UW photography without strobes with the Nikon D3?

I don't feel internal focus itself is an important issue but it does make a lens easier to house and allows you to make better use of working distance. I would prefer IQ to internal focus but I do value a lens that can be housed easily. A housable zoom macro with AF-S is what I should have said is important; internal focus and zoom are just a means to that end.

The Canon 70-200 f/4 is notable because it does not change length with either zoom or focus. Of course, it doesn't focus closer than 1 meter either. Given a lens that houses easily and one that actually does what you want, I'd take the latter.

I think one thing that Canon guys take for granted, and get to optimize their systems around, is fast AF with full time manual override. That's the one thing that the 70-180 doesn't offer that is nice. I'm personally very comfortable with full time MF and macro but I'd still like to have what Canon shooters have (and if they had a 70-180 I believe they'd really like it as well).

Hi,

I believe, particularly in the Nikon system, that the type of auto-focusing motor has much more effect on the lens's speed of focusing than does whether the lens is internal focus or not. The lenses with the motor built right into the particular lens - which Nikon calls the AF-S motor are faster than the lenses whose focusing is driven by the focusing motor built into the camera body.

The AF-S motor also gives those Nikon lenses the advantage of not having to disengage the manual focusing gear ring when auto-focusing, which is a really big advantage when using the lens in most housing in which disengaging the manual focusing ring may be a several step affair and one which can be difficult or nearly impossible at greater depths as it was on my Seacam housings before I totally modified the housing gears so that merely flipping the M-S-C lever also disengaged the manual focusing gear.

My strong preference for having a manual focusing gear is because I feel that in some situations you can achieve a sharper focus manually than by using auto-focus. Especially with wide-angle lenses. This is so because I often want to focus on a spot in hte picture frame that does not coincide with an AF point. And focusing with a AF point and then recomposing involves moving the housing to a different position, which can also change the actual distance between the front of the housing and the subject and thus "defocus" the subject a little.

I also feel that the action finder of my F5 also allows me to see more clearly for manual focusing than any of the special add-on optical finders mounted behind a normal eye level prism I have ever seen including those of Seacam and Subal.

Fred