Sony a7R vs. Canon EOS 6D: Long Exposure Noise Tests, HDR Bracketing, Panoramas and More

I've wanted to try the Sony a7R ever since I read Fred Miranda's review on using the a7R with Canon lenses. In addition to a sizable jump in resolution over the Canon 6D and 5D Mark III, the a7R's 36 megapixel full frame sensor reportedly has better dynamic range. The ability to lift the shadow details in underexposed a7R files is really impressive. Not having an optical low pass filter also makes these files quite sharp straight out of the camera. The a7R's sensor has offset gapless micro-lenses to help with wide angle corner performance.

Would these benefits improve image quality, resolution, and workflow for my type of shooting? What were the trade offs? I rented a Sony a7R and Metabones Canon to Sony adapter from LensRentals.com to find out.

360 Panoramas: Sony a7R vs. Canon 6D

I often shoot 360 panoramas in 4 shots on the EOS 6D with a Canon 8-15mm fisheye lens. The final file is 10,500 x 5250 (55 megapixels). The same lens and shooting pattern on the Sony a7R results in 14,000 x 7,000 (98 megapixels). This resolution gain allows more zooming online, and bigger prints. The 6D would require 6 shots around, 1 up, and 1 down to achieve this resolution.

The a7R files look sharper out of the camera, and wide angle lens edge performance is just as sharp at the edges as the 6D, if not better. The ability to lift shadow detail without a noise penalty is really impressive.

HDR Bracketing: Sony a7R vs. Canon 6D

For those of you who shoot HDR, it's important to note that the a7R's exposure bracketing options are more limited than on Canon.

Canon EOS 6D: Versatile HDR bracketing options Set your own exposure level increment in 0.3 stop intervals. Decide whether you want 2, 3, 5 or 7 shots.

Sony a7R: Fixed/Limited HDR bracketing options 0.3 stops/3 shots - 0.3 stops/5 shots 0.5 stops/3 shots - 0.5 stops/5 shots 0.7 stops/3 shots - 0.7 stops/5 shots 1.0 stop/3 shots - 2.0 stops/3 shots - 3.0 stops/3 shots

Most of the time, a 3 shot bracket at 2 stop intervals is enough for what I shoot. Occasionally I'll shoot a 5 shot bracket every 2 stops with the 6D. That's not an option on the a7R. Considering the added dynamic range of the a7R, perhaps the 3 shot 3.0EV bracketing would work OK though.

Conclusion: Despite the bracketing limitations, the a7R's extra sharpness, resolution, and dynamic range could be a big plus for the 360 panorama shooting that I do.

Long Exposure Noise: Sony a7R vs. Canon 6D

For night photography, having a camera that can produce clean files without the need to run long exposure noise reduction (LENR) is really helpful.  When LENR is turned on in most cameras, noise reduction runs after your exposure finishes.

If your shot is 5 minutes, the camera runs noise reduction for an additional 5 minutes before you can shoot again. During that 5 minutes that camera takes a dark frame that is used to subtract noise and hot pixels from your photo. This process is great for image quality, but can significantly cut into your productivity and battery life.

I know from experience that the Canon EOS 6D is clean in the 6-8 minute exposure range without using LENR (as long as the weather is cold). I was curious to see how the Sony a7R stacked up for night photography. I ran the cameras through a series of tests with long exposure noise reduction (LENR) turned off. The body cap was on. The ambient temperature was 66 degrees. The ISO was set to 100 on both cameras.

Noise Test Results: Sony a7R vs. Canon 6D

For exposures of 15 seconds, 30 seconds, 1 minute, and 2 minutes, both cameras produced clean files. There was little to no performance compromise for leaving LENR turned off in both cameras.

3 minutes: The 6D still looks good. The a7R is just starting to show faint traces of noise and hot pixels. Nothing objectionable.

4 minutes: The 6D is just starting to show a few signs of noise and hot pixels. The a7R has a bit more noise now.

6 minutes: The 6D is still fine at 6 minutes. The Sony a7R has noticeably more hot pixels by this point. Enough to where you'll spend a few minutes with each file cloning them out.

8 minutes: The 6D still is still good. The a7R has reached the breaking point, with additional hot pixels.

10 minutes: The 6D has a bit more noise now. You'll need to clone a few hot pixels, but it's still usable. a7R = nope.

15 minutes: The 6D is past my comfort level for noise at this point. The a7R has galaxies full of hot pixels.

Conclusion: The 6D is good for long exposures up to 8 minutes without LENR.  The a7R is good up to 4-5 minutes. This gives the 6D the advantage for shooting long star trails in one shot, and for doing star trail stacking using less shots.

Turning on Long Exposure Noise Reduction

I also ran some tests with Long Exposure Noise Reduction (LENR) turned on in the camera. Both cameras were perfectly clean on 5 minute, 8 minute, and 10 minute exposures.

15 minute exposure: The 6D still looks great. The a7R file shows a few hints of noise.

30 minutes: The 6D shows some luminance noise that will benefit from additional noise reduction in post, but is still usable. The Sony battery died during the 30 minutes that noise reduction was running. The file was still saved on the memory card, but without any noise reduction.

Other Considerations

Battery Life: Canon is the clear winner here. Both cameras started the tests with a fully charged battery. The Sony battery died during the 30 minute exposure test. The Canon battery still had 40% capacity left at the end.

When the Sony a7R LCD screen is active, it does not turn off all of the way. Even when the screen appears blank, it's still slightly lit up and using battery life. Switching to the EVF may not help, and also makes reviewing images a pain. Advantage: Canon

Timer Remotes: There are a wide number of timer remotes available for shooting long exposures on Canon. Sony doesn't have a remote with a built-in timer, only an expensive manual option. There are only a few third party remote options for Sony, and I'm not aware of anyone who makes a wired remote with a timer. Advantage: Canon

Focusing: I haven't tested the a7R under full moon conditions, but did find Sony's focus peaking feature to be an excellent tool for daytime landscape shooting. Canon's AF is better for faster moving subjects. I don't use AF very much, so this is not really an issue.

Lenses: Canon DSLR's have a wide range of high quality lenses available. You can also use Olympus OM or Nikon lenses on an adapter. Native full frame Sony lens options are much more limited, but Sony's E mount will take a wide variety of lenses with an adapter. If you want to keep autofocus, the adapters can be expensive and AF slow. For landscapes this isn't a problem. For wide angle lenses, having a quality adapter is important to maintaining sharpness across the frame. Advantage: Canon

Size and Weight: The a7R is 5.0 x 3.7 x 1.9 inches and weighs 14 ounces. The 6D is 5.7 x 4.4 x 2.8 inches and weighs 27 ounces. The 5D Mark III is 6.0 x 4.6 x 3.0 inches and 30 ounces. Saving a pound in your gear bag is nice. Advantage: Sony

Build Quality and UI: No problems for me here with either camera, other than needing to test the a7R to make sure there are no light leaks during long exposures. The Canon has a slight edge in UI, but the Sony is pretty intuitive.

File Size: The 6D's CR2 files are about 20 MB each. The Sony a7R ARW files are about 37 MB. Memory cards and hard drives are inexpensive. The a7R RAW files are referred to as "visually lossless" but they do throw away some data to keep the file size down. I have seen one example file where the quality of a star trail shot was affected by the Sony's lossy file type. Something to keep an eye on. Advantage: Canon

Shutter Shake: Much has been written about the a7R's shutter design causing soft photos with long lenses at shutter speeds between 1/30 and 1/125. Luckily, I don't even own any long lenses. WTF: Sony

Price: The a7R lists for $2300, but can be bought new for as low as $1865. Make sure to budget $150-400 for an adapter if you're planning to use Canon lenses on the a7R. This brings the Sony in around $500 cheaper than a 5D Mark III, or $500 more than a 6D.

Final Thoughts: The Sony a7R has a few notable quirks for the types of shooting that I do. I also shoot 1-2 minute night panoramas at ISO 800, and the Sony doesn't perform well for long exposures at higher ISOs. For now, I'm sticking with my EOS 6D. It will be interesting to see what Canon has up their sleeves with the rumored 7D and 5D Mark III replacements.

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