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My mom asked me to scan all her photos both for the reason of having a backup in case of fire and so she can have them digitally.

My scanner (Doxie) has the option of several different file formats and quality: it can scan from 100, 200, 300, 400, 500 or 600 dpi and I think the major formats I can chose from are png and jpeg.

Which settings do I chose and why? I'm mostly interested in the reasoning behind your choice.

The photos will be stored on an external hard drive and also uploaded to the cloud. For it to easily sync with her phone and tablet the photos will be uploaded to Picasa and/or Google+. But this is still up for grabs. What are your thoughts?

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Rushing ... Colour or monochrome? 200 or 300 dpi is enough for "archiving" except for exceptional images. Make reduced resolution copies for phone use. PC & tablet for "just viewing" also OK on say 1/4 res version. For pixel peeping use full version. Save at JPG no lower than JPG 90 (description varies with software - should be essentially impossible to see any change compared to JPG 100 / no compression mode when alternating screens). Save high and redcue allows retrospective decisions. –  Russell McMahon Jul 14 '12 at 20:55
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See this question my answer and others and Ctien's book ref. –  Russell McMahon Jul 14 '12 at 20:58
    
Nice link. It seems that 300 dpi is the way to go. What is your opinion about png or jpeg? Is jpeg recommended? –  Anders Jul 14 '12 at 21:23
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are you scanning the negatives or directly the photos themselves? in any case, be sure to remove as much dust/dirt as you can. Scanners can make it painfully obvious and removing it via software is time consuming, and not always easy. –  Francesco Jul 15 '12 at 8:52

3 Answers 3

up vote 7 down vote accepted

I would scan at the max of 600 dpi - however if the print resolution is so low that printing artifacts are visible at this resolution (e.g. small colored dots), then the result should either be downscaled or a median filter should be applied to eliminate them (or both). Don't go under 300 dpi no matter what or you won't be able to use them to reproduce new prints at 300 dpi later, which is the lowest dpi suitable for printing.

If you have access to the original negatives, consider scanning those instead using a high-resolution negative scanner (typically at least 1800 dpi) - they can be inverted and printed easily in software and you don't lose quality from the printing process.

In serious archival efforts, 16-bit TIFF is commonly used, and the image is scanned using a high-quality scanner along with a frame with color splotches for color calibration. In home applications, this is usually dramatic overkill. Although PNG preserves more detail and is not actually that big, high-quality JPEGs are visually indistinguishable (barring very close inspection), and are more compatible with photo-sharing websites and applications. Stick with 90% or higher quality JPEGs (your scanner may use a 0 to 10 or 1 to 10 or some other scale - just pick something close to max). It's important to ensure your scan isn't overexposed (or underexposed) because clipped data is irrecoverable.

Edit: One option to avoid the risk of clipping is to scan a 16-bit TIFF with no under- or overexposure as your "archive" copy, which will tend to look dark and low-contrast, and then edit in software to generate a high-contrast nice-looking JPEG for general use.

Finally, remember that you haven't archived something if it's sitting on one disk. A disk will inevitably fail. Either store the images somewhere online in their full original resolution, or put them on a second storage device (second disk, flash, CD, DVD, etc.), ideally in another geographic location in case of natural disaster. If it is stored offline, it should also be periodically refreshed (say every 6 months) by copying it to another device and then back (or to a new device) - otherwise the data will gradually become corrupt due to media degradation.

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I agree with the other answers: scan at the highest resolution. Downsampling to the desired size will always give you a better result than just scanning at the desired size.

Getting a good scan is never as easy as simply pressing the "scan" button. Taking the time to set black and white points will get you a much better scan. If your scanning software doesn't support that capability, look at something like Vuescan.

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  • If I cared about the photos I would scan in the highest resolution possible. Storage is fairly cheap and it’s a pity to lose information by scanning in lower resolution. Today it might seem overkill to scan in 600 dpi for display purposes, but then again five years ago I would not have believed I’d have a display with 2048×1536 resolution and 264 ppi.

  • The high resolution might produce uncomfortably big files for uploading, sharing and casual viewing. If that bothers you, you can always make lower-resolution copies for this. Or back to lower resolution altogether (I would not go under 300 dpi).

  • PNG is lossless, but the files would be huge. Saving as JPEG will discard some detail, but at high quality settings (say 95% up) the quality degradation is almost invisible, while the size savings are still big.

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