Thank you everyone. File size vs MP ? I never thought about these 2 being different. My goal is to send the Biggest file size to the Lab to get 16x20 or 20 x24 Photo. Need it to be the Best image i can send them . This might sound stupid BUT can you explain what the difference is between the 2 and which one I should use in jpg form to send to the lab for the Best possible prints. Thank you
First, work with
actual,
exact pixels of your capture. Not MP which isn't precise.
In LR, you can set up the info overlay to show you exactly the number of pixels based on the cropped (if cropped) image as seen below.
You want a 24-inch print. How many pixels can you divide into 24? You want anywhere from a low of 180 pixels per inch for that output. If you don't have enough for that minimum, you'll need to interpolate up which LR can do pretty well within limits. If you have 4320 pixels, you've got that minimum. And anything higher, great.
JPEG compression reduces image quality. IF the lab demands JPEG, well you'll have to do so but this is a good guide to LR's JPEG settings on export:
http://regex.info/blog/lightroom-goodies/jpeg-qualityAlso examine this excellent article on resolution and printing:
https://www.digitalphotopro.com/technique/photography-workflow/the-right-resolution/