The App has been designed considering a Default calibration of several iPads (Optom Vis Sci, 2016). However, you can go for a higher precision of your measurements with a personalized calibration. We offer three possible options to select according to your needs and resources.
It is required to use any iPad equal to 4rd generation (Retina display, 2012, IOS 10.3.3) or later models with screen size equal or higher than 9.7" (iPad mini not recommended). We have designed our apps considering the variability of screen brightness properties of several iPad generations in such a way you can use it in any iPad without a previous calibration. Anyway, if you desire to increase the reliability of your measurements, specially on Contrast Sensitivity, please read carefully this section.
Calibration is related to screen luminance properties, not stimulus size which is automatically adjusted by the App. In Visual Acuity measurements, calibration does not have a relevant impact on the results but could have a major impact in Contrast Sensitivity measurements.
We recommend using the App at 42% of brightness (85 cd/m2). At this condition, the deviation with the real luminance of your device could achieve the +/- 6 cd/m2 of bias and hardly will achieve the +/- 15 cd/m2. Furthermore, the default settings of gamma correction are, R: 2.19 G: 2.21 B: 2.24. You don't have to change these values except you decide to opt for the Options 2 or 3 detailed below.
Although the International Standard Normative recommends a background luminance of 200 cd/m2 for standard clinical practice, clinical studies are usually conducted in 85 cd/m2 (42% of brightness) however the impact in your results by a bias of 15 cd/m2 at this condition can be more relevant than at 200 cd/m2 therefore if you want to conduct a study at 85 cd/m2 we recommend you to opt for the following options 2 and 3.
We have developed the first and the only procedure that allows you to calibrate the brightness and the gamma function of your iPad with a low-cost device in 3 minutes. This is achieved with three resources:
Originally designed for color measurement, it can be also used to measure the iPad luminance with our exclusive PicoDisplay App. Pico device is used but not sold by us, we are not responsible for the performance or distribution of the device.
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This App gives you the brightness you have to select in our apps to achieve a particular value of Luminance (cd/m2) in the background. It also allows you to export a .csv calibration file for computing the gamma correction. Although PICO is not developed or sold by us, the PicoDisplay is a test-eye.com creation.
We can compute for free the RGB gammas of your iPad/iPhone if you supply us the Calibration File. Contact the developer by LinkedIn for further instructions.
The difference with the previous Option is that you are going to use your personal colorimeter instead of the PICO device and the PicoDisplay App for creating the .csv file.
Disadvantages versus PICO:
Advantages versus PICO: