Opticallimits
RF 800mm f/5.6 & RF 1200mm f/8 L USM IS announced - Printable Version

+- Opticallimits (https://forum.opticallimits.com)
+-- Forum: Forums (https://forum.opticallimits.com/forumdisplay.php?fid=4)
+--- Forum: Canon EOS (https://forum.opticallimits.com/forumdisplay.php?fid=11)
+--- Thread: RF 800mm f/5.6 & RF 1200mm f/8 L USM IS announced (/showthread.php?tid=5235)

Pages: 1 2 3


RE: RF 800mm f/5.6 & RF 1200mm f/8 L USM IS announced - Brightcolours - 02-25-2022

Sorry for the confusion, Dave.
The 1st one Klaus links to is the RF 400 f2.8, with 2 fluorite elements in purple. The 2nd Klaus links to is the RF 800mm f5.6, with two fluorite elements in purple.
The Canon one I linked to is the EF 800mm f5.6. With two fluorite elements in blue. You can see the similarity to the Nikkor 800mm f5.6 there. The Nikkor and Canon have a slab of glass in front, to not have the fluorite element exposed to touch (it would scratch).
The newer Canon designs don't have fluorite as front element, which explains why the slab of glass in front is not needed.


RE: RF 800mm f/5.6 & RF 1200mm f/8 L USM IS announced - davidmanze - 02-25-2022

(02-25-2022, 10:26 AM)Brightcolours Wrote: Sorry for the confusion, Dave.
The 1st one Klaus links to is the RF 400 f2.8, with 2 fluorite elements in purple. The 2nd Klaus links to is the RF 800mm f5.6, with two fluorite elements in purple.
The Canon one I linked to is the EF 800mm f5.6. With two fluorite elements in blue. You can see the similarity to the Nikkor 800mm f5.6 there. The Nikkor and Canon have a slab of glass in front, to not have the fluorite element exposed to touch (it would scratch).
The newer Canon designs don't have fluorite as front element, which explains why the slab of glass in front is not needed.

 Well I'm a little bit less confused .... 

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

......... but this optical formula shows one front element ....... and no protective meniscus!!

Perhaps I have scrambled eggs where my brain should be ....... Smile


RE: RF 800mm f/5.6 & RF 1200mm f/8 L USM IS announced - Brightcolours - 02-25-2022

The purple ones are fluorite elements, the front one is glass (so does not need a glass protective slab in front).


RE: RF 800mm f/5.6 & RF 1200mm f/8 L USM IS announced - davidmanze - 02-25-2022

(02-25-2022, 12:27 PM)Brightcolours Wrote: The purple ones are fluorite elements, the front one is glass (so does not need a glass protective slab in front).
 Ok, I get it now ........ Canon has saved weight by using smaller diameter/ light weight fluorite elements not so far forward in the lens body .... whilst only having one glass element which is part of the optical formula in front with the appropriate tough fluorine type coatings amongst others......

  You got to hand it to Canon ....... masters of light weight optics ......

thanks again !!


RE: RF 800mm f/5.6 & RF 1200mm f/8 L USM IS announced - Klaus - 02-26-2022

" You got to hand it to Canon ....... masters of light weight optics ......"

Nikon's 500mm f/5.6 PF has a weight of less than 1.5Kg ... THAT is impressive IMHO.


RE: RF 800mm f/5.6 & RF 1200mm f/8 L USM IS announced - davidmanze - 02-26-2022

The 500mm F5.6 VR PF is a classic birder lens and will be a favourite for years to come .............

........ pity the 600mm F5.6 VR PF never happened ........ that would have been even better !!


RE: RF 800mm f/5.6 & RF 1200mm f/8 L USM IS announced - Klaus - 02-26-2022

I'm somewhat baffled that Canon didn't continue with their DOs. They would be a perfect match for mirrorless cameras.


RE: RF 800mm f/5.6 & RF 1200mm f/8 L USM IS announced - toni-a - 02-27-2022

There's one more thing to keep in mind, the farther the weight to the camera the more the lens feels heavy
if the weight is closer the camera body the lens will balance better when handheld


RE: RF 800mm f/5.6 & RF 1200mm f/8 L USM IS announced - Brightcolours - 02-27-2022

(02-27-2022, 08:55 AM)toni-a Wrote: There's one more thing to keep in mind, the farther the weight to the camera the more the lens feels heavy
if the weight is closer the camera body the lens will balance better when handheld

The farther weight, the more torque is applied by gravity.


RE: RF 800mm f/5.6 & RF 1200mm f/8 L USM IS announced - davidmanze - 02-27-2022

(02-27-2022, 02:47 PM)Brightcolours Wrote:
(02-27-2022, 08:55 AM)toni-a Wrote: There's one more thing to keep in mind, the farther the weight to the camera the more the lens feels heavy
if the weight is closer the camera body the lens will balance better when handheld

The farther weight, the more torque is applied by gravity.

  "The further the center of gravity of the lens is from the camera mount ....... the greater the leverage, compensation and perceived weight by the user" ......

   Not at all keen on "the farther weight"  ....... and torque is of course a rotational force  ........ nothing is rotating here ........ leverage is the term !!

Sorry I can only give you 0 out of 4 ....... not your best BC ........... Oh go then ...... 1 out of 4 ...... for trying !! .......... Smile