How do I export raw images? Do presets work?

Question

I am having trouble exporting full size images.  I have a custom "preset" but inspite of this a 25mb photo comes out at 6mb or less.  An ideas as to what I am missing?

Answer 1

TIFF will, but so will JPG with the right settings.  16-bit TIFF will retain more color information than 8-bit TIFF or JPG (which is limited to 8-bit).
An important and difficult point is that the DPI setting in the export preset has no effect on your image size or file size.  Image size is measured in pixels.  You most likely want to select "original size".  File size (in bytes) is determined by Image size (pixels), color-depth (a/k/a "bit depth"), and compression.  Compression is determined by the file format (JPG compresses unless set to highest quality -- JPG _is_ an image-compression file format developed for the Web -- TIFF is almost always uncompressed).
DPI is used by the _output device_ -- the printer or monitor on which the Image will be "printed" -- to determine printed size in inches.
You can set DPI in the Aperture print dialog to _anything_ and it will not change the pixel dimensions or the file size of the file you create.
RAW, btw, describes a family of proprietary sensor data file formats.  RAW files are not image files -- to create a viewable image file a RAW file must be converted (by, naturally, a program called a RAW converter) to an image-format file.  Aperture has a RAW converter built into it.
So, to the task at hand: crop your Image and make whatever adjustments you want.  Export your Image as a 16-bit TIFF set to "original size" and put "300" in the DPI field (to make the print house staff happy).  Send them the file.
Note that the rule-of-thumb is 300 _pixels_ for every inch of paper to be covered, in order to produce very sharp prints that can withstand scrutiny up close.  The further from a picture the viewer stands, the fewer pixels per inch are needed to make the picture appear sharp.  Some billboards are probably printed at about 4 pixels per inch.