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MarkD

Member Since 28 Sep 2006
Offline Last Active Today, 10:50 AM
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Posts I've Made

In Topic: What wideangle to choose for canon 7dmii

06 June 2018 - 11:28 PM

I agree that the Sigma 17-70 Macro is no Jack of all trades underwater and certainly not a good underwater macro lens. However it does retain a useful specific but more occasional role in my lens collection as a flexible fish portrait lens. It has a good reach for shy creatures but also allows you to fit in all but the largest species that allow closer encounters..

Mark

In Topic: Nikon 8-15mm in the house!

27 May 2018 - 08:56 AM

Hi Mark. I cant offer personal comparative experience with the Nikon 10.5. I would suppose that as a much more modern and expensive lens, the 8-15 might be optically better, but of course as a zoom lens, design compromises will have been made. These compromises arent obvious to me in underwater use.
Regards, Mark
Hi Mark. I cant offer personal comparative experience with the Nikon 10.5. I would suppose that as a much more modern and expensive lens, the 8-15 might be optically better, but of course as a zoom lens, design compromises will have been made. These compromises arent obvious to me in underwater use.
Regards, Mark

In Topic: Nikon 8-15mm in the house!

26 May 2018 - 11:32 PM

Hi Mark. Optically, the greatest difference is substantially less chromatic aberration with the 8-15. Subjectively, the lens is also significantly sharper. As expected, these differences are more pronounced towards the edges of the image.
A downside is the reduced useful zoom range on DX meaning less reach. If youre not careful It is also easy to waste a few pixels by zooming out too far and cutting off the corners. These issues can be avoided by using a Kenko 1.4x teleconverter although this does sacrifice a few degrees of coverage at the wide end. Optically this combination works well behind a dome. When I last looked, no manufacturer offered a zoom gear for the combination so I use the standard Nauticam gear and a removable collar that provides the necessary extension.
For me the image quality improvements far outweigh the minor downsides and I have retired my Tokina.
Regards, Mark

In Topic: Inon Z240 Battery Compartment... Watertight?

06 May 2018 - 09:23 AM

Yes, me too. A thread from the Strobe neoprene jacket caught in the O-ring. Salt water rapidly entered the Strobe body itself from the battery compartment. It is not fully sealed. Maybe gas pressure from the short-circuited battery cells is what does it?
Mark

In Topic: Eneloop Pro venting gas

04 April 2018 - 02:19 PM

This warning by Panasonic doesn't appear to be new. Here's a link to a thread that's 8 1/2 years old, discussing Sanyo's then recommendation that Eneloops should not be used in waterproof lights:

http://www.candlepow...terproof-lights

There must have been very many Eneloop cells used in underwater strobes since then. It would be interesting to know what are the circumstances of use in strobes that might lead to hydrogen venting. I would suppose that any increase in pressure within a sealed battery compartment might be a greater functional concern than a risk of hydrogen conflagration when the gas is released?