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tdpriest

Member Since 22 May 2005
Offline Last Active Yesterday, 03:20 PM
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#339802 Sigma 17-70mm + dome port or Canon 60mm + flat port????

Posted by tdpriest on 23 November 2013 - 04:43 AM

Your lens is probably too wide for most of Lembeh's creatures and your dome too big for close-focus wide-angle on most of the larger "macro" life. Look at the workshop thread. I hope to post my final selection of images soon, from an FX sensor and mostly shot with a 105mm lens, but some with a teleconverter and diopters...

 




#339740 Dive Destination while recuperating from shoulder surgery

Posted by tdpriest on 21 November 2013 - 08:25 AM



I had a cervical fusion last year...
...a supraspinatus repair is quite common...

 
Well, not to rain on your parade, but as specialist in chronic pain I see a fair number of repairs that remain painful, and a fair number of supraspinatus injuries that do well with physiotherapy and pain-killers. Rehabilitation with good physiotherapy and good perioperative analgesia could easily be as important as your surgeon in preventing long-term and intractable shoulder pain.
 
I've noticed that there's a tendency to treat musculoskeletal pain with analgesics and injections on the East coast of the USA, with surgery in the Midwest, and with psychology and exercise in California!

Repeated surgery for pain in the same or related areas of the body rapidly becomes ineffective, as the functional disturbance contributes more to the continued pain than the anatomical damage.


#339697 Dive Destination while recuperating from shoulder surgery

Posted by tdpriest on 19 November 2013 - 04:41 PM

I'm currently diving with an unhealed right collar bone. Its uncomfortable, but not enough to stop me...

 

I'm sorry to hear it. I suspect it's rather worse than diving with a broken rib, and that wasn't too much fun.




#337903 Strobe "Shutter speed"

Posted by tdpriest on 08 October 2013 - 07:39 AM

I couldn't find any info for Ikelite strobes so I emailed them explaining the above and they said that the cause was in fact due to the flash duration.  I asked them about DS160's given they are more powerful and they said the full power flash duration on a DS160 was longer than a DS125.

 

At this stage I just let it go as I was out of my depth.  It would be really interesting to hear from someone with technical expertise in this area and see hard data for different strobes at different power levels.  Maybe I'm completely off track with this and maybe it has no practical application in the underwater world but I would be curious to know - particularly if the make of strobe influences ability to achieve sync speed.

 

Cheers

 

There was concern about colour film being incorrectly exposed at very fast and very slow shutter speeds (reciprocity failure). As far as I know this isn't a problem with electronic sensors, and the duration of a strobe's flash has little impact on underwater photography. Sync speed depends on the camera, not the strobe, and is highest in cameras with an "electronic" shutter (ie data from the sensor is registered rapidly and not integrated over the time that a mechanical shutter allows light to fall onto the sensor):

 

http://electronics.h...utter-speed.htm




#337901 Strobe "Shutter speed"

Posted by tdpriest on 08 October 2013 - 07:26 AM

... you seem to contradict each other as a strobe "lit" duration of 1/1000 puts it within the shutter speed range? Am I right in thinking my fastest shutter is 1/8000? How do the "lit" durations vary with light emitted strength?

 

Strobe power is determined by the duration of the flash, except at very low power when the colour of the flash can also change. I can't find the specifications for a Subtronic strobe, but a typical flash's duration is indeed about 500 microseconds to 1millisecond. It takes a typical camera's shutter about 1/200 second to open and close, so faster shutter speeds (where both shutter curtains are moving at the same time) are incompatible with flash photography, as only a band is illuminated. In practice the only things that you can't freeze with a strobe in underwater photography are the strike of a mantis shrimp and the snap of a hungry frogfish's jaws...

 

... you need studio lights and a fast shutter speed or highly specialised and expensive strobe lighting to freeze a hummingbird's wings!




#337288 Asking for your views on strobes for Nikon D7000 in Nauticam Housing

Posted by tdpriest on 21 September 2013 - 03:49 PM

I used a D70 with Inon Z220 strobes, then a D200 and D300, and now a D800 in a Nauticam housing with fibre-optic cables to twin Inon Z240s for wide angle and twin Inon D2000s for macro, with a Sola 600 for focussing and as a shooting light (at iso 800). Straw filters behind Inon's diffusors work nicely in warm water; in cold, green water the Inon strobe's colour temperature is an advantage.  Ikelite D161s are big, the battery pack is cumbersome and I'm not sure that anything provides top-notch performance as a strobe and a video light...

 




#336772 Parable of the Clyde - excellent economist article on the perils of overfishing

Posted by tdpriest on 07 September 2013 - 02:35 AM

This is one of Britain’s biggest environmental disasters of recent times. But it is not widely known. Until 2010, when two marine biologists predicted, on the basis of historic catch data, that the Clyde was about to become Britain’s first “ecological desert”, it was scarcely mentioned in the national press. Even then the Clyde won no political champions... Nor has the devastation sparked public protests such as those against hydraulic fracturing (or “fracking”, a technique for producing oil and gas) that forced an energy company called Cuadrilla to stop drilling in Sussex this month.

 

 

Not for want of a warning: in 1981, when I first dived in the Clyde, it was obvious that fishing was damaging the Firth: one fellow PhD student had his research wiped out when scallop-hunters began to "frack" apart the maerl beds that shelter fish fry and crustacean larvae. There is a long, long history of British marine biologists picking up the warning signs of over-fishing, being ignored or ridiculed...

 

... then being proved right.

 

Plymouth 2011 047 HMS Scylla Coryphella lineata_1.jpg




#336675 Whale Shark Shooting Tips

Posted by tdpriest on 05 September 2013 - 03:12 AM

You need the "good visibility" setting when choosing the "ocean" mode...

 

:evilgrin2:

 

 

If you get this wrong, then the best that you can do is wait in the mirk:

 

2010 Baja California 836 La Paz whale shark.jpg




#336429 Maybe not important but an interesting take...

Posted by tdpriest on 29 August 2013 - 04:54 AM

:notworthy:  A definite hint of the 60s, John... 

 

... Jimmy Saville and Stuart Hall have muddied the water on our side of the pond, perhaps.  :nea:

 

:evilgrin:  In the 21st century you might include a "ripped" young bloke in the middle (for gender balance) next time (although the whole cover image is fattist, ageist and hence objectionable to the average British diver: why do American divers look svelte)?  :evilgrin2:




#336422 Wide angle improvement suggestion

Posted by tdpriest on 29 August 2013 - 01:48 AM



One of the things I notice about good wide angle shooters is that many times they create depth in the image by having subjects at different distances from the camera in the frame.  No different than in landscape photography really.  Same idea.  Foreground, middleground, background.

 

Steve

 

You have to push the iso in northern light, but you can still balance the strobe-lit foreground (a foot away) with the background (six feet away: super wide-angle lenses make this trick work best); you don't get the superlative sharpness that Steve shows in a tropical image, but the principle works, I think:

 

2013 Shetland 089 334 Bressay cave %22Goose%22.jpg

 

Bressay, Shetland: the Goose at work.

 

Although I have two strobes, the right-hand strobe is turned off to reduce backscatter in front of the Goose.




#336394 Go north!

Posted by tdpriest on 28 August 2013 - 09:04 AM

It may as far north as the Yukon, but Shetland is great for photographers: have I done the islands justice?

 

Don't worry: the underwater images do appear, eventually!

 




#336393 Cold, grey and misty... I'll have some, please!

Posted by tdpriest on 28 August 2013 - 09:01 AM

The full set of images has been prepared at last:

 

 

 

The trip seems to have been even better than I remember!




#336193 Nauticam Nickon v2 housing

Posted by tdpriest on 23 August 2013 - 06:52 AM

When do you need it?

 

There's an Elvis Costello song:

http://www.elviscost...Is_Unrepeatable

 

... I didn't know that he had predicted the rise of Nauticam's shaman of sales!




#335627 Dolphin Dream 2013

Posted by tdpriest on 10 August 2013 - 03:50 PM

 

A few too many though in my opinion Tim

 

I take them to share, not to hide...




#335625 Buoyancy Arms

Posted by tdpriest on 10 August 2013 - 03:40 PM

Stix...