“ Or does the R7 with the mount adapter just not work properly with the Tamron lens? According to Tamron, the R7 is supported with this lens. ”
The problem is most likely the lens, not camera or the adapter. First and foremost, the lens was designed for use on DSLRs, not MILC bodies. Most third party lenses designed for DSLRs are not fully compatible with the advanced AF and subject tracking features found in the advanced Canon R Series camera bodies.
Disable all settings that enable eye or subject tracking. You want to see AF points that look like grid of small AF points or boxes. I use these setting in my R6 Mark II with the Sigma 150-600.
I recommend disabling the “Continuous AF” feature described above. It creates an increased drain on the battery. This feature is most useful during action photography scenarios, when the camera is almost constantly pointed toward your subjects.
The names of some terms does change from the EOS R7 (and EOS R10), this screen is from an EOS R7.
Subject tracking is the description used by EOS R7 in place of Whole area tracking servo AF found in the EOS R6 Mark II.
In theory, a lens that worked on an older Rebel camera will work on the mount adapter on the EOS R7 and support the new tracking capabilities. However, it may be that the new functionalities require the Tamron lens to perform beyond its original design limitations. Tamron introduced the 18-400mm lens in 2017, some five years before the EOS R7, and at least 1 year before the first EOS R camera. Canon also has some older model EF lenses that are not able to work at the speed of the R-series cameras.
If you rented or borrowed a Canon RF lens and the camera delivers its expected performance then it would be clear that the limitation is the lens. If you send the camera and adapter to Canon to check they will only check it with Canon lenses. Canon offers no assured compatibility with third party lenses on mirrorless cameras.
My original suggestion was to disable Preview AF how did you get on when you did this?
Hi and welcome to the forum:
First and foremost, putting a legacy 3rd party lens is not supported by Canon. I personally have not seen a statement by Tamron that their lenses work with the new R-series bodies, and to pursue that the correct course is to contact them.
Sigma made a statement and video that their lenses do work with the R-series bodies, but they demonstrated this only with the the FF R6 body that has a much more sophisticated focusing and tracking system then the R7.
Quite a few people have had challenges with focus using the R7, particularly with 3rd-party lenses. Duade Paton, an Australian photographer, spent a lot of energy on this. While I don't agree with some of his testing methods, the telling part occurred when he sent his copy of the R7 for testing with Canon, along with sample images of his issue.
After some time and references to Japan, their response was that the camera was working as designed. To quote from the response he read out from Canon:
We believe the autofocus issues you have presented are a limitation of the R7 capabilities.
The R3, R5, [R6] and R6MkII have autofocus speeds that are superior to the EOS R7.
AF accuracy may become unstable due to low contrast.
There is a possibility that improvements can be achieved by changing these settings:
Use H (High-speed continuous shooting) instead of H+ (High-speed continuous shooting+)
Lower continuous shooting gives more time to achieve focus thus better 'hit success rate".
Higher continuous shooting will give lower the "hit success rate"
So, what is the context to all this? Here is my personal analysis:
While the R7 claims to have a shutter rate of 30 FPS in full electronic mode, this demands a high performance in terms of image recording, throughput and storage. Any flaw in the data bus will cause a bottleneck and negatively impact performance. I believe that in the R7 this occurs because, to me, the data bus is seriously unbalanced.
What I mean by that is that the shutter can go at 30 FPS in full electronic mode, but because the sensor is not BSI/Stacked, which would interface directly with memory and processor, it's ability to execute the recording of the image introduces significant rolling shutter effect, where a bird's wings in flight will look curved rather than natural because, as the sensor scans down or across to record, the speed is not sufficient to freeze the movement of the wings' displacement over that time. This is also seen when tracking birds in flight, where trees, poles and buildings will look tilted or round objects will look elliptical. Now, this is obviously not an issue if the birds are relatively static, but then one would ask why it is necessary to shoot at 30fps for a bird that's not moving.
Paton showed the following graph to demonstrate the relative focus speed of the R7 vs. other popular models and that it is fairly pedestrian.
The second implication of this is that the buffer is insufficient in capacity and speed for the readout of all that data coming from the sensor. This means that at 30 FPS, shooting in RAW, the buffer will fill up in about 1.2 seconds, and then you can't take any photos. This is also due, in part, to the relatively slow cards - I would have preferred to see at least one CF-Express card to allow for the fast recording speed. It's a classic bottleneck situation.
The 32MP sensor of the R7's APS-C sensor has a pixel density equivalent to about 82MP on a FF sensor - which, as I write, no maker has attempted to achieve. As such, not only does the data output cause write issues as outlined above, but it starts to exhibit noise from about 3200 ISO, becoming noticeable at about 6400.
Furthermore, given that the R7 has a less sophisticated version of the tracking system, because the sensor is so critical in the focusing and tracking processes, the autofocus is challenged and that may be a part of the reason that people have had issues with focusing and tracking. The camera uses the sensor photosites to achieve focus, and with the density in the R7's sensor it means that on continuous focus a lot of focus points are being engaged at a given time. It is not unreasonable that any tiny alteration in some of those focus points at high frame rates will cause a refresh issue or pulsing focus.
I will say that the system is much more sophisticated than those of DSLRs and thus requires more study to configure and use. To be fair, I think that quite a bit of the negative feedback is from those who have not set up their systems to make the best of the technology for their specific needs and the camera's limitations.
The R7 is not weather sealed like the 7D series bodies, nor does it have a OEM battery grip - something that I really prefer with long telephotos, for the extra energy capacity, but more for the balance and the duplicate controls for shooting in portrait mode when using big leavy lenses. Again, those are my preferences and may not be relevant for you.
Now, I am perfectly aware you are shooting with the Tamron, but the lens you are using is even more ambitious in its focusing needs compared to the focal range than the Sigma 150-600 that initiated this issue.
To watch the complete video by Paton see:
