Why do newer Canon cameras lose compatibility with existing 3rd party flashes?

[IndigoEye]

I'm aware that 3rd-party manufacturers reverse-engineer the communication protocol between cameras and flash units, but if a flash system had already been working fine with older Canon cameras, what reason is there for newer Canon cameras to no longer work with these speedlights?

For example, I managed to get my Cactus flash system to work with my EOS 600D and EOS M50, but communication somehow broke with the EOS R6II. TTL metering actually still works fine, but the flash becomes unresponsive after a few seconds of being idle as if the R6II can't wake up the flash system like the 600D and M50 used to do.

In another scenario, my recently bought Powershot V1 keeps on underexposing the TTL flash by 3 stops when using a Godox TT350 even though that issue doesn't happen on the R6II and M50.

Ever since Canon switched to the new multi-function shoe standard, I seem to be getting new issues instead of new features with my existing equipment. Just what are they changing in the flash communication protocol?

[rs-eos]

The onus is upon the 3rd party manufacturers. This is true for any piece of hardware from any company.

When going with 3rd party solutions, about the best you can do is choose a company that has a good track record with their compatibility with Canon.

[IndigoEye]

> The onus is upon the 3rd party manufacturers. 

The camera manufacturers are the ones holding the cards though by not releasing the details of the protocol and forcing 3rd party manufacturers to reverse engineer it.

I don't understand why they even bother at this point given that they're not offering their own studio light system to match the likes of Godox's AD series.

[p4pictures]

Surely this post should be titled Why do existing 3rd party flashes lose compatibility with newer Canon cameras? The compatibility that the 3rd parties claim is clearly not 100% compatible, even Canon Speedlite 550EX from 2000 works fine with EOS R6 Mark II, actually the camera flash metering has improved so flash exposures are more accurate than they used to be with EOS D30 from the same time.

[IndigoEye]

> Surely this post should be titled Why do existing 3rd party flashes lose compatibility with newer Canon cameras?

Nope, I wrote it as intended. It doesn't change the fact that their new products have increasingly limited compatibility compared to their previous ones. Given how the Powershot V1 is primarily a video-centric camera that doesn't even have the 5 pins for supporting legacy flash, I seriously doubt that any changes on that end are intended to make it perform better than the EOS R6 II for flash exposures.

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Note that I am only going through these flashes for workarounds on top of workarounds. The V1 only allows shutter speeds over 1/250s if it doesn't detect a Canon-compatible flash. Covering the 4 rear pins allows me to shoot with flash all the way up to 1/1250s.

The Godox TT350 allows triggering of manual (on-camera) fill flash in this scenario, but I lose reliable on-camera TTL when I use it normally under 1/250s.

The Godox X2T trigger allows me normal TTL with other flash units on top (Canon Speedlite 90EX, Viltrox JY610C), but it won't pop the on-camera fill flash when I try the hack for flash above 1/250s.

TL;DR

I wouldn't be jumping through these hoops if Canon didn't restrict the shutter speed to 1/250s upon detecting a Canon-compatible flash/trigger considering that the V1 is using a leaf shutter.

[IndigoEye · Accepted solution]

update:

Issue resolved by updating TT350C firmware to version 1.7. That said, this firmware update was released back in 2019, so the fact that the R6II worked fine with version 1.6 from 2018 suggests that some cameras (specif. those retaining the 5 pins for legacy support) simply have better backward compatibility.

Still kinda miffed though that I can't do the same for my Cactus flashes since the company shut down in 2020. What's even more annoying is that their TTL actually works fine with the newer cameras; it's just the wake-up signal that had changed.

[deebatman316 · Accepted solution]

Only Canon knows it’s E-TTL flash protocols. The thing is that Canon could use a part of code at any time and break compatibility with 3rd Party Speedlites. Even though they know there flash units support it but wasn’t used. That was already in use by Canon in certain flash units. One example would be Intermittent Flash Firing on the EOS R series. That command usually wasn’t sent on DSLRs to Speedlites. Only certain Speedlites utilized Intermittent Flash Firing by default. But now on Mirrorless it’s being used on every flash units. Also you were close with the release date of the 550EX it was actually released in 1998. I also did notice the flash metering performance is better on cameras that support E-TTL II. The EOS 10D would have some wild exposures at times. 

[deebatman316 · Accepted solution]

I would keep a good eye on your Godox flash. They’re known to lock up cameras in low light where the camera can’t lock focus. Godox hasn’t cracked the code on how Canon is utilizing Intermittent Flash Firing. Which leads to the camera locking up and displaying an Error 70 error code. This is a very well documented issue with Godox and they don’t have a fix. The issue became bad enough that Canon asked users not to use those particular flash units. Canon couldn’t replicate the problem with their gear. 

[normadel · Accepted solution]

The compatibility issue isn't just with aftermarket flashes and Canon cameras. Mixing old and new-system Canon OEM flash models and new and old Canon cameras is also problematic.

That's new and improved technology for ya'.