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Do the math, as they say: 1080px spread over 1189mm is 23dpi.
Do the units, it's 23 ppi. dpi is a measure of output device resolution, not a property of an image. Here it would be the density of dots of ink. Which is highly dependent on the print process and independent of image data resolution.
This is what happens when you resample a 1920x1080 image to the resolution required to print the image 1189mm high at 300dpi
Are you saying you should or shouldn't resample?
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Are you saying you should or shouldn't resample?
What I say doesn't matter; as you suggest, there's going to be resampling in the print process anyway. I was just illustrating how much of an enlargement is involved, something which you can get away with in video (e.g. displaying HD on a 40" screen) because the eye is fooled by motion and fills in the blanks. On a still image, especially one already full of compression artefacts as a screen grab from a video stream will be, it's harder to get away with.
A0 is 1189mm high in portrait orientation. HD video is 1080 pixels high. Do the math, as they say: 1080px spread over 1189mm is 23dpi. Bear in mind also that a screen grab from video may be shite to varying degrees compared with a 1920x1080 still image, depending on how lossy the video codec is and exactly which frame you grab.
This is what happens when you resample a 1920x1080 image to the resolution required to print the image 1189mm high at 300dpi