Explaining ISO: The Who, What and How - Ld
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Explaining ISO: The Who, What and How

Happy Monday! I hope you had a great weekend. Last week I promised you that I would push pause on all the photograph-based posts and get back to posting some more photography tip and tutorial posts. I’m happy to say that I have delivered (although I have some pictures of large and small yellow lady-slippers I’m dying to show you - but that can wait for another time). Today’s topic ties in with learning different settings and modes on your camera, and also is an important term to know about in order to go out and take the best picture you possible can. Today, I will be referring back to one specific post from the past: shutter speed. It may be helpful for you to review it if needed. Go ahead. I’ll be waiting, right here.

All caught up? Ok. Good!

I’m going to let you know that this post may run a little longer than some of my other ones, but I want to make sure I am able to explain this topic enough so that it makes sense. If that means this post is a little long, I’m ok with that. I hope you are too.

I’m going to be 100% honest with you here, and I debated whether or not I should tell you this. That being said, I think it’s important that I’m up front with you. So here it goes. I have been dreading talking about this topic. Dreading. It. So. Bad. Why, you ask? Well, first I think I should tell you what it is.

Today’s topic is: ISO.

What the heck is ISO?

The term ISO has to do with how sensitive your camera image sensor is, or if you’re old school, your camera film is, to available light. Got that? Huh? Yeah, I know.

ISO for some reason always used to confuse me. Always. I’m better at it now, but knowing what it is and being able to describe it are two different things. Although, I know ‘they’ say that in order to truly understand something you should be able to teach it, right? Yeah. I guess so. But anyway, that is the reason for me dreading posting about the topic. However, I knew this post was inevitable, because there is such as thing as a ‘photography exposure triangle’.

As you can see, one of the corners of the exposure triangle is ISO. Therefore, in order to properly control the lighting of your photograph, ISO is a key component.

Aperture is another corner of the triangle. We briefly talked about aperture (measured in f-stops) during the depth of field post, as aperture does have to do with depth of field. For a quick overview, aperture has to do with the amount of light let in via a hole in your camera lens. If you Google aperture , you can find a whole lot of info. I will do a post more in depth about it at a later date.

So, what does ISO do?

ISO, along with help from the camera’s image sensor, captures light and constructs it into an image. But wait, you ask, isn’t that what shutter speed and aperture do? Kind of. I think of it as ISO helps to ‘boost’ shutter speeds and aperture (f/stops) so that they can go farther (don’t worry, I have an example below), which can allow you to shoot in low lighting conditions without a flash and to help caption motion (reduce blur).

Wow! That’s great, you say, this means I can shoot in low lighting! Well, yes, you can, but there is one catch. The higher your ISO, the greater chance for grain and ‘noise’ to show up in your pictures.

ISO Settings

ISO settings can range from 100 (low ISO) to something crazy like 64,000 (high ISO) in today’s newest and biggest cameras. My camera goes up to an ISO setting of 1600. ISO settings usually go up by 2’s (ex. 100, 200, 400, 800, and so on). Each time you go up in number, that means that the ISO is TWICE as sensitive to light as the number below it.

In nature photography, low ISO settings are used for bright, sunny days where you have ample light. As you find yourself in conditions with diminishing light availability, your ISO setting should get higher and higher.

High light = low ISO settings

Low light = High ISO settings

Most of the time, I’m shooting with 100-400 ISO. Anything above that is used for very low lighting situations. Sometimes I can even get away with using 400 in low lighting situations. It’s important that you choose the lowest ISO setting you can for the lighting conditions you’re in. Practice and patience helps here.

Ok. Ready to move on? I know that was a lot of information up there...

Now that we’ve gone over the ISO settings themselves, let’s go through a couple examples. 


Take a beautiful, bright sunny day. I’m shooting this lovely salmon gerbera after a summer rain.

For this picture, there is ample lighting conditions for my camera to take this picture without any help needed to increase my shutter speed or aperture. I’m not worried about motion, because it’s solitary, and there isn’t wind. Because of this, I shoot it at an ISO of 100.

Let’s take a look at another scenario.

I took this picture at sunset. The light was getting really low, and although the flower was fairly stationary, any movement with this low light condition can cause some blur. However, because it wasn’t completely dark; the sun will still providing some light, and because of the minimal movement, I shot this at an ISO of 400. A tripod would have been really handy with this picture, but I was flying by the seat of my pants that night and didn’t have one with me.

Are you still with me? I feel your eyes glazing over. I'm almost done, I promise. 

Now that we’ve gone over what ISO is and what it does, I want to talk about what can happen if you choose the wrong ISO type for your lighting situation.

What Happens if I Choose the Wrong ISO Setting?

Have you ever looked at a photograph and noticed it looked really grainy? Chances are, the ISO was not on the right setting. Don’t feel bad if you’ve done this, I’m pretty sure I’m the master at it. As I’ve mentioned before, I have this issue where I get so excited at whatever it is I’m photographing that I sometimes forget to change my white balance and my ISO. I’m working on it, OK? Anyway...

Let me show you some examples. I took the pictures below JUST for this post, so you can get an idea of what I’m talking about. If you decided to skip reviewing the suggested (shutter speed) post earlier, now may be a good time to do so if you need too. I’ll wait, again.

The pictures below were taken of my beloved banana plant, on a rainy and cloudy day.

The first picture is at an ISO of 200, shutter speed at 1/40, and my f-stop (aperture) at 5.6.

The second picture is at an ISO of 400, shutter speed 1/125 and my f-stop (aperture) at 5.6. As I bumped up my ISO, it allowed my camera to meter at a faster shutter speed in order to reduce blur.

The third picture is at an ISO of 1600, shutter speed at 1/400, and my f-stop (aperture) at 5.6. Dang! Bumping my ISO up to 1600 allowed my shutter speed to go up to 1/400! That’s great! Less blur! More light! Yeah! Yeah! Yeah!

Uhhh...well this is awkward. Notice anything about the picture above? Does it look a little...um...grainy?


That is what happens when you have an ISO that’s too high for the lighting situation you’re photographing in. The ISO tries so hard (bless it’s heart) to showcase those details for you by brightening it up (having a heightened sensitivity to light) that it goes all out and makes it grainy. I’m kidding of course, but you get the idea. Having a correct ISO setting is very important to get a properly exposed picture without grainy-ness. Compare the three pictures together and you can see the difference. Even in the second picture, around the edges, you can start to see some grain.

And let me tell you, it’s VERY heartbreaking to get home, load your pictures onto the computer, and realize they’re all grainy. Learn from my mistakes. And that is a mistake that you can’t really fix, even with a photo editing software. You can try to combat it a little, but it’s still noticeable.

That being said, I don’t want you to be afraid of using ISO. As I mentioned above, it can really help in low light situations and be a great tool to help stop motion.

Finally, I want to talk about how you know what setting to use when photographing.

What ISO Setting Should I Use and When?

Yes, cameras do have auto ISO, but that is if you’re shooting in Auto mode, or a pre-set camera mode (such as the night time ones, or the low light ones, etc.). I challenge you to step out of that comfort zone and apply what you have learned here. Almost all cameras have ISO settings. Even my cell phone camera does! And, if you’re in doubt (I’m going to say that you should have an general idea of which setting to use), and you are able, try taking a couple pictures on each setting. That way, you’ll have your bases covered.

To help determine what my ISO setting should be before I take a picture, I ask myself one question: “Is the Sun Out (get it? I.S.O. (and I didn’t come up with that, I’ve seen it a number of different places)). If the answer is yes, I stay with a ISO setting of 100 or 200. Is the answer, kind of? Or maybe it’s cloudy? I would stay with a 200 or a 400 ISO. Is it sunrise or sunset? I usually stay around 400. Pictures taken in low light conditions inside or at dusk would benefit from an ISO of 600. Night time pictures would benefit from anything above 600.

Now, I bet you’re wondering how on earth you're going to remember all this?

Well, I have a handy little treat for you. I have created this infographic below for you to print and carry around in your camera bag.

There is one slight problem. My blog is created using my photography website. Photography websites tend to not like people being able to save a picture or copy a picture off the website. Makes sense, right? Well it’s a problem because that means you’re not going to be able to save this picture to your desktop via my website.

If you would like the ISO cheat sheet, please contact me using the contact button on the left hand side of the screen. 

This week’s takeaway:

-ISO has to do with how sensitive your camera image sensor or camera film is

-ISO, along with help from the camera’s image sensor, captures light and constructs it into an image

-High light = low ISO settings

Low light = High ISO settings

-Use the lowest ISO setting you can for the lighting conditions you're photographing in to avoid a grainy picture

-Use the handy, dandy infographic to help remind you which setting to use

Make sure you never miss a post! Sign up for my weekly newsletter by clicking here. Psst...newsletter readers also get special discounts, offers, sneak peeks at new photos and more! And I hate spam as much as you do, and will never send you anything other than Ld Nature Photography related items.

What helps you remember ISO settings? Any tricks to help you remember to adjust the settings? I’d love to hear about it!

Happy Photographing!

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