What is ISO? (Part 2)

In the last post I spent a bit of time discussing noise associated with higher ISOs.  Noise for most "normal" ISO values, between 100 and 3200, on most new digital cameras is essentially a non-issue.   Some might balk at that statement, but hopefully as we progress with this Blog, you'll understand why to ME it is a non-issue.  

The first thing I am considering is that most of us are non-professional photographers.   That being said, I would assume that most of our photographs won't be printed.  And, if we do print them, chances are we won't print above 13x19.   I know some of you will go out and get poster size prints from time to time, and that's great.   In fact, we should set a goal to capture that image that deserves to be printed on a poster.    In any case, the reason I am talking about viewing our photos on computers or iPads or smart phones, or even making relatively small prints, is due to the fact that when viewed on these smaller form factors, the noise is even less visible.  

The takeaway here is I want you to use your camera's high-ISO capability to its fullest.   That being said, I do want you to know a common 'rule' with respect to ISO.   It is:  Shoot at the lowest ISO possible.      That probably feels very contradictory.   Don't worry, this will make sense as we move along with this Blog.

I want to start with some scenarios that should be relatively common across most of us.  I am only going to discuss ISO values  (we'll bring in aperture and shutter speed values later):


The first scenario is a very bright day (in this example there is also snow on the ground to further light our image.)   In this case you can use a very low ISO value like 100 or 200.

In this next scenario, we are taking things in the opposite direction.  This time you're in an auditorium with only stage lighting.  Dim stage lighting at best.   In this case you will need to push your camera much further and use a very high setting like 6400 or even 12,800 if you have it.

This next scene is still indoors, but this time you have some focused, but dim lighting coming from a birthday candle.   Since the lighting is so dim you'll need to use a high ISO to capture it, in this case 3200 ISO did the trick.

In this final scenario, we are finding something in the middle.   Our subject is indoors, but is sitting next to a large window with decent light coming in.   For this shot, an ISO of 800 was used.

As you can see, ISO plays a key role in your photography.   For bright scenes you will be able to use very low ISO values, but as the amount of available light decreases, you'll need to increase your ISO to make sure your sensor is capture enough of the light.   Please note, I did not use a flash in any of these photos.   

In the next post, I'll start to bring the triangle together and see how all three components are used in relation to each other.