We have a collection of 50,000 colour slides in our library. In order to scan these, we have bought an Epson V 800 Scanner with Silver Fast 800 software. What resolution and size should I be scanning these images for marketing through any picture library web sites?
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4\$\begingroup\$ Scan them at as high a resolution as possible. You can them scale them down if needed, but you want the highest quality to start with. \$\endgroup\$– Vogon JeltzFeb 17, 2016 at 12:49
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2\$\begingroup\$ @VogonJeltz Short answers as comments – please resist the urge. =) \$\endgroup\$– scottbb ♦Feb 17, 2016 at 15:40
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\$\begingroup\$ Should it be an actual answer then? @scottbb \$\endgroup\$– Vogon JeltzFeb 17, 2016 at 15:40
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\$\begingroup\$ Absolutely, why not? Doing so gives you, or the rest of the community, the opportunity to vote on the answer, as well as edit it to improve it. Comments can only be edited for a short period after being posted. Also, comments may eventually get deleted. \$\endgroup\$– scottbb ♦Feb 17, 2016 at 15:42
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\$\begingroup\$ @Vogon The comments area is for comments, and answers go in the answers area. You have to decide if your reply is a comment or an answer to the question. Length is not a deciding factor. Here's a hint - yours is an answer ;) \$\endgroup\$– osullicFeb 17, 2016 at 20:54
3 Answers
As big as you can! You can always make them smaller for distribution, but when you scan them, you want the highest possible resolution, you can't turn a low-res photo into a high resolution one !
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1\$\begingroup\$ One caveat -- your software (photoshop, GIMP) can interpolate better than your scanner so scan at the maximum physical resolution. \$\endgroup\$– Chris HFeb 18, 2016 at 14:28
As the other answer suggests, the largest and highest resolutions scan is clearly the best option.
However, just to add, the reason why scanners have the options for lower resolution scans is for the reasons listed below, and you have to weigh up what is the most appropriate option for you.
- Images being scanned will only ever be required as small jpeg images for the web.
- A lack of storage space
- Time allocated to scan the images. Smaller Resolution images will scan quicker
- Man power required to carry out the Job. 50,000 scans at maximum resolution can take a considerable amount of time and therefore, can require a dedicated person to carry out this job.
- Post processing – Larger scans can require higher processing power and larger buffers for editing and thus, can further slow down the workflow.
- Finally, exporting all these images to the required file sizes will also take time.
For these reasons, and possibly a few others, quite often, if the image will never be required to be used as an ultra high resolution image and time is of the essence, people choose lower resolution options.
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\$\begingroup\$ Point 5 particualrly applies to text, whether as a digital photocopy or for OCR -- don't forget that (even nice photo-quality) scanners are also used for non-photos. \$\endgroup\$– Chris HFeb 18, 2016 at 14:27
I completely disagree with larger is better. That is only true if you want to reproduce all the smallest grain on the film. However, this is usually a serious overkill.
If you want to preserve only important details, you should apply the Nyquist-Shannon sampling theorem. In this case: find out what the smallest detail you want to capture is, and that should be covered by a 2x2 pixel in scanning. This way you will have full reconstructibility of the image, without creating huge files.
If you increase a resolution above this, you are oversampling, which is not a bad thing, however, actual extra information is not captured. There is one exception: if your scanner has some jitter (e.g. it is sliding, it does not capture pixels equidistantly). This case somewhat increasing the resolution will capture more information, as interpolation will low-pass filter spatial jitter.