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1. How are very large (for eg. 100000 X 100000 pixel) images represented?

JPEG's have a file size limit of 64k X 64k pixels. What is the standard format to save very large images?

2. How are very large (for eg. 100000 X 100000 pixel) images printed in very large sizes?

3. What's the usual resolution or printing (pixels/inch) for such large images? It would obviously depend on the scenario and use, but in general what's the resolution for printing very large images?

  • I don't know much about this. However I think they split one big image into smaller chunks and then combine them – Ruslan Jan 4 '18 at 21:45
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    Please ask one question at the time :) – Olivier Jan 13 '18 at 1:09
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This is from a design perspective, if it helps:

3) From a design perspective, the ‘normal’ resolution for printing is 300dpi (which equates to Apple’s “retina” resolution). At 300dpi, your image would print over 7m wide.

But we never print such large images at 300dpi. For banners and other large prints like exhibition walls, 150 or 75dpi is common, but it drops even lower for billboard sized stuff.

This is because no-one stands close enough to a 7m print to see the detail. There’s some things people can stand close to - pull-up banners and some wall coverings - but they won’t see the whole image up close. For a long exhibition wall with a lot of details along it, it’ll be designed and printed in sections.

For large prints, the image should preferably be printed blurred, not pixelated, so that pixels aren’t too obvious if you’re standing right next to it. But at the distance you’d usually stand to view it, the pixelation disappears.

In practice, it’s rare to print 300dpi images larger than 24”. (Though vectors are always printed 300dpi, because the pixilation on them looks much more obvious).

2) Large prints are broken into sections to print, typically dependant on printer width, but also handling, storage, transport, and mounting requirements. Eg Billboards are printed in strips like wallpaper. Wall coverings on rigid materials (e.g. dibond) are printed in typically no larger than 3x3m sections.

For large prints like this, you would expect to get a printing spec either from the printing company, or the company who makes or installs the wall covering/etc you’re printing.

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1) its a long time since I worked with gigapixel images, but the way they used to be stored was to tile them into squares (1024px at the time, IIRC - probably larger now). These would be saved as jpegs or tiffs.

There was also a lower-res “index” image for use when zoomed out.

Judging by how google maps works, I don’t think this has changed.

The issue isn’t so much how to store it, but that extremely large files are difficult to edit, and large image files require a lot of ram to work with, especially if they’re a compressed format.

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I do not particularly like this question because it is just hypothetical. The question could be asking for another random number and states no case scenario, but let's answer this so there is no misleading information.

What is the standard format to save very large images?

Very large images are not standard. They are experiments, they are technological challenges to prove a point, or to just explore some realm of technology or knowledge.

They are not one photo, they are composites.

JPEG's have a file size limit of 64k X 64k pixels

Let's explore the limit of 64,000 pixels.

  • You would need a 4096 Megapixel camera to take that photo. I only know cameras that can shot at 100-150 Megapixels, and those cameras are not cheap.

  • You need 33 FullHD monitors one next to the other to explore that image... to show only one row... You need 59 rows... or 1947 monitors (Yea, You could use 4K monitors but sounds less dramatic).

  • You would need a wall of 16m to paste an image of a good resolution of 100PPI... and you need 7 additional floors to paste the rest.


Sayed that...

Modules. This is clear from the start of my image. You do a compositing later.

For an art exhibition, you print whatever the printer is capable of printing. If the printer prints on a roll of paper of 90cm you use that, if it prints 1.5 m, you use that and composite later.

If you are displaying on a screen you use a zoom function.

If you are displaying again, in an international EXPO pavilion, you can split the signal, across different files and monitors.

What's the usual resolution or printing (pixels/inch) for such large images?

Again that is not usual, and again the image size does not matter. What matters is the viewing distance. The resolution is inverse to the viewing distances. For a distance of 60cm 150PPI, for 1.2 m away, 75PPI is good enough, regardless of the size of the photo.

The bigger the print, the further away you need to be to see it, so less resolution is needed...

A 24Mpx image can be viewed on your monitor close to your eyes, or a humongous billboard and still will look just fine.

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