craig

The ideal flash tube is a point source. Unfortunately, a tube that small is limited in output. A circular tube is a good design because it more closely approximates a point source than a long, straight tube does. The reason a circular tube is better than a small, straight one like those in Japanese strobes is greater power handling. I've had small, straight video light bulbs that give 180 degrees of the smoothest light you will ever see. A circular tube is not inherently better than a straight one for quality of light IMO. It's hard to separate theory from practice. From the little information I've gathered, hotter strobe tubes are more efficient and that's why the Japanese are running at 5500K. I believe that filtering down to 4500K breaks even on efficiency. As long as the strobe is easily filterable, I'm fine with 5500K. I think it's a given that larger strobes have wider coverage, though how much really depends on the strobes you are comparing. Without diffusers, how much softer are they? With diffusers, how much different are they? The beam pattern is obviously the key differentiator yet it is hardest to quantify. Yes, the Japanese value smallness in strobes like many other things. They are innovating there. They are also pushing fiber connections and optical TTL. I asked where the non-Japanese manufacturers are innovating because I'm not seeing much. Big, heavy packages with custom batteries and fat, circular tubes have been done for a long time now. Some are pursuing integral TTL but I want to get rid of sync cords. Because of bouyancy, size and weight are really two sides of the same issue. The new Inon S-2000 is offering about 125 Ws/kg at over 650 cycles/charge and 1.5 second recycle time. How does that compare to other manufacturers? An Ike DS-200 looks to be about 105 Ws/kg, similar recycle times but with 4x the power and 1/4 the cycle count. Travel weight is potentially worse with custom batteries and chargers. An Inon Z-240 offers over 150 Ws/kg by my guestimate. Inon doesn't publish Ws figures but you can guess by cycle and battery ratings. I feel that mounting and cabling are the big challenges to using multiple small strobes in place of a large one. I'd also like to see a mode of operation where slave strobes can be controlled by a manual master. Of course, like Alex I'd like to see Inon make a wide angle strobe at twice the power of the Z-240 yet stick with AAs.

I would have to ask, then, what have the non-Japanese strobe manufacturers been chasing? Why is a smaller package incompatible with quality of light?

Tubes and diopters work via different means but they accomplish the same thing: closer focusing distances. Tubes have the downside of requiring port (and possibly focus) changes, lowered focusing light, and reduced focusing range (compared to diopters). Some believe that tubes offer better image quality but that appears dependent on the lens. Wet diopters are changeable underwater but you can also use dry ones. The problem with both tubes and diopters is that there's a limit to how close you can get to a subject. Because of that, eventually you will have to go to a TC. There's no reason not to use a TC and a diopter together. My feeling is that once you do to the longer focal length that a TC provides, you won't need the far focusing distance anyway. I usually add a dry diopter at that point. You could also consider the Sigma 150 if you find you really like the 100 + 1.4x combination and use it a lot. The downside is traveling with the extra lens and port and the increased need for a diopter due to the longer minimum focus. The upside is the brighter viewfinder and potentially better IQ. I would rather personally use the 150 than a 100+1.4x and also rather use a 150+1.4x than a 100+2x. The longer option is useful on the 5D.

I agree with Steve. I think it's a mistake to almost get a subject in the frame but cut off its fins. You need either more or less. My impression on the color is that you have crushed blacks too far. I'd like to see more detail in the shadows and that would probably lighten and desaturate the image somewhat. I like the striking appearance but would like to see into the anemone more. I think the second image is technically better. I would prefer both to be slightly less tight on the subject but, like Steve, I don't concern myself with what judges look for. Both of these images compelled me to look at them and I think that's the goal.

Except that's not true. NiMH batteries won't "explode" in the same sense that LiIon batteries can. Besides, the link simply shows that the maker of your light has had products explode. Note that not one but four separate Salvo incidents are referenced in addition to one reference to a LiIon explosion and you might read TobinGeorge's post on page 2. Not everyone has the knowledge and skill to understand how to make such products sufficiently safe and I'm too skeptical to take the word of a manufacturer in fire-fighting mode. It's not just LiIon that's the point here either. Huge energy storage, violent battery chemistries, lethal ballast voltages, and soft plastic enclosures with cheesy clips don't mix in my opinion. There have recently been incidents of notebook batteries catching fire and exploding. You would think, considering the volumes in that market, that engineers would put careful thought into preventing that. It shows you the difference between LiIon and NiMH in terms of potential for catastrophic failure. I have a bias against large LiIon batteries and I have tried to explain my reasoning. It's not important to me to change your mind. Further, I am not advocating anyone undertake a DIY project, I was simply showing what I achieved (quite a while ago) in contrast to your claim that LiIon offers much greater power in the same size package. I believe 100Wh in 3.5 pounds is pretty good achievement and it doesn't involve nearly the injury risk or any full-custom charger solution. LiIon can do better but not with off-the-shelf cells that are designed small enough to be safe in the absence of custom safety engineering. I would still like to know the Wh ratings of those LiIon packs. Ah is not a rating of power. Airlines have restrictions on both Lithium content AND overall power and 100Wh is the largest allowed without permit. Looking at Salvo's current site, it appears they are offering packs in the 250Wh total capacity range. If those are a single pack, then technically they are hazardous cargo and you can't just stick them in your checked bags (legally). I was advised by my engineer whose career was LiIon batteries, charging circuits and power supplies, that my target battery size in LiIon (similar to Salvo's large packs BTW) if exposed to a total flood could very well blow me into pieces underwater. So, yes, that's what I'm trying to say! Just because an anecdotal flood doesn't result in explosion doesn't mean it can't happen.

Certainly you can't deny that explosions have occurred involving Salvo LiIon packs if you read that thread. I read every posting and it doesn't change that basic point. Further, there seem to be plenty there that understand the basic issue that LiIon is much more risky in the event of failure (especially around water) than other battery chemistries. It makes curious what research you did. I'd still like to know what you meant by "Li-ion should react no more violently than NiMh if exposed to salt water if done right." It is not a matter of rapid energy release due to shorting, LiIon batteries can literally explode like dynamite. I have seen videos of small batteries blowing the ICs off of circuit boards and totally destroying an entire computer chassis. NiMH cannot do that. BTW, I would never do business with anyone who relied on Barry's work and I would NEVER put a large LiIon battery in anything Barry made. I have personal experience with Barry's work, he made some canisters for me that I quickly threw away due to their inadequate engineering, and would never risk my life on any of it. I could say worse.

Salvo Li-Ion 35w HID light Explosion

You will see the difference once you get underwater. Anything under an effective focal length of 35mm (the entire range of the 12-24 on DX) will exhibit increasing distortion and reduction in angle of view. The 12-24 shouldn't be used behind a flat port. The 18-55 should be useful in Cocos but I agree that it should also be used with a dome port. If you are shooting fish portraits with the lens then a flat port is fine, but if you want to use the wide end a dome is better.

What does doing it right involve? LiIon is harder to charge and (generally) requires the extra smarts. This isn't a problem for a commercial product but it is a consideration for a DIY project. LiIon chargers need to be matched to their batteries, NiMH don't. The key measure isn't energy per unit volume, it's energy per unit weight. Weight determines travel-ability and dive-ability. LiIon, done right to insure safety, requires a lot more metal packaging to prevent a catastrophic event. The battery chemistry offers a density advantage but it gives it back in packaging weight. Many years ago there were no LiIon off-the-shelf cells that had better energy per pg than the best NiMH. That may have changed but I haven't noticed the proliferation of large LiIon cells recently. When I did my custom batteries a while back I still worked at Dell and was good friends with the battery expert there. He offered to help be build custom LiIon packs and to connect me with suppliers. He also told be that there would be a serious explosion risk at the sizes I wanted. If that's not true, I'd like to see any data that says LiIon doesn't suffer those concerns. LiIon packs in notebook computer sizes have exploded and killed people. My video light batteries were considerably larger. limeyx, is your solution custom or a commercial product? Details? You said 15Ah instead of 10Ah. At what voltage and what size? Here is the rig I did quite a few years ago: Each battery pack was 21 cells of NiMH at 4.5Ah and weighed 3.5 pounds, producing a 25V pack that drove 24V bulbs from 50-400 watts. At high currents I claimed the packs were 100Wh to comply with airline regulations Also shown are the single pack and double pack cannisters that allowed me to dive with up to 450 Wh on my backplate at about 12 pounds of negative bouyancy. The batteries were rated to 3C discharge and would allow up to 1200W for about 15 minutes. The most I ever used was 800W and I got over 25 minutes out of them.

http://wetpixel.com/forums/index.php?showtopic=25163 The 35mm, 50 + TC and 100mm options do substantially different things. A 100mm would not be too long for the right subjects, but adding a TC to a 100mm might. If you wanted more power, I'd say get the TC with the 50. The 35 will be better for fish portraits.

I've had this happen occasionally but not in the last month. What has changed for me in the last couple weeks is the "View New Posts" function. It's never worked well but recently it has changed what it considers "new". I now get 17 pages worth of new threads dating back 2 weeks.

This is not a heated debate, at least not to me, it's an interesting discussion. Don't interpret any challenge I make as advocacy of anything. I'm merely playing devil's advocate to the pro-MCCR points here. Yes, I have no experience with CCR. As for that first statement, is it wrong? The purpose of my question was to lead to the following: The computer is life support equipment even if it doesn't control anything in the CCR. In OC and SCR, the mix and depth determines partial pressures but in CCR they deliberately vary. There is a potential for problems when there is a difference between what you breathe and what the computer thinks you breathe. MCCR doesn't eliminate exposure to electronics, it either reduces them or trades them for other risks. I'd like to understand why someone who feels strongly against ECCR because of risk and complexity, and who advocates MCCR instead, doesn't consider SCR as an alternative. I have had some experience with SCR. I agree with John that photography takes too much of my attention to devote myself to constant monitoring to solve a problem that should be solved with automation. Here's another analogy. Imagine for a moment that someone believed that the pressure sensor in a dive computer posed and unacceptable failure risk and implemented a computer, instead, that required the diver to frequently enter current depth manually. It is inarguable that this new computer would have one less mode of failure, but is it more safe as a result? Does the mandatory user input force the diver into safer diving habits? I think the clear answer to both those questions is no, yet the logic involved is identical to that being used in support of MCCR superiority here.

I don't consider those to be deaths due to failure to monitor gas supply. There are far more problems than that. I also don't view several over a period of years to be "all the time". That's not what you are arguing though. You are claiming that manual is better because it creates a user than is inherently safer in his habits. Not only is this not true for everyone, if there are problems with current automation systems that's not evidence that there shouldn't be automation systems. But then there are electronics that can fail, right? How does a manual CCR diver eliminate any dependency on electrical systems yet ensure that his computer is always modeling his actual partial pressures? Do you also dive tables to eliminate the possibility of computer error or failure? It seems to me that there is additional risk in having a computer model that doesn't correspond to actual partial pressures. You either accept that or you expose yourself to electronics failures anyway. I wonder what people that are afraid of CCR control electronics have against SCR.

No they don't. I don't think OC divers die all the time for any reason, but to the extent they do it's not because of gas monitoring. OC divers cannot experience hypoxia and, depending on conditions, might not be at risk of oxygen toxicity either. If they are no-deco diving, even an out-of-air condition is managable if they don't panic and there's plenty of warning with modern gear. I may suffer serious injury or death if I make other mistakes like fail to monitor depth, bottom time, deco, ascent rate, etc. but I simply won't die if I fail to monitor my gas supply (subject to conditions that I know up front). That's not the analogy I'm making. The analogy is that both approaches claim to solve a problem by removing technology that is valuable yet is perceived to be imperfect. I'm simply saying that mCCR is throwing the baby out with the bathwater. I think that's a reasonable position to take. Different people respond differently and may well be better suited to different gear. I won't ride a motorcycle even though I know they can be ridden safely. With mCCR does your dive computer know the partial pressure of the gas you are breathing?

This is some very weird logic. The manual approach no more compels good habits than anything else and likening the risks of open circuit negligence and rebreather negligence is clearly flawed. Under the right conditions I can dive open circuit and never once glance at my gauges. I shouldn't do so but I won't die if it happens. I'm following this thread with interest, but I find the argument that manual CCR forces good habits and is therefore superior to be akin to claiming that doing away with all traffic lights and stop lights improves traffic safety. It does not, of course, what it does is slow traffic to a crawl. The same effect could be had by outlawing cars. Doing away with rebreathers will "improve" their safety, too, but not in the way people want. A true improvement would be to make a system that really works better, not one that strips functionality to a minimum.

It appears that this strobe has a power supply similar to a DS-160, a color temp at least as warm, and a wider beam width. Anyone have any underwater brightness measurements? I'm curious how bright it is capable of. An optical trigger would be nice.

Just FYI, the difference between 4300 and 4800K is 25 mireds, or an 81B warming filter. The difference between 4800K and 5500K is about the same.

Here is the list of current Sigma lenses. Yes, there are two 17-70 lenses. Both are macro, one is HSM and the other is not. The HSM version is bulkier and does not fit all port systems. There is also a version with more limited zoom range (18-50) but with faster f/2.8 constant aperture. It also comes in two variants.

Can Subal do it? Nikon requires the popup to be fully extended so it needs more clearance than Canon. Seatool also supports popup flash.

I have one of Apple's 256GB SSDs and it is slow. (<100MB/s). I would advise against it especially at their price.

Yeah, my NEC humbles the notebooks when displaying granger rainbows...and it's matte. Surprised to hear about the 24"monitor tho. I've never liked glossy but people here have advocated them. The new MBP's antiglare option isn't matte, it's a coating with an alternate bezel I found less attractive. Since I couldn't see it I opted out. I'll adjust to the gloss and I had no problem calibrating it. Even tho the Dell is glossy it's not nearly as objectionable as the Apple. They've really gone for form over function there.

Yes, although I'm not sure pure blues exist so much underwater. The greens are much wider so I don't know which would be better for water tones. These graphs don't show luminance. I could provide those or even provide the icc files for anyone interested. The MBP showed less posterizing overall because it wasn't so wide in red and green. The Dell showed the worst posterizing in greens and obviously different treatment of blues next to the Mac. It is interesting to see the distinct differences in these displays when displaying Granger rainbows. Both machines are huge improvements over my old CCFL MBP. Both are glossy, but the Dell's gloss is less objectionable. I'll have to get used to a display where I can always see my own reflection.

Recent workstation-class PC notebooks have been shipping with optional wide gamut displays. Although I'm a Mac user, I set out to obtain and test and example and determine the feasability of running OS X on such a notebook. My first machine was the Sony AW series. I ruled the machine out because of the unacceptable size and Sony's policy of refusing parts necessary to perform system upgrades. The LCD looked good but I didn't test it. I ruled out the Lenovo because it has the narrowest gamut and used CCFL. That may have been a poor choice but that's what I thought at the time. I also ruled out Dell's M6400 because of its massive power supply and mandatory $1000 graphics option. I tried to obtain an HP DreamColor notebook but HP direct turned out to be too difficult to work with. I ended up purchasing a Dell M4400 15.4" notebook. Installing OS X is doable on a Dell notebook but supporting the various peripherals is a lot of work and power management isn't great. I made the machine work well enough to test and benchmark but left a number of components unsupported. Having a quad-core processor made the Dell more than a match for any Apple portable running photo software. Shortly after my Dell purchase, Apple announced the new MBP 17s with a wider gamut so my efforts shifted toward comparing the two. Here's the result: The first graph shows the new MBP display against the old CCFL MBP 17. AdobeRGB is shown in white. The new display has a much broader gamut than the old one. The second graph shows the new MBP display in green, the Dell M4400 display in red, and my NEC3090 in blue. As you can see, the Dell has a larger gamut overall than the Apple but not in all areas. It's not clear which display is better for UW shots between the two. Because of that, I have cancelled my pursuit of OS X on the Dell and will be keeping the new MBP. The Dell is much faster and has some nice flexibility features (like dual hard drive) but it's not enough to put up with the downside of OSx86 for me. Leaving "the fold" is only justifiable to me if the advantage is compelling. The Dell doesn't accomplish that but it would make a great choice for Windows users. Both notebook displays are 6 bit and posterization can be seen on test images. On real images I haven't seen a problem.

If anything, this discussion underscores the subjectiveness our eye and our recollection of a scene. Emotions color our memory even to the extent that some aren't sure whether light rays are straight or curved. The truth isn't so important as what people want to see. I am bothered by the curved rays and the unnatural surface while others prefer it. I think the final image posted is a good compromise and would choose it if it were my shot. I think the least change that provides the desired improvement is the right one. The slight curvature in the surface is not unnatural.

I have Fisheye-Hemi. Don't have much experience with it yet. Here's a plugin that appears to be interactive. I've ordered it but haven't gotten to download it yet.