camera buoyancy???

[Spectre]

I guess we won't be seeing too many photos of Whale Sharks, huh?

You just have to be prepared. That's why they sell 100# wings.

 

[O-ring]

Does this same phenomenon apply to digital cameras? Each time you take another photo, you add more photons to your camera making it heavier?

Yes. I alluded to that above, but you want to make sure you match your buoyancy compensator and/or liftbag setup to your memory card with a digital. Those larger memory cards (and esp the 4-5 MP cameras) require, as Spectre pointed out, at least a double bladder 100# wing and/or some large lift bags if you plan to shoot more than a few shots.

 

[Jester]

If your memory cards are almost full when you begin the dive, can you use your camera as a lift bag by deleting the pictures underwater?

 

[Mo2vation]

Good point, Truva! The larger the underwater creature or object, the more negatively buoyant the resulting picture. You can remedy this on a digital camera by deleting bad pictures or pictures of large things to make the unit more positively buoyant, but on a film camera you are stuck!

Although O-Ring over-compensated for years with the Oringadella light, do not be fooled into thinking size matters. This subject-size issue impacting rig buoyancy is a common misconception.

Every underwater photographer knows (even newbies like me) that its not the size of the subject, but the exposure of the subject.

I get dialed in neutral at the start of the dive, with batteries full and card empty. As the batteries drain (making the rig more positive...sort of "off-gassing" electrons) that loss in molecular weight is generally offset by the increase of electrons on the card (effectively "on gassing" the rig.)

A seldom spoken of, little known theory however (Min Olta's law) states that the ongassing of electrons can be offset in camera by simply over exposing your shots. The theory (paraphrased here for space considerations) essentially postulates that over exposed images ("lighter" images) weigh marginally less than correctly exposed images, and significantly less than under exposed images (darker images.)

We at GUE (Glorious Underwater Exposure) have formulae for this, but I don't want to go into them in detail on a public board like this one. Our instructors cover all of this (in our class, PIXL/f) in great detail. I suggest you sign up for PIXL/f and we can teach you precision molecular buoyancy and calculating average exposure on the fly.

By applying Min Olta's law during the dive (doing the math in your head, on the fly... using computers for this rot the brain), you can effectively compensate for the camera's ongassing by simply offgassing some electrons by over exposing your images. This has been well known by Navy divers, Cavers and film users for years, and is only starting to make it into the digital and recreational dive community. I understand there was even a PhotoShop plug-in shown at PMA in Las Vegas last weekend that will correctly compensate for these over exposed shots.

Its the reason most of us shoot in Manual mode underwater. Of course, the use of an external strobe can create the equivelent of a run-away ascent (by over exposing shot after shot) and thus making your rig dangerously buoyant if set incorrectly. This is the reason most new photographers are urged to shoot with on-board strobe in Auto mode for the first several months, until they get a handle on managing their rig's molecular buoyancy using Min Olta's law.

Some agencies still believe you should only control your buoyancy with your BC, and ignore the precision molecular buoyancy control that can be achieved through applying Min Olta's law - but the cutting edge agencies like PADI are all over this one, and they will be offering an underwater photo theory specialty in the near future (with appropriate documentation-for-purchase.)

I hope this cleared up the size-of-the-subject misconception.

K

 

[MarkH]

I am just getting started in photography and have a question about how to set up the proper buoancy for my new camera. On one hand I think my rig should sink so that it doen't run to the surface if I somehow lose it. On the other hand I think it should float in case it gets dropped at the end of the dive. Has any one tried to set their rig up so that it sinks and then attach a small collapsible float to it so that it will float at the surface and sink at depth?

I agree that your camera should be slightly negative or neutral (easier said than done). I find a positively bouyant camera to be annoying during use. If you want it to be negative at depth, but positively bouyant at the surface, why not wrap a piece of neoprene wetsuit material around the camera or strobe? This way the unit will float at the surface and sink at depth as the neoprene compresses.

 

[10X]

Being a newbie to diving and underwater photography, I was totally unaware of Min Olta's law, as explained by Mo2vation. And to think I took an underwater photography class before I went to Hawaii and it wasn't explained. The nerve of some instructors.

I shot some 300 plus underwater photos, most of which were bad. I did not delete then from my camera since looking at a bad picture was better than looking at no picture. Even the bad picture brings back memories of the vacation.

Now that I am home, I have downloaded all these bad pictures onto my desktop computer (and the good ones). Can the excess weight caused by these bad pictures be the cause of the recently discovered crack in my computer desk?

In addition, yesterday I bought a laptop computer. If I take this on vacation, and download another bunch of bad pictures on it, could I be risking a baggage over-weight charge, if I am not careful?

Perhaps Mo2vation would care to elaborate in these areas.

 

[MaresMan1]

Now...... I have heard everything LOL.

Mo2vation......brilliant. I can see an paper coming :cheeky:

Dive Smart; Dive Safe
Enjoy the ride
:cool1:

 

[Dee]

Motivation....could you explain what the effect of Min Olta's Law has on the wieght of our cameras on land? The total weight of all those photos stored on our cards will have even more impact out of the water.

 

[FredT]

I agree that your camera should be slightly negative or neutral (easier said than done). I find a positively bouyant camera to be annoying during use. If you want it to be negative at depth, but positively bouyant at the surface, why not wrap a piece of neoprene wetsuit material around the camera or strobe? This way the unit will float at the surface and sink at depth as the neoprene compresses.

If using an acrylic or polcarbonate housing the housing will slighly decrease in volume with depth. IF you have it trimmed to exactly neutral at 10', then on the surface it will float slowly or remain in position, at depth it will be _slightly_ negative due to housing and seal compression (we/re talking small parts of a gram here either way.) Ideally you should have to chase a dropped camera down current, not vertically in either direction.


FT

 

[MildlyDamp]

Mo2vation's response made me remember another important factor. Each time you use your strobe it gets lighter, because there's less stored light in it. This, together with the used up electrons probably makes the camera positively buoyant over time.

In any case, I believe all this is covered in PADI's Peak Camera Buoyancy course. It's only $350 (excluding equipment).