Scanning Coins

This reply is going to presuppose you know certain things about file processing; it's stuff you need to know in order to maximize your results. Plain and simple. We can help with any areas which are unfamiliar for you.

I've found, with my particular Epson V100 scanner, that 600dpi is the best compromise between detail and file size. Above that, and I get a big ol' file with no real additional detail which I end up sizing down anyways.

Even at 600dpi - set for 24 bit color even if 32 is available, because with coins the additional detail isn't really relevant - the size of the file will still probably be too big to post even at Photobucket or the like. You're going to want to postprocess it in some software which allows you to save a .jpg at reduced quality, to make a same-size picture become a smaller file. Then again, you'll also want postprocessing to crop the excess white space anyways. I use the Gimp, which is freeware but not particularly intuitive for someone who isn't already familiar with graphics processing. There are other free softwares out there with lesser, but still sufficient, capabilities.

I'm not trying to scare you here, just telling you like it is. Successful manipulation of images requires a level of knowledge. No such thing as a free lunch.

Depending on the quality of the software which came with your scanner, it may be more or less easy; there's at least one poster here (Ralph) who achieves very nice scanned results without having to get all geek-like.

Excellent.

The dpi setting will be your "resolution;" I'll assume the number is strictly in dpi but you might want to check documentation in case it's some arbitrary thing on their part. Is it possible to do the "resize" function with the mouse? That'll let you easily crop the scan to the coin itself, which will reduce the starting filesize and make the whole process less intensive. Since you know the Gimp, do "Lighten/Darken" and "Color Adjustment" on Auto. Chances are the Gimp can handle that stuff better than the HP software if it comes to it. I'd stay with "Medium" sharpen as well.

Here's an experiment:

I've grabbed a Morgan and scanned it at 600dpi and 1200dpi. The images were scanned at Epson's equivalent of the settings I recommended for your software (I use Epson's software for image acquisition. For the fun of it, I also acquired a 1200dpi image thru the Windows Scanner and Camera Wizard. The 600dpi image was about 900 pixels in diameter, the 1200dpi ones about 1800 pixels, as you'd imagine.

I opened each raw image in the Gimp, cropped (my in-scanner crop was hasty) and sized them all to a similar 900 pixels, and saved them all at 80% Quality which is my normal compromise between detail and filesize when I'm planning on posting them online. No other postprocessing was done. The 1200dpi Epson scan was the largest at 270kb, the 600dpi next at 239kb and the Windows-acquired 1200dpi by far the smallest at 148kb. Strangely enough, the 600dpi Epson image was actually smaller in terms of kilobytes before the Gimp - only 172kb straight from the scanner.

I then threw them all onto Photobucket, where one can hold images of that pixel size, and am posting the results below.

600dpi:



1200dpi Epson:



1200dpi Windows:



Obviously, the Epson software is doing some processing of its' own. I like the results far better than the Windows result, although I think I've set the Sharpening too high. With my scanner - yours may differ - I actually like the resized 1200dpi image more; it seems maybe my best practice would be to stick with 1200dpi and downsize.

The purpose of this experiment was mostly just to obtain basic results you *ought* to be getting from your scanner in terms of size and quality. My Epson was a cheap $100 piece five years ago; yours should be at the very least, just as good and most probably much better. If you're not coming very close to these results at similar settings, we might need to explore things deeper.

1921-P VAM-3A3:

http://www.vamworld.com/1921-P+VAM-3A3

I got it for $20 off ebay recently, so you'll understand why if I seem all giggly.




Run the resolution up to 1200dpi or better when you're looking to get a closeup. What's happening is, you only get so many pixels of information at 600dpi, and when you blow it up, the same number of pixels have to fill a bigger area and it just blurs.

Too much dpi, though, and you exceed what the scanner's optics are actually capable of. A scanner can only "see" so many dots per inch. When it's "rated" for more than that, it's doing some software magic to interpolate where it thinks points should be between the ones it actually *can* see. In our case, scanning coins for detail, this will clearly manifest itself as reduced sharpness.

So, do some experimenting. Take a given coin with a known detail, and scan it at successively higher resolution. You will find the point at which your particular scanner drops off, when stuff starts to blur. Hopefully you can size the area it scans like I do, so you're scanning only the desired detail; a 2400dpi scan of a full Morgan is a monster file which even the Gimp is reluctant to open.

Here's a 2400dpi image of the important features of the coin I posted above. I can see I'm already losing optical detail, having reached and passed the physical limit of the scanner:

This is what I got from a 600 resolution scan.



What should I change in GIMP?

Sorry for all the posts. I am trying to show you exactly what I am doing. This might make a good step by step guide for someone one day.

Anyways, I now made my scan 900 pixels in diameter. But I am lost after that.



How do I get to the quality scans you have?

Give me one sec. I will try 1200dpi and a black background.

Your scanner is causing horizontal scan lines that devalue the photo. Sort of looks like the coin went through a Fax machine. Might need an alignment or may be the nature of the HP all in one.

When you color correct in Gimp it is emphasizing this defect in your scans.

I am new to scaning. My scanner is a HP 4580 printer scanner combo. The only scanning I have done is the printer alignment sheet. It really is amazing. I would appreciate any help on scanning some coins so I could send to friends on their Email. Thanks