How does scaled resolution work? Please help!

The screen is always 2880X1800 its the scaling that changes to make it "look" like 1680x1050 / 1920x1200
Every resolution is rendered double so 1440x900 is what "best for retina" looks like which is 2880x1800.

 

So Interested

I so want one of these bad boys but I wonder if you can set the resolution to its native 5120x2880 rather than use a scaled resolution.

 

You can set it to the native resolution using SwitchResX I think but everything will look miniscule...

 

Oh I understand the ramifications of it going to be miniscule but if I am paying for 5K I want 5K not upscaled resolutions. Besides, from what I have been reading it seems like the system gets taxed more by scaling.
I admittedly don't fully understand "retina" - I do understand PPI, native resolutions, and upscaling.
On my Surface Pro 3 I have changed the scaling to 100% so its truly running at its native resolution.
I of course could be completely mistaken (because of my lack of understanding) that the screen is 5K native but my menus are scaled.
*sigh* We only have one Apple store here in Winnipeg and I hate going to that mall at any time...perhaps I need to go down and play with it.
I have decided on the i7 and only 8GB (will buy my own upgrade) but still undecided about the GPU. I do not game, and only use this for my photo and video editing. Yes I edit 4K. Taxes in here will get me close to $4K CDN

 

You're right that the system works slightly harder with the scaled resolutions but as long as you keep it on "best for display" (aka 2560x1440), it works pretty well. Any app that isn't updated to support the retina display and it simply pixel doubles everything (like how the iphone works).

The screen is 5K native. The resolution scaling simply affects the size of text, windows, and all the other elements on the screen. As long as the application itself is updated for the retina display, images and videos should appear unscaled.

Interesting read about how it works: http://www.anandtech.com/show/6023/the-nextgen-macbook-pro-with-retina-display-review/6

 

Thanks for that link. So in a nutshell it IS a true 5K screen but scaled elements if you have scaling turned on and retina-aware applications (FCP/Aperture) - interesting.
On my Surface Pro 3 the screen res is ALWAYS 2160x1440 but with scaling on at default (I would gather this the same as "Best for Retina") its displayed resolution is 1440x960 (150%) and 1728x1152 (125%).