DX mode on the Z9

[bleirer]

Thanks. Very interesting link which definitely suggests that you get just under 1 stop less dynamic range in relation to the ISO value in DX mode. I wonder if it is as simple as that or if the reduced sensor area has an impact on the dynamic range measurement. If this dynamic range reduction is for real it would be good to know why it happens.

As I understand it you could say it is the crop factor squared times the original iso value. So for DX vs FX 1.5 squared is 2.25. So ISO 2000 in FX would have similar noise to iso 4500. Dynamic range is primarily lost due to noise in the shadows. So as you say a little more than one stop. This is just due to the area of the sensor, not pixel size or density.

 

[dupcak]

So this is a real question and not any sort of attack. Is the above really true? Other than a quick/silly test of 400/2.8 S + internal 1.4X TC + external 2X TC + DX crop I haven't really done any DX shooting with the Z9 so I honestly don't know. Given that the subject will occupy the same amount of pixels and same number of focus sensors, does the subject detection really improve? I understand that the subject detection by the computer 6" behind the viewfinder will improve, I just am curious if the subject detection by the computer inside the camera improves.

- Rob

As I understand it's not only about how many focus points are on the target. It has to do with how many focus points the AF processor has to analyze in order to determine what the target is. In DX mode less than half of the sensor is active so far less data for the processor to analyze. So it improves AF speed more than accuracy. Particularly with subject/eye detection. Presumably if using a small AF area then DX mode has little/no benefit. On the other hand if using auto area it should be a big difference.

So this is a really old thread (at least in the timeline of internet forums) but I figured I would follow up on my own question and the response of @NorthernFocus

Today I was on a lunch break and had a bunch of birds feeding on berries in my back yard. Z9 + 400/2.8 TC @ 560mm - it would not detect the birds in a very busy background of leaves in FX mode (using Wide Area L). Since I was being lazy and didn't want to get up out of my chair I switched into DX mode and using all the exact same settings (except DX mode), the camera immediately detected the bird.

In DX mode the bird took up just about 1/3 the height of the frame in landscape orientation - so I'm not terribly surprised it wasn't detected in FX mode. However I now have the answer to my own question - DX mode really does help with subject detection. Glad I tried it out.

 

[Anjin San]

Today I was on a lunch break and had a bunch of birds feeding on berries in my back yard. Z9 + 400/2.8 TC @ 560mm - it would not detect the birds in a very busy background of leaves in FX mode (using Wide Area L). Since I was being lazy and didn't want to get up out of my chair I switched into DX mode and using all the exact same settings (except DX mode), the camera immediately detected the bird.

And that is excellent info to have…have to try it myself. Intuitively it doesn’t seem…to me anyway…that going to DX would do anything other than change the viewfinder presentation because the pixels and AF zones are the same…I have to try this and see.

 

[dupcak]

And that is excellent info to have…have to try it myself. Intuitively it doesn’t seem…to me anyway…that going to DX would do anything other than change the viewfinder presentation because the pixels and AF zones are the same…I have to try this and see.

Yup - that was exactly what I thought... until about 2 hours ago