Canon R5 + RF 28-70mm Tips + Tubes

Ephemeris wrote:

Hi folks

Any tips or help for the use of this lens appreciated. It will replace an older EF 100 F2.8 lens and also an RF 28-105 F4 lens (I don't really like this lens - the EF was doing as much work for us).

The lack of IS is making me a little nervous and also that I can't use a TC.

Do any of you use this lens with extension tubes/rings? Is the AF still usable?

What size objects are you trying to photograph in the field?  Your current macro lens will AF down to a field of view of just over 36x24mm without tubes, while the RF macro will go to just over 22x15mm without tubes.  Neither will work with a Canon Extender (TC) without an extension tube between lens and TC, because the TCs penetrate further into the lens mount than the rear elements are recessed.  The RF macro has the advantage that its IS is designed to work in conjunction with your camera's IBIS; the EF 100mm L macro's wasn't, because IBIS wasn't a consideration for Canon when it was introduced in 2009.

First, a 28-70mm standard zoom is definitely not a replacement for a macro lens.  You can't use it with an RF mount teleconverter, because Canon's teleconverters penetrate something like 17mm inside the lens' mount and the rear element is only recessed about 4mm.  It would work if you mounted it on a 16mm extension tube, but then the maximum focusable distance would range from less than 300mm from the front of the lens at 70mm to  somewhere within the filter threads at the wide end.  The lens would work with extension tubes, but a standard zoom lens is a bit of a nightmare with extension tubes and almost impossible to calculate tube length and focus in the field because of its length.

Even if somebody were to produce an RF mount TC without protruding front elements, a 1.4x would turn it into a 40-100mm f/2.8  with probably noticeably worse performance than the RF 24-105mm f/4 and certainly more than twice the weight. A 2x TC would give you a heavy (1kg heavier than the RF 70-200mm f/4)  56-140mm f/4.  I'm sure an R7 would give better quality with this lens than an R5 + a third-party TC. TCs have their place with long lenses if you're trying to get more reach, but they don't really work with standard lenses.