One of the hazard of living in coastal region like ours is high level of humidity. Hot and humid weather we have, is perfect breeding ground for the fungus. The relative humidity (RH) here is around 90% RH during most of the year. When exposed to moisture or high humidity, fungus easily grows on your lenses and are almost impossible to clean. The fungus obviously degrades the optical image quality and very difficult to repair successfully back to original state.
Even electronic circuits don’t fare well in humid conditions and malfunction or shut down. Since prevention is better than cure, for fungal damage, there are several methods to avoid fungal growth. I have covered them in my earlier blog here – Camera’s Worst Enemies – Humidity, Fungus
Dehumidifiers are the easiest and safest way to prevent fungal growth. Most Dehumidifier cabinets use what is called thermoelectric cooling technology to reduce the relative humidity of the air inside them. Dehumidifiers are extremely effective, and can reduce the time you spend on modifying your camera’s environment, they also generally draw insignificant amounts of electricity while doing the same.
My first dehumidifier was Kalabhai’s Digi Cabi. Even though it was advertised as manufactured by Kalabhai in Mumbai, other than his sticker on the machine, every other part was made in China. This analog dehumidifier was pain to adjust. A hairline shifts of the rotary adjustment dial used to change the setting vastly.
I soon upgraded to Ailite brand of dehumidifier which was again made in china with a very awkward motto printed on the cabinet – WETIS MOISTURE PROOF. Despite such a funny motto, it worked well. Soon I outgrew it, and upgraded it over next few years, as my camera gear started filling it up. So from 40 litres, I went to 90 litre one, which few weeks after purchase developed problem with power supply. The unit was replaced by seller. I also did test another brand which was available in India, Benro dehumidifier. I found the cabinet was much flimsier to Ailite. With the purchase of 500mm lens I had to upgraded to Ailite 130 litre, which is what I have at present.
Ailite & Benro were the only two models which were available till now near my place. Both brands do suffer from occasional component failures. Being Chinese products sold in India, they all have only one-year warranty and are difficult to service as we don’t have service centers. It is too bulky to carry the whole cabinet and get it repaired. Main dehumidifier component as well its power supply are the major cause of breakdown in both these brands.
Few days back when I received news that Anish George, one of my favourite camera dealer from Video Links, Kannur was getting new brand of Dry Cabinet – Sirui, I asked him to send one for review. I am familiar with Sirui as I already have used their excellent carbon fibre tripod. Recent Singapore trip I got one more of the tripod from the same company. They are considered Gitzo replacement at ¼ the cost. So I asked Anish to send me a cabinet to test. Few days back he sent me 70 Litre version – Sirui HC-70 Electronic Humidity Control Cabinet. Packing was excellent. Even though it was 70 litre cabinet, but it was physically looking larger than Benro 88 litre cabinet. So I sat down with specification to check the internal volume. Here are the results
Sirui HC-70 Internal Dimension was 24 x 14.4 x 11.6 inches which works out as 4009 inch3 or 65.7 litres. Benro Dry Cabinets LB-88 Internal Dimension was 14.8 x 13.4 x 18.9 inches which works out as 3748 inch3 or 61.4 litres. So Benro is clearly cheating here. It claims to be 88 Litre, but has less internal volume than 70 Litre Sirui! If you notice the side by side comparison photos in this review, you can notice that Benro 88L is significantly smaller than Sirui 70 L.
Once I opened a well packed cabinet and found it has an extremely well built metal body. This cabinet enclosure is constructed from welded 1.2mm-thick cold-rolled steel. It was heavier and very much sturdier than Benro as well as Ailite. There were two plastic shelves which are adjustable vertically in their spacing. Trays were made out of tough plastic and felt very sturdy and can slide out smoothly. All trays came with a foam material mat on top to prevent scratches on delicate equipment.
The front of the cabinet was tempered glass with a steel handle. The door can be locked with a key. Unlike Benro & Ailite cabinets, Sirui cabinet keys are unique to every cabinet. So if your friend brings his Sirui cabinet keys, he can’t open your cabinet. Whereas, other cabinet provide identical keys to every cabinet they sell. On the back of the cabinet, there is a removable power cable with 3 pin 5amps socket. Box also contained an instruction manual and a warranty card. Sirui provides 6 years’ warranty on the cabinet (3 years’ warranty on electronic parts). The cabinet has four legs which are individually height adjustable legs, so as to make the cabinet stand perfectly still even on an uneven surface.
There is a control panel at the above the front door of the cabinet with display which tells the Relative Humidity reading in %, temperature reading in Centigrade or Fahrenheit. There are 4 buttons. One is Lock, other is Set and middle two up & down buttons are for adjusting humidity values. Once you press Lock for a brief duration the lock symbol disappears and you can now set the required humidity using the up and down buttons. Once the desired RH is reached you can lock it using the lock button. I suggest 45% RH as anything between 40-50% RH is ideal for camera equipment. Remember the reading has accuracy of + /– 5% RH. Too much of dryness by lowering humidity to less than 30% RH may lead to drying up of oil components and cracking of rubber or plastic parts on your equipment.
Just to be sure use another hygro meter to cross check the humidity which is shown by the cabinet. I used HTC 288 CTH thermo hygrometer to cross check this cabinet.
After connecting the cabinet, I left it for 4 hours to settle down and absorb all the humidity which was built in during transport. The factory setting of the humidity was 25%, which is too low and raised it to 35%. At the end of the 4 hours I checked the humidity has actually dropped from original 62% RH, to 35% RH. Then I placed my 2 bodies and several lenses to check the performance.
As I opened the cabinet I noticed interior of the cabinet was having a peculiar chemical smell. The cabinet is fitted with photocatalyst Titanium dioxide (TiO2). It is used as microbicide. Titania (TiO2)-based nanocomposites subjected to light excitation are remarkably effective in eliciting microbial death. So bacteria and fungus are eliminated by actually killing them. You can check more about it in this scientific paper published in prestigious science journal Nature (http://www.nature.com/articles/srep04134)
Most dry cabinet manufacturers (both Ailite & Benro) use Thermoelectric cooling technology. Thermoelectric dehumidifiers use a Peltier heat pump to cool a surface and condense water vapour from the air. The condensed water from inside the cabinet is taken out by absorbing sponge on the draining channel and sent out. The design is simpler but, because of its relatively poor coefficient of performance, this design is mainly used for small dehumidifiers. If the electricity stops then the thermoelectric cooling pad will stop working thus allowing the humidity to build up. Imagine going on holiday for 2 weeks and coming back to find that your power had tripped, exposing your camera equipment to whatever levels of moisture allowed into the dry cabinet.
Sirui for its dehumidification uses molecular desiccant sieve (MDS) which is under the micro-computer control. This desiccant is stored inside the Humidity control component box.
When the Cabinet humidity is higher than the set humidity, the MDS absorb the moisture inside the cabinet, thus dropping the cabinet humidity. In that process they get saturated. This process is similar to Silica gel. Once the humidity is reaches closer to the set humidity, vent connecting the interior of the cabinet is shut down and the exhaust vent at the back of the cabinet is opened by micro-computer. The chamber holding the MDS is now heated with built in heater and that releases the moisture inside MDS, which escapes outside. The dried MDS is now capable of absorbing water again. The vent at the back shuts down and the internal vent opens if the humidity is not yet reached to the set point, thus exposing the MDS to the interior of the cabinet. Dried MDS again starts absorbing moisture and the cycle continues.
These molecular desiccant sieves are hydrated aluminosilicates (zeolites) of the alkali earth metals. They have a high affinity for water and have the capability of adsorbing and desorbing it without damage to their crystal structure which makes them useful as desiccants.
This process is totally different from the one, Ailite and Benro which uses Thermoelectric cooling technology. It has advantages. If the electricity shuts down in Thermoelectric cooling cabinets, dehumidifier function stops working as electricity is needed to heat the Peltier element and to create differential temperature between interior and exterior. Without electricity humidity raises rapidly inside the cabinet as the same absorbing sponge which sends the moisture out of the cabinet now without electricity allows the moisture to come inside and equalize with exterior.
In Sirui Cabinet, as the molecular desiccant sieve is not dependent on electricity to dehumidify, it continues to reduce humidity for a longer duration, Sirui claims up to 24 hours. Sirui also uses this process to conserve electricity. As soon as the humidity reaches the set value, the micro-computer drops to power save mode and shuts the electrical supply to the Humidity control box. It will not be activated till humidity raises to 5%RH above the set point. While cabinets which work on Peltier technology need 24 hours electricity and try to maintain humidity, Sirui takes long naps to save electricity.
To actually test I used my Ailite cabinet and a borrowed Benro 88 litre cabinet with Sirui. I set all their humidity to 35% RH and once they reached that I switched off the electricity of all of the cabinets. I switched it on after every hour (for few seconds to check humidity) without opening the door of the cabinet for 6 hours. At the end of 6 hours Sirui has risen to 41% RH and Ailite was at 53% RH and Benro was at 55% RH. Room humidity (outside all these cabinets) during this period was 62% RH. Sirui beat others hands down in this test.
Since Sirui uses pretty aggressive power saving option, it saves lot of power and the cabinet really frugal in power consumption. Sirui claims 1.3-3.4 kW/month electricity consumption for this 70 litre cabinet. Benro and Ailite are usually rated at 5-10kW/month as they need a constant fan rotation. Sirui dehumidifier does not use any fan and thus is silent, whereas the Thermoelectric cooling dehumidifiers need constantly running fan which also increases their electricity consumption.
While in power save mode, Sirui looks almost fully switched off without the normal blinking green LED light. I think they should have provided another light which signalled that it is in power save mode. Only way I could make out is by a very faint LCD panel read out which still shows the humidity reading without any back light.
So here is my verdict. Even though almost all dehumidifiers available in India are from China, Sirui stands apart with following few points.
- Very sturdy high strength well-built metal cladding for the cabinet.
- Innovative dehumidification mechanism
- Long term maintenance of low humidity in case of power failure.
- Nice sturdy plastic trays with soft materials to support delicate equipment.
- Using TiO2 microbicide to further resist fungal growth.
- 3+3 years of Warranty.
- Fan less and silent.
- Extremely low power consumption.
- Internal volume is larger than other brands of the same size.
- No annoying bright LED display to spoil your sleep 🙂
- Power saving mode looks almost fully switched off.
If you are looking for a very sturdy dehumidifier with an innovative technology and 6 years of warranty with extremely low power consumption, Sirui fits your requirement perfectly.
This is my first detailed product review of this kind, in my blog. Please send your comments and suggestions to improve it.
Disclosure: I was not financially compensated for this post. I received a sample for review purposes. The opinions are completely my own based on my experience. I was not required to write a positive review. Some of the photos of the cabinets are used from Sirui website. The dehumidifier mechanism was drawn by me, may not be technically accurate, but only used for illustrative purpose. Building a DIY dehumidifier based on my drawing may not work 😉
EXIF info – Aperture : ƒ/22 | Camera : Canon EOS 5D Mark III | Taken : 5 February, 2013 | Flash fired : no | Focal length : 40mm | ISO : 200 | Shutter speed : 1/2s | Images and content Copyright © Krishna Mohan. Please contact me to purchase prints or for image publication license.