ISO and Aperture

Everything you wanted to know but were always afraid to ask.

Ever look at the settings on your camera and really wanted to know what they mean but felt completely lost? I know I did. The one thing I really wanted to know when I was younger was how to change my shutter speed. Everything seemed so complicated though. Numbers everywhere and letters everywhere like 100, 400, and 1600. Then there were the f numbers, f2.8, f4.0, and f11 just to name a few. But what do they mean?

Well to be honest they really are not as hard to understand as they seem. There are many great books that you can find as well as online resources that will teach you what everything means and how they work together. That’s exactly what I did when I was starting out. I went to Barnes and Nobles (as a photographer you spend a lot of time there, well, there and Starbucks) and found some really great, easy to understand photography books.

The first book I recommend is the Digital Photography Digital Field Guide by Harold Davis. This is a great book. It lays out in newbie terms exactly what everything means and how you can interpret that information into your own equipment. It’s an invaluable tool for a beginner.

The Digital Field Guide publishers make several great books and they even make equipment specific books. I found one for my Canon 30D as well as my Speedlites. This made understanding my equipment much easier than trying to read the ominous owners manual. I highly recommend at least getting the Digital Photography Digital Field Guide by Harold Davis and I just checked on Amazon it runs about $15.59.

So onto our discussion. Let us start with ISO. ISO stands for International Standards Organization. I know right, you probably never would have guessed that. I know I wouldn’t have. I would have thought something like “Intermediary Solar Optics” or “Inner Spacial Output” something technical and specific. Not the name of an organization, but it does. ISO is used to determine the “speed” in which light is captured onto film or in this case digital memory. It works pretty much the same way as a film camera in the sense that the lower numbers (100, 200) are your slower “speed” films and the higher numbers (800, 1600, 3200) are your higher “speed” films. Now what does this mean to you. What this means is that by adjusting the ISO of your camera you are adjusting how much light you are capturing into the digital image. The higher the ISO the more light you will capture. The lower the ISO the less light you will capture. You will tend to notice though that 400 tends to be the norm that your automatic settings use. 400 is the safe setting for pretty much everyday type shooting. Now how to translate this into real world experience.

Well lets say that you are at the park for your kiddos soccer game. It’s 2 o’clock in the South Texas afternoon without a cloud in the sky. The sun is beating down on you and you want to take a photo. Now because your light source (the sun) is very bright you don’t need to allow very much light to be captured. You can set your camera for a low ISO setting usually between 100 and 400. This will give you a sharp, clear image on your final product.

Now let’s say that you are at a wedding, the party is really starting to get good. It’s about 10 o’clock at night and  you are up dancing on the dance floor with your best friends in the whole world. The setting is dark except for the DJ lights and the few dimly lit lights in the venue. You want to snap some photos of everyone having fun. This is where the higher ISO setting will come into play. Because your surrounding light is very dark or not available it is going to take the camera longer to capture the light and translate that into your image. By setting your ISO to something say like 1600 or even 3200 you are in a sense capturing more light onto the image. Now, there is a drawback to the higher ISO. Because the situation is dimly lit and the ISO is faster, the quality is not going to be the same that it would be for a lower speed. Depending on the quality of your camera you will tend to see graininess and color distortion in speeds greater than say 800.

If you are just looking to take everyday pictures while you are out and about then ISO 400 is your safest bet. It is probably the most versatile for the average photo. Now where do you find this on your camera? It will be labeled ISO and how to change that is going to depend on your camera. Normally you have to be in a Program or Manual setting and then select the ISO feature. The Nikon S3000 was able to go to a 1600 ISO. My Canon 30D can go to a 3200 ISO. Some higher-end DSLR’s can even go to 6400. The great thing about that is that you can use what little available light you have and take your photo without using a flash or very little flash thus giving your image a very natural look.

Aperture…

The big crazy photography word that out of everyone you ask, no one knows what it means. I am here to put away the mystery. Simply stated, Aperture stands for how big the opening in your camera is that lets in light to the film, err… digital image. I know, hard habit to break.

The larger the number the smaller the hole. The lower the number the larger the hole. I know, doesn’t make sense right. All numbers are designated with the letter f in front and are commonly referred to as the f-stop number. You will see it displayed on your camera as f11, f3, f2.8. You will also see this on your lenses. The smaller the number the faster the lens. Faster, in this case, doesn’t have to do with actual speed rather the amount of light it lets in. A larger hole lets in more light thus it allows light to pass through more quickly and is therefore faster. A little confusing I know.

Picture this, you are holding your hand up like so and you make a circle using your thumb and first finger. The picture in the middle below is a pretty average sized hole. Lets say that is f8. The photo to the left is quite a bit smaller that could be designated as f11. The photo on the right is the largest and could be a f2.8 or f3.0. Make a little more sense? I hope so.

Aperture has to do with Depth of Field. The quicker the speed or the lower the f-stop number the shallower the depth of field is. Depth of field has to do with the portion of the photo surrounding your focal point and how much in or out of focus it is. Think of your photo in terms of linear planes or sheets of paper stacked on top of one another. The shallower you are the less sheets of paper you hold. The deeper your depth of field the more paper you hold. Translated into your image it means this, the shallower your depth of field, or lower the f-stop number, the more blurry your background will be in the image. The higher the f-stop number, or the deeper your depth of field, the more in focus your background imagery will be. This is a great tool to have in your belt when you are trying to put your signature touches on an image.

For example, you can see the photo of Jacob to the right has a shallow depth of field because the imagery in the background and foreground are less in focus than the focal point which is him. This works great for portraits and closeup shots. Another example is this image of a Lone Star beer bottle. You can see that the label is in focus but the background is not. It has a shallow depth of field.

These are a couple of examples where a lower f-stop number is beneficial in these types of situations. It allows the most amount of light to pass through creating the image. Remember, your camera is nothing more than a light capturing device and everything it does depends on that.

An example of when you would want to use a larger f-stop number such as f11 or f16 would be if you were doing photography in a brightly lit situation such as outdoors or if you wanted to maintain as much of the image as possible in focus such as landscape photography. For landscape photography you image is across a broad area of the photo and thus you probably want most of it in focus. For that you would use a larger f-stop number which would keep more of your image in focus like the image below.

Both the foreground and the background of the image are in focus even though in physical length they are very far distances apart. This is made possible by the deeper depth of field using a higher f-stop number and a lower ISO number.

Now how do you find this on your camera? There are several modes that you can shoot in with your camera. Most will give you the options to shoot in a full automatic mode, a program mode, a shutter priority (Tv) mode, and an Aperture Priority (Av) mode. Sometimes on a point-and-shoot this may be distinguished as a PASM (Program Aperture Shutter Manual) mode. If you see the Av on your camera that is what it is designating. By shooting in Aperture Priority mode, you are telling the camera that you want to adjust the Aperture value and it can do the rest so to speak.  Check your manual for your model of camera to determine how the Aperture Priority mode is selected.

As you can see, these components all work together to create and image. The trick is getting them to work together. In the next post I will dive into shutter speed and explain how ISO, Aperture, and Shutter Speed all have to work together in order to have you image appear in the final product the way want it to.

Until next time, happy shooting!

-Robert Hillis