Canon EOS 700D/Rebel T5i In-Depth Review
The actual sensitivity of each indicated ISO is measured using the same shots as are used to measure ISO noise levels, we simply compare the exposure for each shot to the metered light level (using a calibrated Sekonic L-358), middle gray matched. We estimate the accuracy of these results to be +/- 1/6 EV (the margin of error given in the ISO specifications). In our tests we found that measured ISOs from the Canon EOS 650D and EOS 700D match the marked ISOs within 1/6 stop accuracy, meaning ISO 100 indicated = ISO 100 measured.
Noise and Noise Reduction (JPEG)
At its default ('Standard') level of noise reduction, the EOS 700D exhibits a bit more image noise than many of its peers between ISOs 1600 and 6400. Noise suppression increases dramatically at the camera's two highest ISO sensitivities. And as the samples bear out, image detail falls off significantly beyond ISO 3200.
Looking at the graph it's interesting to note that the 700D also shows higher noise levels than the EOS 600D, throughout nearly the entire range of ISO values. Yet based on the samples here, the 700D maintains a near identical level of image detail while also offering a top ISO of 25,600 (versus 12,800 in the 600D).
ACR Raw noise (ACR 7.4, noise reduction set to zero)
As you can see in the sample images here, the noise performance of the 700D remains fairly uniform up through ISO 1600, with detail retention that is on par with the Nikon D5200 through ISO 3200. The 700D does not produce as clean an image as the Pentax K-30 (which applies noise reduction to its raw files) but in terms of fine detail retention actually holds it own pretty well. Image detail does become significantly obscured though at ISO 6400 and higher.
Looking at the graph of raw file data, you can see that at the sensor level, noise performance of the EOS 700D trails just a bit behind the earlier model 600D beginning at ISO 3200. Referring back to the image samples though, it's clear that there are no meaningful differences in detail retention.