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Member Since 03 Jan 2012
Offline Last Active Sep 03 2015 05:30 AM

Posts I've Made

In Topic: SLR vs. Mirrorless. What is the best camera for macro?

19 July 2015 - 03:50 PM

My wife and I both use micro 4/3 cameras for underwater photography, and I think our results are limited by our abilities, not by our equipment.


M43 suffers from higher noise at high iso and the continuous autofocus is not as good as SLRs.  I think you could also say that the dynamic range may not be as good.  However, it seems to me that none of these issues apply to macro photography.  You control the lighting, so there is no need to shoot at high iso.  In my macro photography I am generally happy if the distracting background drops off to black.  So I adjust the strobes to light the subject well and don't worry about the background.  As a result I'm not too worried about dynamic range for macro.  It is an issue for wide angle stuff.


I think the only strength of SLRs for macro is that you can print bigger.  If you're looking for really large prints then SLRs are the way to go, but you are paying a pretty substantial penalty in weight and size for that ability.


I'm happy to stick with m43 for underwater macro.  Where I'm tempted by SLRs is in wildlife photography on land where the autofocus and dynamic range would be a real benefit.  But that's a different story.

In Topic: Truk Odyssey and Truk Siren are schweckled-What to do?

03 April 2015 - 04:12 PM

I liked the Thorfinn as well.  We didn't like the food, and the hot water in our shower was hit or miss.  We were on the upper deck and apparently whenever someone showered in one of the lower deck cabins they got all of the hot water.  The boat isn't purpose built, so the dive deck isn't as deluxe as the other livaboard we were on, but it worked.  


The guides, and all of the rest of the staff were excellent.  I'd gladly go back.


The boat is old, and very seaworthy.  I'm not surprised that she's the one that survived the storm undamaged.

In Topic: Second thoughts about vacuum systems

26 March 2015 - 08:46 PM

I think you are onto it.  If the gland failure happened once already under water, then no additional air could get into the housing, thus not raise the pressure (decrease the vacuum) enough to trigger the alarm.  


But another interesting issue raised above by junior5  - once sealed, how is it possible for the pressure inside a rigid housing to significantly change at depth?  That would seem to violate the laws of physics. Not counting temperature effects of course.  


The only way the pressure can change is either a huge temperature change, not realistic, or something leaks into the housing to displace volume, and enough has to leak in to compress the air in the housing enough to make a big enough pressure change to trip the alarm.  In other words a fair bit of water.

In Topic: Second thoughts about vacuum systems

26 March 2015 - 08:17 PM

The forces on the housing are a function of the pressure difference between the inside and outside of the housing.  A vacuum of 10 psi at the surface is the same as going down 20' or so with a housing that has no vacuum inside.  So pulling a vacuum before diving is the same as diving a bit deeper.


Having said that, I can see that if you spring a leak at depth this could be a problem.  Lets say you evacuate the housing to 10 psi of vacuum (i.e. 4 psi absolute), and lets also guess that the alarm goes off if the vacuum drops to 9 psi (i.e. 5 psi absolute).  In order to do this you need to compress the air in the housing to 80% of it's original volume.  How do you do that?  By filling the rest of the volume with water.  I am guessing that the alarm deadband on these things is less than 1 psi, but you get the idea.  I don't know what the actual alarm setting of these systems is, but a small pressure change can amount to a fair amount of water in the housing when there is a leak underwater.


I think the real value of these systems is that you can find a leak before you go into the water.  If the leak starts once you're in the water I don't think they're likely to help much.


I still think they're great and my wife and I have them on both of our housings.

In Topic: Configuring a MacBook for Dive/Photography Travel

27 December 2014 - 11:25 AM

My wife has the 13" MBP with the 256 GB drive and I have the 15" with the 500 GB drive, both late 2012 machines.  They both work very well.  The 256 GB drive isn't big enough to store her whole catalog, so we set it up with a travel catalog and move everything over when we get home.  The smaller machine is a little slower than mine, but it works fine for travel using both Lightroom and Photoshop.