Don’t Need No DSLR: Fixing Blurry Photos with Photographer Math

“My camera is too slow.  All the photos I take indoors without a flash or outside when it’s not really bright out are blurry.  Should I get a DSLR?”


Do your low light photos come out looking like the photo on the left instead of the photo on the right? (both taken by me, under very similar lighting conditions, with similar cameras) If so, continue reading.


There are ways that you can probably solve this without buying a new camera (at least, not an expensive one), if this is your main concern.  It all hinges on your understanding of the relationship between three things:  aperture, shutter speed, and ISO.  I call it “photographer math”.  Let me explain that using an old engineer’s saying:

“You can get it fast, good, or cheap.  Pick two.

If you want it fast and good, it won’t be cheap.

If you want it cheap and good, it won’t be fast.

If you want it cheap and fast, it won’t be good.”


The same applies, in a way, to low light photography, only the three factors are “noise” “sharpness” and “depth of field” (DOF).  In low light conditions, especially extreme low light situations, you can only pick two, and each is tied to the three things I mentioned earlier (aperture, shutter speed, ISO).  Here’s my quick and dirty explanation:

ISO is the digital term for what used to be “film speed”, and determines how quickly your camera can “develop” the image it’s exposed to.  What ISO determines is how “light sensitive” the sensor is.  The more light sensitive (higher number), the faster the shutter can take a photo and still have the shot be bright.  However, the higher the ISO, the more “noise” (those grainy little dots) you get in your photos.

Shutter speed is how long the shutter on your camera is actually open and allowing light to create a photo on the sensor.  If it sounds like “CLICK” it’s probably set pretty fast.  If it sounds like “ka-click” or especially “ka———-click”, it’s probably set slow.  The faster your shutter speed is set, the less blur you will get in your photos.  However, the faster you set your shutter, the less light you’re allowing in, resulting in a darker image.

Aperture (also known as the F-stop) is the size of the hole that the light goes through in your lens on its way to the sensor, and it determines a few things.  For one, aperture determines the depth of field in a photo; if you want most of the frame to be in focus, you need a higher aperture (higher number, smaller hole), if you want a shallow depth of field, you need a lower one (lower number, bigger hole).  The way aperture comes into play in low light photography has to do with the fact that the lower (number) the aperture, the more light will flow through your lens.  The lower the aperture, the less time it takes to “develop” the image in the camera, resulting in a brighter image.  However, the lower you set the aperture, the less depth of field you have.

Remember that saying from earlier?  Well, the photography equation goes like this:

If you want it to be noiseless (low ISO) and sharp (fast shutter speed), it won’t have much depth of field (low aperture).

If you want it to be sharp (fast shutter speed) and have a large DOF (high aperture), it will be noisy (high ISO).

If you want it to have a large DOF (high aperture) and be noiseless (low ISO), it will be blurry (slow shutter speed).


If you’re really concerned about light, then you need to choose which of the three factors (noise, sharpness, DOF) is most important to you, and raise the other two using a similar equation.  If you need a large DOF, then set the ISO pretty high and the shutter as low as you’re comfortable so you can have maximum control of the aperture.  If you need a noiseless image, set the aperture as low as it will go and the shutter as low as you’re comfortable with, so that you can get the ISO as low as possible.  If you need a sharp image, set the ISO pretty high and the aperture very low, so that you can make use of a higher shutter speed.  If the main issue you’ve been having is blur, you want to set your shutter speed to relatively fast (say, 1/60th), your aperture as low as it will go, and your ISO fairly high (at least 1600).

As an example of what I mentioned above, take a look at this image.  In order to have a sharp, un-blurry image, I chose to use a high ISO and low aperture setting so that I could maintain a fast shutter speed:

Exposure: 0.003 sec (1/400)
Aperture: f/1.8
ISO: 1600

Now, in a pinch you may need to max out all three of these, but for most situations that casual photographers (or even serious amateurs) will encounter, boosting one or two of the factors will suffice.  Barring that, tripods are extremely useful if you’re going to be doing a lot of low light work.

Now: get out your manual, figure out where your camera’s settings for shutter speed/ISO/aperture are, and go take some low light photos!  If you’re feeling particularly ambitious, post a link to your photo in the comments here!