Originally posted by menessie Right, I gotcha, thanks. So by making the size larger would be if I checked resample and then it would make the pixels bigger too and go blocky. They don't have any specs on the site, so I'll just have to go back to them and ask but I was trying not to appear too dumb!! Even if I am dumb
Actually, when you have resample checked, what it does is "guess" at the pixels and add ADDITIONAL ones around each one to make it your new size. A pixel size is always a pixel.
By resampling, you're adding more pixels to the image, and since your image editing program doesn't really know what it's re-rendering, resampling up in size always results in a downgrading of quality, although 10%, even 20% up resizing can be acceptable. However, on your monitor, always view at 100% of image size to see the actual quality. It can look fine viewing at 50%, but once you view at 100%, you'll see the boxiness--and that boxiness will PRINT at any size. Downsize resampling is fine.
The whole business is complicated and not something you should concern yourself with too much just yet. The main thing is when someone asks you to supply a file, ask for their specs, and if it seems suspicious, ask here.
For example, your JPEG images are RGB, put printers (the machines) use CMYK inks. So what happens is depending on both the application the file is printed from (Photoshop, a layout program such as InDesign, etc.), and depending on the printer driver, this software makes the RGB to CMYK conversion for you. However, when I'm printing for myself directly from Photoshop, I always first convert my RGB images to CMYK, and save as a TIFF.
In a similar vein, let's say you have a 20" by 20" image at 72dpi, but I place it/use it in a layout program at only 5" by 5". Normally, I would go to PS and resize it to 5 by 5 without resampling, thus upping my resolution up to 288. Nowadays, most layout programs "fix" these kind of resolution problems on the fly, but it's nice to know the "right" way to prepare your files if they're going to be used for actual, real offset printing, and not just from your home printer.
Your home printer (the machine again) is capable of amazing things at lower resolutions because there's no screen involved, but once you go to an actual printing press, you need that resolution in there because of what the screen dots do to the final product when ink is put to paper.