Sony Alpha SLT-A77 vs Canon EOS 7D Noise
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To compare noise levels under real-life conditions I shot this scene with the Sony Alpha SLT-A77 and the Canon EOS 7D within a few moments of each other using their best quality JPEG settings
at each of their ISO sensitivity settings.
The cameras were set to f5.6 in Aperture priority mode, the lenses were set to the same field of view and the ISO sensitivity was set manually. |
The above shot was taken with the Sony Alpha SLT-A77 with the 16-50mm f2.8 kit lens. The lens was set to its maximum 16mm wide angle position which provides a similar field of view to the 15mm maximum wide angle of the 15-85mm kit lens on the EOS 7D given the slightly different crop factors of 1.5 on the SLT-A77 and 1.6 on the EOS 7D. For these tests the camera was placed on a tripod and image stabilisation and tonal adjustments were disabled. The SLT-A77 metered an exposure of 1/5 at f5.6 at 100 ISO and the Canon EOS 7D metered 1/6 at f5.6.
The first crop from the Sony SLT-A77 is from its 50 ISO setting and does look to be slightly less noisy than the 100 ISO crop. While it would be impractical to use 50 ISO for everyday use, it's definitely worth considering where the light allows it and you want to squeeze every last bit of quality from the SLT-A77's sensor.
Moving on to the 100 ISO crop there is a little bit of texture in the cream coloured wall that isn't there in the 50 ISO crop. Which is not to say the 100 ISO crop is noisy, but the 50 ISO one is cleaner. And compared with the 100 ISO crop from the EOS 7D the SLT-A77 looks comparable. The detail in the EOS 7D crop is smaller because of the 7D's lower resolution 18 Megapixel sensor and the 7D crop has a more even textured look, but there's not much between them at this sensitivity.
At 200 ISO there's another visible step up in the graininess of the SLT-A77 crop, but nothing to interfere with even fine image detail at this stage. At 400 ISO noise increases by the same degree and now you can see patches of noisy pixels without having to peer too closely. The difference between the Canon and Sony sensors to this point is in the nature of the noise; in the Canon crops it's fairly uniform and unintrusive, in the Sony ones it's patchy and therefore a bit more visible.
Up to now the noise response of the Sony sensor looks fairly linear - it increases in equal amounts as you go up the sensitivity range, but at 800 ISO both the degree and extent of the noise worsens appreciably. There's a visible clumpiness not just in small patches but across the whole of the crop area. The noise is now begining to affect fine and medium inage detail, the text is starting to break up and the flat colour on the wall looks very bitty. The step from 800 to 1600 ISO results in even more of a degradation than the one from 400 to 800 ISO and now even coarse image detail is beginning to suffer, we're beyond the point now where you need to look closely at 100 percent crops to see the effect on image quality.
Despite that, 1600 ISO shots from the A77 look good at average screen sizes and the same goes for 3200 ISO shots though they have visible noise artifacts and lack the detail present at the lower ISO settings. At 3200 ISO and above though, you're really into must-have-at-any-cost territory.
Compared with the EOS 7D at these mid and high range ISO sensitivities the SLT-A77 crops are qualitatively different. First, the nature of the 7D's noise and Canon's noise supression makes for a finer, more uniform grain that I find less intrusive than the patchy clumpy noise in the A77 crops. Despite the smaller detail in the 7D crops fine image detail is less susceptible - compare the left side of the 1600 ISO crops and you'll see what I mean.
In my final results page you can see the effect of shooting in low light with the A77 Handheld Twilight and Multi Frame Noise Reduction modes. Or if you've seen enough, head over to my A77 sample images to see some more real-life shots in a variety of conditions.
Sony Alpha SLT-A77 (JPEG using in-camera defaults) with Sony SAL 1650 SSM |
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Canon EOS 7D (JPEG using in-camera defaults with Caon EF-S 15-85mm IS USM |
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400 ISO |
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1600 ISO |
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3200 ISO |
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6400 ISO |
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12800 ISO |
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12800 ISO |
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16000 ISO |
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25600 ISO Not available |
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