Matt_NJ:
What is a solid (Yet relatively cheap!) lens that I could put on the D50 that would give me the best performance underwater? Should I use a telephoto zoom or a fixed aperature lens?
Thanks,
Matt
The problem is that cheap (and "relatively cheap") don't go well with the term "dSLR". But I know what you're getting at.
With dSLR, you generally need to know what type of shots you're going for before you get in the water - i.e. macro or wide angle. There are some lenses that can do both, but you generally sacrifice something of each when you try to have the ability to do both in one lens. A dedicated wide angle lens and a dedicated macro lens (IMO) will more often produce better results than a single lens that does both. However, if you are set on getting one lens that will "do it all", there are a few out there.
One that I've seen that has been getting some decent reviews is the Sigma 17-70 macro. I believe Ikelite even has a port setup for it as well. At the wide end of that lens, 17mm is going to be decent for wide angle, but it's not going to be anywhere near any of the other wide angle lenses like the Nikon 10.5, 12-24, or Sigma 10-20. For macro, it should do a decent job, but does not do 1:1 macro (I think it's 1:2.3), so your shots are not going to be as close as a 1:1 macro lens like the Nikon 60 mm micro or 105 mm micro.
As for your question on telephoto zoom or fixed aperature lens ... I find that any telephoto lenses (unless for macro work) will have limited use in the underwater world, as underwater photography is all about getting close. This means that using a telephoto to get close will result in washed out pictures due to having lots of water to shoot through. You get close by being physically closer and using a wide angle lens to fit your subject in the frame to minimize how much water you're shooting through - which maximizes the quality of light you're getting.
So depending on whether you need the flexibility of a zoom or a fixed focal length lens (also called prime lenses), which I presume is what you mean when you say fixed aperature, I would go with a wide angle zoom.
You're probably going to be paying a premium for Nikon lenses. Other manufacturers like Sigma and Tokina have some great lenses somtimes for somewhat less than Nikon, and are certainly worth consideration if you are on a relatively tight budget. But do not be fooled - if you're going to house a dSLR it's not going to be cheap no matter how you look at it.
