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Member Since 07 Nov 2004
Offline Last Active Today, 08:58 PM

Posts I've Made

In Topic: Guide number of a strobe

27 May 2016 - 09:49 AM

The strobe's guide number is for the flash exposure only and is mainly useful as a guide to compare strobes. This assumes the various manufactures use the same method to determine guide number. Underwater guide numbers are generally not the same as air as your surmise. However for underwater strobes the angle of coverage is more important than guide number - the wider the better since we tend to use the edges of the light from the flash.


Shutter speed will also affect the overall exposure with longer exposures increasing ambient light. For underwater photography I tend to increase ISO rather than decrease shutter speed to increase ambient light exposure since I want to stay close to the synch speed whenever possible.

In Topic: 5D Mark III / Nikon Lens Underwater housing

15 May 2016 - 10:27 AM

I have used several old manual focus Nikon lenses on Canon DSLRs - pre-Ai, Ai, Ais it makes no difference. For example I have a vintage two-part 1200mm ED lens (not Ai or Ais), - it was a bit less expensive than the Canon lenses that is two stops faster. Good for those long distance wildlife shots over water. I have not however used any old Nikkor under water in a Canon housing.


The issue with Seacam is that the Nikon gears are a slightly small diameter than the Canon gears. The only MF Nikkor that I have tried under water is the 15/3.5 lens. That was over a decade ago and in a Nikon housing. Since I was doing remote control I pre-focused. However only a few pix were in focus - I soon replaced this lenses with the 14mm AF!

In Topic: My New Book: Underwater Photography Masterclass

11 May 2016 - 03:10 PM

I watched the two vids. They are a brilliant way to expand the content of your book. These two alone might be worth as many pages as the book itself given the full screen view of pix that each would require a two-page spread! Obviously a lot of work went into creating the material - such as showing step by variations of lighting as well as diagrams and pix showing you in action.

Very well done!


In Topic: old russian lens with radial blur

03 May 2016 - 11:42 PM

It is an old MIR lens



So which one? They have a number after MIR (in Russian the letters look like an M, backwards N, and a P). See this link for examples: https://en.wikipedia...wiki/Mir_(lens)

In Topic: old russian lens with radial blur

03 May 2016 - 04:53 PM

Which old Russian lens? Specify lens port that was used.