Canon RF 85mm F1.2 L USM DS Lens Wide Aperture Exposure Variance Test

I'm currently working on the Canon RF 85mm F1.2 L USM DS Lens review and an important attribute of this lens to evaluate is the amount of light transmission being lost at the widest apertures due to the Defocused Smoothing feature.

In the example shared in this post, the exposures were determined by an EOS R in Av mode and all appear similar in brightness.

Looking at the shutter speed changes relative to the aperture starting with the bottom right image captured at f/5.6, we see the camera selecting a one-full-stop faster shutter speed at f/2.8 than f/4, indicating that the DS technology is no longer having an impact (though in some testing scenarios, only a 2/3-stop-faster shutter speed was selected for f/4, showing a 1/3-stop impact remaining).

In a normal lens, f/2 should have required a 1/1600 shutter speed with this example illustrating a 1/3-stop loss in light transmission. At f/1.4, the shutter speed should have been 1/3200, indicating that 1-full-stop of light transmission has been lost.

The f/1.2 aperture is about 1/2-stop wider than f/1.4 and the exposure was given the same shutter speed as at f/1.4, showing a total of about 1.5-stops of reduced light transmission, the amount Canon indicated we should expect.