Posted by Barmaglot
on 23 November 2018 - 10:18 PM
Parking the wet wide lens on the bottom of the tray sounds like an excellent way to get it all scratched up when you bring the camera down to the sand for a macro shot. Acrylic domes pick up scratches really easily; you want to park it where it's least likely to touch anything - like, for instance, facing inward off a strobe arm.
Posted by Barmaglot
on 12 September 2018 - 04:35 AM
Okay, so now that I'm back, and on a decent connection, I can summarize my experience, good and bad, from a dozen dives with a pair of ST-100s.
The good part is that they work, after a fashion, and that they're comparably inexpensive, though at $460 for the pair, still not exactly throwaway money. For my first run at using strobes, rather than natural light or constant LED beams, I got some photos that I'm reasonably happy with, for instance:
The bad parts are, unfortunately, quite numerous.
The initial pair of strobes that I received died after a few test fires on land - one stopped charging (the ready light stayed red), while the other had a green light, and the pilot LED would turn off upon triggering, but the strobe wouldn't fire. After an exchange of messages with the Aliexpress seller (Cameraman's Store), they instructed me to ship the faulty strobes back to Meikon in Hong Kong (cost me about $30) and sent me a replacement pair via EMS, with the shipping taking about a week in each direction.
While on land, both strobes appeared to fire, on the first dive I ended up with a bunch of images lit only from the right - the left strobe either wasn't firing at all, or out of sync with the camera. After fiddling with knobs and buttons, I somehow got both of them to work in TTL mode - facing the camera and pulling the trigger, I could see the double flash of TTL from either strobe (was testing them one at a time), but for whatever reason, the left strobe was still firing a single flash while on land - and sometimes this single flash would sync with the shutter, and sometimes it wouldn't.
I'm not sure that the TTL compensation works - I was getting some overexposed shots, and I tried to dial it down to -1EV, and it may have helped, but I couldn't do a controlled environment test, so it may also have been me changing the composition or the camera metering settings.
The manual mode does not work. Whatever I did, at least with the right strobe, I was getting a double flash of TTL. Pushing in the right-side magnetic switch, releasing which helped to activate TTL on the left strobe, did not deactivate TTL on the right strobe.
The YS-mount attachment bolts have large, easy to use handles to turn them - unfortunately, this causes one side to bump into the tray handle when I tuck the strobes in for a CFWA shot, or when I mounted them together with my video lights on triple clamps for night dives. I only had a leatherman with a bit set with me, so I couldn't get at the hex head screws holding the mount adapter, but I think with a longer allen wrench I can flip it around so that both bolts face outwards.
Both mode knobs, regardless of their utility or lack thereof, have tiny black arrows indicating where they're pointing. My eyesight is perfectly adequate, but at depth, these indicators are almost impossible to see without pulling the strobe right under the mask. I suppose a dab of white paint will help with that.
This may be a case of excessive expectations, but I kind of expected to have more power. Trying to light up a fan coral a couple of meters across, at around 20m depth, there just wasn't enough output to kill the natural sunlight - I had to fix the white balance in post and ended up with purple water, to wit:
Yes, I know that the water color can be fixed too, and the shot isn't framed right, and I should've shot at closer range using 10mm focal length rather than 13mm (there was some current and I was afraid of getting too close) but that's not the point. To be sure, it may be a limitation of my camera - I saw a post today, by Pavel Kolpakov, claiming that built-in camera flashes tend to have a maximum burn time of about 1ms, while powerful UW flashes pulse for as long as 4ms, so triggering with the built-in flash may be incapable of extracting the full output of the flash in TTL mode. BM davec13o2 tested it with wired sync, and I understand that for him, the manual mode worked, including the variable power, but I don't have a wired sync bulkhead option on my housing, and I'm kind of reluctant to spend $500+ on a TRT Electronics LED trigger, which might not work with ST-100 to begin with.
Bottom line, while I'm not a particularly angry customer, I'm not a satisfied one either. I expected the same value deal from Meikon strobes that I got from my Meikon housings, and I did not get one. I will be having words with the seller again, but I don't expect much to come of it. I imagine I will use these strobes for a few more trips, then relegate them to backup status when I convince myself to part with the cash for a pair of Z-330s or YS-D2Js. In hindsight, I likely would've been better off paying a couple hundred dollars more for a pair of used YS-D1s or Z-240s.
Worse yet, with a fully sealed housing, sea-level pressure trapped inside while ambient pressure drops may cause your dome to pop out of its seal - it's designed to withstand external pressure squeezing it in, not internal pressure pushing it out - and that may require a factory repair. Therefore, when you're taking your housing on a plane, it's best to ensure that it is not sealed - keep it open, or close it without o-rings, or dismount the port, or remove the vacuum port cap, doesn't matter what as long as it can freely equalize internal and external pressure.
Long focal lengths don't help you underwater - even the most clear water absorbs light very quickly, and you're not always lucky enough to have clear water to begin with; far too often you'll have silt and other particulates obscuring your view. Imagine shooting in a dense fog - how much will a telephoto lens help you there? Therefore, the cardinal rule of underwater photography is to get close, and if you think you're close enough - get closer still. Focal lengths in the 90-120mm range (FF-equivalent) are used for macro shots of small critters, not for shooting from afar.
But if you want to use two handles (because you have two lights and want to have a nice steady grip on the whole rig, getting to the shutter trigger is hard. A trigger on the right handle would be awesome.
I recently came across this on Aliexpress: https://www.aliexpre...2882123729.html- ordered one for my Sony A6xxx housing; it should arrive in a few weeks and then I'll be able to report on how well it works in practice.
The newer SeaFrogs housing fits the entire RX100 line (I through V), is rated for 60 meters rather than 40 meters, and has the zoom knob of the left side of the housing rather than in front, by the lens port, which is a lot more accessible. It is also made of almost opaque plastic, rather than transparent plastic of the first generation housing, which is better at stopping light leakage if you're using the internal flash to trigger strobes. It is, however, considerably more expensive - $250 or so, while the older housing can be easily found discounted to under $150. Note, however, that all Meikon housings for RX100 line, as well as the official Sony housing do not give you access to the rear dial, so full manual shooting is very awkward - you have to assign either aperture or shutter speed to the lens ring, and go to menus to switch between them. Finally, and here I'm not 100% certain, but the lens location in RX100 I/II and III/IV/V is slightly different, which, in the Sony universal housing, results in models I and II having the lens slightly off-center in the port, which makes it incompatible with add-on wet lenses. The SeaFrogs universal RX100 housing uses additional shims to fit the different camera models, so it might or might not be affected by the same issue.
More powerful lights do reach further, but the thing is, the intensity of reflected light reaching your lens decreases with the fourth power of distance - i.e. double the distance, and the light intensity decreases sixteenfold. If you get proper illumination from 14k lm at 1 meter, you'll need 224k lm to get the same effect at 2 meters. You can get a lot more range by using a narrow beam, but it doesn't help with video when you need to illuminate the entire field of view.
Hmmm - I haven't done any research yet into the Sony A6300 but will take a look. Thanks for the heads up on the gear and housing costs - my research had led me straight to that lens but without looking at price tags. Forgive my ignorance, but when you say dedicated Macro Mode, do you have to switch to that before the dive and stay with it for the entire dive, or can you toggle in and out of the macro mode during a dive?
If you use the Nauticam housing ($1450 for E-M5 II, $1900 for E-M1 II) with the dedicated port and gear ($800), you can toggle it on and off during a dive; otherwise it's set for the duration. 12mm (24mm equivalent) at the wide end isn't very wide, but you can augment it with wet lenses, same as you would for a compact. Of course you can also set up for dedicated wide-angle or macro with the appropriate lenses and ports.
I've looked at the mirrorless cameras, but am not super impressed - although the housings are definitely smaller. Ever since the root kit fiasco I refuse to go near Sony, but I am really liking the Fuji mirrorless cameras. If someone makes an inexpensive housing for one of the XT series that would be great.
A Sony A6300 is roughly the same size as your Canon G12, but it packs an APS-C sensor. Olympus OM-D series M4/3 cameras are similarly sized, and Olympus 12-50mm lens even has a dedicated macro mode, although utilizing it takes an expensive gear in a very expensive housing.
A strobe emits a single strong pulse of light that is only a few milliseconds long (disregarding high-speed sync here). This is useful for freezing motion with a short exposure (typically 1/250s or 1/160s for system cameras; less for compact cameras with a leaf shutter), and constant lights can't get even close to a strobe's brightness within that brief instant. However, if you're photographing static subjects (which it sounds like you are), and can manage a long exposure (very much not trivial underwater, but not impossible), you can end up gathering more luminous flux from a constant light than you would from a strobe.
All things being equal, distance is the factor that matters the absolute most - the intensity of the reflected light that reaches your camera lens decreases with the fourth power of distance between the emitter/receiver (your camera rig with lights) and the subject - i.e., if you double the distance (for example, from 5 feet to 10 feet), the amount of light that reaches your lens decreases sixteenfold. Triple the distance (from 5 feet to 15 feet) and your light goes down by a factor of eighty-one. The LX10 has a fixed lens, so it can't natively go wider than 24mm equivalent (add 30% for a flat port), but I would suggest considering getting closer to the floor and either using a wet wide lens to increase the field of view so that you can cover the same area from a shorter distance, or just taking more smaller images and stitching them together in software later on.
If you buy used and focus on macro, a used Sony A7 II body can be found for ~$900 or a bit less, a 90mm F/2.8 macro lens is another $700 or so, a Meikon housing is $140 on Aliexpress, and the KitDive port for this lens is $99 direct from Meikon - total $1840 for camera, lens and housing, give or take a hundred or two depending on what deals you find. Any lights, strobe or LED, will take you over the budget limit though.
Posted by Barmaglot
on 09 September 2017 - 09:11 AM
As a server/infrastructure admin in my day job, I have to stress a point: RAID is not a backup! RAID provides business continuance in the case of a certain class of failures, though it is by no means a guarantee by itself. Furthermore, RAID5 is the least reliable type of RAID besides RAID0 (which, by strict definition, is not RAID at all), especially as your arrays get bigger.
To illustrate, imagine an 8-drive RAID5 array where a drive fails - you're immediately in degraded mode, where reads have to be reconstituted from parity data, and any additional drive failure kills your array dead. Then, once you replace the failed drive, or your hot-spare (if you have one) kicks in, the array, while still degraded, is put into maximum stress mode - the rebuild process reads all the data from all the drives to build the blocks on the new drive, and that's where one of three things can happen: (1) everything is fine, the array is rebuilt and you go back into normal mode, (2) another drive fails under stress (and drives from a single batch sometimes fail close together) and your array dies, or (3) as your data is rebuilt, a bad block is discovered on one of the remaining drives, and with redundancy gone, it cannot be rebuilt, resulting in a condition known as 'punctured stripe' - your array is still online, but some data is bad, and normally you will need to destroy the array, rebuild it with good drives and restore the data from backup.
RAID6 avoids these two latter scenarios by computing two sets of parity data, which enables it to survive double disk failures - at the cost of higher overhead (lower performance) and lower raw space to usable space ratio.
RAID10 (stripe of mirrors) has the highest performance, but also the worst raw to usable space ratio of the common RAID levels (only half of your raw space can be used), and it can survive most, but not all double-disk failures. To illustrate, in the same 8-drive array configured as RAID1, you have drives 1+2, 3+4, 5+6 and 7+8 configured as mirrors of each other, and then your data is striped across these four sets of mirrors. If drive 1 dies, the array can survive the failure of any drive other than drive 2 - better than RAID5 (which can survive no additional failures) but worse than RAID6 (which can survive any one additional failure).
An important feature of any RAID system is proper maintenance and monitoring - drives have to be periodically scanned, and an administrator has to be alerted of any errors, in order to take immediate corrective action.
In a home user scenario, unless your datasets are very very very large (tens of terabytes and up), there is little use for RAID. Almost inevitably, it will provide a false sense of security, while left unmaintained and will eventually die - taking your data with it. I have seen this scenario play out more than once. If your goal is data integrity, then instead of RAID, invest in a proper backup system, with versioning and off-site storage. Backblaze, for example, will let you back up unlimited data for just $50/machine/year. Unlike RAID, this will also protect you against data corruption, user errors, ransomware infections, hardware theft, site disasters, etc.
I think the Meikon housing for A7II series, bought new, will run you a small fraction of a Nauticam and the likes, even used. You won't have the pressurization test system, and your port selection is limited to a single flat port and a single dome, but you get what you pay for.