I have my model setup in the viewport that it takes up all the space, the document is set at 4096x4096. I hit render, it renders. Then when i hit export document, the tif or psd that comes out is like so tiny compared to what i thought id be getting. The model is just a tiny thing in the center of the document, surrounded by blank space. I want the entire model to be rendered at the full size like i see it in the viewport at the full resolution of 4096. How do i do that? Thanks alot
You’re going to have to zoom out until you can see the whole canvas.
The easiest is to size your document to 800x800 or something similar. Draw your model on the canvas and position it the way you want it, then press M to place a marker. Now clear the canvas and resize it to 4096x4096. Finally, click the marker to activate it and redraw the model full size.
i have no clue how this whole marker business works. I drew the model at 800x600, making it the exact position and size, press M. Then clear the canvas, go to document resize to 4096. the document is now resized and its blank. I dont see any marker to click to recall my model or anything like that. Im lost at this point
Markers appear as a gray square on the canvas when you get close to them. When you’re directly over the marker, it turns to an arrow. Clicking on it will then redraw the object – but scaled correctly for the larger canvas.
There’s a Marker Radius setting in the Preferences that will allow you to make the gray dot appear when the mouse is at a greater distance. It’s very handy to crank that setting up after you’ve resized the canvas.
Also, keep in mind that unless you zoom out, the entire canvas will not be visible on the screen. Most of it will actually be off screen. The marker will be drawn at the geometric center of the model, which will normally be near the center of the canvas, but for some models you may need to pan across the canvas a bit before you’ll find the marker. Or zoom out some.
Maybe this will help with your understanding of your problem: The ZBrush canvas is not a 3D viewport like you seem to be used to from animation packages, where you frame your shot in the viewport and what’s visible in the viewport is what is rendered. Instead, ZBrush’s canvas is a lot like a Photoshop document. If you have a larger document than can be displayed on the screen, Photoshop (and ZBrush) will simply show what does fit. Everything else is hidden from view off the window’s edges, but that doesn’t mean that it’s not there. When you drew your object in the center of the canvas and filled the screen with it, you only filled the visible part of the canvas. That’s why your render had so much blank space around the object.
A simple answer would be to setup your document settings before you actually draw anything on the canvas.
For a weird reason, ZBrush doesn’t change the canvas size once there’s something on it.
I had the same problem as you - This simple trick solves it. 
Bye !
TVeyes has written a very handy plugin called Fit Doc in his Tiny Tools . Press the button and your document view is resized to show the whole document. This is really useful if you are working with large canvas sizes. Simply press the Fit Doc button and draw your model to fill the canvas.