ISO Performance at low ISOs (ISO 100-800)
Let’s take a look at how the Sony A77 performs at low ISOs. Here are some crops at ISO 100, 200, 400 and 800:
ISO 100 and 200 images look very clean.
ISO 400 adds a little bit of grain, but nothing to worry about. ISO 800 doubles the amount of noise from ISO 400 and we start to see larger grains in the shadows.
High ISO Performance (ISO 1600-16000)
High ISO performance is a very important measure of DSLR sensor quality. Here is how the Sony A77 performs at high ISO levels between ISO 1600 and 16000:
ISO 1600 adds significantly more noise than ISO 800, but the image is still usable, even at 100% view. Shadow areas have much more noise, but the detail is preserved. At ISO 3200, however, grain gets much bigger, I would say about twice bigger in size, and the details in the shadow areas start to disappear. Colors are definitely affected at ISO 3200.
Anything above ISO 6400 looks pretty bad at 100% pixel view – details are completely lost in the shadows and there is a significant loss of detail in well illuminated parts of the image as well. ISO 12800 and 16000 are downright unusable, in my opinion.
ISO Performance Summary
This is a clear demonstration of what happens with high resolution cameras that have very small pixels. While the low ISO performance is very impressive, ISO levels above 1600 show a significant amount of noise throughout the image. I would say that ISO 1600 is my threshold for the amount of acceptable noise that can be later cleaned up in post-processing. However, keep in mind that we are looking at the above images at 100% view, or “pixel level”. As you will see in the next page of this review, once the 24 MP image is down-sampled to smaller resolution, the camera actually performs surprisingly well when compared to other lower resolution cameras.
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