Go Back   Steve's Digicams Forums > Misc Forums > Underwater Digital Photography

Reply
 
Thread Tools Search this Thread
Old Apr 4, 2003, 12:26 AM   #1
Senior Member
 
Join Date: Dec 2002
Posts: 331
Default underwater housing for 4500

I am considering buying a nikon cp4500 and was wondering if there is an underwater housing available for around $150-200?
ardvark50 is offline   Reply With Quote
Sponsored Links
Old Apr 5, 2003, 2:04 PM   #2
Moderator
 
Join Date: Jun 2002
Posts: 26
Default

Dream on... the EWA Bags are OK for splash, but not for serious 'underwater'.
Harbortronics is offline   Reply With Quote
Old Apr 5, 2003, 4:04 PM   #3
Senior Member
 
Join Date: Dec 2002
Posts: 331
Default

Actually, all i want is a reusable casing that i can take should i ever go snorkling, or take pictures in the rain, like those made for the canon a70.
ardvark50 is offline   Reply With Quote
Old May 12, 2003, 1:47 AM   #4
cz
Junior Member
 
Join Date: May 2003
Posts: 1
Default

I don't know what you possibly thinking? Ewa housings rock! The N-950 housing for the 4500 is less than $150 is as waterproof as any hard case and easier to handle and as far as "splashproof, not for serious underwater" borders on ludicrous. A no brainer!
That's unless of course serious means spend more money! Ewa invented the first flexibles housings in the early 1970's and they are still selling serious flexible UNDERWATER photographic housings faster than they can run them off the assembly lines. My mates have logged 1000's of hrs. with digitals, slrs, and video in Ewa housings w/o a single incident. I know housings and your best bang for the buck is Ewa Marine!

CZ
cz is offline   Reply With Quote
Old Jun 9, 2003, 4:40 PM   #5
Junior Member
 
Join Date: Jul 2002
Posts: 15
Default

Pressure at atmospheric conditions - surface = 14.5 psi

Pressure at 30ft saltwater = 30psi

Pressure at 60ft saltwater = 45psi

Pressure/bending resistance of the EWA bag = none

Your camera is roughly 10 square inches across - you do the math...:-)

For more information on available housings, see www.wetpixel.com

Cheers
James Wiseman
jamesw is offline   Reply With Quote
Old Dec 21, 2003, 1:19 PM   #6
Junior Member
 
Join Date: Dec 2003
Posts: 3
Default

Actually, the pressure is not quite that bad. The differential pressure at depth is the specific weight of water (62.4 lbs/sq ft for fresh and 64 lbs/sq ft for salt) times the depth in feet. At 30 feet we have 1920 lbs/ sq ft or, dividing by 144 sq inches per sq ft, 13.33 lbs/ sq inch for salt water. The inside of the case is already at atmospheric pressure of 14.7 lbs/ sq inch on a standard day so you do not have to add that to the pressure on the case as this pressure acts to counter the pressure exerted by the water. Don't know how the various cases stand up to this pressure.

The same calculation as above is where we get the rule of thumb that for every 33 feet we get one more atmosphere of pressure in salt water (works out to be 33.92 feet for fresh).
Tipper21 is offline   Reply With Quote
Old Dec 23, 2003, 10:24 AM   #7
Junior Member
 
Join Date: Jul 2002
Posts: 15
Default

That math doesn't apply as the fluid inside the bag is air - so it's compressible.

Cheers
James
jamesw is offline   Reply With Quote
Old Dec 23, 2003, 2:54 PM   #8
Junior Member
 
Join Date: Dec 2003
Posts: 3
Default

Should have been clearer. The comments were for a rigid case. The computation above gives the gauge pressure at depth ( or pressure above atmospheric) thus the total or absolute pressure is 13.33 psi + 14.7 psi=28.03 psi absolute at 30 ft. But the pressure inside the case is 14.7 psi thus the differential pressure across the case is 28.03-14.7 = 13.33 psi. This is the pressure the case must withstand.

For the flexible case, the air inside will indeed compress and, by Boyle's Law, will reduce in volume until the pressure of the air in the case is the same as the water pressure outside. Unless the camera has some airtight areas in it, the pressure inside and outside the camera will equalize and be the same, hence no differential pressure and no forces tending to crush the camera. Could still have a problem, however, if the volume of the flexible case is so small that it compresses to tightly surround the camera and can't decrease its volume any more as you descend. In this case a pressure differential will develop between the inside and outside of the camera that could be a problem. Have to look at specific cases to see if this would happen.

You can prove a lot of this to yourself by an experiment the next time you dive. Remember the demonstration where you take a sealed plastic bottle down on a dive? The water pressure will crush the bottle. Next time try this. Take the same bottle down but don't cap it. Hold the bottle upside down so the air can't escape as you descend. The increasing water pressure will compress the air in the bottle and water will be drawn into the open mouth. At depth the bottle will still have the same amount of air in it but compressed to a smaller volume at a pressure equal to the surrounding water pressure. Most importantly, the bottle will not be crushed at all--no differential pressure between inside and outside.

Cheers, Don
Tipper21 is offline   Reply With Quote
Old Jan 7, 2004, 2:24 PM   #9
Junior Member
 
Join Date: Jan 2004
Posts: 2
Default

Ok, so I am not a math wiz--does that mean the EWA bag is ok for snorkeling or no? I went to Wetpixs.com and searched the forums but did not see anything Marine bags.
c3p1 is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 4:25 PM.