Photography Basics ISO


So received your first Single-lens reflect camera or (SLR). Since it is 2020, it is likely a Digital variety (DSLR). Whether you purchased it yourself or received as a hand me down or a gift this is an exciting moment.  You take it outside or to a party and take that first picture and then you are disappointed.  “I thought these were supposed to be top tier cameras” you think.  They are, and just like everything in life it is knowing how to use it. There are the automatic modes, but if you really want to unlock the full power of your camera then you will want to use manual mode. Don’t worry phone users, this writing is for you too if your camera has a manual mode option. Lets dive into part one of my mini series: Photography basics ISO.

What is ISO?  Well the acronym is rather boring and refers to the name of the standards organization, The International Organization of Standards. As to its historical purpose it is the speed of the film. This effected the light sensitivity of the camera to the film. So in the world of DLSR’s it is the measure of the light sensitivity of the sensor. So when you change the ISO higher you are making it more sensitive to light.  A lower ISO is less sensitive. Many modern high end DSLR cameras with interchangeable lenses can reach ISO’s in near or beyond 100,000. The main problem with a higher ISO value is noise or grainy pictures. 

An example of grain and noise.

If you are wanting to take everyday photos you will likely use ISO 100.  It is the standard and default. This value collects the most detail information for editing (post processing).  It is because of this detail I suggest setting the camera to save in RAW.  Once you get the image to a the larger screen you will see all the flaws you are unable to see on the small camera. (Unless of course your camera is connected to a desktop or laptop for for previewing and shuttering.) Be aware when you venture into higher ISO’s. Older DSLR models (and crop sensors) often produce grainy or noisy pictures at the higher ISO values while newer models and full frame sensors are less likely to have noise in the pictures. My current Canon 40D is a rather old model now and it also is a crop sensor camera meaning it is highly susceptible to noisy pictures. I have to do a lot of post processing (editing) work to make a halfway decent picture.  Therefore I am also looking to purchase a newer full frame DSLR.

How do I select an ISO with low Noise?  Simple remember lower ISO is better.  A lot of the high ISO use is reserved for very dark settings such as taking astrophotography pictures as is my hobby. Generally you want to use a high ISO with a low f value ( for a different blog explanation) for a depth of field. A lot of this is easily found through trial an error or through math calculations. I plan to develop a spreadsheet for those who love the images but hate the math.

So when you pick up your camera or switch to manual mode on your cell phone, you now have a better idea what the ISO value is for, being how sensitive to light the image sensor is.

Canon 40D | ISO 800 | 18mm | f/3.5 | 20 sec | Maglite and paper