downhillonwater wrote in post #19421691
That is true, but isn't it fair to say that's true for every camera... fast, high quality glass is better?
Because it's a 1.6x crop sensor this camera receives 39% of the light that a full frame sensor does. Assuming equal sensitivity that's about one and one third stops difference. In my experience, this plays out in the field. The R7 requires about one and one third stops higher ISO than the R5 for the same aperture and shutter speed.
Is that a typo? The same f-number and shutter speed should result in the same ISO and does result in the same exposure. The same ISO is what gives 39% as much light as an entire FF sensor. 2.56x the ISO on top of that would mean 15.26% the total light.
As always and particularly in challenging shooting conditions we balance camera settings to achieve a great image. The R7 brings us great reach and that is balanced by reduced light collection.
Well, if you did a well-controlled comparison of the R7 to a the R5 in crop mode, and processed not to emphasize the extra pixel-level detail on the R7, I think you'd find that the R7 not only has almost 2x as many pixels on-subject, but has less noise, too. The R5 has a fine horizontal banding noise that isn't too ugly like the broad banding of some older cameras which survived downsampling, but which is visible in deep shadows and tends to make the chromatic noise a little blotchier. The size of chromatic blotches in near-blacks, red noise in shade, and blue noise in incandescent light, is larger on the R5 and litters those near-blacks more.
So, which sensor gives you less noise is going to depend on lens usage and subject matter. To really get less noise with the R5, you need to use a larger sensor area than crop mode and use a lens that delivers more total light in the sensor area used in the final product. For some people, that is possible with most of what they shoot; for the focal-length-limited photographer, the R5 gives is a wider angle of view if crop mode isn't used, which may help in tracking active subjects whose changes in direction is large compared to their body size, like dragonflies, butterflies, swallows, etc.. In any situation where you could use crop mode on the R5, however, the R7 will actually have slightly less noise with the same exposure (an exception could occur with extremely fast lenses, where the R5 might become more efficient with the extra light from the outer pupil), but for focal-length-limited photography, lenses are generally at least f/2.8 or slower.
The AF sensitivity for large changes in focus distance in low light, however, is clearly better on the R5 with the same glass, so you do get something in return for the lower number of pixels-on-subject. Put a 1.4x on the R5 to catch up on pixels-on-subject, though, and that 1-stop AF benefit is gone. I do notice more hunting with the R7 in very poor light than the R5, with the same optics. With a 400/4 and a 2xTC, when I want 800mm, the problem is easily solved by not using the TC or using a 1.4x on the R7, but when I choose the much lighter RF800/11, AF is already a little slower than 800/8 in low light, and there's no TC to remove, to help the AF. The RF800/11 will also force me to back up away from a subject more, too, which causes extra subject noise just because of the distance, and even more noise if you need to raise the shutter speed because of the increased distance.