Rescaling effective PPI on large scale graphics for printing

[Disco D]

Hey there,

I have a major printing issue. My photo is scaled approx. 600% to fit my art project. my printer informed me that the resolution of the photo used is not adequate for the size of my project. My effective ppi is around 52, while my actual ppi is 300.

To fix, I tried a few things:

I tried to alter the res through PS, manually changing the resolution to 1200 and then using that photo on my Indesign file. That only changed the ppi 20 points. And I also tried to use the auto resolution tool and that didn’t change anything either. I am currently stuck!

The artboard currently sitting at 90 x 120 Inches.

Any help given is really appreciated!

Thanks

[Derek Cross]

What are the dimensions in pixels of your original image.

[Disco D]

Hi Derek,

The original pixel dimensions are 4928x3280.

[Mike Witherell]

If you want to upsample a file in PS, go to Image > Image Size and make sure the Resample switch is ON. Then set the new rez and inches dimensions. With resample method set to Auto, you can synthetically drive up the resolution. It wont necessarily look better nor acceptable.

Large display graphics can often get away with 72ppi effective rez, but a lot of maybes are included in that, including viewing distance. I would rather see 100 ppi for large public-display graphics, at a minimum.

Better, of course, to have an original, higher-pixel-count file, but it appears you don't have that recourse!

[Disco D · Accepted solution]

Thanks so much, this worked! PPI is now at 129, while the actual PPI is 72. It seems a little reversed but hopefully, the printer will accept.

[Derek Cross]

That's really too low a resolution – you seem to have plenty of pixels in your original so why not resize it to say 300PPI.

[Test Screen Name]

You really can't magically fix this, just fudge it a bit. You NEED to consider effective resolution and work from that back to the original pixels needed. If they aren't adequate get a better picture. If one isn't available, change the design.

[Bill Silbert]

For large scale projects like the one that you describe 100 to 150 ppi is generally considered acceptable. That means that if you scale something up by 600% then your resolution at the size that you're working would need to be between 600 and 900 ppi. Upscaling the resolution in Photoshop from 300 ppi to 600 ppi will almost always create a pixelated mess which will look worse than just having art that is too low in resolution. Professional retouchers will many time be able to retouch art so that it is acceptable but that may not be something that you have access to. If that is the case then your only real option here is getting a higher resolution copy of the photo you're using. If it doesn't exist then you'll need to recreate or reshoot the image at a higher resolution.