The Canon 1.4x Extendeer is not designed to be used with the Canon 28-70mm f2.8 L lens, but I have heard of photographers using an 8mm extension tube (Brand X, since Canon's smallest is a 25mm) which allowed the 1.4x Extender to be coupled to lenses that otherwise could not be used. Is this a legitimate or practical solution ? If so, is your distant focusing comprimised ? Bruce Gowdy bruce@martinron.com

-- Bruce Gowdy (bruce@martinron.com), September 01, 2001

Answers

The short answer is yes, this works. :-)

I've not heard with a 8mm tube -- 12mm is the minimum in use, & yes -- you do lose infinity focus.

Another trick I've heard of is combining a 1.4 Canon TC + 12mm tube + 2x Canon TC between the body & lens -- it's supposed to work.

Kenko makes a nice set (12mm + 20mm + 36mm) of automatic tubes (no loss of AF, etc.) for considerably less than Canon.

-- Hung James Wasson (HJWasson@aol.com), September 02, 2001.

If 12 is the mininmum that works, then you could use the Canon 12mm which is their smallest. Their bigger one is 25mm. However, in doing so, you may loose infinity focus.

Next question is why? Why would you want to use a 1.4X TC on a 28-70? That would give you 40-100 (approx), and the optical quality will probably drop below that of the 28-105, and the lens speed is not better (in fact slower at the wide end than the cheaper lens). Buy the 28-105, get more range, optical quality and muhc lighter weight, or even the optically better 28-135 IS, with the same benefits.

The TC + extension tube trick has been used for a long time, to mount the 1.4X onto the 2X, giving a 2.8X extender. With the newer series 2 TCs, this is not necessary, as the 2X has been redesigned to make this possible without the extension tube, and no loss of infinity focus.

Anyway, I would not bother in this case.

-- Isaac Sibson (Isibson@hotmail.com), September 06, 2001.

Isaac,

I'd not heard that the elements on the Mk II 2x TC had been altered to allow stacking without use of extension tubes, and the attendant loss of infinity focus. I thought that both the new 1.4x & 2x just got weather seals to match the 1v & newer L lenses. How certain are you of this? It seems like a very important design change for Canon to overlook mentioning in their literature. Does this work only with a 1.4x + 2x combination, or can one stack two 2x TC's together to create a (horribly dark & "soft") 4x TC? :-)

-- Hung James Wasson (HJWasson@aol.com), September 07, 2001.

The new 2x TC is a completely new optical design. The 1.4X is indeed just a new weathersealed version with a new light absorbing material inside the barrel, but the 2x is entirely new.

Art Morris said: "When I stacked the new TCs by inserting the nose-end of the 1.4X II into the rear of the 2X II (remember, it is no longer necessary to use a 12mm extension tube), I was pleasantly surprised to find that the setup autofocused accurately and fairly quickly as long as there was sufficient light and some contrast to work with. This is a huge advantage because focusing manually with stacked multipliers is a difficult proposition at best... "

Seems to work then.

-- Isaac Sibson (isibson@hotmail.com), September 07, 2001.

Isaac,

Thank you for the quick reply. That is very cool!

-- Hung James Wasson (HJWasson@aol.com), September 08, 2001.

I suspect that Canon don't tell us about it because they don't REALLY want the TCs to be stacked, as this will compromise the optical quality of L series. I think another factor is that with the new F8 AF bodies, the TCs can be stacked on an F2.8 Lens (eg 300 F2.8, 400 F2.8, 70-200 F2.8) and maintain AF. Thus there is more demand for this combination now (as not many people use the 200 F1.8 or 135 F2, and they're also a little short for TC use). Thus there was enough demand for them to make the new 2x stackable. You can stack as many 2x TCs as you like, but only 1 1.4X TC can be used, as it is the back of the 2x which now allows another TC to be mounted to the back of it. The 1.4X has not been optically changed, so they still have a large element very close to the back, preventing them from being mounted on another TC.

-- Isaac Sibson (Isibson@hotmail.com), September 09, 2001.