Photo settings I'm playing with for wood.

Photoshop
1) Anything to improve image
2) Unsharp: 100%, 12.5 Radius, 20 Threshold

PhotoGraV
Adjust Gray: off
Enhance: off (I did in Photoshop)
Screen: Pattern, DPI=60, Black width=1, Gray width=40, degrees=45
Threshold: Screen:51%, threshold=126

Driver
Power =100%, Speed =50%
LPI = 500 (-5), PPI=1,000 (Versa default)
Image Enhancement : Contrast&Definition= (have not tuned these, used default), Density = (100% seemed slightly better than 0%)

Laser
ULS Versa: 40W, 60ips (Units specs.)
1.5" Lens

 Edited to specify settings for photos.

Ken,
Thanks for posting your settings......

I found the speed is for wood is not too critical. Slowing it down will give more burn and a darker image. (Important for darker darks) The brightest part of the image will be the wood itself. Maple gives better contrast than Alder.

I did not like the image as much when dark areas are engraved away, but the depth of burn was necessary for contrast. I felt this approach gave a good trade-off.

I also tried using the PhotoGraV output as a mask for the original picture, which was then engraved using the drivers 3D setting. It gives the PhotoGraV image, but lighter in the lighter parts of the image. It is more work/time to create final image to send to laser. If anyone tries it, you will need to adjust the grayscale histogram prior to applying the mask. You'll need to "crop" the whites. (Anything lighter then X should be set to X) - if you don't make this adjustment you will loose detail in the lighter areas.

I am hoping people will post their settings and experiences/opinions to this thread. Lets see what this forum is capable of.