IPD: the distance between your pupils
Binocular goggles have a separate screen and lens for each eye. For a clean image, the centre of each lens has to sit in front of your pupil. The distance between your pupils is the interpupillary distance, usually shortened to IPD. Oscar Liang's goggles guide says a wrong IPD setting makes the edges blurry or misaligned, and recommends knowing your IPD before you buy, so you can check that it falls inside the goggles' range.
Box goggles, with one large screen and a big lens, do not care about IPD. They are also usually the ones that fit over glasses.
How to measure it
If you have a recent prescription for glasses, your PD (pupillary distance) may already be on it. All About Vision notes that not every eye doctor includes it automatically, so you may need to ask. At home you need a mirror and a ruler with millimetres:
- Stand about 20 cm from the mirror and hold the ruler against your eyebrows.
- Close your right eye and line up 0 mm with the centre of your left pupil.
- Look straight ahead, open your right eye and close your left.
- The mark at the centre of your right pupil is your PD.
It is easier with a second person holding the ruler. All About Vision suggests measuring three times and taking the average. If one reading is far from the others, measure again.
Ranges of current goggles
| Goggles | IPD range | Focus range | Source |
|---|---|---|---|
| DJI Goggles 3 | 56-72 mm | -6.0 to +2.0 D | DJI manual |
| DJI Goggles N3 | no adjustment | no adjustment, fits over glasses | DJI FAQ |
| DJI Goggles 2 | 56-72 mm | -8.0 to +2.0 D | Oscar Liang |
| DJI Goggles Integra | 56-72 mm | none, prescription lenses instead | Oscar Liang |
| Walksnail Avatar Goggles X | 54-74 mm | -6.0 to +2.0 D | Oscar Liang |
| HDZero Goggle 2 | 58-72 mm | +4 to -7 | HDZero docs |
| HDZero Goggle (first version) | 57-70 mm | +2 to -6 | HDZero docs |
Treat advertised ranges with some caution. In his review of the Fatshark HDO2, Oscar Liang measured roughly 59-69 mm against an advertised 54-74 mm. A reader comment on his guide pointed out that the Fatshark Attitude V3 reaches only 69 mm instead of the advertised 72, and Fatshark corrected its product page. If your IPD is near either end of a range, try the goggles on before you buy. Oscar Liang suggests going to a meetup and asking other pilots to let you try theirs.
Focus: diopter adjustment
Goggles with focus adjustment can correct short- or long-sightedness without extra lenses. Oscar Liang says the range is typically somewhere between -6 and +6, depending on the model. Negative values are for short-sightedness.
In a separate article he gives a quick test of whether you need correction at all. The image in the goggles appears roughly 2-3 m away. If you can watch a TV comfortably from about 2 m without glasses, you will probably be fine without any correction.
Setting it on DJI Goggles 3
The adjustment knobs are on the bottom of the goggles. The manual describes this order:
- Unlock the knobs. They pop out.
- Slide them left and right until the image is aligned. That sets the IPD.
- Rotate them slowly to set the focus. The screen shows the current value.
- Press the knobs back in and rotate to lock them.
The first time, DJI recommends setting a value slightly weaker than your glasses, letting your eyes adapt, and then fine-tuning. Do not go above the power of your glasses, which can cause eye strain. The adjustment does not correct astigmatism.
Setting it on HDZero goggles
The HDZero manual uses a three-step routine that works on most binocular goggles:
- Close one eye and turn the focus knob until the image is sharp. Repeat for the other eye.
- Close one eye and slide the IPD control until the image sits in the centre. Repeat for the other eye.
- With both eyes open, fine-tune until you see one clear, merged image.
If you wear glasses
There are three ways around it, depending on your eyes and your goggles.
Goggles you can wear over glasses. DJI says the Goggles N3 have room inside for glasses and need no adjustment or extra lenses. They have no IPD adjustment either. Box goggles also usually fit glasses. With binocular models it depends on the frames: in his Skyzone Cobra review, Oscar Liang notes that small frames fit but frames taller than about 30 mm may not.
Built-in adjustment. If your prescription falls inside the focus range and you do not need much astigmatism correction, the built-in adjustment is the simplest option.
Corrective lens inserts. These are needed for strong prescriptions or astigmatism. The DJI Goggles 3 come with a pair of -2.0 D lenses that extend the range to -6.0 to -8.0 D. With them fitted, the real correction is the value on the screen plus -2.0 D. For anything else, DJI tells you to take the bundled lenses with their frames to an optician, who will make lenses in the same shape and size with your astigmatism axis and an edge thickness under 1.8 mm. DJI's example: for -9.0 D glasses, buy -3.0 D lenses and set -6.0 D on the goggles. Fit the lenses with the concave side towards your eye. The manual also warns that with lenses fitted they sit closer to your eye, so your eyelashes may brush them. The fix is the extra forehead pad included in the box.
HDZero sells made-to-order lenses for Goggle 2. To order you give your PD and the SPH, CYL and AXIS values from your prescription. User reviews on that page are mixed: some say the lenses sit loosely and blur at the edges, and one reviewer suggests trying the built-in diopter adjustment first. For older Fatshark and Skyzone models, Oscar Liang mentions sets of -2, -4 and -6 inserts for about $18.
Fogging
Goggles fog up in hot and humid weather. Oscar Liang calls a fan important if you fly in hot or humid places. All the DJI goggles in his table have one, and HDZero uses three soft-mounted fans that cool the electronics and keep the lenses clear.
DJI Goggles 3 have a "Goggles Defog" option in the settings. According to the manual, it makes the cooling fan run at high speed to clear the fog. Uplink Imaging recommends it in cold or humid weather, at the cost of battery life.
Care: sun, cleaning, storage
- Keep the lenses out of direct sunlight. Oscar Liang warns that direct sunlight can burn the screens. The HDZero manual says it can damage the OLED displays, and the DJI Goggles N3 FAQ talks about irreversible damage. His advice: when you put the goggles down, turn the lenses away from the sun. He also notes that dark-coloured goggles heat up more in the sun.
- Clean gently. DJI recommends wiping the lenses with the supplied cloth in a circular motion from the centre outwards. Do not use alcohol wipes on the built-in lenses. Disposable alcohol pads are allowed only on the add-on corrective lenses.
- Mind the temperature. DJI gives an operating range of -10 to 40 °C for the Goggles 3. Store them dry at room temperature.
- Check the switches. In the HDO2 review, Oscar Liang notes that the controls can move when the goggles are in a bag. If the image suddenly looks blurry, check the IPD and focus before blaming the video link.
Fit and weight
The DJI Goggles 3 weigh about 470 g. DJI suggests placing the battery compartment, which also has the headband adjustment knob, on the upper back of your head so the weight spreads evenly. Comfort is very individual. Oscar Liang points out that the same headset can sit perfectly on one face and press on another person's nose, which is one more reason to try goggles on before you buy them.