Why You Can't Use An Exact Shutter Speed of 1/346 sec :: Digital Photo Secrets

Why You Can't Use An Exact Shutter Speed of 1/346 sec

by David Peterson 3 comments

Have you ever wanted your pictures just a little bit brighter or darker than what your camera gives you? Sure, you can always go into Photoshop Elements and adjust it after the fact, but shouldn’t the camera allow you to do it as you’re taking the photo? Why can’t you just pick an exact shutter speed, aperture, or ISO speed and use that to control the brightness? Allow me to explain.

Simply put, cameras just don’t work that way. It’s impossible to pick a shutter speed like 1/346 of a second or an aperture of F7.38 because camera settings are separated into what are known as “stops.”

What is a stop? The best way to learn is to play with your camera’s settings. Adjust the shutter speed, aperture, or ISO speed up or down. Notice they only go up or down in certain increments. Each of those increments is a stop. You can’t pick a shutter speed, aperture, or ISO speed in between the stops.

Why the limitations?

Because it costs too much to design a camera that can take any old shutter speed or aperture setting. With aperture in particular, you would need the camera to make a lot of micro-adjustments to the size of the hole that the light goes through. To do so would require some very finely tuned equipment that is too expensive to put into a consumer grade camera.

I think people get a bit confused by camera settings. The controls are digital, after all. Because they’re digital, you expect to have almost full control over what the camera can do. Unfortunately, at the end of all those digital controls is something physical. Since cameras aren’t physically built to handle exact settings, the digital controls only allow you to select settings that the camera is physically capable of using to take a photo.

But it's not all doom in gloom. Being limited to 'stops' actually helps you.

Stops make your job as a photographer easier

You might not be able to control the aperture and shutter speed to a super fine degree of precision, but you do get the next best thing. Stops are designed to give you a convenient reference. Let’s have at look at how they work.

Each time you increase or decrease your shutter speed, aperture, or ISO speed settings you are actually increasing or decreasing the amount of light that gets into your camera by an exact multiple of 1/4, 1/2, or 1 (depending on the camera you’re using). Why is this handy? Because it allows you to coordinate aperture, shutter speed, and ISO speed settings to get exactly the picture you want.

Here’s an example. Let’s say you’re out taking pictures at your son’s running meet. The pictures you’re taking aren’t that bad. They aren’t too bright or too dark, but you’ve noticed one small problem. Your son is blurred on the frame.

If you’ve been reading my tips, you’ll remember that you have to use a faster shutter speed to stop motion blurring from happening, so you adjust your shutter speed up by two stops.

Now for the interesting part. Because each aperture, shutter speed, and ISO speed stop gives you the exact same increase or decrease in light entering the camera, you realize that you only need to decrease the aperture by exactly two stops to get an image with the same brightness as the one you took earlier.

The same goes with ISO speed. If you don’t want to adjust the aperture, you could increase the ISO speed by two stops to get a picture with the same light levels. Each ISO speed stop is equivalent to a shutter speed or aperture stop in terms of the amount of light entering the camera. They are interchangeable, which is why the system works so well.

Will they ever invent a camera that gives you full control of shutter speed, aperture, and ISO speed to such a fine degree? Probably not. Plus, even if they did, it would confuse most people. It’s much better to know how all three of these settings affect the exposure (or brightness) than to be able to set them exactly.

Got a question? Ask Dave. Just leave a comment below or send me an email directly.

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  1. MHG says:

    I recently noticed such shutter speeds on pictures taken by Samsung Galaxy S5 smartphone.

  2. Johann de Jager says:

    Good info for the novice, David.

    There are cameras, however, that allow you to set half or third stops, thus allowing you to select something between stops.

  3. Cami Cort says:

    Absolutely written subject matter, regards for information.

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