1DX III vs R5 AF

[Fast Glass]

This really could also be titled phase detect AF vs dual pixel AF.

So one of the things that surprised the socks off of me was that normal AF was far superior to dual pixel in even moderate low light, normal indoor lighting at night. And in dark situations it wasn't even funny the difference.

In good lighting dual pixel AF was pretty good. But I found traditional AF still more accurate and consistent especially with razor thin DOF of the105mm f/1.4 and the 50mm f/1.2.

So my question is the R5 AF better compared to the 1DX III's dual pixel AF? Because from what everyone was saying the 1DX III dual pixel AF reached mirrorless level and was able to be used in both capacities. And I have yet to hear a bad thing about mirrorless AF.

Now the eye detect was amazing to use, but not accurate enough for me to trust it for an important shoot. At least not without lots of chimping. Granted I am using very thin DOF/challenging lenses and I do realize that it's not the same as focusing for a landscape, but found that there was a big difference in accuracy between the two AF systems.

Has anyone else experienced this? Because if this is the AF experience of mirrorless I can't say it is mature enough to replace DSLR's just yet. At least not for me personally.

[Kayaker72]

The R5/R6 have DPAF II while I am pretty sure it is DPAF Mk I on the 1DX III. The difference is not something I have done a deep, or even shallow, dive into, but yes, there may be (likely is) a technical difference.

Nuances in the actual performance between PDAF and DPAF II is something I would be interested in but have not seen a good evaluation. What I would suspect is that you would see different strengths and weaknesses. Personally, without having tested it myself, in conventional modes (single point AF/expanded point AF) I would probably rank the R5 about the same maybe a bit better than my 5DIV in good light. I agree that I have noticed a fall off with the R5 in moderate to low light. Not bad, but I think there may be something there similar to what you have observed. Whether the PDAF falls off as much or at the same levels of brightness, I am not sure, but it is well established PDAF also falls off with decreasing light (Popular photo used to run a great test on new camera bodies showing this). But, then with my personal experience, I know the 5DIV falls off in dark settings and the R5 has been doing pretty well there. So, it might take some series testing to really figure out which is better when and were. As for shallow DOF, I have not had much of an issue when trying to use my f/1.4 lenses, but those situations are much more limited as I've primarily been using my R5 for birds. In fact, I have yet to try human Eye-AF (pandemic times). But animal eye AF has worked well on birds, dogs, cats, and a fox so far.

Let me know if there is some sort of test you'd be interested in. I do not have the 1DXIII (it was a loaner), but I could try the 5DIV vs the R5.

Also, let's not lose track of the fact that the PDAF system in the 1DXIII is amazing. I still get excited thinking of how quickly it came into focus.

[Joel Eade]

This really could also be titled phase detect AF vs dual pixel AF.

So one of the things that surprised the socks off of me was that normal AF was far superior to dual pixel in even moderate low light, normal indoor lighting at night. And in dark situations it wasn't even funny the difference.

In good lighting dual pixel AF was pretty good. But I found traditional AF still more accurate and consistent especially with razor thin DOF of the105mm f/1.4 and the 50mm f/1.2.

So my question is the R5 AF better compared to the 1DX III's dual pixel AF? Because from what everyone was saying the 1DX III dual pixel AF reached mirrorless level and was able to be used in both capacities. And I have yet to hear a bad thing about mirrorless AF.

Now the eye detect was amazing to use, but not accurate enough for me to trust it for an important shoot. At least not without lots of chimping. Granted I am using very thin DOF/challenging lenses and I do realize that it's not the same as focusing for a landscape, but found that there was a big difference in accuracy between the two AF systems.

Has anyone else experienced this? Because if this is the AF experience of mirrorless I can't say it is mature enough to replace DSLR's just yet. At least not for me personally.

I guess I am a bit confused about this issue. Did you take photos with a 1DXIII and an R5 when you noticed this difference or was it some other camera compared to the R5 or 1DXIII?

I think dual pixel AF has been around at least 6 or 7 years and is used on many Canon models but I'm unsure which ones have it as opposed to the "traditional" phase detect AF.

My understanding is that cameras with "traditional phase detect AF" use separate (smaller) areas of the sensor for phase aligning focus and other areas for image capture such that all pixels are not involved in focusing. Dual pixel autofocus is sort of a variant of phase detect where each pixel has a dual diode with a micro lens and the camera can use the entire sensor to phase align the image within each dual diode pixel then combine them to capture the image.

As Brant described both the R5 and the 1DXIII utilize versions of dual pixel AF. I also do not know the nuances of those versions to say how their performance would compare in low light. One possible difference is pixel size where the 1DXIII pixels are bigger and I think it is well established that bigger pixels tend to perform better in low light in terms of signal to noise ratio. Not sure if this includes DPAF performance.

In my experience the R5 autofocus system has performed well in various lighting situations. I don't notice any particular difficulty with lens hunting. I have shot many indoor images with relatively low light but usually with a Canon 16-35mm f/2.8 or Canon 24-70mm f/2.8. I have a 35mm f/1.4 but have not yet used it with the R5. Also have had good success with eye detect on humans and animals but I have the SET button programmed to scroll through 3 or 4 different AF settings so I can immediately switch to a zone AF method or spot AF when needed.

I'm sure AF technology will keep moving forward but I can't say the R5 AF is a problem or inferior to DSLR systems .... I don't own a 1DXIII but I do own a 5D MKIV, 1DX and 5DS-R.

[Kayaker72]

Not trying to jump in for Fast Glass, but also to clarify if my assumption was incorrect. I took the question to be a comparison of the PDAF through the viewfinder and DPAF using liveview both on the 1DXIII.

Overall, my key takeaway would be in line with Joel's. I am not having any significant issue with the AF on the R5. The AF definitely performs best with targets within a certain range and with plenty of light, but that is something that is true with all AF systems.

One possible difference is pixel size where the 1DXIII pixels are bigger and I think it is well established that bigger pixels tend to perform better in low light in terms of signal to noise ratio. Not sure if this includes DPAF performance.

I have thought about posting on this topic to see what others think. But, I am not sure this is true anymore. I see it referenced all the time, so I may be incorrect. But, after microlenses were first introduced and optimized, and the architecture size of the sensor chips decreased, I think those steps have largely taken away the pixel size issues. Before light either fell into the pixel well or hit the physical pixel well wall, essentially being lost. For the same side wall thickness, the more pixels you have, the ratio of pixel well area to top of side wall area decreases, so more light is lost bouncing off the top of the sidewalls of the pixel wells. But, microlenses act as funnels directing more light into the pixel well. Then, Canon switched to a smaller architecture, that also decreased the thickness of their sidewalls.

I could easily be wrong. But, I have also played with real world ramifications. What I can say is that I do not see much of a correlation between DR performance and pixel density, but I see a very strong correlation between DR and sensor size.

Another way to look at this, but Quantum Efficiency (efficiency of a sensor at capturing light) of the 5DII was 35%, 5DIII was 47%, and 5DIV was 54%. Move to the most modern sensors, the R6/1DXIII are 55% and 53% respectively (all taken from Photons to Photos website, but based on S/N ratio from DXO Mark). For the record, Sony's A7R III is 59% efficient. So, bottom line is modern sensors are capturing 53-59% of the light, a dramatic improvement over 35% of the 5DII. What is fun, still some headroom to improve into.

But, playing with pixel density, the 5DIV and 80D (same generation of sensor) have the same 54% efficiency. Even go back before that, the 5DSR had 49% efficiency compared to the 47% of the 5DIII. So, almost the same efficiency (5DSR released a year or two later, so perhaps some slight improvements).

[Joel Eade]

Not trying to jump in for Fast Glass, but also to clarify if my assumption was incorrect. I took the question to be a comparison of the PDAF through the viewfinder and DPAF using liveview both on the 1DXIII.

Ah .... that makes more sense to me now. With mirror up in live view the 1DXIII is functioning like a mirrorless camera but instead of contrast detect focusing like many prior cameras used in live view it is using DPAF.

I also wonder if the more powerful battery in 1DXIII has any effect on how fast it can achieve focus in terms of physically driving the lens faster?

[Fast Glass]

Yes, my experience was with a rented 1DX III only and I didn't have the pleasure of comparing them side by side with the R5.

DPAF was fine with good lighting but it never did live up to the PDAF of 1DX III. But compared to my 1D III the 1DX III is on another level.

I couldn't actually get a low enough light level for the 1DX III to not focus. I was shooting in light so low I could barely see and it was focusing with the Sigma 105mm f/1.4 and take a ussuable pic. Well kind of, 800,000 was ridiculously noisy!!!!

VS no matter what I did DPAF just couldn't lock on at all.

This is an extreme example but it was a testament of how incredible the AF of the 1DX III is. It is truly next level.

[Kayaker72]

So, the PDAF is rated at -4 to 21 EV and the DPAF is rated at -6 to 18 EV based on Bryan's write up on the 1DX III.

So, theoretically, the DPAF should have out performed the PDAF on the 1DXIII. My thought would be to try another lens as 3rd party lenses do occasionally have impacts. For example, Canon lens on the R5, I can AF at pretty much the entire sensor. My Sigma lenses, just a subset in the center..

[Fast Glass]

Perhaps, but I tested this with the 50mm f/1.2 and the Canon 24-105mm f/4. In every lens the PDAF outperform the DPAF significantly in low light. In bright light it was fine, but even with indoor light the PDAF was clearly superior.

Not to say it was bad, but when your standard is the 1DX III that is a very high bar indeed to surpass. So I am not exactly disappointed but more so surprised that nobody mentioned it. On one discussion I posted this very same thing another person did actually know this and said it was because the AF sensors are much larger than the pixels used in DPAF.

But what intrigues me is a real world comparison between the R5 and the 1DX III.

[Kayaker72]

That is odd as I have usually found the exact opposite. For example, on the 5DIV, I often had to AF dark situations with DPAF as PDAF would not hit. I did not try that when I had the 1DX III. For a direct comparison, we would need someone that has both.

What I can say about the R5 is that I have not noticed an issue in low light. This includes shooting a couple of sunsets and sunrises as well as my usual sitting on the couch firing off a few shots around the living room that is only illuminated by the TV as I get to know the camera. It's AF rating is for -6 EV to +20 EV. Is there a specific scenario you are concerned about? If I can, I'll give it a try.

But, as a quick example, I was very surprised that the R5's AF picked up and AF'd Saturn and Jupiter for this shot.

Small-9040 by kayaker72, on Flickr

This is an insane crop, as I was only at 1000 mm. But I am not sure how much better I need than being able to AF on two little dots of light in an otherwise dark sky (there were little blue boxes around each). BTW, it was very winding with some high clouds. I think that caused some distortion.

[Joel Eade]

Interesting from a technical point of view but I've never been a "live view" shooter so no impact on my personal style.

The 1DXIII, when using the optical viewfinder, does use a separate focusing sensor with it's own dedicated Digic 8 processor .... wonder if that is a factor as well?