This is the real question of U/W photography when it comes down to brass tacks. How much of a pain it the ass are you willing to put up with for improved image quality? This question ranges from the micro 4/3rds cameras up to the Scarlet systems. Smaller is easier and you can argue that it is "just almost about as good". Bigger is ( so much harder to carry and pack) but slightly better. Logistics is the task-master of underwater photography. Do your put all of your photo gear in carry-on, or do you tell your wife that you are checking 200 pounds of photo gear, and she can not bring her entire shoe collection?
You knew the answer to this question before you asked it. A huge mega dome WILL make a difference in image quality. A big friggin' dome always has better optics than a smaller dome. The question is "is it worth the trouble?" It is impossible to answer that question for you! Can you take an increadibly good image with a smaller dome? YES!, Would the same image taken with a larger dome probably be a little bit better? YES! Is a bigger dome a lot bigger pain in the ass to travel and free-dive with? YES!
The other posts above have great merit, but you really need to decide what lengths you want to go to, in order to get the best possible image.
I use the red beam on my Sola 800 photo 90% of the time when I am night diving. It attracts way fewer bloodworms. Even when I might use the white light to look for creatures, I switch to red once I locate one. I find most creatures out at night tend to shy away from the white light more than the red.
Turbohampster asked "Maybe a stupid question but has anyone noticed any difference in the buoyancy of their housing when using a vacuum?"
The density of air at sea level at 15°C is 1.225 grams per liter. Pumping the housing down to negative 10" Hg at the surface will decrease this by roughly 33%, resulting in about 0.408 grams per liter change in weight by applying the vacuum. Most DSLR housings have an internal volume of less than 2 liters, so the change in buoyancy will be less than 1 gram.
Sorry about that Draq! I will try to clearly answer the 2 questions posted in this thread using what little expertise I have in the area as a hyperbaric physician. I will not get drawn into a pettifoggery once again.
Your question if the negative pressure generated by the Nauticam system will make it less likely to flood -the answer is yes, because the o-ring is sucked into the mating surfaces of the housing, preventing blow-by.
watboy, your question if an additional benefit of a vacuum system would be that it would eliminate condensation issues , the answer is no. It will greatly decrease them though. If you close your housing at 30°C and 75% relative humidity, condensation will form when the housing wall reaches 25°C. Under the same conditions, If you pump the housing down negative 10 inches Hg, condensation will form when the housing wall reaches 18°C. Starting conditions will certainly modify the results, but not the manner in which you can calculate the benefit. The explanation is below.
Condensation forms at the dew point which is when relative humidity (RH)= 100%
RH= partial pressure of water vapor (PW) / vapor pressure of water (VP) at a given temp.
Vapor pressure of water at a given temp. (VP) is independent of pressure
When you decrease the pressure by 10 inches Hg, you are decreasing the pressure inside the housing by 30%
Following Dalton's law, decreasing the housing pressure by 30% will decrease the partial pressure of water (PW) by 30% once the temperature equilibrates. Therefore, relative humidity will decrease by 30%
So starting at 30°C and 1atm and a RH of 75%, pumping the housing down to .7atm will yield a RH of 67.5% once the housing equilibrates with the 30°C ambient temp.
Using the dew point curve we know that at 30°C and 75% RH the dew point = 25°C
Using the dew point curve we know that at 30°C and 67.5% RH the dew point = 18°C
So after vacuum there will be a 7°C degree difference in how cold you have to get the housing wall before condensate will form.
I will be happy to answer any questions not originating from Interceptor.
2. If he has a comprehesion deficit issue and really belives what he is posting, he has my condolences.
Either way, he does not care to understand or is unable, and will continue to argue in esoteric circles. I have, to no avail, done my best to help him grasp what most find to be a fairly easy concept. I apologize for helping to so horribly hijack this thread.
If anyone ELSE is still interested in this material, follow the links provided to see the lab set-up we use for our undergraduates, which demonstrates the physical properties described in the preceding discussion.
"I would have thought you could have logically solved this by just looking at extremes" Indeed Watboy, but there is the rub. Sometimes logic falls upon deaf ears.
"Knowledge and truth may be within us without judgment, and judgment without them; but the confession of ignorance is one of the finest and surest testimonies of judgment that I know" Michel de Montaigne,
I'm not entirely sure what you're saying here, sincerely hope you are finally agreeing with what we've been trying to explain to you and the reams of information that has been shared
Doubtful, Interceptor, you have just agreed that dew point temperature will decrease as you create a vacuum, this means that the realtive humidity decreases BY DEFINITION. So you CAN derease the relative humidity with a hand pump. Q.E.D.
I watch the relative humidity INCREASE in the chamber with every treatment. I have supervised 2 treatments already today. I will certainly post is the converse happens for any remaining treatments today, and I will also let you know if the sun decides to set in the east today.
Condensaton occurs when a partialy saturated gas is cooled or compressed to the point where the molecular density of the solute gas molecules reach the maximum threshold. Decreasing the the molecular clusters in a given volume (if you pump the housing down to about negative 10 inches Hg the decrease in molecular clusters is about 30%) will allow a greater degree of compression or cooling prior to reaching the condensation threshold. So YES, a vacuum system can decrease internal condensation issues. For illustration, if you take a volume of gas which is very humid (near saturation) and compress it (via like gas injection) in a pressure vessel, condensate will form on the lining of the vessel.