I seem to have stumbled into a tarpit, said the mastodon.
Apparently the Great Fujifilm X-Series Exposure Compensation (EC) Dial Controversy has spilled into TOP, and lots of people have opinions about what knob or dial should do what. And I spoke too fast.
It's really a question of what should do what. All I can do is explain what I would expect:
I conceive of EC controls as being primarily for the purpose of correcting metering where metered values might be wrong (i.e, when you know from experience the meter is being "fooled"); so EC is really most convenient to use with autoexposure modes only.
In manual mode, the shutter speed and the aperture are measured values and should not shift from the values you set. So in Manual mode with Auto ISO, I would expect the EC dial to affect the ISO.
Which it doesn't.
Why? Well, here's one possible explanation. I've just spent a bit of time fiddling with the camera. In practice, with the X-T1 set to Manual exposure and Auto ISO, the camera doesn't seem to adjust very well. I would need to use it more to be sure, but my guess is that letting the camera adjust precise exposure via Auto ISO isn't very practical with this camera. It's not a method of shooting I've ever used, so I don't really know much about shooting this way. My guess is that this is why EC is disabled in Manual mode/Auto ISO—because Fuji knows it doesn't work all that well and they'd prefer you not use the camera that way.
So I guess I'd take back what I said previously. EC is there primarily for use in correcting incorrect meter readings in Aperture-priority autoexposure or Shutter-priority autoexposure, and really shouldn't be used in Manual exposure mode—regardless of the ISO setting.
Does that make sense?—Or is it just useless to struggle when you're in a tarpit?
(Thanks to Mike Steinbach)
Tech. Ed. Ctein adds: "As to how exposure compensation works, it's actually pretty simple if you step back a level. It changes the exposure the camera makes according to the exposure mode you have the camera operating in. For example, if you're in aperture priority mode, dialing in exposure compensation changes the shutter speed (the same way a changing light level would). If you're in shutter priority mode, it changes the aperture. If you're in program mode, it may change one, the other, or both—it'll depend upon the algorithm the camera uses for trading off aperture against shutter speed.
Me, personally, I use it all the time. I just about never do manual metering. My preferred mode is aperture priority (keeping a watchful eye to make sure the shutter speed is within a tolerable range). I have a very good internal sense of how the meter in the camera will respond to different subject/lighting conditions. When I see one that I think is likely to introduce an exposure error, I'll dial in some exposure compensation before I even make an exposure. I'm pretty good at guessing it right. And, of course, with instant previews and histograms and shadow/highlight callouts, it's really easy to see if I did guess right. Considerably more than half the time, my first guess at the exposure compensation will be satisfactory. In the cases where it's not, a second exposure will be right on.
For me, this is both faster and more intuitive than messing around with manual readings and adjustments. In fact, my camera almost never comes off of aperture priority, with me manually tweaking the exposure with exposure compensation.
Of course everyone's mileage will differ. This is just mine.
Now, it makes sense that exposure compensation wouldn't work when you're in manual mode, because how is the poor camera supposed to know what to do? Should it adjust the aperture? Should it adjust the shutter speed? Should it split the difference? It's going to guess wrong more than half the time. Which sorta flies in the face of manual control.
Of course, it feels weird to have a "mechanical" dial that doesn't work, sometimes, but what you going to do?
I don't have any idea how "Auto ISO" actually works, because I never use that mode, but I'll bet you it creates a similar conundrum—that exposure compensation would result in the camera doing nonintuitive things.
Mike replies: Like you, I habitually use Aperture-priority and Exposure Compensation. However, when you say, "I have a very good internal sense of how the meter in the camera will respond to different subject/lighting conditions," that's a very important point, and it's crucial for using EC.
EC compensates for scenes where the meter makes errors. Therefore it's necessary to have a good sense of where the meter will make errors for you to be able to apply the correction.
It's something I wrote about years ago with the Nikon FA and N8008, the first cameras with evaluative metering (Nikon called it "Matrix Metering" at the time, although I don't know if they still do). The point then was that it was harder to know what the meter was doing and therefore more difficult to apply EC effectively. In the early days of evaluative metering I tended to ignore it and continue to use averaging metering because it was easier to correct. Later, when evaluative metering got so much better, I gradually switched to trusting it—and used EC less often.
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Featured Comments from:
Dave Parry: "Surely in Manual mode the EC dial should just effect the meter reading? Hence why on many manual cameras the EC dial is built into the ISO dial."
Mike replies: Took me a little while, but I've come around to agreeing with this. EC is primarily a metering adjustment. So, in an ideal camera, with all three values (ISO, aperture, shutter) set on hard values (i.e., nothing on automatic), the EC should still be applied to the meter readout, yes.