Tips For You #1 - ISO Basics

I have decided to start doing posts with different photography related tips for my fans.  I realize that everyone is at different levels when it comes to photography, but I plan on doing posts on a wide range of topics.

If you have a specific question, feel free to send me an email and I'll see what I can do to help you out!

One of my fans asked about how I decide on what settings to use.  Before I can answer that question, I think it'd be best to teach you about the different things that will affect the exposure/look of the image.  Today I am going to focus on ISO.

What is ISO?
ISO (International Standards Organizations)  is essentially how sensitive your sensor (or back in the day film) is to light.  The lower the number the less sensitive it is to light and conversely the higher the number the more sensitive it is to light.  

How does ISO affect my image?
ISO obviously affects the exposure of your image, but also the quality.  The higher your ISO, the more noisy/grainy your image will become.  In addition, as the grain increases, the detail/sharpness of your image will decrease.
I took pictures of these flowers using a wide range of ISOs (I also had to changed the shutter speed so I would have the same exposure throughout all of the images).  When you compare ISO 200 to ISO 6400 you can see an obvious difference in quality.  The noise/grain (the colored dots on the image) is VERY noticeable at 6400 ISO.  You are also able to see noise in the 800 ISO and 1600 ISO examples.  Each camera is different when it comes to its noise tolerance.  More expensive cameras allow you to shoot at a higher ISO before noise starts to become noticeable than the less expensive ones.

To figure out your noise tolerance, set up a picture like I did above and increase the ISO for each shot.  Compare the different images and see at what point the noise/grain starts become a distraction.

How do I know what my ISO should be?
I made a couple of charts to help you know what ISO you should be using in specific lighting situations.  Hopefully they will help you out a bit.

Now could you shoot at a higher ISO in the bright sunlight and get a good image?  Absolutely!  However why shoot at 800 ISO when you could shoot at 100 ISO and have less noise and more detail?  Now, there could be situations in which you might want to use a higher ISO on a bright day, but that's a lesson for another day.  The charts above are just a general rule of thumb.

I hope this tutorial helped you to better understand ISO.  If you have any questions let me know!