You say "I need to export photos at the highest resolution with no compression. "
Then, from your export panel screenshot, you seem to be exporting as a Jpeg.
All Jpegs are compressed. If you need a non-compressed file, as you state, then export as a Tiff.
And, of course, when exporting as a Tiff, LR won't let you set a maximum file size as any limitation on file size can only be achieved by compression.
Good point, I'd overlooked that.
Even setting the quality factor to 100% (100 in LR, 12 in Photoshop) there is still lossy compression on conversion to jpeg because:
- The data is reduced to 8 bit
- The color information is normally reduced in resolution by a factor of 2.
With quality 100%, the file size of a 12Mpixel jpeg is likely to be over 10Mbyte. To reduce it to 5Mbyte you can either reduce the resolution (in the "Image sizing" part of the export dialogue) or increse the compression (in the "File settings" part of the dialogue) either by reducing the quality from 100 or by reducing the "Limit File Size" number.
For full resolution, no compression: export as 16-bit TIF. For a 12M pixel D700 image, that will be about 70Mbyte.