Jump to content


Barmaglot

Member Since 30 Mar 2017
Online Last Active Today, 06:51 PM
-----

#395598 Meikon vs Meikon SeaFrogs for RX100

Posted by Barmaglot on 20 May 2018 - 09:50 PM

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.




#394962 Show me your GH5, How you trim your buoyancy?

Posted by Barmaglot on 01 May 2018 - 01:50 PM

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.




#393353 The DSLR / Compact Dilema

Posted by Barmaglot on 14 March 2018 - 10:24 PM

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.

 

Someone does - https://meikon.com.h...r-fujifilm/x-t2




#393312 The DSLR / Compact Dilema

Posted by Barmaglot on 14 March 2018 - 09:37 AM

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.




#392974 which of 3 strobes for cave diving, imaging for science

Posted by Barmaglot on 04 March 2018 - 12:15 AM

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.




#388291 Switching to a Mirrorless

Posted by Barmaglot on 11 October 2017 - 07:25 AM

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.




#387432 RAID suggestions

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.




#385514 WTB: Sony A7Rii Housing & Gear

Posted by Barmaglot on 02 July 2017 - 05:07 AM

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.




#383566 BlueFire 5000 Lumens Diving Light

Posted by Barmaglot on 25 April 2017 - 07:20 PM

If you look under the 'feedback' tab here, someone has measured it to draw approximately 2.2A, which results in an output of some 600-800LM.