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**Klaus** · (This post was last modified: 02-24-2022, 02:18 AM by Klaus.)

1200mm f/8
https://www.canon.co.uk/lenses/rf-1200mm...fications/

800mm f/5.6
https://www.canon.co.uk/lenses/rf-800mm-...fications/

I'm not overly impressed when looking at the optical design, to be honest.

The 1200mm f/8 is basically the 600mm f/4 with 2x converter
The 800mm f/5.6 is the 400mm f/2.8 with 2x converter

There's surely a little gain in quality due to the integration but there's probably not too much in it.

davidmanze · (This post was last modified: 02-24-2022, 07:48 AM by davidmanze.)

(02-24-2022, 02:02 AM)Klaus Wrote: 1200mm f/8
https://www.canon.co.uk/lenses/rf-1200mm...fications/

800mm f/5.6
https://www.canon.co.uk/lenses/rf-800mm-...fications/

I'm not overly impressed when looking at the optical design, to be honest.

The 1200mm f/8 is basically the 600mm f/4 with 2x converter
The 800mm f/5.6 is the 400mm f/2.8 with 2x converter

There's surely a little gain in quality due to the integration but there's probably not too much in it.

Canon have certainly kept down the weight of their 800mm F5.6 lens at
3.140 Kgs ......

........ against Nikon's 800mm F5.6 which weighs in at 4.560 Kgs including 150 gms with the built in 1.25X TC which makes the lens a 1,000mm F7 .....

The 1,200mm Canon weighs in at 3.340 Kgs .......

I'm surprised that there is such a difference !!

My Nikon AF-S600mm F4E VR FL weighs 3.8 Kgs .......

Rover · 02-24-2022, 07:47 AM

Was the existing EF 800/5.6 lens also the same kind of construction, that is, actually a 400/2.8 with a non-detachable converter?

Brightcolours · (This post was last modified: 02-24-2022, 08:37 AM by Brightcolours.)

The TC group used is pretty different from the RF 2x TC, with much bigger elements on the whole, and an SUD element, and without the bulbous back element. So, it appears to be highly optimized for these two long tele lenses. But if you can compare the manufacturer MTFs (can we do that at all, Klaus?) the Nikkor AF-S 800mm f5.6 FL VR look to perform better, so the TC route does seem to give a resolution hit?

The published Canon MTFs of the 400mm and 600mm are pretty great, and the 800mm and 1200mm look much better than those of the 400 and 600mm + RF 2x TC....

(02-24-2022, 07:47 AM)Rover Wrote: Was the existing EF 800/5.6 lens also the same kind of construction, that is, actually a 400/2.8 with a non-detachable converter?

No, the front part of the EF 800mm f5.6 L IS USM (6 elements) is pretty similar (but not exactly the same in detail) to those of the EF 400mm f2.8 L IS USM, but the other elements (both in front of the aperture and the elements further in the back) are all specific for their respective lenses.

**Klaus** · 02-24-2022, 09:28 AM

You must be seeing something different:

https://cweb.canon.jp/eos/rf/lineup/rf40...uction.png

vs

https://cweb.canon.jp/eos/rf/lineup/rf80...uction.png

The front part is pretty much identical. The schema in the 800mm image is comparatively smaller to fit into the same image width.

The difference starts at the green element on the 800mm.

Brightcolours · (This post was last modified: 02-24-2022, 09:34 AM by Brightcolours.)

(02-24-2022, 09:28 AM)Klaus Wrote: You must be seeing something different:

https://cweb.canon.jp/eos/rf/lineup/rf40...uction.png

vs

https://cweb.canon.jp/eos/rf/lineup/rf80...uction.png

The front part is pretty much identical. The schema in the 800mm image is comparatively smaller to fit into the same image width.

The difference starts at the green element on the 800mm.

You must be reading something different. I replied to Rover's question, and clearly stated "EF" two times.... ;-)

**Klaus** · 02-24-2022, 09:34 AM

Ah, yes, sorry.

davidmanze · 02-25-2022, 05:17 AM

I was looking around the net for the optical formula for the equivalent focal length lens from Nikon ........ ie the AF-S 800mm F5.6 etc ......

I'm guessing from memory that there were two flourite elements at the front of the Nikkor 800mm lens ..... plus possibly a protective meniscus front element .......
........ just to satisfy my idle curiosity as to the weight difference between Canon's and Nikon's designs .....

I can only open these two links by clicking here, but the script is in Japanese .... what are these two lenses ??

https://cweb.canon.jp/eos/rf/lineup/rf40...uction.png

vs

https://cweb.canon.jp/eos/rf/lineup/rf80...uction.png

can anyone post a link for the optical formula of the Nikon's 800mm FL lens??

Brightcolours · 02-25-2022, 07:39 AM

Canon has used fluorite in tele lenses since the 1970's. The two purple elements are fluorite. Nikon has, for decades, touted that thei "ED" glass was superior... until they finally were able to use fluorite element. Their FL lenses use fluorite in a similar way as Canon does.

https://imaging.nikon.com/lineup/lens/f-...ic_003.jpg

Canon:
http://allphotolenses.com/public/files/o...18c337.gif

davidmanze · 02-25-2022, 10:03 AM

(02-25-2022, 07:39 AM)Brightcolours Wrote: Canon has used fluorite in tele lenses since the 1970's. The two purple elements are fluorite. Nikon has, for decades, touted that thei "ED" glass was superior... until they finally were able to use fluorite element. Their FL lenses use fluorite in a similar way as Canon does.

https://imaging.nikon.com/lineup/lens/f-...ic_003.jpg

Canon:
http://allphotolenses.com/public/files/o...18c337.gif

Thanks for that BC !!

I remember the Nikon had a double fluorite front elements .... the Canon has a similar arrangement then?

Quite a weight saving on the Canon!

What were the lenses that Klaus linked with only one front element then? I don't have a translate on my browser ...... and I don't read hieroglyphics Smile