Subject:	Of teleconverters and diopters
Author:	whaletale
Date:	2/17/2002 3:02:57 AM
Message:

I read the post below and thought I would share my experiences to date with regard to teleconverters and diopters.

My macro tools include a Kenko Pro 300 2x teleconverter, 3T and 5T close up lenses, and 105mm and 200mm Nikkor Micro lenses.

The 2x teleconvter does indeed increase magnification to 2:1 when mated with a 1:1 lens. The downside is a 1/2 reduction of DOF and a 2 stop loss of light. The Kenko allows AF with all lenses except for AF-S lenses and the 200mm micro lens.

The close up lenses are a 1.5 diopter.

I've used the 2x tele and 105mm with modest success. AF becomes difficult to impossible with spot, single servo settings without using AF lock. The slightest movement of the camera or subject causes it to refocus. I spent ten minutes trying to shoot an anemone blowing in the current. It is best to let the lens hunt until it gets close, turn off AF and just move until your subject is in focus.

The 2 stop loss of light was not a problem with two SS-200 set on TTL. The teleconverter set between body and lens means that I cannot change the f-stop since the gear no longer works. I set it at f22 and fired away. Yes, it is strange seeing the effective f64 through my viewfinder. Rooster has an F100 that controls aperture by the command dial.

When combining the 2x tele with the 3T diopter, I couldn't get the camera to AF on anything. As a matter of fact it's hard to even find your subject manually focusing. Eventually I found the ruler I was test shooting. Wow, was it big. Now I've got 3:1. But alas, I've lost 2 stops of light, the DOF is paper thin, edge to edge sharpness is reduced and I can't AF.

Now, with the 200mm lens, all the above applies only everything is worser. I've used the lens topside with AF and hand held without a problem. Underwater, the lens needs to be manually focused. I find manually focusing underwater a real chore with long lenses. Again, it's best to get your focus close to where you want it and then move the camera to get the final focus and cross your fingers that your eyesight is OK.

BTW, I've switched to an Aquatica housing. The standard flat port matches the 60mm lens. With its bayonet mounting, you simply add an extension for the 105mm or a different extension for the 200mm. You can combine the two extensions and use the 2x tele on the 200mm.

Now, when I use the 200mm extension with the 2x tele and 105mm lens, with the two strobes pushed forward to almost match the focal length of the lens, the system weight is way out of kilter. It wants to fall forward. On top of that the system weight makes me want to roll forward when shooting. I moved my tank, shifted my weights to help. I'm either going to have to add some ankle weights or stick a couple of two pounders up my ass before each dive.

Oh yeah, so how did the photo's turn out? Some good, some not so good. The loss of DOF is quite noticeable.

Subject

Author

Date