Just how out of focus does every background need to be?
We photographed this image of Selena at Willy Nelson's small Texas town (he's moved a bunch of cool, old, Texas buildings to a ranch somewhere outside of Austin (NDA signed....). It's a popular location for period movies about Texas. Selena had a band called, "Rosie and the Ramblers" and she needed some publicity shots. And there we were.
At the time I was playing around with some Canon 1D mk3 cameras and a complement of Canon glass and I could have easily used a wide open aperture to make all the details in the background nothing more than a blurry wash of colors. It would have been in keeping with the prevailing compulsion among photographers to make everything into a bokeh experiment. But, practical person that I am I assumed that we get permission and travel out to a cool, private ranch just to blur the background into anonymity so I stopped the lens down a bit until I got a balance between emphasis on Selena's face and some descriptive texture in the background.
There's also a bit of flash being used to make the photo but I tried to make that as invisible as possible.
Could I have done the same shot with a m4:3 sensor camera? You bet. Could I have done it with a full frame camera? Yes, of course. The idea though is that neither format would have been demonstrably "better." Each would have resolved the detail we needed for every application we intended for the files. Each could be color corrected into the right box. We just had to decide what was important in the overall look and select the controls that would make the image happen the way we wanted it to.
It was a windy day and that was something we could not control. Saved us from having to rent a wind machine to blow Selena's hair around...