Resolution Size when exporting

[ttitzer]

If I want to print a photo on a 16x20 canvas print, what would the ideal resolution size be when exporting from Lightroom CC? I have no idea how I should be sizing it. 

[Conrad_C]

The optimal resolution is typically between 240–360 ppi depending on the printer, ink, and substrate being used (in your case, canvas). If you're sending it out, see what the printing company recommends. If you're unable to find out, a safe number is 300 ppi.

[ttitzer]

I have it set to 300 ppi, but on the Image Sizing when I’m exporting I’m not sure what category I need to be using. The options are Width and Height, Dimensions, Long Edge, Short Edge, Megapixels and Percentage. I’m completely new to all this.

[Conrad_C]

First, is the image already cropped to 16x20 (4:5) proportions?

[ttitzer]

How would I check that?

[Conrad_C]

Select the Crop tool, and choose the 4 x 5 / 8 x 10 aspect ratio, since that matches 16 x 20. If the crop rectangle already fits the picture border exactly, it's good to go. If it doesn't fit, you need to decide how to crop it for 16 x 20, and apply that crop. In my example below, the picture is too long for 16 x 20, since my DSLR camera sensor is 3 x 2 aspect ratio, not 4 x 5. So I'd have to crop it to the 4 x 5 aspect ratio, to be consistent with the proportions of a 16 x 20 print.

Then you can go on to Export and set up the size and resolution there.

[GoldingD]

Printing on your printer or sending out to a service?

[Just Shoot Me]

A 16x20, (is that Inches? I take it to mean inches) inch print would require the image to be cropped in the 5:4 ratio (20 / 5 = 4  4 x 4 = 16) so if you used a PPI (that is Pixels Per Inch) of 300 your image would need to be 300 pixels x 16 = 4800 and 300 x 20 = 6000 for a grand totqal of 28 Million pixels, 28 MegaPixel or larger sensor.

If your image cropped to that 5:4 ratio does not have that many pixels available then you need to decrease the resolution to the point your image will file up that 16 x 20 inch piece of paper.

I've had very good prints at a 240 PPI setting. But that all depends on Viewing Distance.

[TheDigitalDog]

On a decent photo ink jet, you can easily get away with 180-200 pixels per inch. You don't absolutely have to have 300 PPI. So assuming 20 inches, if you can get say 4000 pixels, with good output sharpening (which LR can provide set to Print), you'll be just fine. 

[DdeGannes]

If you are saying you are going to export from Lightroom before printing I expect that you are sending the file to an external source to print. If so I would suggest that you proceed as follows.

a. Check with the printer as to the resolution of the image they require for their printing equipment. Check if they recommend a specific embedded profile e.g. RGB, Adobe RGB, ProPhoto RGB, or if they have a specific profile that they can supply.

b. If they do not supply any specific advice, I would do the following. Resize the exported image from lightroom using the following settings, Long Edge to 6000 pixels (20"x300). See the screen capture for additional info. I would expect Lightroom Classic would do a better job than the printer driver to resize the file to the required resolution for actual printing

[josephlavine]

A good starting point is to use 360 ppi for Epson printers and 300 ppi for Canon printers. This is based on their print head designs. However, this might not be possible, and although using a lower pixel per inch, based on print viewing distance you might not notice the lower quality.

[DdeGannes]

I agree Joseph, and if you are using Lightroom with the original image be it raw or say a tiff with additional edits done in PS and returned to LR. Lightroom will resize the image to the appropriate resolution for the printer you have attached so there is no need to export the file from Lightroom. In my earlier post I was specifically refering to creating a file to be sent to a printing service.