Exposure compensation or ISO sensitivity? [duplicate]

Question

If ambient light isn't enough and I don't have a tripod with me for long exposure, which one should I prefer to increase the brightness of my photo?

I know high ISO comes with noise. Is there any side effect of high exposure compensation?

What I do is open full aperture & increase exposure till 1/10s. If not enough, increase ISO till about 300. After that noise is noticeable so I resort to exposure compensation, all the way up to +5. Then back to ISO. Last option is flash, if possible. Is this the best practise? Should I increase Exposure compensation before increasing ISO?

Answer 1

You misunderstand how exposure compensation works.

Exposure compensation is not an actual physical thing the camera uses to control light - there are only 3 real things that control the amount of light: Aperture, Shutter speed and ISO.

Exposure compensation is a way to tell the camera in one of the auto/semi-auto modes you want to override the light meter reading.

In A/Av mode the exposure compensation changes the shutter speed (and maybe ISO, depending on how you set things) in S/Tv mode it changes aperture (and again, maybe ISO) in P mode it can change any of the 3.

If you are in full manual mode exposure compensation does nothing because it has no auto setting to adjust.

So, to answer your question, if you are already shooting wide open and at the slowest acceptable shutter speed all you can do is increase ISO or add flash, the exposure compensation feature has nothing to adjust to help you here.

BTW, don't be afraid of ISO, the modern camera can handle ISO values much higher than reading photography sites will lead you to believe and even when you push it too far there are excellent noise reduction tools out there.

Answer 2

Exposure compensation is just another means of changing either shutter or aperture. I is not some fourth component of exposure, there are still only three: ISO, Shutter Speed, Aperture. If you have manually selected an aperture, changing EC will reduce shutter speed. If you have manually selected a shutter speed, changing EV will increase the size of the aperture, unless it's already at max.

ISO 300 is NOTHING. Cameras these days can easily be used at ISO 1600 or even 3200 without serious problems with noise. I think your being much too critical of noise, and I think your severely hurting yourself by forcing the use of ultra wide apertures or ultra slow shutter speeds, both of which can affect IQ in ways that cannot really be fixed in post. Noise is predictable, and therefor easy to reduce and clean up in post. A thin depth of field, however, cannot be fixed in post...if you end up with too much of your scene out of focus because you used the maximum aperture, your simply stuck with too much of your scene out of focus. If you end up with motion blur or camera shake blur, then your image is simply blurry.

When it comes to deciding which tradeoff to make, you should generally make the tradeoff of more noise first, then move to a wider aperture or a slower shutter speed as a last resort. I would also make sure you fully understand what exposure compensation is and what it's doing. EC isn't some fourth option for changing exposure...it is simply an alternative means of changing shutter speed or aperture. If you select maximum aperture and an ISO setting, then using EC to increase exposure means your exposure time (shutter speed) is getting longer. That means you run an increased risk of blurring the scene because of shaky hands or subject motion.

Noise, as much as it is demonized these days by photographers, is one of the more manageable artifacts in digital images. Don't fear it...at least, not as much as you do. ISO 300 is VERY, VERY LOW. You should be pushing ISO 800 or 1600 before you really start worrying about noise. With a good camera (modern APS-C DSLR at least), you should be able to use ISO 1600 without fear, and FF DSLRs like the 6D can be used at ISO 6400 or higher. For compacts, many use very advanced processing for JPEGS, making ISO 1600, 3200, and sometimes even higher very viable options.