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#21 Interceptor121

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Posted 18 June 2019 - 09:15 AM

I am not sure what you are saying, but my curiosity was whether the shape or pattern of the light output would change underwater.  It is really an academic question, I suppose.   I am not sure it could realistically be tested.  I was not really talking about the power of the flash.


The shape of the two flashes will be the same however as one is 50% more powerful than the other practically the light at the edges will drop to a value that is considered dark before the other one pretty much of a factor of 1.5 or 0.67x depending in which one is the reference
Underwater or land makes no difference in relative terms but in absolute terms underwater the distance will be shorter due to absorption


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#22 Tom_Kline

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Posted 18 June 2019 - 12:49 PM

I am not sure what you are saying, but my curiosity was whether the shape or pattern of the light output would change underwater.  It is really an academic question, I suppose.   I am not sure it could realistically be tested.  I was not really talking about the power of the flash.

 

It will and is a variable due to the dome shape of the port used on the strobe. Like with the dome port of a housing the interaction with water results in a lens different from when it is used in air. Recall the difference in infinity focus position with dome optics. Some strobe domes are truer domes than others. Looks like there is a trend with new strobes more dome like, especially the Inons. I think the effect is not academic.


Thomas C. Kline, Jr., Ph. D.
Oceanography & Limnology
Currently used housed digital cameras: Canon EOS-1Ds MkIII, EOS-1D MkIV, and EOS-1DX; and Nikon D3X. More or less retired: Canon EOS-1Ds MkII; and Nikon D1X, D2X, and D2H.

Lens focal lengths ranging from 8 to 200mm for UW use. Seacam housings and remote control gear. Seacam 60D, 150D, and 250D, Sea&Sea YS250, and Inon Z220 strobes.

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#23 Interceptor121

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Posted 18 June 2019 - 01:12 PM

 
It will and is a variable due to the dome shape of the port used on the strobe. Like with the dome port of a housing the interaction with water results in a lens different from when it is used in air. Recall the difference in infinity focus position with dome optics. Some strobe domes are truer domes than others. Looks like there is a trend with new strobes more dome like, especially the Inons. I think the effect is not academic.


He is talking about the two retra pro/prime whose construction except power is identical he is not comparing different brands


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#24 Tom_Kline

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Posted 18 June 2019 - 02:01 PM

He is talking about the two retra pro/prime whose construction except power is identical he is not comparing different brands


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From post 16:

"With regard to the image above showing the dispersion pattern, I am wondering if the pattern in air is similar to what one would get under water?  In particular should one expect a non-diffused Z330 to have such a pronounced cross shape in actual use?"

 

The question was under water vs in air.  Retra vs. Retra (the new ones) is more obvious. If both were used at full power the more powerful one would cover a bit more as you suggest but could be overexposed in the center. Should be the same if exposure was equalized.


Edited by Tom_Kline, 18 June 2019 - 02:20 PM.

Thomas C. Kline, Jr., Ph. D.
Oceanography & Limnology
Currently used housed digital cameras: Canon EOS-1Ds MkIII, EOS-1D MkIV, and EOS-1DX; and Nikon D3X. More or less retired: Canon EOS-1Ds MkII; and Nikon D1X, D2X, and D2H.

Lens focal lengths ranging from 8 to 200mm for UW use. Seacam housings and remote control gear. Seacam 60D, 150D, and 250D, Sea&Sea YS250, and Inon Z220 strobes.

http://www.salmonography.com/

 


#25 Interceptor121

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Posted 18 June 2019 - 02:20 PM

We moved on from there
The test that bill has done in water shows that actually the inon drops quicker at the edges than sea and sea
In addition to the dome effect you also need to consider how wide the beams were to start with
The retra seacam and ikelite have circular bulbs it looks like with the right reflector those strobes can be wider
The sea and sea has a single large tube and the inon has two smaller rectilinear it is very hard to compare

The idea behind inon strobes is that you get two linear bulbs you put them 90 degrees to each other and with a diffuser you smooth the beam this is not a simple model like a lens behind a dome

Bill measurement seems to show that the sea and sea strobe and the z240 actually are more evenly distributed than the z330 although they have less power overall if you look at fstop
Instead if you look at pure intensity qs the z330 is more powerful you will get some light also far away from centre but that doesn’t mean the intensity is the same across the incident angle


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#26 Tom_Kline

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Posted 18 June 2019 - 02:28 PM

I have the S&S 250 as well as the older Z220s.  I also have the Seacam strobes (250D, 150D, and 60D) and have used just one of these strobes to successfully light up fisheye shots to the corners which is not possible with the others. Used diffusers for all shots. So I concur with post 25. IMHO it is end results that count, not wall test shots!!


Thomas C. Kline, Jr., Ph. D.
Oceanography & Limnology
Currently used housed digital cameras: Canon EOS-1Ds MkIII, EOS-1D MkIV, and EOS-1DX; and Nikon D3X. More or less retired: Canon EOS-1Ds MkII; and Nikon D1X, D2X, and D2H.

Lens focal lengths ranging from 8 to 200mm for UW use. Seacam housings and remote control gear. Seacam 60D, 150D, and 250D, Sea&Sea YS250, and Inon Z220 strobes.

http://www.salmonography.com/

 


#27 Draq

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Posted 19 June 2019 - 07:00 AM

Thanks for the information.  When I get the Z-330 strobes eventually I plan on leaving the diffuser on.