Introduction:
As of January 2011, for nearly three years I have been imaging with "Version III" of my whole camera peltier cooler as detailed HERE. The cooling system has been working very well and astro images taken with the cooled camera can be seen HERE. The cooler has been providing a temperature drop of up to 44 degrees Fahrenheit. For the peltier/heatsink/fan assembly, I used a unit from a Thermo-Electric Travel Cooler branded "RubberMaid". The cooler was made by Vector, Inc. and is branded under other names as well. It operates on 12 volts DC and Vector also makes a 6-Amp AC/DC converter to operate the cooler using 120 volts AC.
RubberMaid is no longer marketting the cooler but these type of low cost coolers have become widely available for vehicle use and are available from many manufacturers. In order to locate a peltier device that would perform as well as the peltier used from the RubberMaid cooler, I purchased two other brand coolers and tested the cooling performance of all three coolers as detailed below.
Thermo-Electric Coolers Tested:
The three coolers were all purchased from online sources. The specifications of each as provided by the manufacturer are below:
1. RubberMaid Cooler - Model #VEC222RB
2. RoadPro Cooler - Model #RPAT-788
3. Wagan Tech - Model #2260
The three coolers tested outside of their boxes:
For the testing I used the same Canon T2i (550D) camera body with body cap and its viewfinder taped over with electrical tape. The temperature probe was taped to the top of the camera body in front of the flash shoe. A timer remote control was used to take 24 exposures over a 2 hour period, each 5 minutes in length, with a 15 second interval between exposures at ISO 1600. A Vector 12V DC 6-Amp AC/DC converter was used for powering all three coolers. An AC power adapter was used to power the 550D for all tests.
The camera settings of the 550D for all tests were as shown below:
The photo below shows how the camera was placed inside each cooler for testing:
Test Results:
Keep in mind that these cooling results were with the camera body just resting on the bottom of each cooler. The testing was done solely as a comparison of the cooling power of the coolers. The level of cooling and noise reduction obtained is less than that if a whole camera peltier cooler is made with the same peltier devices, since the cooling chamber would be sized for cooling the camera and would be directly and firmly connected to the camera body. The level of actual cooling using the peltier from the RubberMaid cooler for a whole camera peltier cooler can be seen HERE.
The graph below compares the temperature readings from the camera body temperature probe over the two hour period. The upper line shows the temperature increase of an uncooled camera. The RubberMaid and RoadPro coolers dropped the camera body temperature at nearly the same rate and to the same degree. The Wagan cooler lagged the other two coolers by about 3 degrees Fahrenheit. Since the RoadPro cooler (7 Liters) is larger than the RubberMaid cooler (5 Liters), the slightly slower rate of cooling with the RoadPro cooler is understandable and at the end of the two hour period the RoadPro cooled the camera a little lower than the RubberMaid.
On the graph below the temperature readings from the EXIF data of the captured 5-minute RAW files were plotted along with the camera body temperature probe readings in the above graph. The EXIF temperature plots show how quickly the camera's electronics heat up during the first half-hour of taking exposures before the cooling effect begins to lower the temperature. There are a few obvious out-of-expected-value EXIF readings and I think they point to the inaccuaracy of the method used by Canon to measure and record temperature in the EXIF data. The EXIF data shows the same general cooling effect for all three coolers.
The graph below shows for an uncooled 550D how the temperature readings using a camera body temperature probe compare to the EXIF temperature readings as recorded in the RAW frames:
Dark frame noise test results:
For the graph below, I converted the ISO 1600 Canon five-minute dark frame raws to TIFs using Images Plus and then recorded the luminosity standard deviation of the whole color image for each dark frame. All three coolers appear to have reduced dark frame noise in a similar fashion.
The graph below is the same as above without the "uncooled" plot in order to better display the cooler plots.
Next, I plan to compare how well each of four Canon DSLR models respond to a whole camera peltier cooling system.
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Astro Imaging with Canon Digital Rebel XT Camera