Teleconverters RF vs EF

Thinking, I just realized something about the RF Big White Lenses.  Take for example a RF 600mm F4 lens - it is basically a EF 600 F4 mk iii with a built in RF to EF adapter.  Putting a RF teleconverter on the RF 600 F4 gets you:  camera -> RF tele -> RF to EF adapter -> 600mm Lens.

With my EF 500 F4 ii lens on my R5 it is:  camera -> RF to EF adapter -> EF tele -> 500mm lens.

Does switching the order of the adapter/teleconverter make a difference?  I may have to borrow my wife's RF 1.4 tele and try:  R5 -> RF tele -> RF to EF adapter -> Lens and see what the difference is (or is this combo even possible?).

Does anyone have any experience with this?

Shawn

I'd honestly expect some difference between the performance of the EF and RF extenders on the EF/RF versions of the 600mm, just due to the fact that they're intended for lenses designed for different flange distances. I wonder if the assumption for RF versions of the big white lenses was that the image as projected by the rear element is close enough to parallel to the sensor that the position of the teleconverter wouldn't make as much of a difference (particularly since the RF teleconverters seem to be optically better than the EF versions).

I doubt there are too many people with both the EF and RF versions of the 600mm sitting around that could do a proper controlled comparison on the same body though :-D.

I had the EF 600 F4 II with both version III tc’s and now have the RF600 F4 with both RF tc’s.

I don’t notice any image quality difference between the two but the RF is lighter and the IS is much quieter

It doesn’t affect the quality.

your assumptions are 100% correct.

what a tc does is basically just crop the image, but it’s not that simple, since it is in the optical path.

if the angle of incidence is perpendicular, which it almost is for super teles then this does not matter, at least if it was perpendicular at the exit point of the tc as well.

there is a similar effect with nikon badged tamron lenses, everyone assumes they are the same, but the different thickness in optical stack will make a difference for wide angle (due to the angle of incidence as well).

for what it’s worth, I assume it’s better to be closer to the sensor, so the rf tc setup should be better

Abbott Schindler wrote:

If I understand you correctly, you want to try this:

R series camera - RF Extender - RF-EF adapter - EF big white

This is a nonstarter: the RF Extender won't fit into the RF end of the adapter.

It is nonstarter with Canon adapter. Third party adapters can be modified to fit.

The combination works and  1.4x is optically (slightly) better than EF 1.4x III. EF 1.4x II is much worse. What you get is slightly better optics. What you loose is aperture number correction in EXIF and correct working of IBIS - the combination doesn't see the TC, so corrections are based on base lens focal length. With big whites that may not be critical as IBIS is relatively inefficient with those focal lengths.

If you want to use an Extender with an EF big white, you need to do this:

Camera - RF-EF adapter - EF Extender - EF big white.

Yes - this naturally works. As a side note - so does Camera - RF extender - RF-EF adapter - EF extender - EF big white. The combo still doesn't see the RF extender, though.

OTOH, I've tested, and extension tubes work both ways:

Camera - RF-EF adapter - EF extension tube - EF lens

Camera - RF extension tube - RF-EF adapter - EF lens

Those naturally make no difference, but if you try to add an extender to the mix, don't but the extension on camera side of extender.

You will likely not notice it telephoto lenses but you might on WA lenses.

https://petapixel.com/2019/06/17/canon-this-is-why-rf-lenses-are-outstanding/

https://www.youtube.com/watch?v=43ZEGok4U78

KiloHotelphoto wrote:

I had the EF 600 F4 II with both version III tc’s and now have the RF600 F4 with both RF tc’s.

I don’t notice any image quality difference between the two but the RF is lighter and the IS is much quieter

R tech IS and IBIS is now electromagnetic. The EF IS used springs.

You will probably enjoy reading The Digital Picture's article on adapting an RF - EF adapter ring so that you can fit :
R Camera -> RF 1.4x Extender -> RF-EF adapter -> EF 600 F4 mk iii

https://www.the-digital-picture.com/News/News-Post.aspx?News=35054

He simply files the opening wider so that the extender will fit into it !

Hopefully new third party RF - EF adapter rings will appear having wider holes allowing this.

Abbott Schindler wrote:

If I understand you correctly, you want to try this:

R series camera - RF Extender - RF-EF adapter - EF big white

This is a nonstarter: the RF Extender won't fit into the RF end of the adapter.

If you want to use an Extender with an EF big white, you need to do this:

Camera - RF-EF adapter - EF Extender - EF big white.

OTOH, I've tested, and extension tubes work both ways:

Camera - RF-EF adapter - EF extension tube - EF lens

Camera - RF extension tube - RF-EF adapter - EF lens

Not true. There are RF-EF adapters that can accommodate the RF TC snout, including the Commlite CM-EF-EOS R, and these can connect to any EF lens, even ones that don't connect to an EF TC.

https://www.dpreview.com/forums/post/65820763

The problem with this setup is that Canon didn't intend to support this, so the EXIF data does not contain the correct focal length with the TC.

Shawn1519 wrote:

AwesomelyBad wrote:

I'd honestly expect some difference between the performance of the EF and RF extenders on the EF/RF versions of the 600mm, just due to the fact that they're intended for lenses designed for different flange distances. I wonder if the assumption for RF versions of the big white lenses was that the image as projected by the rear element is close enough to parallel to the sensor that the position of the teleconverter wouldn't make as much of a difference (particularly since the RF teleconverters seem to be optically better than the EF versions).

I doubt there are too many people with both the EF and RF versions of the 600mm sitting around that could do a proper controlled comparison on the same body though :-D.

The question isnt the optical difference between a EF and RF teleconverter.

The question is how does the added space (distance) on a RF lens between the rear element of the RF lens and the RF teleconverter affect image quality. Comparing the distance between the EF 600 f4 iii rear element and the front element of a EF 1.4x iii teleconverter VS the distance between a RF 600 F4 rear element and the front element of a RF 1.4 teleconveter - the RF combo the distance is quite a bit more than the EF combo - the length of the RF to EF adapter to be exact. Again, the RF 600 F4 and the RF 400 F2.8 lenses are identical lenses to the EF 600 F4 iii and the EF 400 F2.8 iii, except the RF versions have a RF to EF adapter welded onto them. Canon even states this on their website under the product descriptions for the RF 600 and RF 400 lenses.

I dont think the statement of the RF teleconverters were designed for a different focal plane because put a RF teleconverter on the RF 100-500 and zoom the RF 100-500 all the back as you can (approximately 300mm) and the back element of the RF 100-500 is practically touching the front element of the RF 1.4x teleconerter.

Asking the question a different way, take any lens/teleconverter combo (staying with the same format of EF or RF), put an extension tube between the lens and the teleconverter, and how does that effect image quality? That is in effect what Canon did with their RF 600 F4 and RF 400 F2.8 lens by incorporating the RF to EF adapter into the lens.

Shawn

There's already a decent amount of air between lens groups in a longer lens like the 100-500mm (or especially the 600mm), so I honestly don't think the optical impact of the amount of air between the rear element and the teleconverter is enough that even the highest resolution sensor available today could measure it. The RF 100-500mm in particular has the converter right up against the rear lens element at 300mm, but if you zoom in to 500mm, the rear element actually moves quite a ways away from where the TC sits, but I can't see any loss of quality at 500mm vs 300mm with the 1.4x.

There's already a decent amount of air between lens groups in a longer lens like the 100-500mm (or especially the 600mm), so I honestly don't think the optical impact of the amount of air between the rear element and the teleconverter is enough that even the highest resolution sensor available today could measure it.

yes, and typically there is even more air between the front element an the subject, particularly at 600mm. Not to mention between the left and right ear of most photographers

SafariBob wrote:

There's already a decent amount of air between lens groups in a longer lens like the 100-500mm (or especially the 600mm), so I honestly don't think the optical impact of the amount of air between the rear element and the teleconverter is enough that even the highest resolution sensor available today could measure it.

yes, and typically there is even more air between the front element an the subject, particularly at 600mm. Not to mention between the left and right ear of most photographers

Sometimes I fill the space with rocks, so it's not always air.

AwesomelyBad wrote:

SafariBob wrote:

There's already a decent amount of air between lens groups in a longer lens like the 100-500mm (or especially the 600mm), so I honestly don't think the optical impact of the amount of air between the rear element and the teleconverter is enough that even the highest resolution sensor available today could measure it.

yes, and typically there is even more air between the front element an the subject, particularly at 600mm. Not to mention between the left and right ear of most photographers

Sometimes I fill the space with rocks, so it's not always air.

Yes, it’s great to have a been bag behind the viewfinder for some support.