Canon continues to work away at “big white” lens designs. This patent isn't so much about a specific lens and more about what the design shows. Canon is working on a way to have a drop-in teleconverter.

The goal here is to add an extender without increasing the length of the lens just like a built-in teleconverter would do, but this patent is more about showing the importance of where in the lens the teleconverter is placed.

The placement of a built-in or drop-in teleconverter has an effect on the size of the lens. We had never thought about this before, but it makes sense. As we all know, manufacturers are all in on making lenses smaller and lighter. We're good with that focus in lens design.

As far as the optical design in this patent, Canon is using a 100-300mm f/2.8 base lens and shows the empty space where a 1.4x teleconverter can be “dropped in”. Dropped-in can also mean built-in.

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slotting into the empty gap of a telephoto zoom Two scaled strips of the same lens at the wide-angle end. Top: the base lens with a 72.6mm empty air gap between the negative fourth group and the positive fifth group. Bottom: the same lens with a negative 1.4x extender filling that gap. Total length stays 370mm. Base lens (Example 1) 103–294mm · f/2.91 L1 L2 L3 L4 L5 aperture L2 slides to zoom 72.6mm empty air stays 69–73mm across the zoom sensor 370mm total length slide the extender inWith extender (Example 4) 144–411mm · f/4.10 L1 L2 L3 L4 Extender L5 aperture −114mm ×1.4 fills 47mm of the gap sensor 370mm total length (unchanged) Positive group Negative group Extender Aperture Wide-angle end, drawn to scale along the axis from the patent prescription (Examples 1 and 4). Block heights are not lens diameters.

If we just go with the drop-in part of the patent, we could see it being something to do to keep the price point down on a longer supertelephoto zoom lens. If it's something like a 300-600, you could make available a new style of teleconverter to sell to people that want longer reach and not change how the lens feels in your hand and save some money if you have no interest in a built-in converter.

Canon would have no problem selling you a brand new type of teleconverter at Canon prices either.

The teleconverter is placed toward the rear of the lens. This is to take advantage of the narrowing light path before it hits the sensor. Because the light beam is smaller here, the teleconverter glass itself can be smaller than if it was more forward in the design.

We'll have to think more about what a drop-in teleconverter would mean and how it would make a shooter's life better, over simply having it built-in.

Canon is going to be bringing new lenses in the near future with built-in teleconverters, or maybe even a drop-in converter. This just seems like a new way to implement a teleconverter.

As always, a patent just shows us what Canon is up to, and not always what we can expect to be announced. A drop-in teleconverter would be a new way to do it, but as mentioned earlier, we're not sure why shooters would prefer this solution over just building one in other than up front cost savings.

This is definitely an interesting bit of research and development.