RF 100-400 vs 2x EF 70-200 F4 on an R6

I caved and bought an R6. The main 400MM I am looking at is the f5.6 400 prime, but I am doing a trip that needs the variable range of a 100-400 shooting marine mammals. The EF 100-400 ISII is sadly out of my budget and renting isn’t an option. Would a teleconverter on the 70-200 work? The slower aperture won’t be a problem as the other within budget option has the exact same shortcoming. The RF will shoot and focus faster, as well as track more accurately, but I am looking for the highest possible raw image quality. Anyone have any idea if the EF combination would work? I get that it is a pretty niche thing not many people would have tried, but if anyone has, or has technical knowledge to answer, I’d appreciate it a lot!

I don't use either, but expect the RF 100-400 to be more versatile and deliver better IQ than the 70-200 f/4 plus 2x converter, so I would take the RF over the TC combi. Best possible IQ is the 70-200 plus the 400mm prime. The latter is a full stop faster and (by far) the sharpest option.

Edit : the RF has IS, which helps a lot a lower f-ratios.

Sandor.

I can confirm that the EF70-200 f4 L IS (mark i) with the TC 1.4x (mark iii) works just fine on the R5. However it is rather slower to autofocus than many EF lenses, and slightly worse with the TC. I sold that lens and bought an RF100-400 which is the same physical size as the EF 70-200 (actually smaller when you consider you need the adapter too) and in my view a better package - maybe a little better IQ, but twice the reach, and much faster AF.  If you can afford it, the RF100-400 is a good option.  It isn’t weather-sealed.

I still have my EF 100-400 L mkii and the 1.4 TC, which I will continue to use when weight and size are not an issue.

The EF 400/5.6L has always been a good lens and will be stabilised on the R6, but my understanding is that the max frame rate is reduced. In the UK, a good used 400/5.6 L and a new RF 100-400 are about the same price.

maarensv wrote:

I don't use either, but expect the RF 100-400 to be more versatile and deliver better IQ than the 70-200 f/4 plus 2x converter, so I would take the RF over the TC combi. Best possible IQ is the 70-200 plus the 400mm prime. The latter is a full stop faster and (by far) the sharpest option.

Edit : the RF has IS, which helps a lot a lower f-ratios.

Sandor.

I don't think it's a foregone conclusion that the 70-200 plus TC is worse. Looking at The Digital Picture's crops, the V2 f/4.0 with the TC is very comparable, if not better. Feel free to check for yourself, Crops.

But here is a low-res snippet:

RF 100-400 on top and 70-200 II f4.0 + 2x on the bottom.

That said, I'd by the native lens over a new TC for the EF body as I too would assume everything else would be better without going through the TC.

drsnoopy wrote:

I can confirm that the EF70-200 f4 L IS (mark i) with the TC 1.4x (mark iii) works just fine on the R5. However it is rather slower to autofocus than many EF lenses, and slightly worse with the TC. I sold that lens and bought an RF100-400 which is the same physical size as the EF 70-200 (actually smaller when you consider you need the adapter too) and in my view a better package - maybe a little better IQ, but twice the reach, and much faster AF. If you can afford it, the RF100-400 is a good option. It isn’t weather-sealed.

I still have my EF 100-400 L mkii and the 1.4 TC, which I will continue to use when weight and size are not an issue.

The EF 400/5.6L has always been a good lens and will be stabilised on the R6, but my understanding is that the max frame rate is reduced. In the UK, a good used 400/5.6 L and a new RF 100-400 are about the same price.

I'd use the RF-400/8 over the EF400/5.6 (I own both). The RF has better contrast (especially if you stop down to f/9), and I like the subjective look of the images better. AF will be faster and more precise with the RF, so you will probably get better IQ on the R body. And IS will be way better.

Bigger wrote:

drsnoopy wrote:

I can confirm that the EF70-200 f4 L IS (mark i) with the TC 1.4x (mark iii) works just fine on the R5. However it is rather slower to autofocus than many EF lenses, and slightly worse with the TC. I sold that lens and bought an RF100-400 which is the same physical size as the EF 70-200 (actually smaller when you consider you need the adapter too) and in my view a better package - maybe a little better IQ, but twice the reach, and much faster AF. If you can afford it, the RF100-400 is a good option. It isn’t weather-sealed.

I still have my EF 100-400 L mkii and the 1.4 TC, which I will continue to use when weight and size are not an issue.

The EF 400/5.6L has always been a good lens and will be stabilised on the R6, but my understanding is that the max frame rate is reduced. In the UK, a good used 400/5.6 L and a new RF 100-400 are about the same price.

I'd use the RF-400/8 over the EF400/5.6 (I own both). The RF has better contrast (especially if you stop down to f/9), and I like the subjective look of the images better. AF will be faster and more precise with the RF, so you will probably get better IQ on the R body. And IS will be way better.

Odd, all the crops I've seen of the two suggest the L is significantly better (contrast and sharpness wide open and stopped down). Maybe you have a bad copy of the 5.6 L. However, I understand why some prefer the 400 f/8.0 because it seems to work a little better AF wise. That would be a tough call, but I think I'm still on "Team 400L 5.6" in that head-to-head.

A friend let me borrow his 400 5.6, and I was very close to buying my own copy after. I loved the sharpness that lens gave, especially a third stop down at 6.3. I decided to wait for a new optic (likely at a significant price bump) but have still found myself considering that 20+ year old lens here and there.

Tazz93 wrote:

Bigger wrote:

drsnoopy wrote:

I can confirm that the EF70-200 f4 L IS (mark i) with the TC 1.4x (mark iii) works just fine on the R5. However it is rather slower to autofocus than many EF lenses, and slightly worse with the TC. I sold that lens and bought an RF100-400 which is the same physical size as the EF 70-200 (actually smaller when you consider you need the adapter too) and in my view a better package - maybe a little better IQ, but twice the reach, and much faster AF. If you can afford it, the RF100-400 is a good option. It isn’t weather-sealed.

I still have my EF 100-400 L mkii and the 1.4 TC, which I will continue to use when weight and size are not an issue.

The EF 400/5.6L has always been a good lens and will be stabilised on the R6, but my understanding is that the max frame rate is reduced. In the UK, a good used 400/5.6 L and a new RF 100-400 are about the same price.

I'd use the RF-400/8 over the EF400/5.6 (I own both). The RF has better contrast (especially if you stop down to f/9), and I like the subjective look of the images better. AF will be faster and more precise with the RF, so you will probably get better IQ on the R body. And IS will be way better.

Odd, all the crops I've seen of the two suggest the L is significantly better (contrast and sharpness wide open and stopped down). Maybe you have a bad copy of the 5.6 L. However, I understand why some prefer the 400 f/8.0 because it seems to work a little better AF wise. That would be a tough call, but I think I'm still on "Team 400L 5.6" in that head-to-head.

A friend let me borrow his 400 5.6, and I was very close to buying my own copy after. I loved the sharpness that lens gave, especially a third stop down at 6.3. I decided to wait for a new optic (likely at a significant price bump) but have still found myself considering that 20+ year old lens here and there.

Maybe my RF copy is good and my EF copy is poor, but I just got the EF back from Canon again yesterday and they claim it is working up to factory specs. I've had it for 10 years, and it's gone up to more than a few crazy high places with me. But even if the IQ is theoretically better on the EF, you will still get more keepers with the RF.

Bigger wrote:

Tazz93 wrote:

Bigger wrote:

drsnoopy wrote:

I can confirm that the EF70-200 f4 L IS (mark i) with the TC 1.4x (mark iii) works just fine on the R5. However it is rather slower to autofocus than many EF lenses, and slightly worse with the TC. I sold that lens and bought an RF100-400 which is the same physical size as the EF 70-200 (actually smaller when you consider you need the adapter too) and in my view a better package - maybe a little better IQ, but twice the reach, and much faster AF. If you can afford it, the RF100-400 is a good option. It isn’t weather-sealed.

I still have my EF 100-400 L mkii and the 1.4 TC, which I will continue to use when weight and size are not an issue.

The EF 400/5.6L has always been a good lens and will be stabilised on the R6, but my understanding is that the max frame rate is reduced. In the UK, a good used 400/5.6 L and a new RF 100-400 are about the same price.

I'd use the RF-400/8 over the EF400/5.6 (I own both). The RF has better contrast (especially if you stop down to f/9), and I like the subjective look of the images better. AF will be faster and more precise with the RF, so you will probably get better IQ on the R body. And IS will be way better.

Odd, all the crops I've seen of the two suggest the L is significantly better (contrast and sharpness wide open and stopped down). Maybe you have a bad copy of the 5.6 L. However, I understand why some prefer the 400 f/8.0 because it seems to work a little better AF wise. That would be a tough call, but I think I'm still on "Team 400L 5.6" in that head-to-head.

A friend let me borrow his 400 5.6, and I was very close to buying my own copy after. I loved the sharpness that lens gave, especially a third stop down at 6.3. I decided to wait for a new optic (likely at a significant price bump) but have still found myself considering that 20+ year old lens here and there.

Maybe my RF copy is good and my EF copy is poor, but I just got the EF back from Canon again yesterday and they claim it is working up to factory specs. I've had it for 10 years, and it's gone up to more than a few crazy high places with me. But even if the IQ is theoretically better on the EF, you will still get more keepers with the RF.

That last statement is why I think it would be a tough call. I thought the 400L 5.6 was one of the lenses that was only "fine" on the R5. Not sure why I felt like it wasn't great, because it focused fine, but for some reason it didn't wow me like others. However, IQ-wise it looked great and was unbelievably sharp for the price and weight. I think the f/5.6 speed and sharpness would win me over though, but it would be a tough call.

drsnoopy wrote:

I can confirm that the EF70-200 f4 L IS (mark i) with the TC 1.4x (mark iii) works just fine on the R5. However it is rather slower to autofocus than many EF lenses, and slightly worse with the TC. I sold that lens and bought an RF100-400 which is the same physical size as the EF 70-200 (actually smaller when you consider you need the adapter too) and in my view a better package - maybe a little better IQ, but twice the reach, and much faster AF. If you can afford it, the RF100-400 is a good option. It isn’t weather-sealed.

I still have my EF 100-400 L mkii and the 1.4 TC, which I will continue to use when weight and size are not an issue.

The EF 400/5.6L has always been a good lens and will be stabilised on the R6, but my understanding is that the max frame rate is reduced. In the UK, a good used 400/5.6 L and a new RF 100-400 are about the same price.

TBH I am more than willing to sacrifice some framerate and AF precision in exchange for sharpness and image quality, I am just a little unsure as to how they compare in that respect technical superiority of the RF aside

I have all of these:  R6, 100-400 EF MII L, 70-200 2.8 EF MII L and the 2x TC MII.    I rarely use the TC on the 70-200 because I have the 100-400 but it does work just fine.

I recall that when I went to Cape Town I only brought 70-200 and the 2x TC because this gave me 2.8 speed with the 70-200 and 400mm with the TC.  This took up less space than dragging along the redundant 100-400.

I'll try to catch my resident woodpecker tomorrow with the 100-400 and the 70-200 + 2x TC and provide samples if it works out.

My fine feathered friend finally decided to show up this afternoon.  It was quite overcast.

I set the camera (R6) and then swapped the lenses.  They are both at f 5.6 but for some reason the auto ISO used 8000 for the EF 70-200 f2.8 MII L + 2x TC MIII but used 6400 for the EF 100-400 f 4.5-5.6 MII.    Hand held.  1/2500th.   Both at 400mm

That is the only difference.

These were edited with DXO Photolab.  The settings for the first were applied to the second.  I did use the DXO Deep Prime Denoise.  Heavily cropped!!!

I won't tell you which is which.  I think it is obvious which was shot the 100-400 and which used the 2x TC on the 70-200.  I hope this will not dissuade anyone from using the 2x TC.  In good light it still performs pretty well.  The 100-400 is just a monster lens.

Tazz93 wrote:

Bigger wrote:

Tazz93 wrote:

Bigger wrote:

drsnoopy wrote:

I can confirm that the EF70-200 f4 L IS (mark i) with the TC 1.4x (mark iii) works just fine on the R5. However it is rather slower to autofocus than many EF lenses, and slightly worse with the TC. I sold that lens and bought an RF100-400 which is the same physical size as the EF 70-200 (actually smaller when you consider you need the adapter too) and in my view a better package - maybe a little better IQ, but twice the reach, and much faster AF. If you can afford it, the RF100-400 is a good option. It isn’t weather-sealed.

I still have my EF 100-400 L mkii and the 1.4 TC, which I will continue to use when weight and size are not an issue.

The EF 400/5.6L has always been a good lens and will be stabilised on the R6, but my understanding is that the max frame rate is reduced. In the UK, a good used 400/5.6 L and a new RF 100-400 are about the same price.

I'd use the RF-400/8 over the EF400/5.6 (I own both). The RF has better contrast (especially if you stop down to f/9), and I like the subjective look of the images better. AF will be faster and more precise with the RF, so you will probably get better IQ on the R body. And IS will be way better.

Odd, all the crops I've seen of the two suggest the L is significantly better (contrast and sharpness wide open and stopped down). Maybe you have a bad copy of the 5.6 L. However, I understand why some prefer the 400 f/8.0 because it seems to work a little better AF wise. That would be a tough call, but I think I'm still on "Team 400L 5.6" in that head-to-head.

A friend let me borrow his 400 5.6, and I was very close to buying my own copy after. I loved the sharpness that lens gave, especially a third stop down at 6.3. I decided to wait for a new optic (likely at a significant price bump) but have still found myself considering that 20+ year old lens here and there.

Maybe my RF copy is good and my EF copy is poor, but I just got the EF back from Canon again yesterday and they claim it is working up to factory specs. I've had it for 10 years, and it's gone up to more than a few crazy high places with me. But even if the IQ is theoretically better on the EF, you will still get more keepers with the RF.

That last statement is why I think it would be a tough call. I thought the 400L 5.6 was one of the lenses that was only "fine" on the R5. Not sure why I felt like it wasn't great, because it focused fine, but for some reason it didn't wow me like others. However, IQ-wise it looked great and was unbelievably sharp for the price and weight. I think the f/5.6 speed and sharpness would win me over though, but it would be a tough call.

Since I got the EF400/5.6 back from Canon, I decided to test it against the RF-400/8 again. While there is a measurable difference in center sharpness, it's hardly noticeable (<10% lp/mm). As you move away from the center, the RF sharpness falls off, while the EF actually improves, so by the time you get to the corner, there is a considerable difference.

If you can center the subject and crop the corners , e.g., a perched bird, I think the smaller, lighter RF lens would give you more shooting opportunities, with more good images from each. If you can center the subject, but want to blur the corners, then the EF will give you an extra stop of blur natively, but you might be able to offset this in post with negative clarity. If you are shooting BIF, where you are lucky to get both wingtips in the frame, much less center the eye, then the EF would have an advantage at fixed range, e.g., a bird leaving the nest; but if the bird flys towards you, then the RF zoom will get you images you would miss with the prime. So, yes, a tough call.

Tazz93 wrote:

maarensv wrote:

I don't use either, but expect the RF 100-400 to be more versatile and deliver better IQ than the 70-200 f/4 plus 2x converter, so I would take the RF over the TC combi. Best possible IQ is the 70-200 plus the 400mm prime. The latter is a full stop faster and (by far) the sharpest option.

Edit : the RF has IS, which helps a lot a lower f-ratios.

Sandor.

I don't think it's a foregone conclusion that the 70-200 plus TC is worse. Looking at The Digital Picture's crops, the V2 f/4.0 with the TC is very comparable, if not better. Feel free to check for yourself, Crops.

But here is a low-res snippet:

RF 100-400 on top and 70-200 II f4.0 + 2x on the bottom.

That said, I'd by the native lens over a new TC for the EF body as I too would assume everything else would be better without going through the TC.

I compared the original 70-200 f/4 , which is the one the OP has in the gear list. That still is a fine lens, but less so when used with a 2x TC. The version II does a lot better and is no compare.