Ideal size for postcards gallery scans?

This one is for the actual Postcrossing folks:

Is there an ideal size to make our postcard scans for the image gallery? Larger = better quality BUT also will take up more of your server space.


This is a great question.

To add, it may not be the physical size of an image that makes the file larger. The higher the dpi when scanning a photo, the larger the image file will be. I’ve found that 300 dpi keeps the file size small while still maintaining the integrity of the photo.

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I scan with 300 dpi and resize all scans to a width of 800 px (landscape) - for both the wall here on Postcrossing and for my external postcard gallery


I use my phone to snap pictures of the cards. I crop the image and resize the final picture to 1200 px on the larger side.

1200 px seemed to be a good cutoff for me between quality and size. I save them as jpeg with quality 10/12.

It depends on what you want to achieve.

Looking at my Postcrossing wall, Postcrossing seems to resize all postcard pictures to a width of 500 pixel. So you get the best result providing it that way, or in full multiples of 500 pixel width (1000, 2000). Only these can be converted without artifacts.

I usually scan in both 200 dpi (on most monitors this roughly equals the actual size of the item) and in 600 dpi for the Colnect postcard catalog. The reason I use 600 dpi for the catalog is that most postcards (as well as other printed items) are printed in 300 dpi resolution. By doubling the resolution, the individual printing matrix dots are visible, which can be helpful to distinguish between several printings of an item.

If you want to show the full detail of a postcard, scan them in 300 dpi, because that is most likely the printing resolution.

If you want a specific picture size (e.g. 800 pixels wide), it is best to directly scan in the desired size than to resize afterwards - resizing (except for whole multiples of 2, e.g. 2x, 4x, 8x, half, quarter, eighth) always creates artifacts in the resulting image, though how visible they are depends on the quality of the resize algorithm. Expect low-quality (and fast) algorithms on servers that force an automatic resize (like Postcrossing), so you’re better off by resizing yourself with a decent (and slower) algorithm before uploading pictures to such servers.


Perhaps I should clarify… I know aaaaaaall about HOW to resize/scan stuff, I just want to know what the PC site-mods prefer. I know of quite a few forums who specifically want a certain size photo/scan or smaller so as not to clog up their storage.

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As I have written above, looking at my own Postcrossing gallery, all images are 500 pixel wide on their longer side (be it vertical or horizontal), with the other side being different from picture to picture. As I upload my 600-dpi-scans (around 3,500 x 2,500 pixel), it is clear that the Postcrossing server resizes all uploaded image to a maximum length of 500 pixel. So that is obviously the preferred size for Postcrossing. If you want an answer from the Postcrossing team, it may be easiest to contact the Postcrossing support.

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