If you resample a raster image you will loose image quality. You discard details you have for the image when you reduce the number of pixels you have for an image. If you increase the number of pixels you have to make up details you do not have for your image. Decreasing the number of pixels you have in a high quality print size document for use on the web works well. Increasing the number of pixels you have in a Web size image so you can print the image with small high resolution pixels does not work well if you greatly increase the number of pixels in a raster image. Only vector graphic images scale up and down in size well. The paths are generate via math and pixels are rendered to the Paths and the Areas they enclose.
Resolution is Pixel size. Displays have one size pixel they do not play the resolution game the have one resolution. Printers do play the game. You can print your X number of pixel wide by Y number pixels high image any size you want by changing the print pixels size. The Print DPI the pixels density the print resolution.
Set the print resolution around 180 to 190 DPI or change the height or width to the size you want and Photoshop will set the other side and dpi in the image size dialog with RESAMPLE NOT Checked.
Wow, if I could only understand those terms you use @JJMack!
So you're saying:
1/ What I have is a raster image
2/ If I can increase the size of each pixel I could print out a clear image at larger sizes
I usually work with vector images, not photographs. That's why I'm having trouble here.
The reason PDF is confusing is because PDF can contain both vector data (fonts, paths) and raster data (pixel images). How well a PDF scales depends on the quality of the contents:
I had Acrobat open the PDF you attached, and had Acrobat pop open the embedded images in Photoshop. This revealed several problems with the attached PDF:
The ideal way to do this:
Also — if you used Image Size in Photoshop to preview scaling it up, and it said it was still 300 ppi, that’s probably because the Resample option was turned on. When Resample is on, Image Size will maintain or increase the resolution by “making up” additional resolution from the existing pixels, but that never looks as good as having full resolution graphics in the first place. If you want to see how ppi is really changing as you scale it up to 5.5" x 7", turn off Resample.
Thank you for that awesome explanation @Conrad C . I understand an amazing amount more about this whole topic now. I can finally understand how to check resolution and how pdfs handle images and type. I can't even tell you how much I appreciate you for sharing this with me.
Conrad is a world-famous Photoshop expert, it might be worth you (and all of us!) having a look at his outstanding book ”Photoshop Classroom in a Book”.
Glad it helped. I should add one more thing…if you open a PDF in Photoshop and look at the ppi Resolution value in Image > Image Size, that won’t tell you anything about the resolution of the PDF, for two reasons:
(In case you’re curious about this part) Then how did I find the ppi values of the individual images in the PDF? I opened the PDF in Acrobat, clicked the Edit PDF button, selected an image, clicked Edit Using, and chose Photoshop. That opens the selected image in Photoshop, where I can check that image’s own ppi value in Image Size.