Photo Tutorial: Control Your Camera’s ISO For Maximum Quality and Minimum Size

You know what? We’re going to start off this little discussion with an analogy to try and make things a little easier. I want you to think of your camera as if it was a third eye – because at the end of the day, that’s really all it is. Just a little man-made mechanical facsimile…

Unless you are endowed with some super-human abilities, your eye needs light to see things. And your eye has a lens (that clear part on the front) through which the light passes and is absorbed by a little area on the back of your eyeball that senses the different colors of light. Well, guess what? That is exactly how a camera works! Light comes in through the glass and is sensed by the “sensor” inside the camera.

Now, if you bought a cheap little pocket camera your third eye has a relatively small, dirty lens (cheap glass), and a tiny little sensor. If you bought a big camera, you’ve got a high quality, extremely clear lens and a large sensor. But either way, the more light you allow to enter the sensor, the sharper your photos are going to turn out and the smaller the file sizes will actually be!

Let me be a little more precise. There is actually a range of perfectly acceptable light that a camera needs in order to see a scene properly. But since our technology is so crappy compared to the human eye, cameras often need a lot more light than you think they do.

How the Camera Controls Light

When you put your camera in “automatic” mode (and the cheapest little cameras ONLY have automatic mode), it is going to choose more light over more quality every time. And it does it in essentially three ways:

1. How long the shutter remains open.
2. Which ISO, or film camera equivalent speed of film, it chooses to take the photo. (The lower the number, the better.)
3. The aperture setting of the shutter. (We’ll deal with this at the very end.)

Now, for excellent photo clarity in an ideal world you would like to be taking photos at ISO 100 and with a shutter speed of around 1/60th of a second or faster. The problem is, at these settings most cameras practically require outside daylight. So, when you are indoors or somewhere that is a bit darker, the camera turns the ISO setting up in order to try and let in more light.

Unfortunately on most cameras anything over ISO 400 becomes so grainy that you just don’t even want the photos that are coming out of the camera.

So, if you get a good camera, like the Canon G11 I recommended, you can manually tell it to take the photo at ISO400 or less. Fantastic, right!?! Well, there is a catch. Let’s say you manually set the ISO to 100 – the problem now is that your shutter has to stay open much longer! And in some instances it might get so slow that simply hand holding a shot will make it too blurry to use!

Doah!

So, this is where a camera’s flash can help out – although they often make a photo look washed out and crappy – just in a different way. Again, a camera like the G11 helps out here because it can accommodate an external professional grade flash (or several) which can even be remotely triggered or moved off the camera body with an Off-Camera Flash Sync Cord (or remote triggers) to make the lighting more natural.

Sample Photos

Before we go on, let’s take a look at the difference these settings can make (be sure to click the images to see the large versions)! The following images were taken hand-held with the Canon G11 with no flash, in AE (aperture priority) mode at F/2.8 with the ISO set manually and taken back-to-back with different settings.

This first image of me was taken at ISO 3200 and with a shutter speed of 1/1,250th of a second. Note that the size of the large version of this image is 260kb. But the next one is only 160kb! That is because all of the additional noise in this image looks like detail to the JPG compression and therefore cannot be compressed as much! So not only is the image crappier… it’s larger!

This next image was taken at ISO 100 with a shutter speed of 1/50th of a second. Notice the amazing difference in quality? (I know I’m still ugly. Pay no attention to that.)

Ok, so you can’t concentrate with my ugly mug staring at you? Fine. Here is the lovely Jennifer Conley taken at ISO 3200 and shutter speed of 1/500th of a second. Click to see how grainy the large version is. It’s basically unusable.

And now with an ISO 100 with a shutter speed of 1/15th of a second. Note that the G11 has built in optical image stabilization which is why I was able to hold it still enough for it to look reasonably sharp even at a pretty slow shutter speed. Anything below 1/15th would begin to become blurry, which would ruin the photo just as much as the graininess.

The End

Now, there was one last little thing which I ignored previously, which was the Aperture setting. The aperture is the number written on your lens that looks something like f3.5-5.6, and refers to the size of the opening you set to let light in to the sensor. Sometimes it opens larger, sometimes smaller, and you can control this. This diagram illustrates the relative difference between aperture settings.

Notice that at F/5.6 the opening is about one quarter the size of F/2.8? Guess what. That means it lets in 1/4 the light in the same amount of time (say 1/60th of a second)! So to get the same amount of light with a smaller setting you will need a much longer exposure. At this point you might be saying, no problem! I’ll just always use the larger setting! Ahhhh, that would be nice… except for two things:

1. The lower aperture values also decrease depth of field (where everything behind the subject is out of focus) which is not always desirable.
2. Cheap camera lenses often can’t go below about F/3.5-5.6! (The G11 goes down to F/2.8.)

So yes, you can get a better camera and capture better images almost all the time, but at some point you’ve bought the best camera available you still can’t get certain images. You just have to accept that each tool has it’s limitations and learn how to work best within them. For most cameras that means keeping it in the ISO range of 100-400 and keeping the shutter speed faster than 1/30th of a second to eliminate blur no matter the aperture setting you are using.

The Very End

So, that’s about all I have to say on this matter. Hopefully you better understand the difference that your shutter speed and ISO make in the quality of your photos. If you pay attention to these things it can make a huge difference. And if your camera is too crappy to let you compensate… well, at least now you know why and you can get one of the ones I recommended.

Images other than the ones of Jennifer and myself are courtesy of Sausyn, Harshad Sharma and Bart.