Anthony Yan
@anthonyyan
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Hi Clay, Everyone,
More experiments with a CCD flatbed scanner (Epson V33). All of the images were scanned at 600dpi, and are un-edited except for being resized to 800 pixels for their long dimension. Using “adjust curves” one could have improved the contrast if needed. A clear transparency sheet was used to protect the glass platen.
Learn something every day: I was wrong about flat-bed scanners having absolutely no perspective effects! :ohmy: See below for details.
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First I scanned a bunch of knives at once, hoping to save time. Cardboard background didn’t work so well. Top to bottom, the knives are a Victorinox Pioneer Pruner (Silver), Spyderco Dragonfly Salt, Leatherman Wave, Kershaw Cryo, and a Spyderco Paramilitary 2 in M390.
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Next, I tried the same thing with white graph paper as the background. Pretty reasonable, very usable, although the Swiss Army Knife is a bit dark.
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At this point, I noticed something odd about the scan of the Blue Paramilitary 2: It is not a pure side view of the knife! You can actually see the top of the knife. So I tried scanning just Blue PM2 at several different positions in my scanner.I’m using my flatbed scanner in “landscape” layout, and the scanner head is a vertical line that moves from right to left.
First, bottom of the landscape. You can see the top of the knife.
Next, mid way between top and bottom of the landscape. Looks good! Pretty much a dead-on side view.
Top of the landscape. You can see the bottom of the knife.
That was pretty interesting, so I tried the same thing going from the right to the left of the landscape.
Right side of the landscape. Looks normal for the most part.
Mid way between left and right of the landscape. Looks normal.
Left side of the landscape. Looks normal.
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Conclusion:In landscape mode, my particular scanner (Epson V33), has perspective effects going from top to bottom, but no perspective effects going from left to right. Pretty interesting!
So I think the moral of the story is:
For flat bed scanners, place your knife in the middle of the platen.That being said, the distortion is probably too tiny to matter when we use a flatbed scanner. I suppose if you were absolutely crazy, you could scan a bunch of identical cubes (say 5mm per side) which were distributed over the entire platen, and then compare their images to measure the distortion. Personally, I’m too lazy to do that! So I’ll just scan in the middle of the platen.
If any of you test your scanner, let us know how it went.
Hi Clay, Everyone,
Hmm… I did an experiment, and made two photos of my Benchmade Griptillian. First, I used my tablet to take a photo as described above, but it didn’t come out very well. Then I tried my flatbed scanner, and the image was much better. Discussion below.
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Using my tablet, I took a photo. I used a carpenter’s level to make sure the desk was level with respect to the ground. Then I put the carpenter’s level on my tablet, to make sure the tablet was also level with respect to the ground. This would ensure that my tablet camera is pointed perpendicular to the plane of the knife. Unfortunately for me, my tablet’s camera isn’t very good. I’m not too happy with this image.
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Next, I tried my Epson V33 scanner (a low end flatbed scanner). This worked much better. I placed a clear transparency between my knife and the glass top to prevent scratching. I have heard that CCD flatbed scanners tend to have a larger depth of focus, so they are better for scanning shallow 3d objects (like leaves, feathers, and for us, knives). The other common type of flatbed scanner is CIS (if I remember right), and usually as a much shallower depth of focus, so I don’t know if it would scan knives well. But it is worth a try.
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One problem I should have anticipated, but did not: The knife edge is silver, and I used a paper white background. That makes the edge rather difficult to see when zoomed into the photo. Instead, we should use something with more contrast, maybe a black background or something.So I now recommend the following:
(1) Use a flatbed scanner. The image quality is much higher, plus there is no image distortion from the camera or 3d perspective (so long as the knife will lay flat and parallel to the scanning bed).
(2) With a flatbed scanner, keep the ruler in the image. But graph-paper is unnecessary. Instead, choose a background which has high contrast with the knife edge.
(3) Scan the entire knife, including the handle. This will help us understand and visualize the results.
(4) I think scanning at 600 dpi is optimal for small knives. That sounds really high, but suppose we want to accurately trace a 3-inch blade on a 1080p monitor. At 1080p, we have 1920 pixels across the monitor to cover three inches in real life. So that is (1920 pixels)/(3 inches) = 640 dpi. Here is the blade only at 600 dpi (right-click to download or open the full sized image in a new tab).
Here is a test scan with a darker background (just carboard).
Just remember, some modern steels are very hard. (ZDP-189 can be super hard at 65 HRC.) I don’t know if they are hard enough to scratch glass, but I say better safe than sorry.
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P.S. If you are curious about the CCD vs CIS difference in flatbed scanners:
https://en.wikipedia.org/wiki/Contact_image_sensor
