[Klaus]

https://www.canonrumors.com/here-is-the-...st&slide=0

They seem to be visible in the rear here.
So the 600mm f/11 is as long as the 100-500mm @ 100mm - not too shabby IMHO.

[davidmanze]

https://www.canonrumors.com/here-is-the-...st&slide=0

They seem to be visible in the rear here.
So the 600mm f/11 is as long as the 100-500mm @ 100mm - not too shabby IMHO.

Rumour has it the 600mm retracts to 11" and the 800mm retracts to 15" ......

[Rover]

I wonder if the aperture is really fixed?

[Klaus]

Would it ever make sense to stop down with such a lens?

[Rover]

Would it ever make sense to stop down with such a lens?

Probably not, that's why they could probably save on the aperture mechanism. If they're cutting corners why not start with the most obvious one.

[toni-a]

One question, will those lenses suffer from diffraction already at maximum aperture ?? Once stepped down how would the output look at f32 or even f64 ?

[Brightcolours]

One question, will those lenses suffer from diffraction already at  maximum aperture ?? Once stepped down how would the output look at f32 or even f64 ?

Yes of course, all lenses suffer from diffraction at maximum/any aperture. It depends on the sample frequency how you rate if the result is acceptable. Most lenses wide open suffer from worse aberrations/distortions/defects than diffraction itself, which then masks the diffraction.

In this case, I doubt that the lens(es) will have other issues wide open that are so bad that it will mask the diffraction. And the diffraction probably will be comparable to other 600mm and 800mm lenses at f11, because the DO elements sit in front of the aperture and will not shorten the distance of aperture to imaging plane much.

Canon's software (DPP and internal camera conversion) can get rid of some of the diffraction softening, by applying deconvolution algorithms.

[Klaus]

I'd say that at 600/800mm diffraction is usually not the problem. You tend to have quite a distance to your subject with such lenses thus air diffusion becomes an issue.
That's already noticeable in lab conditions and it's worse in real life, of course.

[toni-a]

I remember watching a video about a new technology by Canon specifically for air diffusion for tele lenses photography... will try to find it

[Brightcolours]

It seems like the 600mm and 800mm have the very similar optics, except that the 800mm lens has one extra (front) element and the DO groups have slightly different shapes.

Lens construction RF 600mm f11 IS STM:
https://cweb.canon.jp/eos/rf/lineup/rf600-f11/image/spec/spec-lens-construction.png

Lens construction RF 800mm f11 IS STM:
https://cweb.canon.jp/eos/rf/lineup/rf800-f11/image/spec/spec-lens-construction.png

MTF 600mm:
https://cweb.canon.jp/eos/rf/lineup/rf600-f11/image/spec/spec-mtf.png

MTF 800mm:
https://cweb.canon.jp/eos/rf/lineup/rf800-f11/image/spec/spec-mtf.png

The lenses have a fixed f11 aperture, the 600mm's IS is rated at 5 stops effectiveness, the 800mm's IS at 4 stops.

Sample images for the RF 600mm f11 IS STM (on EOS R):
https://cweb.canon.jp/eos/rf/lineup/rf600-f11/image/image-sample/image-sample-media-img-popup.jpg
https://cweb.canon.jp/eos/rf/lineup/rf600-f11/image/image-sample/image-sample-media-img-02-popup.jpg

Sample images for the RF 800mm f11 IS STM (on EOS R):
https://cweb.canon.jp/eos/rf/lineup/rf800-f11/image/image-sample/image-sample-media-img-popup.jpg
https://cweb.canon.jp/eos/rf/lineup/rf800-f11/image/image-sample/image-sample-media-img-02-popup.jpg

---

Some more sample images (resized).

600mm:
https://downloads.canon.com/nw/camera/products/lenses/product-9/sample/original_sample_1.jpg
https://downloads.canon.com/nw/camera/products/lenses/product-9/sample/original_sample_2.jpg

800mm:
https://downloads.canon.com/nw/camera/products/lenses/product-10/sample/original_sample_1.jpg
https://downloads.canon.com/nw/camera/products/lenses/product-10/sample/original_sample_2.jpg

Not the best works of art, in true sample image tradition!