Canon’s announcement of a new RF 100-500mm f/4.5-7.1L
has sparked vigerous online discussions, pro and con -- especially with
regard to the rather slow f/7.1 max aperture at 500mm. Inevitably,
comparisons are being made with the highly regarded EF 100-400mm f/4.5-5.6L II. Assuming
one finds the EF lens to be useful, how does the RF 100-500mm compare
as a potential replacement, albeit only for use on R-series cameras?
Since there has only been a development announcement as of May, let’s stick with
what we know at this point, and what may reasonably be inferred based on
optics, engineering and precedent, leaving aside wishes, flights of
fancy and fervent hopes
that have little basis in fact and a low probability of being realized. All
considerations are, of course, conditional on obtaining and
testing a real lens. Points to consider:
If one is interested in using the EF 100-400 with
a 1.4X extender in order to gain additional focal length, then the RF
100-500 may be more attractive than otherwise. In this case, the fair
comparison is the EF with and without 1.4X extender vs the RF bare lens.
The extender adds cost and weight to the EF 100-400 lens and probably degrades optical
quality throughout its range while it is in use. In addition, there is the
inconvenience of putting on and taking off as well as managing another
accessory. Adding the 1.4X extender to the EF lens makes it a 140-560mm
lens, losing some at the wide end in comparison with the RF lens while
gaining at the long end. The important
of these differences is, like beauty, in the eye of the beholder.
The RF will have a built in control ring which the
EF lacks. To gain similar functionality if the EF lens is to be used on
an EOS R-series MILC camera, purchase of a separate control ring adapter would
be required. At a minimum, the basic adapter would be needed, if
not the control ring version.
Optical and performance considerations include: a) What is the
f-stop of the RF at 400mm? The answer is unknown at this point, but it
is possible that it will not be f/5.6, but rather somewhat slower. b)
What is the optical quality of the RF between 400mm and 500mm? If it is better than the
EF with 1.4X extender, then the RF has an advantage. c) Also, will the
RF lens autofocus with an RF 1.4X extender and what will be its optical
quality? If the answers are positive compared to the EF with 2X
extender, this confers an advantage to the RF lens,
albeit with a slight loss of maximum focal length.
How well will AF acquisition and tracking of the
RF compare at 500mm relative to the EF with 1.4X extender? The fair comparison
will be the bare RF lens to the EF with 1.4X extender, not
to the bare EF at 400mm. At f/7.1 the
RF may AF slower than at 400mm on either lens -- but will it be faster than
the EF 100-400 with extender, at f/8?
Size and weight are currently unknown. From the
one photo available showing the EF 100-400 side-by-side with a mockup of
the RF 100-500 (DPReview, from Canon display at WPPI), the RF lens looks a bit longer and appears to have a
slightly thicker barrel, implying a modestly larger, longer,
heavier lens. The 500mm focal length makes this almost inevitable -- although one also has to consider the weight and length
of an adapter and an extender when using the EF lens on an R-series
camera. But, appearances in photos can be misleading, and newer
designs may be lighter than old ones, even if overall size is larger.
Specs are TBD at this point.
Price is an unknown. As a newly introduced lens,
the RF may well initially cost more than the current street price of the
a differential that may persist for quite some time, although one has to
consider the added cost of purchasing a 1.4X extender for the EF, if such
isn’t already owned.
What's the Answer?
How one judges these factors is a matter of
performance, operability, use cases, personal preference and cost. For some,
and assuming the specs and tests of the new RF lens are favorable, this may
be a worthwhile upgrade from the EF lens, particularly if one is inclined to
use a 1.4X extender on the EF lens. For others, the current EF lens
may be more than satisfactory for the foreseeable future.
Some have expressed a wish for a different lens,
perhaps with a faster max aperture at the long end or a different focal
length range -- or any of a plethora of
other possibilities. Any such lens would be a different lens and would
likely be different in weight, size, optical characteristics, potential use cases and
cost. Therefore, as desirable as such an alternative might be, this would
nevertheless not be an evenhanded comparison to the EF 100-400mm lens.