. I then used an old software (paintshop pro) to fit the image to the page, and then print out the page.

All (6) images were somewhat grainier than the original copy. This is probably entirely due to the scaling. Unfortunately, I will always have to be scaling my images.

Attempting to use my flatbed printer/copier/scanner is probably not a good idea. I imagine that the constant wear and tear on the springs and hinges connected to the cover of the flatbed will make them erode. Beyond that, using a flatbed against a book is problematic.

In examining various overhead scanners, I noticed that the key difference between a $100 and $300 scanner is that 8mp goes to 20mp. I question whether this will help, since I will (still) have to scale the image to frame the image in the pdf page. The situation seems curious and suggests that overhead scanners are not generally used for book copying. Obviously, I am speculating here.

At 300 dpi, the magazine page has a canvas size of 2480 x 3437. If my understanding is correct, this roughly equates to 8.5 mp (megapixels).

I wonder if there are any other properties of an overhead scanner that I should be looking for, in addition to the stated number of megapixels.


In Conclusion

Each of the Youtube videos on the topic have employed a camera, rather than an overhead scanner. This is leaving me with the impression that it will be hard to escape the truism that you get what you pay for. I do wonder, however, what the effect will be, with a modern camera, when the images are (still) subjected to the necessary scaling.

Note that attempting to present each of the images in landscape mode will be awkward, because my chapter summary pdf file will be presenting all of the (pdflatex) Math in portrait mode.

For what it's worth, I am somewhat mis-using the equipment-recommendation tag. That is, I am not asking about hardware versus budget considerations. I can evaluate that myself. I am asking which hardware specifications that I should be looking for, for my specific goal.

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You are probably overthinking it.

A 8.5×11" sheet of paper, at 300dpi is (8.5×300)×(11×300)=8.415Mpix. But most documents I see scanned in professional life (contracts, etc...) and meant to be mostly viewed on screen) are scanned at 150DPI.

So definition-wise any decent camera will do, you problem being to find the proper lens and shooting distance to frame your documents.

Scaling down (reducing the size in pixels) should not significantly degrade the quality with current algorithms if done properly. Yes a 600DPI print can look better than a 300DPI one but you need to look very close, and this is true for printed text no for images. Of course if you pixel-peep the 300DPI one looks more grainy, but in real use you are not going to look it up that close. There is also the question of the output file size, and how much quality loss is acceptable.

At 10 images a day, you aren't going to have significant wear of anything (hinges of flatbed scanner, shutter of camera...).

Things to look for for both camera and overhead scanner:

  • distortion: do rectangles remain rectangles? This is the quality of the optics. Note that flatbed scanners also distort, but in a different way.
  • color aberrations if you scan color documents (and color is important to you).
  • Depth of field: if you scan a book, the page will likely not be flat, so can you keep everything sufficiently in focus?

This said, if you need half an hour of set up before you can make you ten images (take out tripod and camera, set up, add lighting, make a few test shots), you will not do it in the long run. The best solution is the one which is practical.

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  • I was scaling the image after the file was created, and saved to the hard disk. Thanks for the response! You have clarified a couple of things that I was wondering about. I wondered whether a camera could produce a clear image if you set the parameters so that the relevant portion of the picture did not need to be scaled post-image-file-creation. I was also wondering whether the result would be different. From the evidence, and your response, it looks like I need to avoid post-image-file-creation scaling. ...see next comment Jul 2 at 8:28
  • Now, the question is pending whether overhead scanners can also be similarly set. Unknown how much flexibility will be available with (for example) a 20mp overhead scanner, other than adjusting the height of the scanner (i.e. distance to page). Also, I will be taking 5-10 pictures per week, not per day. Jul 2 at 8:30
  • Also, I haven't succeeded in getting any good picture of a book on my flatbed printer/copier/scanner. I simply can't flatten the pages well, depending on whetherI am in the middle of the book or near the beginning or end of the book. Also, I have to disagree with you about wear and tear on the hinges/springs of my 7 year old printer. I suspect that if I open the flat bed once a day, that after about 1 year, either the springs or the hinges will be shot. On the other hand, using the printer as is, I expect it to last another 5 years. Jul 2 at 8:36
  • As for things to look for: I need some way of flattening the pertinent page as I am shooting the picture. I am considering a remote trigger which I could hold as I was using my hands to position the book to flatten the page. As for the possible distortion or color aberration, those are symptoms. I need to know what technical specifications to require from the hardware so that these symptoms are avoided. Jul 2 at 8:44

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