70 degree vs 80 degree wide angle

Hi,

I'm looking at an amphibico housing that comes with a 70 degree lens and offers an optional 80 degree add on wet lens. I'd appreciate it if someone with a better understanding than mine, could explain how this translates into usefullness in wide angle shooting.

Thanks,

Steve

Well basically Steve you can fit more in. Alternatively you can fit the same amount in but be closer to your subject, which means less water between you and the subject and therefore a clearer image.

Nick

Thanks for the reply, I get the concept of wide angle, I guess I should have asked a more specific question. What I'm looking for is how big a subject & from what distance. So, if I'm filming a whale shark from say 20 ft away or a wreck from 40 ft away, is an 80 degree lens going to give me significantly greater coverage than a 70 degree? Is there a guide line for distance and subject size based on lens degree?

Thanks again for any input!

Steve

Steve the 80 will certainly be an improvement on your underwater image like Nick said, and you can get closer and have more of a large subject still in the frame.

Being wet though you will have to make sure you get all the bubbles of it before you put in on and also will have to take it off if you swim over divers bubbles etc to clear it again of bubbles. You can simple take it off if you think you don't need it for a shot.

If you can get it you will certainly use it.

Well, to calculate field of view as a length you need trigonometry ... a subject which brings me out in a cold sweat.

Perhaps someone with a maths bias might chip in with the correct equation.

Alternatively get a protractor and draw it out to scale.

Well, to calculate field of view as a length you need trigonometry ... a subject which brings me out in a cold sweat.

 

Perhaps someone with a maths bias might chip in with the correct equation.

 

Alternatively get a protractor and draw it out to scale.

A rough rule of thumb which you can use is the 1:60 rule.

For a one degree difference at 60 units distance, you will be able to see one unit more. I only know this from flying so will use that analogy. If I fly for 60 miles and am 1 degree off heading, I will be 1 mile from the place I am supposed to be.

So in the case of 10 degrees wider (5 degrees extra around the centre) for a shot at 30ft you will see 2.5 ft more. (60ft would be 5ft more and therefore 30ft would be 2.5ft more).

HTH