I just bought a Canon 50D on ebay with low shutter count. I like many things about it. I had a Canon A2 film autofocus body back in the 1990's so I leaned toward Canon. And am now learning the ins and outs of digital after years of point and shoots.
I like how when I am metering and I am in Tv or Av, the shutter, aperture and ISO numbers show on the bottom of the view screen. And I can turn the front/top camera dial and as the aperture or shutter changes the shutter or aperture changes to maintain the exposure. But, when the camera is metering, and I press the ISO button, the shutter and aperture metering numbers disappear. Then after I make changes to the ISO, when I press the ISO button again, the view screen goes dark as if the camera is off.
Ok. Ok. Ok. After I make changes to the ISO I can press the shutter button and re-initiate metering and the new shutter and aperture numbers show up. But, I don't like how when I change the ISO I can not see the new shutter or aperture numbers. When I change aperture or shutter I see the change to the shutter or aperture. When I change ISO. I am blind. I have to change the ISO, press the shutter to check the new metering, then maybe change the ISO again.
Maybe first I need to ask if I am missing something. Is there some setting where pressing the ISO button temporarily changes the front/top dial to ISO where I can change ISO while the shutter and aperture remain visible and change, and then it times out back to changing the shutter or aperture?
Otherwise, do higher end Canon cameras, or enthusiast level crop body cameras from other manufactures handle changing ISO more like how my camera changes shutter or aperture? If the exposure triangle is so important, how come there is not a a dial that clicks through shutter, aperture, ISO, exposure compensation, program shift, sharpness, saturation, contrast settings, while the other dial rolls through the values. And when in shutter or aperture or ISO settings you could set any of those to auto. So you would not have P Av Tv M settings, you would just put shutter and aperture in auto for P etc. Is there something about the electronics of the sensor that makes changing the ISO different than changing the shutter or aperture?
I like many things about this camera and am learning and practicing and am planning on eventually getting a 70 to 210 L lens. But as I uncover things that frustrate me, I would be willing to go to another system before I get pro level glass. I would love to have more direct control of ISO and would love to have manual mode - auto ISO - exposure compensation. How do I find out about what cameras have this ability in a world where most of the reviews talk about sensor size, low light performance, and frames per second? Is there a name for this, like full triangle control during metering?
Let me know.
Thank you.
Tim.

...Though I do miss Kodachrome's colors.
