Finally, here is my comparative review of the Canon 200D/SL2 and Nikon D5300. It will be split across a number of posts because of the size limit for images in a single post.
If you want to skip to end, the conclusion is here:
I bought the Canon 200D/SL2 and Nikon D5300 because I wanted an "entry-level" backup camera for astro-imaging. The idea was to compare the two and then keep the "winner". Why did I select these two cameras in the first place? The Nikon D5300 was chosen because it is inexpensive and seems to be one of the most recommended budget DSLR cameras for astro-imaging. The Canon 200D was chosen because it is believed to be the first Canon entry-level camera that has on-sensor analog digital converters (ADC) instead of using a separate off sensor unit. It was thought this should make it closer to being an ISO-less camera than any previous entry level Canon. Unfortunately this turned out not to be the case but now I'm jumping ahead of myself.
My review is mainly focused on technical details pertinent to astrophotography that you won't find elsewhere. So I won't review usability, touch screens, fold out LCD panels etc. I didn't even notice that the Canon 200D had a touch screen until I brushed it by accident!
Let's start with read noise etc.
Read Noise, Gain etc.
Read noise at each ISO can be looked up at PhotonsToPhotos.net so I won't repeat it here:
This shows that the Nikon has slightly lower read noise. My figures were similar to those shown except for Canon 200D read noise at ISO 100 and ISO 200.
Canon 200D read noise:
ISO 100 7.4e 4.9e
ISO 200 5.0e 3.6e
My figures showed a much steeper rise with a read noise of 7.4e at ISO 100 and 5.0e at ISO 200 instead of 4.9e and 3.6e respectively. I've been sent bias frames from other 200D owners that agree with my figures. Neither Bill Claff (the author of PhotonsToPhotos) nor myself understand this difference. It remains a mystery.
Estimates of other parameters such as quantum efficiency (QE) and the ISO that gives unity gain can be found here:
My values for the ISO that gives unity gain were 215 for the Nikon and 240 for the Canon. Again we are seeing a big difference on the Canon for some unknown reason. It should be pointed out that one cause of slight differences is the calculation of gain.
Neither camera has a completely linear curve of pixel variance (the square of standard deviation) against mean pixel value so one tends to obtain slightly different estimates of gain depending on how bright the pixel values are.
Note also that the Nikon value is for the green pixels. The Nikon red and blue channels are scaled differently, as is typical of Nikon cameras. One noticeable effect of this is histogram combing in the red and blue channels. However it's not thought to have any effect on astro-images.
QE will be touched upon later in the review when the spectral response is examined.
Edited by sharkmelley, 21 October 2018 - 04:40 AM.