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Canon 20Da / 50D DSLR Comparison

 

  

 

 

 

 

 

 

 

 

 

 

 
  Shown below are multiple views of M66, taken on the same night, in 4-hour period, first using the older Canon 20Da 8mp DSLR, then the newer Canon 50D 15mp DSLR.  Critical focus was checked/adjusted immediately prior to both exposure sequences and so focus was identical and perfect in both. 

Note that the 20Da has been factory-modified for higher red light sensitivity, whereas the 50D used for this comparison has not yet been modified and so has lower red-light sensitivity.  For that reason, a galaxy was chosen as the comparison object since galaxies are generally more color-balanced than nebulae.

Three comparisons are shown:
     (1) Same pixel crop width of 1080 pixels wide resized to 800 pixels;
     (2) Same sky coverage area around M66; and
     (3) Same sky coverage, both resized to 800 pixels wide

Note that due a higher pixel density, the 50D has an effective 1.35x (approximately) magnification when the same pixel crop from the raw image is used; M66 appears larger in the 50D photos in the first two comparisons for that reason.

All 6 photos in all three comparisons were processed in ImagesPlus and Photoshop using identical parameters for Digital Development, levels/curves, and median filters.

Conclusions:  the 50D shows greater detail and finer stars than the 20Da.  Also, the 20Da has an obvious amp-glow (not shown in the comparisons below due to cropping) in the lower-right corner of most images that is quite visible when the brightness is stretched, but the 50D shows virtually no amp-glow at all.  Noise comparison is inconclusive at present; more comparisons are planned that will hopefully bring conclusions on noise characteristics.
  Object Spiral Galaxy (M66), in Leo
  Telescope (Photo) Celestron 8" SCT OTA @ f/6.3 on Losmandy G11 Mount
  Telescope (Guiding) Meade ETX 90mm OTA @f/13.8 on Losmandy G11 Mount
  Camera (Photo) Canon 20Da and 50D DSLR (back-to-back comparison)
  Camera (Guiding) Meade DSI Pro II w/PHD Guiding
  Exposure Detail BOTH IMAGES:  Excluded-Average combination of 15 images at 300 seconds each, ISO1600; RAW file conversion, calibration (bias and dark only), and initial image processing using ImagesPlus 3.75; final image processing using Photoshop CS3
  Location Cincinnati Astronomical Society's Dark-Sky Site (Adams County, Ohio) (N38.876, W83.464)
  Date 04/25/09
   
SCROLL DOWN FOR 20Da/50D COMPARISONS

 

First Comparison:  Same Pixel Crop (1080 resized to 800 Pixels Wide)

Comparison 1

 

Second Comparison:  Same Sky Area Coverage

Second Comparison

 

Third Comparison:  Same Sky Area Coverage, Both Resized to 800-Pixel Width

Third Comparison