The ‘standard’ definition of penetration depth in skin only considers the incident wavelength and optical properties of the skin. While this may be useful from a physics perspective, it is not particularly useful when considering clinical treatments.
A more useful definition must include wavelength, anisotropy, spot diameter and incident fluence.
All of these have an effect on the reaction within the target, in the dermis. Our new video shows how these parameters can all affect what happens deep in the skin:
Knowing this should help to improve clinical results when treating tattoos, hair, blood vessels or other targets.
Ciao for now,
Mike.
Mike Murphy's Blog 
The second You tube video is excellent. Nothing I didn’t know but great to se it quantified.
Thanks so much for sharing.