How to tell the potential dimensions of an unlocked crop Lightroom image?

[Abipicantos]

Hi there, I have edited an image with an unlocked crop so it has unconventional dimensions. I am printing on large pieces of plastic in an industrial printer - the first time I have done this! How to I tell in advance what size to cut the material so I don't lose any of the image. I appreciate that it could be huge but is there a way to work out the length and height of the image in relation to each other?

 

[john.margetts]

If you know the PPI of the image, you divide that number into the pixel length of the image. 200ppi with 3000x2000 pixels gives a print of 15 inches by 10 inches. If you do not know the PPI, you cannot calculate the size of the print.

 

[sk66]

I appreciate that it could be huge but is there a way to work out the length and height of the image in relation to each other?

Yes, the pixel dimensions, just reduce them to the lowest common denominator. I.e. if it's 3000 x 3000 pixels it is a 3:3 (1:1) aspect ratio and will print to any size with that same ratio without loss of image.

PPI is an aspect of image quality. If you want the absolute max quality the printer can deliver then you want your PPI to match it's (actual) DPI... I have no idea what printer you are using, but the max printer resolution tends to be between 240 - 300 dpi. You divide the image pixels by the printer resolution to get the max print size at max resolution. I.e. your 3000 x 3000 ='s a 10" x 10" print at 300 DPI/PPI and 1:1 aspect.

But, much lower resolutions are usually acceptable (i.e. unless you have a high end monitor your computer screen is probably around 100 PPI, maybe even less). So if you are willing to sacrifice max resolution for larger print size you use the lower PPI number instead. I.e. your 3000 x 3000 ='s a 30" x 30" print at 100 PPI and 1:1 aspect (it will still be printed at 300 DPI if that's the printer's setting/capability).

The minimum PPI for acceptable quality is determined by the "normal" minimum viewing distance which is equal to 1.5x the diagonal of the print (some use 2x). To determine the minimum PPI divide 3438 by the minimum viewing distance (if the minimum is less or greater than "normal", use that distance instead).

 

[Deckard]

Not sure if I'm coming at your question from a different angle, are you saying you want to know the precise pixel dimensions of the image as it's an odd crop? If so, press "i" to cycle through view options in loupe view [pretty sure it works in develop too from memory] which will show the exposure data then the pixel information of the cropped image if you keep pressing it. Hope that helps.