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Pre-printed or Hard Targets are available direct from Reikan in the online store as well as via our Reikan US distributor. Pre-printed targets do not need to be measured as FoCal will recognise the design and apply the correct dimension automatically.
- The FoCal Target
The FoCal target is specifically designed to work with the...
- Document Downloads
Downloadable FoCal Targets. Download and print your own...
- The FoCal Target
- Feasibility Study
- Calculating The Camera Alignment Errors
- Aligning The Camera
- Designing The Target
- Building The Target
Understanding AF Micro Adjust Step Size
Auto focus adjustments are made in fractional amounts of the lens’s depth of field. This is necessary, as an absolute unit would only apply at a single distance. Adjusting the lens’s focus point back 1 foot may work fine when photographing a subject 20 feet away, but it would result in severe errors at say 2 feet away. According to this Canon paper, an AF micro adjust are made in 1/8thdepth of field steps. Though the document is specific to the EOS-1D and EOS-1Ds, it’s a fair bet to assume th...
Targeted Testing Distance
Since depth of field is dependent on distance, the next consideration is a minimum distance to design the target to be sufficiently accurate. However, since the depth of field narrows as the distance decreases, and thus the required accuracy increases, reducing said distance too much immediately results in an impractical limitation for a home design. With that in mind, I’m going to shift consideration from the min test distance to the actual test distance for a moment. The officially recommen...
Targeted Aperture
In addition to distance, the aperture controls the size of the depth of field. Wider aperture resulting in shallower depth of field also put increased demands on accurate construction. Though one certainly can target any aperture they desire, I see little sense in targeting an aperture value that you’ll likely never own or use, at least in the near future.
The Alignment Problem
Alignment is an important, if not the most important, part in any autofocus test system. The real question is how much room for error actually exists. As a point of note, in this article I assume an ideal target and ignore any errors in target flatness or construction. While the last part focused on the errors in flatness and construction, this article focuses on the alignment errors caused by not having the camera perfectly centered on the target. The standard case is show below, where the c...
AF Target Size
Before I calculate the angle α, a reasonable estimate for Doffsetis necessary. While a detailed investigation of AF sensor coverage is certainly possible, a rough calculation is sufficient for this discussion. The longest side of an EOS-1D’s AF box to be about 0.924°. Since the AF point can cover more than the viewfinder displays, it’s desirable for the target to be larger as well. The question of how much boundary area allowed is certainly an open discussion, though I’m assuming 100% just fo...
Calculating α
The angle α is calculated using the following equation. For the small (6-inch) target described above, α is equal to 1.647°. For the larger target I used in my prototype, α is 1.318°. The larger α is the more room to misalign the camera before affecting the results.
The actual alignment of the camera and target is certainly one of the major considerations, if not in the accuracy of the test, at least in how easy it is to setup for the testing. One strategy is simply to do what I suggested in the previous article and use a tape measure to position the target in the necessary spot. It works, and can be accurate ...
While the target’s construction tolerances are important, if there is nothing to focus on and no scale to read, none of that matters. The non-obvious part is that how the target is designed can seriously affect how the auto focus system performs.
Once you understand the considerations that go into designing an autofocus adjustment target, the actual process of building the target is comparatively trivial. The principal consideration is simply to insure the target is flat enough to meet the requirements imposed by the first part and rigid enough to not flex appreciably. I built my target for...
The FoCal target is specifically designed to work with the FoCal software and the camera autofocus system to allow not only reliable calibration, but also the ability to warn and/or adjust various settings under changing test conditions.
Apr 16, 2012 · Just make sure that you have a flat target, perpendicular to the optical axis, and with clear sharp contrasty details that span the active area of the AF sensor being tested. You can use the target that I made, scaling it to an appropriate size.
Downloadable FoCal Targets. Download and print your own target for use with FoCal.
Nov 29, 2022 · As for the actual autofocus testing, you must use the printable FoCal Target. If you use multiple cameras, you know how frustrating it can be to keep them synced. The FoCal Mobile app lets you sync your cameras to the same time as your phone or tablet.
People also ask
Do I need a printable focal target for autofocus testing?
Is your autofocus target less than optimal?
Can I use focal if I don't have a printer?
How do I design an autofocus adjustment target?
If you don’t have a printer, then you can get the software with actual test targets. Reikan FoCal and printed targets are also available in the US from B&H as well as directly from Reikan. Software requirements (as of V2.4.3) Reikan FoCal is designed for computers running Windows and Mac OSX with the following specifications:
