Canon 7D versus 50D (and 5DM2) Black Frames


I've owned a Canon 50D but recently upgraded to a Canon 7D. One interesting comparison is shooting with the lens cap on to generate "Dark Frames" to see what residual noise there is in the sensors. These test images were taken in a dark room (with the lens cap on!) at F/16 with a 1/1000s shutter speed - would be interesting to do long exposures to check for amplifier noise and hot pixels. You normally will see some noise, even at low ISO's, unless the near zero RGB values are clipped by the camera/processing; but that, of course, results in a loss of shadow detail ... which also happens as you crank up noise reduction. Note that in the RAW processing, the default black level is used (5 in ACR), so this makes the images look cleaner, but reduces detail/noise. While appropriate for normal pictures, 0 would have been better for this test - pointed out by AndreasH - thanks! Because the 7D's sensor is 18MP versus the 50D's 15MP, the crops are a per pixel (rather than per image) noise comparison. Finally, I was also able to get some images from a full-frame Canon 5DM2 which is the current king of low noise cameras.

Since the image is pretty dark (DUH!), I have pushed it six (!) stops in Photoshop (Image->Adjustments->Exposure) after applying a "Threshhold Level 1" correction to zero out RGB values of 1 - this makes it much easier to see differences. ACR does some noise/dead-pixel filtering even if it is set to zero noise reduction, and this is very clear if you compare to the DPP processed images. Javascript is used to "flip" the images so give it a few seconds the first time as the browser caches the image; after that, you can quickly go back-n-forth to compare.

Simply click on the link below of the camera you would like to see the image from, which ISO, how shot, and which view. Choose Camera: 7D - 50D - 5DM2     (see conclusions below)
Choose ISO: 100 - 200 - 400 - 800 - 1600 - 3200 - 6400 - 12800
Choose How Shot: RAW+ACR - RAW+DPP - JPEG w/no NR - JPEG w/max NR
Choose View: original resized or actual pixels cropped from center

Canon 50D at ISO 6400 - RAW with DPP and Pushed Six (!) Stops in PS - original resized

Some Initial Observations/Conclusions
  1. Turning on JPEG noise reduction helps considerably, but this test does not show how much quality is lost.
  2. Even at ISO 100, there is residual noise that shows up - look at actual pixels ... but this is being pushed six stops.
  3. CS4/ACR does some noise reduction, even with the NR sliders set to zero.
  4. DPP is doing some sort of processing (appears to be less noise) different than the in-camera generated jpegs.
  5. The 7D has much less horizontal banding - click on the "original resized" and compare the 50D to the 7D at high ISO.
  6. This lack of pattern in the noise produces a more grain-like appearance.
  7. Even on a per-pixel basis, the 18MP 7D appears to have less noise than the 15MP 50D.
The combination of less noise/pixel and more pixels means that Canon 7D images will be less noisy than the 50D

An Internet Surfer sent me some dark frames from a Canon 5DM2, so I have added those. This is a full-frame camera with a much larger sensor and therefore not exactly a fair comparision to the crop format 50D & 7D. However, the Canon 7D compares well to it, but size matters when it comes to imaging sensors, and the 5DM2 is still the low noise champ.


P.S. I first used Photoshop Equalize, but that didn't provide a similar comparision. One could also use Threshold, but pushing 6 stops seems to provide an interesting comparision of not only noise levels, but how dynamic range suffers at higher ISO's. Photoshop CS4 was used to process the photos - note that ACR5.5 only has a Beta profile for the 7D. DPP was version 3.7.

This is a brand new 7D and there is negligable dust on the sensor ... which would not have any bearing anyway.

Yes, I'm a bit of a gearhead ... on a related note, here's a High ISO comparison of the Canon 7D and the 50D
Also, the Canon 50D can shoot fine pictures and did an excellent job in Antarctica and Falklands & South Georgia Islands.



I welcome any comments/suggestion on all this - back to the main Canon 7D versus 50D page