http://www.learn.usa.canon.com/resources/articles/2017/eos-77d-image-quality.shtml
DIGIC 7 processor — superior high ISO noise reduction
Previous EOS digital SLRs with APS-C size image sensors have offered 24.2 million pixel resolution, but the advent of the latest DIGIC 7 processor means even greater noise reduction than earlier EOS models, such as the EOS 80D or Rebel T6i. Full-resolution JPEG image files, when set to Standard noise reduction levels, show up to a full stop of improvement in visible digital noise, vs. the previous-generation EOS Rebel T6i. ISO 6400 files from the 77D are similar to T6i files shot at ISO 3200. And, the maximum standard ISO for still images has been raised to 25,600 (ISO expansion to the equivalent of ISO 51,200 is possible on the Rebel 77D).
Lens Diffraction Correction
Armed with additional processing power of the DIGIC 7 processor, the EOS 77D can take on additional lens aberration corrections, in-camera. New to this camera category is Diffraction Correction.
Lens diffraction is an image softening phenomenon that naturally occurs when pictures are taken at small lens apertures, like f/16 or f/22. Canon’s diffraction correction is tailored to the actual optical properties of specific lenses, and applies a very specific sharpening to directly counter this loss of detail and sharpness at high f-numbers.
And, even at more moderate and wider apertures, the same diffraction correction is able to counter the softening impact of the low-pass filtration layer on the camera’s imaging sensor, and other anomalies that may impact final image quality.
Listed as a new Lens Aberration Correction item within the camera’s red shooting menu, Diffraction Correction is active by default, but can be turned off by the photographer at any time. While the impact of this feature is usually subtle, it’s an improvement any quality-conscious still imaging photographer should examine and be familiar with.
DIGIC 7 processor — superior high ISO noise reduction
Previous EOS digital SLRs with APS-C size image sensors have offered 24.2 million pixel resolution, but the advent of the latest DIGIC 7 processor means even greater noise reduction than earlier EOS models, such as the EOS 80D or Rebel T6i. Full-resolution JPEG image files, when set to Standard noise reduction levels, show up to a full stop of improvement in visible digital noise, vs. the previous-generation EOS Rebel T6i. ISO 6400 files from the 77D are similar to T6i files shot at ISO 3200. And, the maximum standard ISO for still images has been raised to 25,600 (ISO expansion to the equivalent of ISO 51,200 is possible on the Rebel 77D).
Lens Diffraction Correction
Armed with additional processing power of the DIGIC 7 processor, the EOS 77D can take on additional lens aberration corrections, in-camera. New to this camera category is Diffraction Correction.
Lens diffraction is an image softening phenomenon that naturally occurs when pictures are taken at small lens apertures, like f/16 or f/22. Canon’s diffraction correction is tailored to the actual optical properties of specific lenses, and applies a very specific sharpening to directly counter this loss of detail and sharpness at high f-numbers.
And, even at more moderate and wider apertures, the same diffraction correction is able to counter the softening impact of the low-pass filtration layer on the camera’s imaging sensor, and other anomalies that may impact final image quality.
Listed as a new Lens Aberration Correction item within the camera’s red shooting menu, Diffraction Correction is active by default, but can be turned off by the photographer at any time. While the impact of this feature is usually subtle, it’s an improvement any quality-conscious still imaging photographer should examine and be familiar with.