This question has been asked a lot lately since the new YS-03 Solis was released. On first glance, it seems the old YS-03 and new YS-03 Solis strobe may not have any differences at all!
The new YS-03 Solis strobe has features that are the same as the old YS-03 strobe, it has the same guide number of 20 and still has no manual settings, TTL only. However, Sea&Sea has made great improvements to the new strobe to make it as easy to use as the original YS-03 strobe but as accurate as the higher end strobes.
The new YS-03 Solis strobe is now equipped with the same light intensity, the same TTL accuracy (DS-TTL II) as the popular Sea and Sea YS-01.
In-depth explanation on how DS-TTL II works can be found here.
You can find the new YS-03 Solis strobe here.
- Sony a1 Underwater Housings – May 28, 2021