Anybody here using base-ISO exclusively or predominantly?

Started Feb 13, 2014 | Discussions thread
OP nixda Veteran Member • Posts: 5,374
Re: Anybody here using base-ISO exclusively or predominantly?

Jeff Charles wrote:

nixda wrote:

I am asking, because ETTR is a popular approach, but it's useful at base-ISO only.

The idea behind ETTR is to put as much light on the sensor as possible, short of blowing essential highlights. The technique uses the histogram as a gauge: When it is pinned to the right side, we've achieved "maximum" ETTR.

It's said that ETTR is "useful at base-ISO only", because, although increasing ISO will move the histogram to the right, it does not increase the actual exposure of the sensor. Only changes to aperture and shutter speed can increase actual exposure.

In real life, "maximum" ETTR is rarely possible, because the shutter speeds and apertures we choose are constrained by our need to control motion blur and to get sufficient DOF. However, maximizing the amount of light reaching the sensor should still be the goal. That can be achieved by using the widest aperture and the slowest shutter speed that the situation permits.

Your general approach described below is a good one. I use it too. But not for ETTR at non-base ISO. In fact, your recommendation that "maximizing the amount of light reaching the sensor should still be the goal", is not good when dealing with higher-than-base ISO. The use of ETTR at higher ISOs is precisely what gave ETTR a bad reputation. There are very good reasons why it's really useful only at base-ISO. At higher ISOs, one should try to match the scene brightness but not expose higher by opening up the lens or choosing slower shutter speeds. When over-exposing a high-ISO scenario and adjusting the brightness down afterwards, the danger is that the tone curve gets irreparably distorted.

So, in my OP I am asking about any experiences with going at it from the opposite: what about exposing for correct shutter speed and aperture but actually under-exposing in terms of ISO (staying at base-ISO), then adjusting image brightness afterwards. But it seems as if no one here has looked into that with the X-Trans cameras.

In fact, auto ISO can serve as a useful aid in achieving this objective, because it indicates the actual exposure that will result at the shutter speed and aperture we've set. For example, if we set shutter speed to 1/250 and aperture to f/5.6, and auto ISO goes to ISO 6400, it means that the sensor will receive very little exposure at those settings. We can then consider if 1/125 and f/4 would be "good enough." If we decide that they are, that gets us ISO 1600, and much better IQ.

 nixda's gear list:nixda's gear list
Fujifilm X-E1 Fujifilm XF 14mm F2.8 R Fujifilm XF 18-55mm F2.8-4 R LM OIS Fujifilm XF 55-200mm F3.5-4.8 R LM OIS Fujifilm XF 27mm F2.8 +1 more
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