DAZ Studio can render to the active viewport, to a separate screen, or to a separate file written to your hard drive. You can control all these options plus the size of the final render in RENDER OPTIONS.
To do this, go to RENDER --> Render Options in DAZ Studio. In the menu, you can see the choices for changing the size of the render and where the render is saved.
Look in the box labeled 'Dimensions.' The drop-down is labeled 'Presets.' You can choose 'Active Viewport,' 'Custom,' or one of over a dozen preset ratios.
'Active Viewport' Your render ratio and dimensions will be exactly what you have available in your current view port. This can be nice for a render of a work in progress. There is no frame in the view port with this setting.
'Custom' The ratio and sizes can be whatever you like.
Other Presets are based upon other standards in the print, photography, and cinematography industries.
Pixel Dimensions, Aspect Ratio, Constrain Proportions
These control the height and width of the picture, the proportions, and whether or not you want the Pixel dimensions locked to the chosen 'Aspect Ratio.'
Use this to toggle between a still picture or an animation. For this article, only a still picture is considered.
There are three choices here: Active View port, New Window, and Image File. If your desired render size is larger than what's available in the 'Active View Port' (for example, if your rendered size will be more pixels in width or heighth than your screen size), you should New Window or better yet, Image File. If you want to save a render to your 'Active View Port,' then go to FILE --> Save Last Render. Choose the name and location for your render.
If you choose 'Image File,' you will need to give a name and location to the rendered picture before you render it.
Be aware that the larger the dimensions of a picture, the longer the render will be. Also keep in mind that the 'thumbnail' for your scene is usually 91 x 91 pixels. This is not the render for your scene. It's just a thumbnail to help you keep track of it.
Final note on DPI
Keep in mind that picture for print should usually be rendered at 300 dpi, that is 300 dots (or pixels) per inch. DAZ Studio does not have a way of doing dpi, but with a little simple arithmetic, you can figure it out. If you want a print picture of 8 1/2 by 11 at 300 dpi, then you know your picture should be 2,550 pixels by 3,300 pixels. You may need to change the set dpi in another application like GIMP or Photoshop, so your printer doesn't think it's printing at 72 dpi and fill up several pages.