Exposure Compensation -- What's Really Happening

KED

Taking a chance on another possible opportunity to parade my ignorance: Many of our cameras allow us to manually adjust exposure compensation. In difficult lighting conditions (a gym being the best example) I shoot in manual at widest aperture (within reason for DOF requirements), maximum shutter speed to eliminate motion blur and, last stop, push ISO as high as necessary to get close to correct exposure. Is exposure compensation ineffective in Manual, or if not, what other magic is the camera working?

Even though everyone on this forum is terrific, I'm really wary about the "duh" risk, so apologies in advance if I'm asking about something that is common knowledge, much-posted-upon, or otherwise a waste of time. I'm an outdoor sports shooter mostly and only just finding a need to understand this.

Nikolai

Ked,
in manual there is no "compensation", you control everything. What you can do is simply overexpose or underexpose. Cameras will even show you what you're doing. There is no magic to it.

jfriend

KED wrote:

Taking a chance on another possible opportunity to parade my ignorance: Many of our cameras allow us to manually adjust exposure compensation. In difficult lighting conditions (a gym being the best example) I shoot in manual at widest aperture (within reason for DOF requirements), maximum shutter speed to eliminate motion blur and, last stop, push ISO as high as necessary to get close to correct exposure. Is exposure compensation ineffective in Manual, or if not, what other magic is the camera working?

Even though everyone on this forum is terrific, I'm really wary about the "duh" risk, so apologies in advance if I'm asking about something that is common knowledge, much-posted-upon, or otherwise a waste of time. I'm an outdoor sports shooter mostly and only just finding a need to understand this.

Same questions asked and answered here today.

The ONLY thing that exposure compensation should do when you are in manual mode is change how the metering readout in the viewfinder displays. You should be in total control of your shutter, aperture and ISO.

If you are manually matching your exposure to the metering readout in the viewfinder, then adjusting the EV will cause you to dial in a slightly different exposure.

What you are doing for exposure sounds like exactly what auto ISO is made for. On some of the later model Nikon cameras (I don't know about Canon models), you can set the camera to shutter priority, set your desired shutter speed and set the ISO to "auto". The camera will then do it's normal metering job. When the light is low, it will open the aperture all the way. If that's still not enough light, it will then raise the ISO just enough to get a proper exposure. You can set max ISO so it won't exceed a certain value if you want.

I find this useful in low light sports shooting sometimes where I want max aperture, 1/500th and as low an ISO as I can, but still get a good exposure.

Nikolai

jfriend wrote:

... On some of the later model Nikon cameras (I don't know about Canon models), ..

Canon 40D has it, I think 1DMkIII series too. It's a REALLY handy feature!

KED

Nikolai wrote:

Canon 40D has it, I think 1DMkIII series too. It's a REALLY handy feature!

John & Nik --

The MkIII has a custom function called "safety shift" that can be enabled in Av or Tv modes (or program, for that matter, but not manual), that will adjust ISO if it can't otherwise get a correct exposure by adjusting shutter speed (in Av) or aperture (in Tv). My understanding of Nikon's auto-ISO has been that it functions even if both aperture and shutter speed are set manually; if that understanding is correct, that would be a sweet feature to have, especially with ISO range up to 25K or whatever on the D3. But, I honor my commitments, especially my now rather deep economic commitment to Canon.

KED

jfriend wrote:

Same questions asked and answered here today.

Sorry for making you repeat yourself, John, I don't know how I missed that.

jfriend

KED wrote:

Sorry for making you repeat yourself, John, I don't know how I missed that.

No problem. I found it a funny coincidence that a question that I've never seen asked here before got asked twice within 24 hours. Anyway, it was easy to answer the 2nd time.

jfriend

KED wrote:

John & Nik --

The MkIII has a custom function called "safety shift" that can be enabled in Av or Tv modes (or program, for that matter, but not manual), that will adjust ISO if it can't otherwise get a correct exposure by adjusting shutter speed (in Av) or aperture (in Tv). My understanding of Nikon's auto-ISO has been that it functions even if both aperture and shutter speed are set manually; if that understanding is correct, that would be a sweet feature to have, especially with ISO range up to 25K or whatever on the D3. But, I honor my commitments, especially my now rather deep economic commitment to Canon.

On the latest Nikon cameras, you can use auto ISO in manual mode, program mode, shutter priority mode or aperture priority mode. It's pretty sweet as long as you know how it works and don't let it have control when you didn't realize it was going to raise the ISO on you. I now just think of it like a third factor that can be automatically used to control exposure along with shutter and aperture. Fix either one or two of the three factors and the camera will set the other(s) for a proper exposure.

When using flash, you then have a fourth factor (the power of the flash) and auto ISO + flash can get really confusing to understand (I don't use that combination yet).

KED

jfriend wrote:

On the latest Nikon cameras, you can use auto ISO in manual mode, program mode, shutter priority mode or aperture priority mode.

I have no bid anymore for the Nikon vs Canon debate, so I have no problem admitting that this is a feature that I admire and wish I had!

jfriend

KED wrote:

I have no bid anymore for the Nikon vs Canon debate, so I have no problem admitting that this is a feature that I admire and wish I had!

Yeah, I never get the religious wars on brand either.

Given that auto-ISO is quite useful, I'm sure Canon will do it soon. It's just firmware logic - doesn't even need anything that isn't already there in the hardware. Besides, the smaller guy has to occasionally have some advantages.

KED

jfriend wrote:

Given that auto-ISO is quite useful, I'm sure Canon will do it soon. It's just firmware logic - doesn't even need anything that isn't already there in the hardware.

If I'm Canon, I'm putting it into the MkIII N, not handing it out as a free firmware update . . . and unfortunately, if I'm Kent (and I am), I'm probably taking the bait!