RF100-400 & RF100-500 comparison (and with 1.4x TC)

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Karl_Guttag Senior Member • Posts: 1,778
RF100-400 & RF100-500 comparison (and with 1.4x TC)
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During a discussion on another thread (https://www.dpreview.com/forums/post/66492271) I discovered that the RF100-400 and other Canon lenses had a $100 off sale (BHPhoto and elsewhere -- sale due to end on the 25th - 2 days from now). So I decided to get the RF100-400 as a lightweight carry-around lens (which now costs 1/5th that of the RF100-500). I had seen a lot of good things about RF100-400 and think it has replaced the RF24-240 as my "best value" in the RF lineup.

The difference in weight is significant, particularly on a 4-mile walk I took with both lenses in the same week. The IS on the RF100-400 seems to be extremely good, and the lighter weight likely helps as well. It also focuses pretty close giving a "semi-macro" with a large stand-off. It has (single) nano-USM focusing, which is nice and responsive.

Over the same focal range as the RF100-500, it typically gives up 1/3rd to 2/3rds of a stop and is neither weather-sealed nor as rugged. And obviously, it gives up 20% of the RF100-500's range.

Image quality-wise it gives just up a bit, but mostly in the corners. I think in real-world photos, it would be hard to tell the difference in sharpness.

I ran some quick comparisons (not shown) to my 20-year-old EF100-400 IS mk1 (push-pull), and it seems to beat it pretty much on everything at the same aperture, but the old EF-L does have a full stop on it most of the time.

Overall, I would say the RF100-400 has its peak overall sharpness at f11. F11 will sharpen up the corners without softening too much due to diffraction. By f16 you can see diffraction started to soften everything.

Since I also had the 1.4x TC, I ran a couple of tests with it. I have posted at the end at 100mm x 1.4 = 140 and 300 x1.4 = 420 (I didn't have enough room to test at 580mm). The sharpness is clearly degraded a bit. I did these at f11 and f16, but the f16 ones looked softer than at f11 due to diffraction. Overall, a bit softer than I had hoped, but probably still worth using over cropping. With the RF100-500, you can hardly tell you are using a 1.4x TC as it loses very little sharpness (other than the dang zoom range problem).

My test chart is about 1 meter wide, and I move the camera to frame it. I then take full-resolution crop samples from the Center, Mid Upper Left (M-UL about at the corner for APS-C), and the far Upper Left Corner at the various apertures.

Overall as many have said, the RF100-400 punches above its weight (and cost).

RF100-400 at 100mm and various fnumbers

RF100-500 at 100mm and various fnumbers

RF100-400 at 400mm and various fnumbers

RF100-500 at 400mm and various fnumbers

RF100-400 at f11 (the best number I found for overall sharpness with the TC).

 Karl_Guttag's gear list:Karl_Guttag's gear list
Canon EOS R5 Canon RF 15-35mm F2.8L IS USM Canon RF 24-70mm F2.8L IS USM Canon RF 70-200mm F2.8L IS USM Canon RF 24-240mm F4-6.3 +14 more
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