I took a series of test images using a new Canon SL1 (100D) for comparison to test images of other Canon DSLR (1.6 crop factor) APS-C models popular for astro imaging. Comparison tests below also include those for a Full Frame Canon 6D. The test images include long exposure dark frames in bulb mode. Some information on the SL1 model along with tests and comparison results follow.
Note: The test results below for the T4i (650D) model are identical to the T5i (700D) model, because they are identical camera models with different labels by Canon.
SL1 Specifications:
In the chart above are specifications for the SL1 model compared to a few of the Canon models that are available for sale at this time and are popular for astro imaging. The prices are based on refurbished body only kits available from Canon, and online camera shops such as B&H Photo and Adorama. A more complete listing of models dating back to 2003 can be seen HERE.
The SL1 model became available in March 2013 and was introduced at the same time by Canon along with the introduction of the T5i (700D) model to replace the T4i (700D). The SL1 was advertised as the "the world's smallest, lightest APS-C DSLR". The SL1 model was built by Canon to offer an alternative to mirrorless cameras while maintaining compatibility with Canon EF and EF-S lenses. The SL1 is significantly smaller and lighter than the T5i, while offering the same 18MP resolution and DIGIC 5 processor. Differences between the SL1 and T5i models are below:
In the table above showing the differences between the two models, I think the most important for astro imaging is the articulating screen. If you've owned models with fixed and articulating LCD display screens, you understand the advantage of the articulating screen if you mount your camera on a telescope or a tripod. An articulating screen allows the display to be easily flipped out to the side and pivoted up or down 270 degrees and avoids having to bend into awkward positions to see the camera back display or cricking your neck.
The advantage of having a lighter camera for astro imaging is important to most, in order to avoid extra stress on the telescope's focuser. The smaller size of the SL1 may also be advantageous for those imaging with HyperStar SCT systems. From the chart above you can see that the sensor of the SL1 is the same as used in the T4i and T5i models. The T4i and T5i models test very well for long exposure noise and sensitivity as can seen in my tests posted HERE.
The photos below show the difference in size between the SL1 and T5i models:
Front View:
Top View:
Side View:
Battery:
The battery used in the SL1 model is different from other recent Canon APS-C models. It is the same battery (LP-E12) that is used by the Canon EOS M mirrorless camera. The LP-E12 battery is an 875mAH battery as opposed to the more powerful 1120mAH LP-E8 battery used in other Canon APS-C models. Canon claims the SL1 can take 480 stills if using the viewfinder on a fully charged battery. The T5i can take 550 stills. A comparison of the T5i battery (LP-E8) to the smaller SL1 (LP-E12) is shown below:
This review is from an astro imaging perspective and focuses mainly on camera features that are most important for astro imaging. You may want to see other camera websites for normal daytime imaging reviews of the SL1 model if you plan to do regular photography or infrared photography with a modified camera. The Canon models tested and compared here for long exposure dark frame noise were all non-modified.
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, 600D, 650D, 700D, 1000D, 1100D and 6D models. 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. All testing was done at room temperature. The settings information from Canon's DPP for the 100D, 600D and 650D camera dark frame test images is below. Please note that the setting of "High ISO speed noise reduction" was disabled for all models tested:
Below are the histogram displays using Canon's Digital Photo Professional software for the initial 5-minute ISO 1600 dark frame exposure of eight Canon models for comparison.
As seen in the above graphic, the 450D model that was king of the APS-C models for lowest initial dark frame noise is still best, but the SL1 (100D) is close behind. The 1000D continues to have the highest level based on DPP histogram displays. The initial 5-minute dark frame noise of the 550D and 600D are similar with the 650D being slightly better. 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 nine 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 6D image has 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 nine Canon models and are displayed in the graph below:
Relying on the initial dark frame performance is not representative of how DSLR cameras are used in the field for multiple continuous exposures. The histograms for four 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. Between the four cameras, the 600D has the highest noise level at the end of the imaging session based on the histogram display with the 650D having the lowest.
The image below compares the final 5-minute (after two hours) ISO 1600 dark frames of four 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 SL1 appears to be the noisiest.
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 six 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 eight camera models and plotted them below. In the past, with each new in-camera video capture model, Canon has been able to lower the internal temperature recorded in the EXIF data, but that didn't happen with the smaller SL1 model.
Summary:
Based on my review and testing of the SL1 camera and earlier Canon camera models, these are my observations most applicable for astro imaging:
What I liked:
What I didn't like:
Because the SL1 camera had a higher level of dark frame noise than recent APS-C Canon models when taking continuous exposures, I decided to return my SL1 kit to Canon. The advantage of having a smaller and lighter camera comes with the disadvantage of increased temperature and dark frame noise for long exposure deep sky imaging. I did not do my usual long exposure sensitivity tests, because I returned my SL1.
Additional test results for comparisons of the Canon Digital Rebel T4i (650D), T3i (600D), T2i (550D), T1i (500D), XSi (450D), XS (1000D), T3 (1100D) and 6D 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 camera CLICK HERE.
.....Order DSLR Astro Imaging Guides on CD-ROM by Jerry Lodriguss HERE......