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Wide wet lens, actual angle of view?


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#1 oskar

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Posted 30 January 2014 - 06:18 AM

I have a Sea & Sea we lens made for the compact cameras DX-1G/2G.

 

I though it was equivalent to a 16mm  (35mm film lens), but reading the specs it does not seem that impressive any more:

 

To me it seems like it is in fact only 24mm equivalent in water.  Like I would care that it is a 16mm in air :-).

 

Am i reading the specs right?

 

Check this out:  

 

[Lens] 3 elements in 3 groups
[Underwater angle of view] 85° (106.5° on land)
[Magnification] 0.65x
[Depth rating] 60m / 200ft
[Weight] Approx. 406g / 14.2oz (underwater: Approx. 230g / 8.1oz)
[Dimensions (DIAxD)] 97x48.5mm / 3.9x1.9 inch

 

http://www.seaandsea.../001.html#52116

 

Cheers

O

 

 

 



#2 Interceptor121

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Posted 30 January 2014 - 07:24 AM

Probably the 0.65x is on land not in water so 0.65*1.33=0.8645 remove a few decimal point to account for the distance between lens and port and voila you basically have the same fov the little camera has on land

 

Also this lens is made of 3 elements whilst almost all high quality lens on the market are made of 4


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#3 oskar

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Posted 31 January 2014 - 01:44 AM

Thanks, that seems about right as the camera's wide end is 24mm equiv.

 

Which also means that now that i transitioned to EM5 m43, the 12mm (24eqv) should work with the same type of documentation images.



#4 Interceptor121

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Posted 31 January 2014 - 02:31 AM

Get yourself a nauticam wetmate that is glass and has no aberrations instead of this bulky lens


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#5 kc_moses

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Posted 31 January 2014 - 08:18 AM

The nauticam wetmate would give him back 24mm equivalence 80 degree fov, how would that help?

 

Also, can you share the source and info for formula of 0.65 x 1.33? I read that the magnification factor determine the fov of the result. So if you have a 24mm lens, an add on lens of 0.65x will give you 0.65x24 = 14mm result.

 

The Inon UWL-H100 (http://www.inon.jp/p...28m67/spec.html) is 0.6x, so taking 0.6 x 1.33 doesn't give 108 degree fov.

 

I thought most wide angle should be 0.45x, and 0.3x would become fisheye. I'm getting confuse with all these calculation.



#6 Interceptor121

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Posted 31 January 2014 - 08:49 AM

Inon values are in water and that is the value of the lens itself. The cAmera lens doesnt sit right on the port so you always loose something

The sea and sea value instead seem to be air hence multiply at least for 1.33 and then there is the issue of lens to port distance

 

Also putting a wet lens on a zoom lens is not usually recommended hence the dome suggestion.

 

If you want wider fov you put a wide angle lens on the camera, is it not the whole idea of a micro 4/3?


Edited by Interceptor121, 31 January 2014 - 08:59 AM.

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#7 oskar

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Posted 02 February 2014 - 12:16 PM

I'm asking for my old camera   (I've also got a m4/3 now, but forge about that now).

 

The dodgy thing about this wet lens is the comment 84degrees in water and 106,5 on land. This is the only comment specifying in water.  So the magnification doesn't seem trustworthy after that.

 

If this is right, I agree the dome would have been better, and a proper WA lens would have been better still.

 

Cheers

/O