A bit of history about Canon and catadioptric (mirror) lenses

Mar 19, 2021
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Needing teleconverter if shooting big butterflyes with 5200mm .
and something like this to push it around.
 
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AlanF

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Needing teleconverter if shooting big butterflyes with 5200mm .
and something like this to push it around.
Its minimus focal distance is 120m. So, it will give you the equivalent of the magnification of a 520mm lens at 12m. So, a 2x TC will be needed, or better still a 4x.
 
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Oct 22, 2014
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And if you adapt your 5200mm to an APS-C camera...

Or, and here me out, attach it to a high megapixel full frame. And then crop. Same effect, more raw image to work with.

You're not adding reach to your images, only cropping the full frame.

Unless both your full frame and crop sensor are the same resolution, anyway.
 
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RunAndGun

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Dec 16, 2011
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I am not sure that I would trust selling something worth $50K on eBay.

I’ve actually seen way more expensive things on eBay. YEARS ago, in the live(TV) sports world, there were two main companies that provided the wireless transmission services for the handheld cameras and other remote/robotic cameras. At one point, the smaller company failed and was put up for sale. I about fell out of my chair one day when I was looking around on eBay and the company was listed for sale on an eBay auction.
 
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LDS

Sep 14, 2012
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What it interesting is Canon is no longer using the old Maksutov-Cassegrain design of those lenses, which was cheaper than the Schimdt-Cassegrain one, not using the aspherical front element. It looks inspired by recent Busack-Honders-Riccardi designs, with the reflective coating on the mirror back instead its front surface, and the positive front lens.

So it looks Canon did some real new researches and designs for these lenses.
 
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Dragon

EF 800L f/5.6, RF 800 f/11
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If Canon brings out some cat lenses, I hope they're a bit lighter than these puppies!
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I kinda remember the Nikon cat lens (for F models), and it was comfortably light (hand-holdable) at 500mm.
The Canon FD 500mm Cat is lighter than the Nikon and quite usable on an R5 with IBIS on. It is also pretty reasonable on fleabay.
 
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Sep 20, 2020
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I wonder how 2000mm f/11 would work for shooting action sequences on bright days with modern low noise cameras. Got to think you would get all the lens compression you will ever need with out the need for a ton of ND.
I am obviously a Canonite but I also use micro four-thirds because I swore off heavy telephoto lenses.
However, I have not seen micro four-thirds lenses longer than 800 mm.
2000 mm with APS-C would blow micro four-thirds out of the water.
There is still a sweet spot for micro four-thirds with telephoto zooms since the extra crop increases the zoom range.
After that, the main advantage is IS.
Only the R5 and R6 rival my G9 in image stabilization at twice or three times the price.
 
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JoeDavid

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Feb 23, 2012
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I still have my FD500 f8 reflex lens, works well with a cheap FD to EF adapter: sadly no AF or IS in 1985. Doesn't get a lot of use but am happy to see the possibility of new reflex/cat lenses coming. View attachment 197632
Yea, back in film days I had a 500mm f8 Tokina lens that was quite sharp. It was compact enough that no one thought it was a 500mm lens. Once you get over the donut bokeh, one with autofocus would be welcome in my kit. I wish Canon had used a reflex/cat design with the 600 and 800 lenses. They could have been smaller and faster. Those are stuck at f11. I’d rather be stuck at f8.
 
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AlanF

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I am obviously a Canonite but I also use micro four-thirds because I swore off heavy telephoto lenses.
However, I have not seen micro four-thirds lenses longer than 800 mm.
2000 mm with APS-C would blow micro four-thirds out of the water.
There is still a sweet spot for micro four-thirds with telephoto zooms since the extra crop increases the zoom range.
After that, the main advantage is IS.
Only the R5 and R6 rival my G9 in image stabilization at twice or three times the price.
Micro 4/3 may have a crop factor of 2 over FF but the resolution of the G9 sensor isn't two times higher than that of the R5 because of the much higher pixel density of the FF. The pixel pitch of the G9 is 3.32 µ compared with 4.38 µ for the R5, which means the G9 has only 32% more "reach". The 90D and M6II both outresolve the G9 or Olympus equivalents.
 
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SteveC

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Or, and here me out, attach it to a high megapixel full frame. And then crop. Same effect, more raw image to work with.

You're not adding reach to your images, only cropping the full frame.

Unless both your full frame and crop sensor are the same resolution, anyway.

Yes. "Reach" depends on pixel density and focal length, not the size of the sensor. Of course if it's a big sensor you end up having to crop in post (or use the crop mode if the camera has one) but you still get the same results as you would with a smaller sensor of the same density.

That being said, crop sensors tend to have a higher pixel density, so it's easy enough to get a little lazy just equate them with better reach because of the APS-C sensor. And as far as I know the best pixel density Canon has to offer is on the M6-II and the 90D. The R5 has the same density as a (hypothetical) 17MP APS-C camera. Not so long ago that would have been killer megapixels, today the APS-C birders and the like find it a step down, and it actually is, from their 7Ds.
 
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Sep 20, 2020
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Micro 4/3 may have a crop factor of 2 over FF but the resolution of the G9 sensor isn't two times higher than that of the R5 because of the much higher pixel density of the FF. The pixel pitch of the G9 is 3.32 µ compared with 4.38 µ for the R5, which means the G9 has only 32% more "reach". The 90D and M6II both outresolve the G9 or Olympus equivalents.
While you are correct, I do also have an R5 which makes me use the G9 less but Panasonic MFT lenses are much smaller for the same reach.
The main point of my comment was that advantage is getting less and less but it does still exist.
MFT and RF have the exact same flange distance and MFT is smaller so I am not sure why there is no MFT to EOS R adapter.
I guess maybe the size difference is not enough to fit an MFT adapter into an RF mount.
 
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Ozarker

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While you are correct, I do also have an R5 which makes me use the G9 less but Panasonic MFT lenses are much smaller for the same reach.
The main point of my comment was that advantage is getting less and less but it does still exist.
MFT and RF have the exact same flange distance and MFT is smaller so I am not sure why there is no MFT to EOS R adapter.
I guess maybe the size difference is not enough to fit an MFT adapter into an RF mount.
If they have the same exact native flange distance, doesn't adding the adapter change the flange distance from lens to sensor? Absolutely. That is probably why there is no adapter. The reason EF to RF works is because EF lenses have a naturally greater flange distance than RF. So adding the adapter makes up for that. So, to me, this is the same reason RF isn't adapted to EF. You increase the flange distance with an adapter.

*I have no idea what the flange distance measurement is for MFT vs RF.* Just assuming @EOS 4 Life is correct. :)
 
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Del Paso

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If they have the same exact native flange distance, doesn't adding the adapter change the flange distance from lens to sensor? Absolutely. That is probably why there is no adapter. The reason EF to RF works is because EF lenses have a naturally greater flange distance than RF. So adding the adapter makes up for that. So, to me, this is the same reason RF isn't adapted to EF. You increase the flange distance with an adapter.

*I have no idea what the flange distance measurement is for MFT vs RF.* Just assuming @EOS 4 Life is correct. :)
Sometimes it works!
A Spanish company (Leitax) replaces Nikon F bayonets with EOS EF ones, or Leica R's with EF bayonets, so there's no need for an adapter which, as you mentioned, adds flange distance. Due to the high precision manufactoring of these bayonets, F Nikons or R Leicas work perfectly well on EOS DSLRs (with RF-EF adapter also on EOS R).
Of course, would adapting MFT to RF make sense??? That is the question...
 
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Sep 20, 2020
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If they have the same exact native flange distance, doesn't adding the adapter change the flange distance from lens to sensor? Absolutely. That is probably why there is no adapter. The reason EF to RF works is because EF lenses have a naturally greater flange distance than RF. So adding the adapter makes up for that. So, to me, this is the same reason RF isn't adapted to EF. You increase the flange distance with an adapter.

*I have no idea what the flange distance measurement is for MFT vs RF.* Just assuming @EOS 4 Life is correct. :)
There is no glass in the adapter so it would not necessarily increase the flange distance.
It would just be one mount inside of another.
The diameter seems like a bigger challenge because the adapter would need to connect to the RF pins while at the same time having the MFT pins for lenses to connect to.
 
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Sep 17, 2014
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Yea, back in film days I had a 500mm f8 Tokina lens that was quite sharp. It was compact enough that no one thought it was a 500mm lens. Once you get over the donut bokeh, one with autofocus would be welcome in my kit. I wish Canon had used a reflex/cat design with the 600 and 800 lenses. They could have been smaller and faster. Those are stuck at f11. I’d rather be stuck at f8.

Oh, please no! At least those 600mm and 800mm lenses have pretty good image quality with nice bokeh. If they were mirror lenses I would just ignore them as the usage is very limited. I don't mind Canon making few mirror lenses but we need affordable high quality telephotos also.
 
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