Any hope for an extender?

Started 11 months ago | Discussions thread
Tony D Senior Member • Posts: 1,019
Re: Restated: Any hope for an extender?

You want a straight answer?

It will be Canon will not for a number of reasons.

Just look at the EF situation Canon has never made one for any of their own lenses which don't allow the extender to 'extended' in to the lens body, for a good optical reasons. To do otherwise will compromise image quality (and cut sales of their better higher cost lenses). It is also optical difficult to do with no separation between last lens element and the extenders elements (check the Canon extenders and the lenses they are compatible with and you will see the last lens element is some distance from the first extender element, there is a gap). Also with the RF600, 800 and RF100-500 out there (all compatible with their own extenders) where's the logic for them?

Optically the extender is another lens element in the optical train, it magnifies the image, losing the field edges (much like EF lenses do on cropped sensor bodies). To do this they need to magnify and move the image plane back on to the sensor.

Another manufacturer may try but the optical design will need to introduce a gap. They would need to introduce a separation between last lens element and the first lens in the extender, in a place were they can achieve the correct magnification and still have the image plane on sensor but just magnified & correctly in focus. The space will be need to find a place where the light path is at the required size/magnification and then refocus it to the sensor. A simple light ray path diagram can show how these work and why a separation is needed.

When I get I chance I could contact some Zeiss engineers I know (my day job involves working with Zeiss on more specialized lenses, the several million dollar type) but I know they will say similar or would want to know the exact element parameters for the current Canon lenses so they can model this and give a good answer.

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