I use the old fisheye converter : Sony VCL-ECF1 but I read that there is a ECF2 : is it better?
IIRC one of those is silver and the other black; the optics are the same.
Or is there another fisheye lens with a better sharpness in Sony E mount?
Alas, not a native autofocusing one, no. It's either a marginal quality lens with a converter (16mm f/2.8 + VCL-ECF on crop, 28mm f/2.0 + SEL057FEC on full frame), or an adapted lens such as Tokina 10-17mm, Canon/Nikon 8-15mm, or Sigma 15mm. There's a recent leak about a Sigma 15mm f/1.4 fisheye coming out in FF E-mount in about a week, but again, that's FF - and with an f/1.4 aperture, it's bound to be large and expensive.
Wet lenses : They are very heavy and the FOV seems narrower than the Sony fisheye converter. And for splits, it seems to be very complex
It's not as wide, but I find it to be wide enough. Weight... I guess it's a matter of personal preference, but I find it manageable.
- Option 1 : Sony A7III + metabones + Canon 8-15 : that would be the perfect setup : very wide FOV, very good Sharpness, better dynamic range, better burst image etc... BUT Is there a seafrogs dome port compatible with this setup? The 6'' glass dome port? And it seems that when used with strobes and optical fiber cables, TTL doesn't work : is that right?
It should work; the dome is a little large for CFWA, but it's not
too big. You will have to play around to find the proper extension though, as SeaFrogs doesn't maintain a proper port chart, unlike most other housing manufacturers. Until recently they didn't even have extensions for their ports, but a couple months ago they finally started making them, so you can customize the port extension length for your lens.
If you want to take advantage of the zoom capability of Canon 8-15mm, you will also have to come up with your own zoom gear. Note that on its own, this lens basically has two settings - circular fisheye at 8mm and 180 degree diagonal at 15mm; anything in between just gets you some vignetting. It is, however, popular with a 1.4x teleconverter (on the Canon side of the adapter mount, not Sony), which gives you a useful zoom range of about 11-15mm, i.e. you get the 180 degree diagonal at 11mm, but you can narrow it down somewhat if you want to. A 2x teleconverter would, in theory, make the entire zoom range useful, but in practice it produces unacceptable image degradation.
If you don't want the zoom/circular fisheye capability, then Sigma 15mm in EF mount is a cheaper option.
TTL capability depends on what trigger you use. Using TRT Electronics s-TURTLE system should get you TTL even with your existing strobes, although I don't know how accurate it would be. UW-Technics is another option, but you'd need to replace the strobes, as they don't have a profile for YS-100a. If you use a manual-only trigger, such as the SeaFrogs one, or a TRT manual trigger, or the AOI one, then you will have to run the strobes in manual mode. Likewise if you use wired triggering straight off the hot shoe.
- Option 2: Sony A7III + Sony 16-35 F4 + 6" glass dome port : better sharpness (even if 6" dome is a little bit small for this kind of lens), better Burts images etc... but narrower field of view and less compact than my actual setup
I would go for 8" dome rather than 6" for this lens, and I wouldn't call it a
bad setup per se, but it gives you a different kind of shot. It might be better for wrecks, for example, keeping straight lines straight, or possibly for video, where you don't want the fisheye distortion for subjects moving across the frame, but for still images of wildlife, fisheye is generally better.
