R6 Mark II / Tamron 150 - 600 darkness issue

[Fandango739]

I recently upgraded my older R6 to the Mark II and thus far it has been a love / hate relationship. I was advised that my Tamron lens would do just fine, with an adaptor. I have been using a Ykeasu adaptor thus far. When there is plenty of light, the results have been wonderful. When there is even the slightest amount of shade or overcast, the image immediately becomes ridiculously dark.

Given that I am still a bit of a noob and very often trying track fast moving, tiny, erratic birds, I continue to use the TV setting. In order to compensate for the drop in exposure, I am forced into absolute blursville. Given that sometimes I’m trying to photograph a bird that I may never have the chance to document again, my situation is not good.

Is this a product of the different camera?
The camera plus the lens?
Or perhaps that particular adapter?

Any insight would be appreciated!

 

[KJ_North]

Shooting in TV mode your camera will be adjusting the aperture to the correct setting. BUT what is your ISO set at? Is it set at a value like 200 instead of "AUTO". If so you are likely running out of a significant enough adjustment aperture wise for the shot to work and you are then adjusting the shutter speed to compensate. If you need the speed and the aperture has maxed out as wide as possible (Lowest F number) then the ISO needs to be adjusted up higher to compensate.

 

[Fandango739]

KJ_North, I thank you for the suggestion. Unfortunately my experimentation in that area didn't really help. So, an update. While in TV, it automatically defaults to auto. With the darkness continuing, I thought I would fall back to P. Poor choice...the slightest amount of shade led to utter blur.

So back to TV, but the problem persists for the meantime.

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I may have actually just found the 'problem.' It may have to do with the spot metering setting.
I'm off to give it a test!