For almost everything in photography there is usually a simple way to figure out what it is you are trying to accomplish, whether it is figuring out how to light something, what shutter speed to use to stop motion or to create a sense of movement. The hardest thing to do is to figure out how much depth of field will be in your images. While you can sometimes get a preview or you can always do the shoot-chimp-repeat dance until you get what you want. The trick is to actually know how to calculate the amount of depth of field you will get based on your aperture and focal length. This is where the Expoaperture discs come into play. If you want a specific effect without the trial-and-error, then the Expoaperture discs will save you tons of time and once you get a solid feel for how the system works you will eventually be able to setup your shots without it.

Summary
It’s one thing to know that throwing your aperture open to 2.8 will give you a shallow depth of field and closing it down to F22 will extend the depth of field. If you do a lot of portraits you probably have a good formula you use for a particular lens like setting your 50mm prime lens at F11 so that at a 10′ shooting distance you will get 12″ of depth so that an entire head is in focus. You may have learned this from numerous shots until you instinctively have a base setup even if you don’t have notes on your exact setup. But what do you do when you want a very specific shot and don’t want to spend all day doing trial and error?

Features
The Expoaperture² kit comes with two discs, one covering focal lengths from 15 – 135 and focal distances of 2′ to about 30′. The second disc covers 70mm – 600mm and focal distances from 30′ to about 1200′. The nice thing about how the discs work is that you set your sensor size and then you can use any combination of variables to come up with the remaining number. For example, if I set the dials for 24mm I can see that at f4 I will get 2.5 zones, if I then turn the disc over I can calculate the shooting distance I will see that a shooting distance of 3′ will give me a DoF from 2.5″ to 3.75″. If I am unsure of the aperture to use to obtain a 1′ DoF at a 6′ distance I can see that I will be looking for a 1 zone width so by making sure my focal length is at 24mm I see I will need an f1.6 aperture for the short distance I want or if I move to a 50mm I will need to shoot at f8 for the same result. Using the discs in this way will not only help you determine the amount of DoF you can get, but it can also be used as a tool to help you plan what lenses you will need for a given shoot.

Let’s say we want to shoot a football game and want to know what kind of shots we can expect from different lenses. Knowing that my long lenses is a 70-300 and the average shot will be around 100′ away, I want to make sure I have about a 10′ +/- DoF, I see that I will only need about ¼ of a zone I can quickly see that shooting at 70mm will give a HUGE amount of DoF because the maximum aperture for this lens is 4.0 so that’s going to give me a DoF range from 55′ to 150′. If I move to 150mm and shoot at f5.6 my DoF drops to about 60′ to 160′, and shooting at 300mm at f5.6 cuts the DoF down to about 90′ to 120′ which is going to give me the DoF I am looking for, not too short, not too long.

Usage
To demonstrate how this system works, we decided to set up a shoot that would utilize how the discs work. For this shot to work we wanted to show the model’s face and hands but wanted the gun barrel to be out of focus. Since we are using a Canon 30D, we first set the sensor size/format to 1.6 as that is the crop factor for the 30D sensor. Second, we are going to start with a 50mm Prime lens so we set the yellow focal length to 50mm. On the back of the disc we look at the shooting length of 10′ and we can see that the focus length we want to work with is within 1 zone in each direction, flipping the disc back over and finding the #1 on the dial (for 1 zone) we see that the actual aperture we want to use is going to be between f8 – f11 to get the entire rifle and model in focus and using f5.6 is going to give me about 18″ of focus distance so I can either get the model and part of the rifle or the front part of the rifle to about the mid-point. Before using the disc, I would have probably started up at f2.8 and then would have spent quite a bit of time and test shots getting the DoF correct. With the Expoaperture disc I actually had the shoot planned out with a handful of shots I wanted prior to even setting up the camera.

Results
The discs may seem a little confusing at first because there are multiple ways to actually use them. If you watch the video and work through some scenarios in your head a few times like I did above, it won’t take long at all to get a really good feel for how they work. Using the discs to pre-plan a shoot like I did for this article is a huge time saver, especially if you are using assistants since you can just give them a shot list and have them setup your camera almost perfectly before you even look through the shutter. The discs themselves are made from what feels like a plastic laminate that should hold up to a lot of usage and they come with their own soft plastic carrying cases to keep them from getting dinged up in your camera bag. Unless you simply have a knack for understanding what settings you need to obtain the exact depth of field you want, then getting a set of Expoaperture discs is a worth considering. As a training tool, using the discs a few times will help you to understand the correlation between the settings and will help you to learn how to judge the settings you want better.

Equipment Used

Author: Kerry Garrison
Model: Taylor Thorne

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