RF and EF extenders on the EF 600/4L IS II

neuroanatomist

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After getting both the RF extenders to use with my RF 100-500L, I became curious about whether they would perform better than my EF MkIII extenders when used with my EF 600/4L IS II on my EOS R3. As most will know, the protruding elements of the RF extenders do not fit into the Canon EF-RF mount adapters, even the drop-in filter version that has a much wider opening. I purchased a Commlite EF-RF adapter (which has a wider opening than the other 3rd party adapters or the OEM versions), and modified it with a Dremel until the opening was sufficiently wide to accept the TCs.

The resolution charts on The Digital Picture allow comparison of the EF TCs on the EF 600/4 III with the RF TCs on the RF 600/4, but they are done with two different bodies, and that complicates interpretation. With the modified adapter in hand, I had the ability to test both sets of adapters with the same lens. Of course, being able to mount the EF TCs in front of the adapter and the RF TCs behind the adapter gave me the opportunity to test the various combinations of stacked TCs as well, which I did.

I did two sets of tests with all 8 possible combinations of TCs and the bare lens, all at the lens' maximum aperture:
  • EF 2xIII + RF 2x + EF 600/4 II = 2400mm f/16
  • EF 2xIII + RF 1.4x + EF 600/4 II = 1680mm f/11
  • EF 1.4xIII + RF 2x + EF 600/4 II = 1680mm f/11
  • EF 1.4xIII + RF 1.4x + EF 600/4 II = 1200mm f/8
  • RF 2xIII + EF 600/4 II = 1200mm f/8
  • EF 2xIII + EF 600/4 II = 1200mm f/8
  • RF 1.4xIII + EF 600/4 II = 840mm f/5.6
  • EF 1.4xIII + EF 600/4 II = 840mm f/5.6
  • EF 600/4 II = 600mm f/4
For both sets of tests, I used the same enhanced ISO 12233 charts than Bryan uses for the TDP tests, which test resolutions up to 4000 lw/ph. The first set of tests was performed in the same way the TDP tests are done, by changing the distance from the camera to the subject such that the 3:2 region of the chart fills the frame. Note that for the 1.4x and bare lens shots, I needed to switch to a larger chart because the smaller one was closer than the MFD – that resulted in a change in the lighting but the charts themselves are printed such that the resolutions shown are independent of chart size.

Below are the first set of results. I cropped larger regions than Bryan does (about double the size). The image below is scaled down for upload here, the full size version that shows 1:1 crops can be viewed HERE.

EF+RF extender tests_constant framing-reduced.jpg

The second set of tests were a more 'real world' approach similar to that used here by @AlanF to test lenses and extenders. For those tests, the distance was kept constant, which is more relevant for something like bird photography where you can only get so close to the subject and must rely on extenders and/or cropping. For these tests, the distance was ~10 m / 33', which was the distance needed to fully frame the smallest test chart (~150 x 100mm). The image below is scaled down for upload here, the full size version that shows 1:1 crops can be viewed HERE.

EF+RF extender tests_constant diatance-reduced.jpg

As expected, stacking two extenders results in a loss of sharpness. However, the 4x magnification increase with the stacked 2x TCs results in about 3x the resolving power of the bare lens. It will be interesting to see how that translates into real-world subjects that benefit from higher magnification, the moon for example.

Looking at comparisons more relevant for everyday use, the EF and RF 1.4x TCs deliver very similar performance. The EF version appears very slightly sharper in the center, the edges are equivalent. There is a noticeable difference between the EF and RF 2x TCs on the EF 600/4 II, with the EF 2xIII delivering sharper results in the center and periphery. The RF 2x actually performs pretty much identically to the two 1.4x TCs stacked (which yields the same final 2x magnification as the 2x TC). Also, though it's not evident from the crops, the RF 2x introduces a noticeable level of barrel distortion that the EF 2x does not. I wonder if that's in keeping with Canon's other RF lenses that leave substantial barrel distortion in the optical design in favor of digital correction (note that I would not consider the RF 2x to have substantial distortion, but it is evident).

For my personal use, I'll stick with the EF TCs when using the EF 600/4 II on my R3, possibly with the RF 2x added behind the EF 2x when I want the maximum focal length I can achieve.
 
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Del Paso

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After getting both the RF extenders to use with my RF 100-500L, I became curious about whether they would perform better than my EF MkIII extenders when used with my EF 600/4L IS II on my EOS R3. As most will know, the protruding elements of the RF extenders do not fit into the Canon EF-RF mount adapters, even the drop-in filter version that has a much wider opening. I purchased a Commlite EF-RF adapter (which has a wider opening than the other 3rd party adapters or the OEM versions), and modified it with a Dremel until the opening was sufficiently wide to accept the TCs.

The resolution charts on The Digital Picture allow comparison of the EF TCs on the EF 600/4 III with the RF TCs on the RF 600/4, but they are done with two different bodies, and that complicates interpretation. With the modified adapter in hand, I had the ability to test both sets of adapters with the same lens. Of course, being able to mount the EF TCs in front of the adapter and the RF TCs behind the adapter gave me the opportunity to test the various combinations of stacked TCs as well, which I did.

I did two sets of tests with all 8 possible combinations of TCs and the bare lens, all at the lens' maximum aperture:
  • EF 2xIII + RF 2x + EF 600/4 II = 2400mm f/16
  • EF 2xIII + RF 1.4x + EF 600/4 II = 1680mm f/11
  • EF 1.4xIII + RF 2x + EF 600/4 II = 1680mm f/11
  • EF 1.4xIII + RF 1.4x + EF 600/4 II = 1200mm f/8
  • RF 2xIII + EF 600/4 II = 1200mm f/8
  • EF 2xIII + EF 600/4 II = 1200mm f/8
  • RF 1.4xIII + EF 600/4 II = 840mm f/5.6
  • EF 1.4xIII + EF 600/4 II = 840mm f/5.6
  • EF 600/4 II = 600mm f/4
For both sets of tests, I used the same enhanced ISO 12233 charts than Bryan uses for the TDP tests, which test resolutions up to 4000 lw/ph. The first set of tests was performed in the same way the TDP tests are done, by changing the distance from the camera to the subject such that the 3:2 region of the chart fills the frame. Note that for the 1.4x and bare lens shots, I needed to switch to a larger chart because the smaller one was closer than the MFD – that resulted in a change in the lighting but the charts themselves are printed such that the resolutions shown are independent of chart size.

Below are the first set of results. I cropped larger regions than Bryan does (about double the size). The image below is scaled down for upload here, the full size version that shows 1:1 crops can be viewed HERE.

View attachment 202198

The second set of tests were a more 'real world' approach similar to that used here by @AlanF to test lenses and extenders. For those tests, the distance was kept constant, which is more relevant for something like bird photography where you can only get so close to the subject and must rely on extenders and/or cropping. For these tests, the distance was ~10 m / 33', which was the distance needed to fully frame the smallest test chart (~150 x 100mm). The image below is scaled down for upload here, the full size version that shows 1:1 crops can be viewed HERE.

View attachment 202199

As expected, stacking two extenders results in a loss of sharpness. However, the 4x magnification increase with the stacked 2x TCs results in about 3x the resolving power of the bare lens. It will be interesting to see how that translates into real-world subjects that benefit from higher magnification, the moon for example.

Looking at comparisons more relevant for everyday use, the EF and RF 1.4x TCs deliver very similar performance. The EF version appears very slightly sharper in the center, the edges are equivalent. There is a noticeable difference between the EF and RF 2x TCs on the EF 600/4 II, with the EF 2xIII delivering sharper results in the center and periphery. The RF 2x actually performs pretty much identically to the two 1.4x TCs stacked (which yields the same final 2x magnification as the 2x TC). Also, though it's not evident from the crops, the RF 2x introduces a noticeable level of barrel distortion that the EF 2x does not. I wonder if that's in keeping with Canon's other RF lenses that leave substantial barrel distortion in the optical design in favor of digital correction (note that I would not consider the RF 2x to have substantial distortion, but it is evident).

For my personal use, I'll stick with the EF TCs when using the EF 600/4 II on my R3, possibly with the RF 2x added behind the EF 2x when I want the maximum focal length I can achieve.
Thanks for the test, you helped me save a few hundred Euros...:)
 
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AlanF

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After getting both the RF extenders to use with my RF 100-500L, I became curious about whether they would perform better than my EF MkIII extenders when used with my EF 600/4L IS II on my EOS R3. As most will know, the protruding elements of the RF extenders do not fit into the Canon EF-RF mount adapters, even the drop-in filter version that has a much wider opening. I purchased a Commlite EF-RF adapter (which has a wider opening than the other 3rd party adapters or the OEM versions), and modified it with a Dremel until the opening was sufficiently wide to accept the TCs.

The resolution charts on The Digital Picture allow comparison of the EF TCs on the EF 600/4 III with the RF TCs on the RF 600/4, but they are done with two different bodies, and that complicates interpretation. With the modified adapter in hand, I had the ability to test both sets of adapters with the same lens. Of course, being able to mount the EF TCs in front of the adapter and the RF TCs behind the adapter gave me the opportunity to test the various combinations of stacked TCs as well, which I did.

I did two sets of tests with all 8 possible combinations of TCs and the bare lens, all at the lens' maximum aperture:
  • EF 2xIII + RF 2x + EF 600/4 II = 2400mm f/16
  • EF 2xIII + RF 1.4x + EF 600/4 II = 1680mm f/11
  • EF 1.4xIII + RF 2x + EF 600/4 II = 1680mm f/11
  • EF 1.4xIII + RF 1.4x + EF 600/4 II = 1200mm f/8
  • RF 2xIII + EF 600/4 II = 1200mm f/8
  • EF 2xIII + EF 600/4 II = 1200mm f/8
  • RF 1.4xIII + EF 600/4 II = 840mm f/5.6
  • EF 1.4xIII + EF 600/4 II = 840mm f/5.6
  • EF 600/4 II = 600mm f/4
For both sets of tests, I used the same enhanced ISO 12233 charts than Bryan uses for the TDP tests, which test resolutions up to 4000 lw/ph. The first set of tests was performed in the same way the TDP tests are done, by changing the distance from the camera to the subject such that the 3:2 region of the chart fills the frame. Note that for the 1.4x and bare lens shots, I needed to switch to a larger chart because the smaller one was closer than the MFD – that resulted in a change in the lighting but the charts themselves are printed such that the resolutions shown are independent of chart size.

Below are the first set of results. I cropped larger regions than Bryan does (about double the size). The image below is scaled down for upload here, the full size version that shows 1:1 crops can be viewed HERE.

View attachment 202198

The second set of tests were a more 'real world' approach similar to that used here by @AlanF to test lenses and extenders. For those tests, the distance was kept constant, which is more relevant for something like bird photography where you can only get so close to the subject and must rely on extenders and/or cropping. For these tests, the distance was ~10 m / 33', which was the distance needed to fully frame the smallest test chart (~150 x 100mm). The image below is scaled down for upload here, the full size version that shows 1:1 crops can be viewed HERE.

View attachment 202199

As expected, stacking two extenders results in a loss of sharpness. However, the 4x magnification increase with the stacked 2x TCs results in about 3x the resolving power of the bare lens. It will be interesting to see how that translates into real-world subjects that benefit from higher magnification, the moon for example.

Looking at comparisons more relevant for everyday use, the EF and RF 1.4x TCs deliver very similar performance. The EF version appears very slightly sharper in the center, the edges are equivalent. There is a noticeable difference between the EF and RF 2x TCs on the EF 600/4 II, with the EF 2xIII delivering sharper results in the center and periphery. The RF 2x actually performs pretty much identically to the two 1.4x TCs stacked (which yields the same final 2x magnification as the 2x TC). Also, though it's not evident from the crops, the RF 2x introduces a noticeable level of barrel distortion that the EF 2x does not. I wonder if that's in keeping with Canon's other RF lenses that leave substantial barrel distortion in the optical design in favor of digital correction (note that I would not consider the RF 2x to have substantial distortion, but it is evident).

For my personal use, I'll stick with the EF TCs when using the EF 600/4 II on my R3, possibly with the RF 2x added behind the EF 2x when I want the maximum focal length I can achieve.
Thanks Neuro. There was a lot of work there, and most useful - removed any temptation of my buying an EF telephoto and a Commlite. More importantly, it's telling R owners that it might be better to buy EF 600 and 400 f/4 IIIs rather than the RF versions, which are optically the same as they will perform better with TCs.
 
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neuroanatomist

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Didn't neuro use the 600 II ? The third version has the same glass as the RF 600 has.
Correct, but that is consistent with what @AlanF is suggesting.

My results suggest that the 1.4x TCs are equivalent but the EF 2x is better than the RF 2x. Mounting the extenders behind the 600 III vs. 600 II should not affect the performance of the extender itself. Also, at least according to Bryan/TDP, the 600 II is actually slightly sharper than the 600 III (it seems the latter was primarily designed to reduce weight significantly compared to the MkII, although the MkIII also has less CA and gives an extra stop of IS benefit).

So, since the EF III and the RF are optically identical, if the EF 2x is better than the RF 2x, the EF III may be a better choice for someone who plans to use the 2x TC a lot. OTOH, the RF version is supposed to focus faster than the EF III on an integrated-grip body like the R3.

Personally, I only use the 2x TC for about 5% of my shooting, but that was on my 1D X where the f/8 combo means only the center AF point is available. The R3 will track across the whole frame at f/8 so I may use the 2x more.

If I were buying a 400/2.8 or 600/4 today, I’m pretty sure I’d get the RF version. But since I already have the EF 600/4 II, I was not planning to swap it for the RF version…and these results make me feel even more comfortable with that decision.
 
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AlanF

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Based on my minimal experience of using the EF 2xTCIII in the EF 300mm f/2.8 II and the EF 400mm f/4 DO II and the RF 2x on the RF 100-500mm and RF 800mm f/11, the RF 2x gives less image degradation on the RF lenses than the EF 2x on the EF, but the EF 1.4x and RF 1.4x about the same. Unfortunately in that respect, the RF 600mm f/4 and 400mm f/2.8 are EF lenses and the RF extenders are not optimised towards them.
 
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Czardoom

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Based on my minimal experience of using the EF 2xTCIII in the EF 300mm f/2.8 II and the EF 400mm f/4 DO II and the RF 2x on the RF 100-500mm and RF 800mm f/11, the RF 2x gives less image degradation on the RF lenses than the EF 2x on the EF, but the EF 1.4x and RF 1.4x about the same. Unfortunately in that respect, the RF 600mm f/4 and 400mm f/2.8 are EF lenses and the RF extenders are not optimised towards them.
It seems to me, considering how many times this is mentioned on forums, and users have experienced it, that copy variation may be playing a part in Neuro's results, and that he may just have a better copy of the EF 2x than RF 2x. So, I wouldn't necessary assume that the EF 2x is better optically than the RF 2x. All we know is that Neuro's EF 2x is better than his RF 2x.
 
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snappy604

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fantastic work.. and damn if I'm not curious what you might get with it.. some real world samples with 4x would be neat... the chart results honestly seem pretty good
 
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AlanF

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It seems to me, considering how many times this is mentioned on forums, and users have experienced it, that copy variation may be playing a part in Neuro's results, and that he may just have a better copy of the EF 2x than RF 2x. So, I wouldn't necessary assume that the EF 2x is better optically than the RF 2x. All we know is that Neuro's EF 2x is better than his RF 2x.
Copy variation can indeed be important. Roger Cicala's optical measurements as reported in lensrentals blog show that there is less copy variation in extenders than lenses, but I found copy variation in the three 1.4xTCIIIs I had. I have written several times here that the only copy that counts for you is your own one. Neuro's measurements show that for his copies he should stick to his EF for his EF lens.
 
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PCM-madison

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I purchased a Commlite EF-RF adapter (which has a wider opening than the other 3rd party adapters or the OEM versions), and modified it with a Dremel until the opening was sufficiently wide to accept the TCs.
Neuro, can you post a photo that shows how much of the Commlite adapter was removed?
 

neuroanatomist

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No reason to faint - it's not that many $$$. ;) I've contemplated buying one and carefully mounting it on the lathe. Neuro - does that strike you as doable?
Sure! The adapter has a tripod foot, I just attached a RRS plate to it and put it on a tripod, then took a Dremel to it (with a coarse sanding bit).

2B220CCE-8C1B-4CAA-9C2D-F68E39C986BA.jpeg
 
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AlanF

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Sure! The adapter has a tripod foot, I just attached a RRS plate to it and put it on a tripod, then took a Dremel to it (with a coarse sanding bit).

View attachment 202271
Nikon didn't think into the future for its FTZ adapter. It has a tripod foot that works fine with the Z6 and Z7 series but with the Z9, the foot gets in the way of holding via the built in grip so Nikon has had to bring out a FTZ II without the foot.
 

neuroanatomist

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Nikon didn't think into the future for its FTZ adapter. It has a tripod foot that works fine with the Z6 and Z7 series but with the Z9, the foot gets in the way of holding via the built in grip so Nikon has had to bring out a FTZ II without the foot.
The Commlite foot is removable. Same design as the Canon EF-M mount adapter.
 
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tron

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Thanks for the info Neuro. Coincidentally yesterday I ordered Canon Extender EF25 II to put it between EF2XIII and EF1.4XIII to try to increase my 500mm 4L IS II lens focal length for static birds not at infinity of course where the lens will not be able to focus.

EF12 II would probably do the job (EF1.4XIII will be the addon behind the 500/2X/Extender combo) but I could not find it easily (and reasonably cheap) so I took the longer one in case it is being used for macro cases too.

I also have the RX teleconverters but going by the book for now....