I am considering these 3 new Tamron lenses for UW photo, in particular the 20mm for WA shots and the 35mm for macro. Note that I plan on using them on a A6400 and a Seafrog SL housing, with the standard port (given the dimensions, it should fit and the front glass should be quite close to the glass of the flat port). These 3 lenses have 1:2 (0.5) magnification ratios.
I really don't see the point. 20mm (30mm equivalent on A6400) is not wide at all, especially after flat port magnification, and you can't attach wet lenses to the SeaFrogs standard port. I can kinda sorta see the 35mm being used to shoot medium-large nudis and the like, but Sony 30mm f/3.5 macro is just better for that. The 16-50mm kit lens with short macro port and wet lenses will be far more versatile.
2 hours ago, pascastel said:
Hi all,
I am considering these 3 new Tamron lenses for UW photo, in particular the 20mm for WA shots and the 35mm for macro. Note that I plan on using them on a A6400 and a Seafrog SL housing, with the standard port (given the dimensions, it should fit and the front glass should be quite close to the glass of the flat port). These 3 lenses have 1:2 (0.5) magnification ratios.
They are not particularly wide in UW terms, the 20mm behind a flat port on an APS-C camera is equivalent to 40mm lens on full frame. The 35mm has about 60mm of working distance from the front port at max magnification, so could probably make a nice fish portrait/ semi macro lens. The 20mm would only have about 20mm or working distance from the port glass at max magnification so taking advantage of the the 0.5x magnification would be difficult.
I own the 20mm and 24mm like all wide lenses that focus this close at 1:2 you are about two inches (60mm +/-) from the subject. This helps with smallish dome ports because virtual image may be very close to the lens but you are focusing inside the port. With a flat port you will be very close to the subject and close enough that you may do damage. I agree with Barmaglot that the Sony 30mm macro would be a much better choice. The Sony goes to 1:1 and has a much better working distance at 1:2, the down side is that it is an F/3.5 lens.
