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£672
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54
backers
Funding Unsuccessful
The project's funding goal was not reached on Sat, February 14 2015 9:14 AM UTC +00:00
Last updated February 14, 2015

Lens Focusing Jig

This test is the easiest and quickest way to test if your DSLR has an autofocus issue. This test can detect front or back focus issues.

Lens Focusing Jig

This test is the easiest and quickest way to test if your DSLR has an autofocus issue. This test can detect front or back focus issues.

£672
pledged of £5,000pledged of £5,000 goal
54
backers
Funding Unsuccessful
The project's funding goal was not reached on Sat, February 14 2015 9:14 AM UTC +00:00
Last updated February 14, 2015

About

How it works

For example, I will be using the Nikon D300 + Tamron 28-75 mm F2.8 as a reference camera for this article, but any modern DSLR capability can be used for the same test.

Set Up

Set up the camera on your tripod and make sure that the camera is placed parallel to the focus chart. Make sure that the camera is not tilted left/right/up/down – it must be parallel to the focus chart. To check if your level is good, look from the side and make sure that the lens is pointing directly at the centre of the focus chart.

The distance between the camera and the focus chart depends on the focal length of the lens you are testing. If you are using a 50mm f/1.4 lens, then the distance between the camera and the test chart should be approximately 25 - 50 cm. If you are using a wide-angle lens, then stand closer and if you are using a telephoto lens stand further away. The goal is to stand close enough to be able to have a shallow depth of field. 

To calculate the distance between the camera and the focus chart, use Apps on Android or IOS.

Android:

 or IOS:

Camera Setup

When testing the autofocus accuracy of a camera or lens, it is always best to have exposure consistency. Therefore, I recommend switching to Manual mode and keeping the same exposure for each shot.

Here is a summary of what I would recommend in terms of camera setup:

1. Switch your camera to full Manual Mode.  

2. Set your lens aperture to maximum aperture. For example, if you have a Tamron 28-75mm f2.8 lens, set your aperture to f/2.8.  

3. Set your ISO to base value such as ISO 100 or 200.

4. Use the exposure meter inside the camera to determine the optimal shutter speed. Take sample shots and make sure that you can see the chart clearly. Ideally, your shutter speed should be pretty fast at something like 1/500 of a second. If you are getting really slow shutter speeds like 1/10, then it means that you do not have sufficient ambient light. Either take the setup outside and do it in bright light, or add more light to illuminate the focus chart. If the amount of ambient light is insufficient, your test will be flawed. It is extremely important to make sure that you are doing this in a well-lit environment, since the Phase Detect sensor on the camera needs plenty of light.

5. Make sure that AF Fine Tune/AF Micro Adjustment is turned OFF if your camera has it.  

6. Set the focus point to the centre focus point. The centre focus point is always a cross-type sensor, so it is the most accurate in your camera.  

7. Turn off any sort of lens corrections in your camera (vignetting, distortion, chromatic aberration, etc.). You do not want anything to potentially influence the test results.  

8. Set the camera to AF-S/Single Servo mode.  

9. While this test should work for both JPEG and RAW images, cameras add extra sharpening, colours, etc to JPEG images. Therefore, I would recommend to capture test data in RAW format.

Capture

Now look through the viewfinder and rotate the focus ring on the lens until the focus chart looks completely out of focus. We want to force the camera to reacquire focus. Now half-press the shutter button or press the AF-ON on the back of the camera to acquire focus and wait until you see a green mark inside the viewfinder or the camera beeps (if you have beep turned on), confirming that focus is acquired. Take a shot. Again, rack the focus by rotating the focus ring until everything is out of focus and repeat the process. Ideally, you should capture at least 3 shots this way, since you need to eliminate any possibility of a potential autofocus error.

Analyze the Data.

Now that we have a sharp reference image, along with a bunch of other images, it is time to analyze the data. Import your images into your computer with whatever post-processing tool you use. Open up the very first image and make sure that it looks sharp in the centre. Here is a crop of my reference shot that I captured with the Tamron 28-75 mm f2.8

 In my case, I set up value on -5.

What tolerance levels for calibration are acceptable? For me, anything below ±10 for a camera or lens is acceptable. Ideally, I want to stay in the ±5 range, but if fine tuning takes care of the problem, I do not bother sending my gear to manufacturer for tuning. If a new camera I buy requires -5 to -10 with all of my lenses, I will just take care of it with AF Fine Tune. If it is anything above that, I will send it to Nikon for tuning. The same thing goes for lenses.

And test after calibration

 Kit includes:

Lens Focusing Jig and camera spirit level.

Risks and challenges

This project is very simple so haven't any risks but need the die-block for start the production. The project will be created in UK.
I did test selling some Lens Focusing Jig on eBay. It was successful and very good feedback from costumers which led to more orders.

Here are some feedbacks from eBay:
- Positive feedback rating Excellent produit, simple et pratique, envoi rapide, à recommander.
- Cheap and Efficient Way to Calibrate Your Gear, with Downloadable Instructions.
- Exactly what I needed & delivered fast- many thanks!
- super easy to use and got the job done

and I have many more good feedbacks on eBay.

So product has low risk. The die-block is quite expensive and I need money for die-block to start regular and better quality production.

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Funding period

- (30 days)