Resolution Questions

[ex_reven]

Sorry if the topic of ppi is a bit repetitive guys, but looking around through a few threads still didnt quite answer my questions.
This is extremely confusing for me

I know that a higher resolution means more pixels per square inch (or cm), and I know that you cant just get a 72ppi image and change it to 300ppi and expect it to look beautiful at large sizes...so heres my questions.

1) What is the resolution of an image before touching it in PS?
Say for example i take a photo with my Nikon D80 at 3800x2600 pixels.
I right click the file and "open in photoshop.
What resolution (in terms of ppi) is the image?

2) What would make this resolution change?
Say for example my camera's photos are in 300ppi resolution, i open that in photoshop and manipulate it a bit. When I open the "image size box" and I change it to 600ppi, why does my image lose size? Is it downsizing the image for optimal quality?

3) When do I need to resample?
Say Ive changed my 300ppi image to a 600ppi image and it reduces the size of the image. Is resampling done to increase the image back to its original dimensions?

4) My printer says that I should be printing at 600ppi, and I want to do this, but it lags my computer alot since the image is about 2 metres long by 1 metre high. If my image is that big do I need to have 600ppi resolution? Or can I get away with 300ppi in this case?

Thanks for taking the time to read and respond guys

 

[theKeeper]

Greetings ex_reven...

To answer all of your questions at the same time, just use 300ppi/dpi. You won't see any difference visually by going to 600. Save that resolution for much larger projects.

Just to be clear though... when going from 300 to 600, your image does not lose size. Its 'print' size remains the same while its pixel dimensions are increased. The reason for this increase should be obvious -- you asked PS to fit more pixels into an inch. Therefore it needs to increase the pixel dimensions in order to do that.

Also... all cameras are different in their default photo resolution. I'd have to think that by changing the photo quality, one's camera should also increase the print resolution to allow for the increase in quality.

Hope this all helps.