35MM CAMERA -- THE LENS -- APERTURE -- SHUTTER SPEED -- ISO -- DEPTH OF FIELD -- SENSITOMETRY --

__TABLE OF CONTENTS__35MM CAMERA -- THE LENS -- APERTURE -- SHUTTER SPEED -- ISO -- DEPTH OF FIELD -- SENSITOMETRY --

**D.O.F FORMULA**

35MM CAMERA -- THE LENS -- APERTURE -- SHUTTER SPEED -- ISO -- DEPTH OF FIELD -- SENSITOMETRY --

The definition of Hyperfocal distance is: The hyperfocal distance is the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp.

When using hyperfocal distance, you are focusing the lens to a particular distance determined by the focal length and Aperture combination that you are using, to ensure that everything from half the hyperfocal distance, till infinity, is acceptable sharp. This is mostly used in landscape photography where the photographer will decide on a focal length and Aperture combination, that gives him the hyperfocal distance he needs. Once you learn what it means and its uses, Hyperfocal distance will become very useful in other fields of photography too, such as studio photography, where its important to get the whole subject acceptably sharp.

When its your intention to get absolutely everything in focus, for example a flower with everything in front and the whole landscape and mountain behind it in sharp as well, then it will not always be best practise to just focus on the flower and select a large aperture and shoot. If you did it that way you will find it difficult to get absolutely everything sharp. In order to get everything acceptably sharp you'd need to set the focus of the lens to the hyperfocal distance for your specific situation you're in.

The easiest way to find out what the Hyperfocal distance is, is to use a technique that involves the DoF (Depth of Field) scale and distance scale on your lens. In preparation for this article though, I discovered that none of the modern lenses today have the DoF scale. So writing about how you can use that technique wouldn’t help anyone who is breaking into the field of photography. Therefore you need to calculate your Hyperfocal distance through the use of the mathematical formula below.

When its your intention to get absolutely everything in focus, for example a flower with everything in front and the whole landscape and mountain behind it in sharp as well, then it will not always be best practise to just focus on the flower and select a large aperture and shoot. If you did it that way you will find it difficult to get absolutely everything sharp. In order to get everything acceptably sharp you'd need to set the focus of the lens to the hyperfocal distance for your specific situation you're in.

The easiest way to find out what the Hyperfocal distance is, is to use a technique that involves the DoF (Depth of Field) scale and distance scale on your lens. In preparation for this article though, I discovered that none of the modern lenses today have the DoF scale. So writing about how you can use that technique wouldn’t help anyone who is breaking into the field of photography. Therefore you need to calculate your Hyperfocal distance through the use of the mathematical formula below.

The circle of confusion is a part of this formula, and its important to realise that the size of the circle of confusion depends on the size of the sensor you are using. As you know, not all digital cameras have the same size sensor. Some have a sensor that is the same size as the 35mm format for film (36mm X 24mm), cheaper entry level cameras have a sensor that is 1.3 or 1.6 times smaller than that.

The Circle of confusion size that you need to use in the above formula are as follows, and I only included the camera formats that are used mostly by digital SLR users today:

- Full Frame Camera (sensor size of 36 X 24mm) = 0.03mm
- Sensor with 1.3 times crop factor of Full Frame = 0.023
- Sensor with 1.6 times crop factor of Full Frame = 0.019mm

Here is an example: lets say you are out in the field and you decide to shoot the scene in front of you. You have a 35mm lens on your camera because its wide enough for your scene, and your camera is already set to quite a small aperture, lets say f/11. This is how you'd insert this information into the above formula:

With this information, if you focused your lens at 3.747m and used an Aperture of f/11 with the 35mm lens you had attached to your camera, everything from half of the hyperfocal distance (1.8735m) till infinity will be rendered acceptably sharp in the photograph.

Getting to know and understand how and why you’d use the Hyperfocal distance to maximize the use of your DoF will naturally make you wonder about where else you could use this kind of technique. For example, if you were being paid by a magazine or any kind of client, to photograph something in a studio, and part of the client’s requirements is that the entire object be sharp. How would you go about making sure that the object in the picture is completely sharp, would you wing it? Or would you be a professional and make sure the job is done properly the first time? Below is a diagram explaining the situation in the studio, and its your aim to get the entire table sharp. In other words, **you’re trying to fit the entire Depth of Field over the entire table.** There is a way to calculate what the minimum Aperture and focus distance should be, to make your DoF just the right size for the object you’re photographing to be rendered sharp.

- The closest point to the camera that needs to be sharp is called the “near DoF limit’, and is designated with this symbol
__'DN'__ - The farthest point to the camera that needs to be sharp is called the ‘far DoF limit’, and is designated with this symbol
__'DF'__ - The focus distance setting of the lens (subject distance) is designated with this

symbol__'s'__ - The Aperture that we need to use in order to get the whole object sharp will be designated with this symbol
__'N'__ - In this situation I am using a 35mm format digital camera, which has a sensor dimension of 36mm X 24mm. This camera format has a circle of confusion size that is 0.03mm, and circle of confusion is designated with this symbol
__'c'__

So you’re standing in the studio with this table in front of you, and you know that the closest point to the camera that needs to be sharp is 1.5metres away, and you know that the farthest point that needs to be sharp is 3.5 metres from the camera. You could ascertain this information by either measuring the distances yourself, or by focusing on each point and reading the distance off of your lens. The first thing you need to work out is what your focus setting should be, and you are able to calculate this with the information you already have. Use the following formula and solve for “s”

Now you know that with the camera at the distance from the closest and farthest part of the table, the lens focusing distance should be set to 2.1m. At this point you can guess where 2.1m is and just manually focus the lens to that point, or you could take out a measuring tape, your choice.

Now to calculate what the aperture is that we need to use, we need to work out the following formula and solve for N.

Now to calculate what the aperture is that we need to use, we need to work out the following formula and solve for N.

And there you have it. With the aid of mathematics we have calculated that the focusing distance should be 2.1m, and that the Aperture we should be using is f/16. Now you can go forth with confidence and fulfil the brief explained above, if you ever get one like that. On the other hand there are much easier methods to work out the information that we have just worked out. There are Depth of Field and Hyperfocal distance calculators online, and available to download to your cell phone or tablet device. These are much easier and time saving, but at least now you understand what these devices are doing.