Histogram strangeness

[stolzy]

I'm trying to shoot with ISO at native level and do the necessary amplification in post.
However, in many shooting situations this makes the viewfinder image too dark to compose.  To counter this I set 'Preview Exp' to off.  Now I can see the scene fine, but the histogram doesn't respond to changes in exposure.  It responds to changes in the scene, but not to changes in exposure.

Anyone have a clue?

 

[Doug Pardee]

Fuji derives the live-histogram from the viewfinder data. By turning off Preview Exp. in M Mode, the viewfinder and the histogram no longer reflect the (predicted) captured image. This isn't a problem with the usual usage of that option, which is flash photography, because the live-histogram isn't particularly useful in flash photography anyway.

There's little advantage in using too low an ISO. All that you gain is some highlight headroom, and you can achieve that with DR200 or DR400 without messing up your workflow so much. Doing amplification in post will increase posterization of gradients. And if you're shooting at ISO 200 when you should've been at 800 or above, you're going to have higher noise due to the dual conversion gain (quantum-to-analog) structure of the X-T2 sensor.

For best results, shoot at the highest ISO setting that gives you adequate highlight headroom (for a given shutter speed/aperture setting).

[stolzy]

Thanks for the reply.  On reflection it was a daft question since using the native ISO in low light conditions makes the histogram something of an irrelevance.

I like the idea of just using the native ISO and gaining all the available highlight headroom because you can't get back a blown highlight.  The camera DR is not relevant since I'm only shooting in RAW.  My own investigations suggest that amplifying in post is indistinguishable from increasing ISO in terms of noise and shadow gradation.  Which is only to be expected since the sensitivity of the sensor isn't changed by increasing the ISO just the in-camera amplification.

I like the highlight headroom and I like being able to choose a shutter seed free from the requirement to get the exposure 'correct' in the camera.

Cheers