Equivalent exposures

Changing, say, the aperture on your camera changes things beyond the amount of light that gets into your camera. As such, you might decide that you want a smaller aperture, in order to get a greater depth of field. A smaller aperture means that less light comes in to the camera. How do we solve this?

Your camera has three different adjustments for exposure: Shutter speed, aperture, and ISO. If you adjust one so the exposure would be brighter, you can adjust another one to compensate for the additional light captured.

For example: Let’s start with an exposure taken at 1/100 second, f/4.0 and ISO 200. Now, you can change your camera settings to 1/200 second. That would let half the amount of light into your camera compared to 1/100 second, because the shutter is only open for half the duration. Your photo will now be darker. If you change your ISO to 400, the sensitivity of the sensor is doubled, and the photo will come out looking more or less the same, from a brightness point of view, as with your original exposure.

You can change any of the settings to compensate for any of the other settings: A smaller aperture can make up for a higher ISO, a faster shutter speed can make up for a larger aperture, and a lower ISO can make up for a slower shutter speed.

Other effects of exposure changes

Of course, ISO, Aperture and shutter speed don't just affect the brightness of the image... Here's a handy reminder for what else they affect:



Easy peasy!

Emergency tripod? Piece of string!


The main problem of taking photos free-hand is that your hands aren’t particularly sturdy. Myself, I find using a heavier camera makes it a lot easier (the inertia of the camera means it is reluctant to move, so up to a point, a heavy camera is easier to hold still for the duration of a photographic exposure than a very light camera), but what about lighter cameras?

The obvious answer is a tripod or a monopod, but these devices can be terribly heavy, and they are not particularly portable. One solution is to hold the camera against a surface (a tree, a building, or a signpost), but that doesn’t always work either, and none of these items offer an awful lot of flexibility.

How do you stabilise your camera most often?

  • Quadrapod
  • Tripod
  • Monopod
  • Mini Tripod or similar
  • Gorillapod or similar
  • String tripod ('chainpod')
  • A rock / table / whatever
  • Freehand with a fast lens
  • Freehand with an IS lens
  • Freehand
  • Stabilise my camera? But why?
  • I don't take photos

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I often find myself thinking 'Damn, if there was only a way to anchor the camera to the ground…', and I recently found a solution that works: A String Tripod (also known as a Chainpod)!

It is a laughably simple device: You get a wing nut bolt (or anything that screws in) that fits into the tripod hole of your camera (you are looking for a bolt with 3.5×8″ threads), and drill a small hole into the bolt. Then, you attach a length of string to it, with a loop at the end. If you use the shearing lines available for tents, you can vary the length of the loop, and, as such, the height of the camera.

To use one of these string tripods, put your foot (or feet) through the loop, and pull the string taut against your foot. Now, out of nowhere, your camera will be a lot more stable, as it has an axis against which it cannot move (up/down). This means that you can hold the camera a lot calmer – you would be surprised how much of a difference this can make!

But… But…

Sure, it will never replace a proper tripod or monopod, but I wouldn’t be surprised if you gain a couple of stops on your shutter time by using this system. And the best thing? Making one of these is going to cost you less than a bottle of milk and a loaf of bread!