Hi all, I'm new here but a regular reader on this site. From the graphs the RF 100-400 looks to have a bit less contrast and sharpness than the EF 100-400 and RF 100-500, looks quite promising despite f/8 aperture.
Surprisingly, one thing that nobody has mentioned is the PMo (plastic-molded) aspherical lens element.
We've also recently seen the use of a molded plastic aspherical lens element in the RF 50mm f/1.8.
This seems like a strange trend in new Canon RF lenses, considering that PMo aspherical lens element were reserved for cheap kit lenses in the past. The next level of lenses used molded glass aspherical elements, with ground glass aspherical lens elements being the mainstay in L-series glass from what I can figure.
Scouring the internet, I can only find the following Canon lenses which utilise pMo aspherical elements:
- Canon EF-S 18-200mm f/3.5-5.6 IS - one PMo (precision molded) aspherical element
- Canon EF-S 18-135mm f/3.5-5.6 IS STM - one PMo (precision molded) aspherical element
- Canon EF-S 18-135mm f/3.5-5.6 IS USM - one PMo (precision molded) aspherical element
- Canon EF-S 10-18mm f/4.5-5.6 IS STM - two aspherical lens elements, one is a high-precision large-diameter PMo (Plastic-Molded) lens.
- Canon EF-M 15-45mm f/3.5-6.3 IS STM - three aspherical elements, one is glass-molded and the other two are precision molded,
- RF 50mm f/1.8 STM - one precision molded optic (PMO) aspherical element
- Canon RF 100-400mm F5.6-8 IS USM - one precision molded optic (PMO) aspherical element
This lens looks so much like a full frame version of the EF-S 55-250mm IS STM, (which provides the crop equivalent of 88-400mm @ F9). Even though Canon was so miserly as to not even put a metal lens mount on that lens, its optics were really good, and from what I can ascertain, this lens had no PMo elements. This lens also had no sealing, so it wasn't dust proof and drip proof either.
From the Canon Camera Museum -
https://global.canon/en/c-museum/special/exhibition1.html
Plastic-molded (PMo) aspherical lens elements
PMo aspherical lens elements are formed by injecting resin into an aspherical surface mold. Highly suitable for mass production, they play a major role in improving the image quality of entry-level lenses, such as the EF-S10-18mm f/4.5-5.6 IS STM (released in 2014), which need to be kept relatively affordable. Resin is injected into a high-precision mold that takes the shape of an aspherical lens. After the lens element is separated from the mold, coatings are added to finish the lens.
Trying to find the life expectancy of optical resins proved frustrating. I've yet to hear of an optical plastic as durable as glass., and I suspect that all plastics degrade over time, and won't have the life expectancy of molded or ground glass elements. I've had a Canon EF-S 10-18mm for many years, and the optics are still good. Perhaps only time will tell if or when these resins decrease in optical clarity as they age.
I'm not sure what this trend indicates. Is it cost cutting to increase profits, or is Canon cutting back on its construction of 'budget' lenses, even more so than in the past?
Looking forward to seeing how the RF 100-400mm compares against the EF 100-400mm II, RF 100-500mm and even the EF-S 55-250mm. Then we'll know what kind of image quality, construction and durability we're getting for our money ($649 USD, £699, 730 €, $1,200 AUD).