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How to get quality digital scans for banknotes


Balaji Murthy
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I have a reasonably good sized collection of banknotes, and want to create digital images, but always find it hard to decide what method to use for getting the optimal image quality.

 

The online scans I see run the gamut from extremely high quality images (including showing the details of the watermark etc) even on small file sizes to rather uninspiring images with huge files and everything in between. For myself I have tried using our consumer quality scanner and have been less than happy with the size/quality ratio. The better quality images invariably get too big and the lower the resolution I use, I start losing the details that I want to capture.

 

So I wonder if those with good quality images use a scanner or rather use a digital camera to photograph the notes.

 

Are their best methods other members employ? I would keen to know of them.

 

Many thanks in advance.

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As for myself (assuming that you find my scans adequate) I scan everything at 300dpi and it seems to do the trick fairly well for images that I want to keep for my personal use.

 

But the size is then too large for posting, and I therefore resize everything down to fit more comfortably onto the screen. The amount of resizing depends on the size of the picture itself. I try to make the image fit comfortably onto the screen so that there is enough detail and also so that it doesn’t appear too large.

 

Once that’s done, I upload it to www.tinypic.com and use that link to post into the forum topic.

 

I suppose that you'll have to be the judge on wheter or not that process will suffice for your needs, but it works well for me.

 

Good luck!

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I use a scanner also at 300 dpi this creates rather large images. I resize the images to 1024x768 pixels for the web (Max dimensions, i keep the aspect ratio) this gives me fairly good results. Colors can vary greatly depending on what color you scan your notes on I used to use have a black piece of card to scan against I have since removed this in favor of a deep purple and this seems to give good colors (better scanner quality might overcome the need for this).

 

Depending on the software you use to resize your images your results will vary, paint and other free programs are very poor at keeping the quality. I use photo shop for one off image resizes and my development version of compass collectables does the resizeing for me for my web site images. I use JPEG at the highest quality setting this often gives a file around 160KB

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Like the above posters, I've found that scanning at 300dpi or better, and downsizing for web posting, is the only way to go. Scanning at 100dpi, or whatever lower resolution you indent for web posting, is going to leave you with all sorts of artifacts (moire, most obviously).

 

Dave

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I scan my banknotes at 300dpi. The resolution and size is good enough for me. I use photoshop to resize it for web posting and display in jpeg medium solution. This will enable it to display faster on the webpage. No point having a very high resolution when the loading them is long. You will put away many viewers who may be using a slow internet connection.

 

If I need to do closeups of certain areas on the banknote, I will scan at a higher resolution, maybe 500 to 600 dpi.

 

Most people will scan their banknotes with a piece of black background. This is to enhance your banknote image which makes it stand out against the black background. To further make your scan look sharper, you can use the feature "sharpen" in the photoshop. The feature does give you a clear sharp image but it also makes your image look flat and artificially sharp. It just does not look natural. If you like it, you can use it. I usually do not use this feature. It may be useful in some instances. Inside photoshop, you can play around with brightness and constrast features. There is one useful feature know as auto adjustment. It will work miracle for your note but sometimes, due to the quality of image, it will look funny with the automatic colouration. )

 

Experimentation is the key to better images.

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Wow! Looks like it is pretty unanimous. I will try 300 dpi. I especially appreciate the detailed comments by all.

 

One thing I had not tried was placing a black background. I have usually used a white background or just the note itself without any background directly on the scanner.

 

Thanks again.

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