1 hour ago, ChipBPhoto said:

Correct and good strategy. Just remember a TC + an SMC is next level of difficulty.

Also keep in mind the further you are away from the subject, the more chance of particles in the water column between the lens and subject. Your lighting output will also need to be increased. Sounds like you already understand that part.

Let us know how it goes!

Yes. I tried the smc2.. and oh my... Good results but hard to nail down. Smc1 is easier to manage.

Good note on the particle bit.

9 hours ago, hellhole said:

Yes. I tried the smc2.. and oh my... Good results but hard to nail down. Smc1 is easier to manage.

Good note on the particle bit.

I think the answer is with a 1.4/2x you are always further away than you would be with a bare lens and with a wet lens. With a 2x you can match nearly a 100mm macro with an SMC-3 (2x vs about 2.2-2.3x depending on which macro lens). Basically more water between you and your subject which will degrade the image.

If you back off to get 1:1 with a 100mm_macro/2.0x you have the reach of a 200mm macro, so if you had a 100mm lens with 300mm focus distance and 150mm working distance at 1:1 you would double that distance with a 200mm focal length lens depending on how much the lens reduces in focal length to achieve 1:1 with and IF design. It gets worse as you progressively shoot larger subjects.

A 1.4x might be a good compromise to give a bit more working distance compared to the bare lens and wet lens at a given magnification.. Also bear in mind that the longer focal length of the lens + TC combo will give you significantly more magnification than the bare lens with the same wet lens. For example the m43 Pany 45mm lens gets 1.6x with CMC-1 while the 60mm macro gets 2.0x (both 1:1 lenses) and 60mm is near 1.4x 45mm. so the new Sony macro might go from 2.4x with SMC-3 to 3.3x with a 1.4x and 4.8x when used with a 2x.

So a 1.4x/2.0x locks you into smaller subjects than a bare lens/wet lens combo does and the impact would be noticeable I think in the 0.5x -1:1 range and lower magnifications unless the water was crystal clear. It may work well for skittish mobile subjects like small fish if this was the sole subject of your dive.

You might also degrade AF performance with the 2x at max magnification again depending on lens/body combination