Explain these basic optic terms

[RogerAGrimes]

I own a L&M Bluefin Pro. I'm thinking about updating the standard lense to something with better glass and wider field of view. Here's L&M's optics' table:

http://www.uwimaging.com/shots/opticstable.jpg

I'm embarassed to say that after over 10 years of shooting underwater video as a hobbyist, I don't know what many of these terms mean, including distortion, TM, and diopter.

Can somone explain these terms, and also the trade-offs between the various lenses offered here?

 

[ronscuba]

If you are only shooting wide angle, you don't need to worry about TM or diopter.


Distortion: image or object looks different. for example a perfect circle may look oval depending on amount of distortion

TM: tele-macro, some camcorders have a tele-macro mode allowing the camcorder to focus on objects physically close to the lens. Useful for macro video using zoom.

Diopter: an add on filter that functions like TM. Useful for macro video using zoom.

 

[jcpiota]

Ron, if you were going to add one wide-angle lens to you bag; what angle would you choose? Thanks.

 

[ronscuba]

Ron, if you were going to add one wide-angle lens to you bag; what angle would you choose? Thanks.

For underwater ? What camera and housing do you have ? Usually we are limited to what the housing manufacturer offers. Where/what you usually shoot is also a big factor.

 

[RogerAGrimes]

For underwater ? What camera and housing do you have ? Usually we are limited to what the housing manufacturer offers. Where/what you usually shoot is also a big factor.

I'll reply for me: Underwater, Sony HD (XR-HD550), Light & Motion Bluefin Pro.

 

[ronscuba]

I'll reply for me: Underwater, Sony HD (XR-HD550), Light & Motion Bluefin Pro.

For wide angle, the Fathom WP90 looks like the only real choice. A little expensive but it you shoot a lot of big stuff like wrecks, wide reef shots or get close to big animals it might be worth it to you. The thing about wide angle is, it's not just big animals. You need to get close. That 10 ft shark looks tiny in a WA lens from 25 ft away.

Looks like your housing comes with a flat port ? If so, you can experiment with macro video for free if your camcorder has a TM mode or buy a diopter set for about $50. Both TM mode and the diopter do not make the image larger. They allow the camcorder to focus on objects closer to the lens when zoomed in. You can try this on land. Try filling the frame in focus with an 1" or 2" object or a coin. Most likely you can't unless you have TM mode or a diopter.

Just a warning. Marco video footage is very interesting, but very tough to shoot. You will want a tripod or set your camcorder down on a rock or sand to prevent shaking.

 

[jcpiota]

Similar set up. Thanks for the feed back. Those lens do get expensive and I never can find them for sale used...

 

[RogerAGrimes]

Thanks for all the great advice and info. My normal shots are Carribbean reefs, shipwrecks, and lots of fish and shark shots. I'm usually fairly close. Often the big sharks get crowded out of the frame (I'm so close), so this wide angle lense might be the ticket. I was worried that adding more water to the scene might make video harder, but if I have to get closer (and with less distortion), it could be a better shot. The Fathom 90 it is...when the next bonus comes. <grin>