At what resolution and size should I scan colour slides?

Question

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?

Answer 1

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 !

Answer 2

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.

1. Images being scanned will only ever be required as small jpeg images for the web.
2. A lack of storage space
3. Time allocated to scan the images. Smaller Resolution images will scan quicker
4. 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.
5. Post processing – Larger scans can require higher processing power and larger buffers for editing and thus, can further slow down the workflow.
6. 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.

Answer 3

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.