In June 2011, I took a series of test images using a new Canon T3i (600D) for comparing to test images of other Canon DSLR models popular for astro imaging. Some info on the T3i along with comparison results follow.
What camera features are new?
The T3i camera kit includes a newer version (II) of the 18-55mm IS zoom lens that Canon has been providing with earlier models. Other than minor cosmetic changes on the lens, the new Version II of the lens seems very similar to the old version. According to Canon: "The major changes are the shape of the zoom ring rubber grip and the tapered area at the front of the lens." This is the same kit lens that comes with the T3 (1100D) model.
Articulated Screen:
The main difference between the earlier T2i (550D) model and the T3i (600D) is the articulating (swivel) screen added to the T3i. This feature can be a very useful one for those using the camera back display, as opposed to a computer screen for astro imaging. No more bending into awkward positions to see the camera back display or cricking your neck. If the camera is mounted in a telescope focuser, piggybacked on a telescope, or tripod mounted; the display screen can be easily flipped out to the side and pivoted up or down 270 degrees. The display screen can be positioned outward in its normal position on the back of the camera, as with previous models or completely turned facing inward, so the LCD display is not seen. This is a good feature to avoid errant light emitted from the display at dark sky sites and also to protect the LCD display glass from scratches. Both camera model screens are 3" in size and have the same resolution, 1.04 million dots. Because of adding the articulated screen, the camera weight and body dimensions have increased over that of the T2i. The T3i will not fit inside the Whole Camera Peltier Cooler if built to the dimensions on my web site.
T2i and T3i compared side by side:
Front View:
Top/Side View:
In the above photos, notice that the T3i (on right) has two port flaps as opposed to one on the T2i. The extra rubber grippy material of the T3i gives it a better feel when handheld and it provides a more secure grip on that side. The larger size of the T3i is very noticeable in the above photos.
The chart below has some key specifications for the T3i that can be compared to five other Canon models popular for astro imaging at this time. Notice that the T3i has the same number of effective pixels (18.7 million) and same pixel size (4.3µm) as the T2i, pointing to the same sensor used in both cameras. Both cameras have the same Digic 4 processor and use the LP-E8 battery. Both have a sensitivity range of ISO 100 to 12,800.
Movie Mode:
For planetary, lunar and solar imaging, the Canon camera model that has stood out because of its special "movie crop mode" is the T2i (550D). In movie crop mode, only the center 640 X 480 pixel area of the CMOS imaging sensor is captured at a speedy frame rate of 60 frames per second. The movie crop mode provides a 7X fixed zoom without video interpolation. This feature is not available on the T3i. Instead, a similar feature "Video Digital Zoom" is a function of the T3i that captures the center of the imaging chip, in a cropped zoom mode that is adjustable from 3X to 10X magnification. A drawback of the Video Digital Zoom feature for astro imaging is that the capture rate is limited to 30 frames per second, half the capture rate of the T2i. As an example, if imaging Jupiter with a 2 minute video, the T2i at 60 fps can capture 7200 frames from which to select the most detailed frames for stacking. Using a T3i at 30 fps would capture 3600 frames. I have an example of Jupiter taken with the T2i movie crop mode here.
Dark Frame Noise Testing:
My first testing with this camera model was to take a series of 5-minute dark frame exposures at room temperature and ISO 1600 over a two hour period as was done in previous testing that I have done for the 450D, 500D, 550D, 1000D and 1100D. A 15-second delay was used between each exposure. Camera settings were adjusted to be similar to those used for other models and found to be most conducive for astro imaging. The settings information from Canon's DPP for the 550D, 600D and 1100D camera dark frame test images is below:
Below are the histogram displays using Canon's Digital Photo Professional software for the initial 5-minute ISO 1600 dark frame exposure of all six Canon models for comparison.
As seen in the above graphic, the 450D continues to have the lowest initial 5-minute dark frame noise with the 1000D having the highest level based on DPP histogram displays. The initial 5-minute dark frame noise of the 550D and 600D are similar. For the purpose of these tests, please be aware that the dark frame noise levels for cameras of the same model type that I have tested over time can vary from unit to unit as discussed HERE.
The image below compares the initial 5-minute ISO 1600 dark frames of all six Canon models. RAW dark frame files were converted to 16-bit TIF files using Canon's DPP software and the TIFs were then cropped at center to 300 X 300 pixels using Photoshop CS5. The 600D image appears to have the lowest noise.
For the Full Frame TIF dark frame images, image pixel standard deviation values for luminosity of the initial dark frames were recorded using Images Plus for all six Canon models and are displayed in the graph below:
The histograms for three camera models are shown below, for both the initial 5-minute dark frame and the last 5-minute dark frame of the two-hour imaging sessions. The 1100D model with its minimal video circuitry maintains the lowest dark frame noise level at the end of the two-hour period based on the histogram display. Between the three cameras, the 600D has the highest noise level at the end of the imaging session based on the histogram display.
The image below compares the final 5-minute (after two hours) ISO 1600 dark frames of three Canon models. RAW dark frame files were converted to 16-bit TIF files using Canon's DPP software and the TIFs were then cropped at center to 300 X 300 pixels using Photoshop CS5:
For the final Full Frame TIF 5-minute dark frame images (end of 2-hour period), image pixel standard deviation values for luminosity were recorded using Images Plus for all three Canon models and are displayed in the graph below:
For the 5-minute dark frames taken continuously over a two hour period, I recorded the EXIF temperature readings from the RAW dark frame files over the two hour period for all six camera models and plotted them below:
Summary:
Based on my review and testing of the T3i (600D) camera model , these are the key features I found most applicable for astro imaging:
What I didn't like:
Check back for test results of the T3i (600D) compared to other camera models with peltier cooling.
Additional test results for comparisons of the Canon Digital Rebel T2i (550D), T1i (500D), XSi (450D), XS (1000D) and T3 (1100D) can be seen HERE.
For discussions on DSLR modifications and cooling for astro imaging, please consider joining the DSLRmodifications Yahoo Discussion Group HERE.
For my low cost astro & infrared modification service for your Canon DSLR cameraCLICK HERE.
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