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What's in focus? The answer is determined by the Focus Distance and the Depth of Field (DOF).

Welcome to the Harris Tech Locus website!

Our site is dedicated to provide information and support for Locus, our computer program for photographers with PCs running Microsoft® Windows® 8, 7, Vista or XP.

Have you wondered why parts of your photos are unexpectedly out of focus? Have you been frustrated when your backgrounds are not as sharp or blurry as you want? Enter Locus, a computer program that removes the guesswork from focus. "Locus" is a Latin word that means "place" or "location" and that's what it is all about. It takes the camera location and settings and locates the parts of the scene that will be in focus. It also evaluates the out-of-focus locations and tells you how blurry they will be. It calculates distance and angles, megapixels and resolution, and lots more. If you can compose and expose a photo, Locus can help with the rest.

In the "old days" of film cameras, many lenses had manually controlled apertures. They also had scales to indicate the focus distance, depth of field (DOF) and hyperfocal distance. This helped trained photographers set up their shots. But that was "yesterday" when film limited the number of available format sizes. Today our digital cameras come with a myriad of different image sensor sizes and resolutions, have lenses without focus aids and maintain a wide-open aperture during auto focus.

Some camera manufacturers have tried to help by including a "DOF preview" button on their SLR cameras; but it isn't useful unless your scene is very brightly lit. That's because a through-the-lens (TTL) viewfinder quickly dims as you make the aperture smaller. Add to that the fact that many of today's TTL viewfinders, themselves, are smaller and darker and you'll have a difficult time evaluating the focus of the scene you're about to photograph.

Whether you want a tightly focused portrait with lots of background and foreground blur or a wide landscape with deep focus, Locus can help. It even gives you an idea of the perspective you can expect to view through your lens. It provides the information you need to answer questions like: Do I have sufficient scene resolution to photograph a large group of people? Will there be enough pixels to resolve each face in the group? What about a distant shot? Will I have sufficient pixels to read the lettering on a sign a great distance away if I use a 300mm lens? If not, what about a 400mm lens?

A view through the camera viewfinder.What do you want to capture with your camera?

What depth of focus (depth of field) do you want?
How blurry do you want the background?
How large of a view do you need?
What perspective do you desire?
Do you know what lens and settings to use?

These are just some of the questions that Locus will help you answer.

The main window of Locus.Locus can help...

You may have heard that traditional DOF calculators aren't accurate with today's digital cameras. In many cases this is true. Fortunately, Locus is not your typical DOF calculator—it is accurate. This is due in part to its advanced way of handling the circle of confusion (COC), the property of every optical system that determines when something is in focus or out of focus. Locus provides tools to help you adjust the COC for your output size (enlargement factor) and viewing distance. With a little input from you, it can adjust the COC automatically. Or you can have full manual control when it is needed.

If terms like the "circle of confusion" are confusing, don't worry. Locus includes a great on-screen User Manual that explains the terms. It's illustrated dictionary is a great resource.

But Locus is much more than a DOF calculator.
In addition to focus and blur, Locus can also calculate or estimate:

  • image aspect ratio
  • true camera megapixels
  • circle of confusion (COC) on the camera focal plane and in the output
  • field of view factor
  • minimum suggested shutter speed to avoid camera shake
  • minimum suggested shutter speed to "freeze" a moving subject
  • lens focal length required for a specified field of view and focus distance
  • net lens focal length with a teleconverter
  • angle of view (AOV)
  • lens classification (ultra wide, wide, normal, moderate tele, telephoto, super tele)
  • lens perspective
  • diffraction limit
  • net aperture with teleconverter
  • aperture diameter
  • hyperfocal distance
  • focus distance required to achieve a desired field of view
  • field of view (FOV) at the focus distance
  • scene resolution at the focus distance
  • magnification at the focus distance
  • total depth of field (DOF)
  • near focus limit
  • far focus limit
  • front focus depth, including percent
  • rear focus depth, including percent
  • near bokeh (the blurriness at a user-specified foreground distance)
  • far bokeh (the blurriness at a user-specified background distance)
  • bokeh at infinity (the blurriness of the picture in the far distance)
  • required number of pixels and crop size for a specified output

Since Locus is designed to run on a Windows PC, you'll need a notebook computer if you want to run the program in the field. This may not be convenient on a remote shoot so Locus can print a variety of information that you can easily carry with you. You can print:

  • all of the information in the main window, including the perspective drawings
  • depth of field tables, including focus limits and fields of view

Plus you can send the same information to the Windows clipboard so it can be pasted into your favorite word processor or page layout program. -click for here for more information-

What Locus can't do...

Locus can do many things but it can't do everything. At its heart, Locus is an accurate focus and photo geometry calculator. It is not an exposure calculator—it won't calculate the lumens or coverage required for flash or strobe photography. If all you need is a "light meter" program, then Locus is not for you.


The title window of Locus.

Free Demo If you are new to Locus, you can download it and use it for free during its built-in evaluation period. You'll have 30 days to run it up to 12 times so you can test its compatibility with your computer and its suitability for your needs.

Purchase Locus Purchase Locus for just US$ 29.95. Note: 10% of all profits from Locus go to Life Outreach Int'l.

Locus Updates 14-Jan-14 Version 1.0.6 Locus program update.

Camera Database Updates 18-Jan-14 Latest Locus camera database update.

Locus Press Release 10-Mar-10 Official Locus Press Release.

Copyright © 2014 by Harris Technologies, Inc. All rights reserved worldwide.