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rwe

Member Since 08 Jul 2005
Offline Last Active Apr 23 2018 10:07 AM
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Posts I've Made

In Topic: Looking for photographer friendly dive operater in Cozumel

30 March 2018 - 05:34 AM

I have used Tres Pelicanos on my last 3 trips to Cozumel http://www.trespelicanos.com/and was happy with them. 


In Topic: Caribbean Turtle Images

26 February 2018 - 02:45 PM

I am definitely not a professional but I have donated quite a few fish images to Ross Robertson's Shorefishes of the Caribbean.  If you can find a photo that is useful for your purposes on my Flickr site ( https://www.flickr.c...9071@N08/albums) then you can use it.  Most of my turtle pictures are Hawksbill but I do have some loggerhead and green.  This is what I suggest:

  1. Go to my flickr site and search for 'green turtle' and then 'loggerhead turtle'.  If it only shows a few pictures then look just above the last picture for a link that says 'View all X'' and click it.  Not all my pictures are labeled but when I did this I found 17 green turtle and 25 loggerhead turtle pictures.  If you see one that looks useful, click on it and then scroll down and the folder name will define the location and month/year the picture was taken.
  2. I don't have any Leatherback pictures or in ocean Kemp's Ridley pictures. 
  3. I do have a few pictures of a 34 year old Kemps Ridley male that I took through a window at Marineland.  I never went to the trouble to edit these but could do so if you are interested or could try to take some better ones since I volunteer there 3-4 days/month.  Unfortunately, they won't allow me to get in the tank.  This particular individual was hatched in an incubator in Texas as part of the Head Start program attempting to 'save the Kemps Ridleys' in the late 70s through 80s.  It was not released because it was born with a bone deformity in one front flipper but while it swims slowly, the deformity is not physically obvious.

In Topic: Wetpixel strobe review

20 February 2018 - 01:45 PM

Because f-stops are a ratio of lens focal length to lens opening, the f-stop has no units, it is a pure ratio of two lengths.

 

From a purist point of view, f-stop does have units.  As an example, mm focal length/mm effective aperture diameter.  Since the 2 lengths are referring to different parameters, they do not cancel.  While I realize that ignoring the units greatly simplifies communications, as a chemist, I find that many professionals can't solve problems by simple unit conversions because they think things like vapor/liquid distribution constants (concentration vapor/concentration liquid) also have no units.  :)


In Topic: wide angle wet lens

17 February 2018 - 08:08 AM

Here is what you're looking for:

 

https://www.bluewate...eview-and-tests

 

The AOI UWL-09 is the same thing as the Fantasea UWL-09F

 

 

Thanks, this is what I was looking for.  Anyone seen a comparison of the Kraken KRL-01 and the Fantasea UWL-09F?


In Topic: Flash duration?

14 August 2017 - 12:52 PM

YS-D2 full flash duration - 4.2 ms. You can use full energy at shutter speed slower than 1/250.

YS-D250 full flash duration - 23 ms. You can use full flash energy at shutter speed slower than 1/50.  

But how often do you need full energy? - very rare. In many cases we use only a small part of it, and there is no problem to set more fast shutter speeds (up to Nikon's max synch speed 1/250).

Sorry, I don't know Seaflash-60 flash duration. There is a round tube inside, but tube's diameter and thickness are small. I can suppose duration about 5...8 ms. 

 

Underwater objects move rather slowly because of the water, flash freezes them fine, independently of strobe type and duration. There is no need to specifically take care of this.

 

 

 

Not all underwater objects move slowly as can be seen by the blurred critters in this photo taken on a night dive with an Inon Z-240 (shutter at 1/125):