I have been designing graphics for years. I have gone through a dozen printers. I have not found any difference in the printing of my 300 resolution images, and the 100 resolution, I changed the 300 resolution to. Changing from 300 resolution to 100 saves space and I find no difference in quality or size of printed image. Am I missing something?
I turned it into a vector image, printed it, and it turned out very nice.
If you're using real vectors than there's no need to talk about resolution. Resolution only applies to raster images (eg. jpg, tif, png, etc.)
Vectors will always print well at any size!
If your software asks you about resolution when you work in vectors, it's usually because you use some kind of effects or special filters. Then in this case, it's better to keep the resolution high when possible.
Changing from 300 resolution to 100 saves space and I find no difference in quality or size of printed image. Am I missing something?
If you do use a raster image, you might see a difference in quality if you lower the resolution; that's not always obvious on inkjet/home printers or digital printers though, but very important to keep it close to the 300ppi or higher when using commercial offset printing for example.
Maybe you don't notice any difference in the quality because of the type of printer you use but there's definitely a difference in size and the output quality when lowering the resolution.
One way to lower the file size of your images is to try other file formats instead of lowering the resolution. You can't go back once you lowered the resolution and you might regret lowering the resolution of your images one day!
You don't mention which software you use, but in the case of raster images, it's still better to save in high quality JPG or EPS with JPG preview than lowering the resolution, and the file size will be much smaller than a TIFF for example.
And as ErickP suggested, buying an extra external hard disk is a great idea! If you store all your images on your computer, you might get a bad surprise one day and you'll really hate yourself for not keeping a backup of all your artwork :/
I am not sure if this is an answer, and I am not sure there is a question or it is a self-reinforced afirmation.
In general terms, regarding the question "Am I missing something?" probably the answer could be "Yes, quality".
But quality is a very relative term. "Print" is a very broad topic, "designing graphics" is too.
I have not found any difference in print of my 300 resolution images, and the 100 resolution.
We can go 2 paths here. 1) If you are ok with the quality you provide in your specific projects using 100 ppi resolution go ahead. As the matter of fact I agree that in some "graphics" and "printed projects" it is an ok resolution.
2) But probably you are really asking what are you missing here.
300 ppi is a standarized file resolution for comercial prints on a coated paper using 150lpi output screens in sheeted lithographic or offset presses.
Do you see all the components needed? Coated paper, 150 lpi screen, sheeted paper offset press.
I agree that at naked eye depending on the design, viewing distance, size, details, fonts, etc. there is little diference using the 300ppi, 212ppi, 150ppi, but there is diference.
But all this 3 resolutions I mention are above the 150lpi barrier. 100ppi is below this barrier, meaning that you are repeaing info across diferent lines. I dont know why you do not see diference there.
Unfortunately at this moment I can't show you right now some samples that I made methodically.
Here is an explanation on how the ppi relate to the lpi. It is in spanish but the images are self explained. http://www.forosdelweb.com/f6/hablemos-resolucion-697586/index2.html
We do not know your design methodology
Probably you are using a low resolution image all the way, or printing in screen printing, or using a digital plotter, or designing for T shirts. Again, depending on your specific area of design a 100ppi resolution could be fine.
I agree with @janus Bahs Jacquet. Perhaps you are printing your images very small but in either case there is a clear "visual" difference. The other reason for the higher resolution, is for editing/retouching purposes. You really don't want to be retouching with a 100dpi image. In general the higher resolution gives you more flexibility. Also, in todays day and age with storage being so cheap, "saving space" shouldn't be an issue.