Slide scanning


TPF Noob!
Nov 16, 2007
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Can others edit my Photos
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I recently used Family Memories Video (they also go by the name Infinity Productions) in Sunnyvale, CA to scan slides into digital files. The results were not satisfactory. I would like to share what I learned from this experience. Any advise on where I should go for better scanning would be greatly appreciated.

Here is the problem. Family Memories Video advertises 4.7 Megapixel resolution on slides on their website. See . That works out to a 1800 dpi scan.

If the scanner outputs 8bits per pixel the file size of each slide should be 4.7 Mbytes. The actual files sizes I got from Family Memories varied from 100- 700 Kbytes. I suspect that the scanned images were processed with image compression.

When magnifying the images I can clearly see the 8x8 DCT image compression coding, confirming my suspicion. See the end of this message to links to example of full image, and zoom showing 8x8 compression blocks. In this example the scanned file is 297 Kbytes.

I spoke Ms Chordia, the president of the company, about this problem. I pointed out that compression losses some detail, that the images after compression were not true 4.7 megapixels, and that I could not use the images with compression. I suggested that possibly their scanner set to output compressed files.

I failed to get my point across to Ms Chordia. She insisted that the images were 4.7 megapixels. It was apparent that she did not understand technical points such as DCT coding artifacts, the fact that 4.7 Mpixels can not be squeezed into 297 Kbytes, etc. I offered to speak with one of her technical people. I am still waiting to be contacted by this person. In the meantime I think I have learned enough to be more careful with selecting a slide scanning service. I need to find a more capable service company, one that understands and is devoted to meeting professional needs.

I have posted the Slide61 example here…

A magnified view of the same slide, showing 8x8 DCT coding is here…… magnified.jpg

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