Smaller birds and animals, chipmunks for example, often need longer focal lengths to have a substantial size in the frame even at close distances. If the last time you used a teleconverter was with film or with a DSLR, you're in for a treat because teleconverters work GREAT on mirrorless with no apparent slowing of autofocus and no dimming of the viewfinder; the image just gets bigger and that's it. Mount an extension tube behind this lens to modestly decrease and increase those respective numbers. The Canon RF 100-400mm F5.6-8 IS USM Lens vs. Canon EF 70-300mm f/4-5.6 IS II USM Lens comparison shows the RF 100-400 modestly lighter and slightly longer.

Decreasing the maximum aperture opening reduces the lens element diameter requirements, which enables those other desirable attributes. Impressive for a consumer-grade lens is that the RF 100-400mm F5.6-8 IS USM Lens gets Canon's high-performing Nano USM (Ultrasonic Motor) driven AF system now seen in numerous RF lenses.As we mentioned, this Canon 100-400mm lens is about 50% heavier than the competing Sigma version – and what's more, it's almost three times as expensive. So, what does all that extra weight and cash actually get you? Conceptually, what I appreciate about this “budget” RF 100-400mm is that what is there is good, and what would have been hard or expensive to implement well has been cut completely. To me, it’s a better strategy to do it this way as compared to the alternative which would have been to include mediocre or worse performance that would have brought the whole experience down. 200mm | f/11 | 1/320s | ISO 100 Are There Alternatives? Above: Heading out to the corner at the maximum f5.6 aperture shows the lens essentially maintaining this performance with only the very slightest hint of softness or fringing if you’re really pixel-peeping. I’d be happy using it wide-open at 100mm though which is good news since the maximum aperture of f5.6 isn’t exactly bright to start with. Here’s the same image taken at f8 and now at f11 to show there’s little to be gained by closing the aperture.

Axial CA remains somewhat persistent when stopping down, with the color misalignment effect increasing with defocusing.Just because the lens is from the consumer lineup does not mean that attention to design details were ignored. Astigmatism is seen as points of light spreading into a line, either sagittal (radiating from the center of the image) or meridional (tangential, perpendicular to sagittal). Above: Heading into the corners tells the same story as the shorter focal lengths: so a very minor softening, but really nothing to be concerned about, and little to no benefit to closing the aperture any further. But then at this point the lens is already at f8 with the aperture wide-open, so you wouldn’t really want to close it any further other than to boost the depth of field.