Originally posted by K2 to K50 If this is such a large crop, you must have been working at quite a distance, esp if you were using the TC on the 450mm. In which case, there is little benefit (at such distances) of shutting down to F11 for depth of Field. In such circumstances I think an aperture of around 6.3 or 7.1 (or, with the TC, leave it at the minimum F8) would give you more leeway re ISO.
From the image size (the owl only) at about 4 mm on sensor, and focal length, the math suggests this was 100 meters away although it doesn’t seem like that when I am shooting
As I said this is work in process, where I am playing with the lens, and body combination, with the K1 I was shooting wide open. But even wide open this would leave me at ISO 5000. It was an extremely overcast and rainy/misty day, but I agree with you that wide open would be better.
Having said that the shot is not too bad and shows what the sensor can do