MTF Comparison: Canon RF 15-30mm F4.5-6.3 IS STM

We grabbed some of the older EF F4L lenses to compare them against the new RF 15-30mm IS STM. While it's really not that far to compare a consumer STM lens against the F4L's, it gives a good basis for comparison on how the RF 15-30mm should perform.

Granted, all of Canon's MTF diagrams are computed, but we have found them to be a fairly good representation to compare a Canon lens to another Canon lens in terms of performance.

In this comparison, we'll use the Canon EF 16-35mm F4L IS USM which is considered a very good optic, and also the older 17-40L USM which for most users is pretty adequate.

Canon EF 16-35L vs Canon RF 15-30 STM

Compared to the Canon EF 16-35mm the 15-30 tails off in the corners faster on the wide end and doesn't have as good of bokeh, and suffers from greater astigmatism. Resolving power overall is a little less than the 16-35L. Center performance is comparable with contrast and slightly less resolution between the two. This is fairly good performance especially when we consider that the 15mm is 1mm wider. All in all, where you are most likely to use the lens most often in the ultra wide zoom position, it performs fairly well against the 16-40L.

On the telephoto end, the 16-35L pulls ahead in terms of resolution, but the 15-30 holds its own with contrast. You probably won't' see much difference in performance between the two on the telephoto end.

Canon EF 17-40L USM vs Canon RF 15-30 STM

Canon has come a long way since they released the Canon EF 17-40L, and it shows when we compare the consumer RF STM lens against the 17-40L. There's really no comparison here, the RF 15-30 STM is superior in every way. If you find the 17-40L good for your needs then the 15-30 IS STM will be excellent in that regard.

Conclusion

From looking at the MTFs of the three lenses, it appears as if Canon just may have a bang for the buck winner on their hands. Of course, the proof is in the actual use and to see if the Canon RF 15-30mm uses stretching to fit the image circle. To be fair, the L's are faster and built better - but they also carry a higher price tag.