How sharp does a virtual tour need to be?

“My panorama is 100 megapixels, it will be sharp.” It is the most widespread mistake among drone pilots delivering their first aerial virtual tour, and it costs return visits.

In 360, megapixels mean nothing. What counts is angular density: how many pixels your image devotes to each degree of the field of view. One number, one division, and you will know before take-off whether your deliverable will hold up to zoom.

Why megapixels lie

A conventional photo covers perhaps 70° of field. A spherical panorama covers 360 across and 180 up. At equal resolution, the spherical image therefore spreads its pixels over an angular area five times larger.

Angular density, at equal image width

Conventional photo

86 px/°

6,000 pixels wide spread over 70° of field.

Spherical panorama

17 px/°

The same 6,000 pixels, spread over 360°.

In practice: an equirectangular panorama of 6,000 × 3,000 pixels proudly reports 18 megapixels. But those 6,000 pixels across cover 360° - which is 17 pixels per degree. A recent laptop screen asks for three times as much when the visitor zooms in. Hence the impression of softness, even though the file “is 18 megapixels”.

The calculation, in one line

The angular density of an equirectangular panorama is worked out like this:

density (px/°) = image width ÷ 360

That is all. Here is what it gives for the resolutions you actually meet coming off a drone:

Against that, what the visitor’s screen actually needs. It depends on the maximum zoom the player allows - in our case, 40° of vertical field:

What those two tables actually say

Three conclusions, and they change how a job gets prepared.

At the resting field of view, almost anything passes. When a tour opens, the player shows 90° of field. The requirement then falls to 9 px/° on a phone and 20 px/° on a retina laptop: an 8,000-pixel source is sharp on opening on both.

That is why a mediocre panorama can “look fine” in the screenshot attached to a quote, and disappoint the moment the client starts playing with it.

Softness only appears at zoom, and it depends on the visitor’s screen. A phone is served from 7,500 pixels wide; a retina laptop asks for 16,000. That is the useful gap to remember, and it explains how the same tour can be judged sharp and soft on the same day.

The threshold that tips it

45 px/°

That is what a retina laptop asks for at maximum zoom, and only a source 16,000 pixels wide reaches it. Below that, the softness shows as soon as the visitor moves in from a desktop screen.

Mobile is more forgiving than desktop. Counter-intuitive, but mechanical: a phone screen has fewer pixels vertically than a retina laptop. If your client approves the tour on their phone and complains from their desk, it is not bad faith.

What you can do at capture time

Density is won at the moment of the flight, not afterwards. Three levers, in order of effectiveness.

The number of frames. A panorama stitched from 26 photos mechanically has more pixels than an automatic sphere from 21 frames. On recent aircraft the full sphere mode is a good compromise; manual stitching on the ground stays better when resolution matters.

Altitude. Flying lower does not change angular density, but it changes what each degree contains: at 25 metres, one degree covers less ground than at 60. Perceived detail increases, at identical resolution. It is the most underrated lever.

Ground stitching. Stitching software produces outputs well beyond what the drone generates on its own. We accept up to 32,000 pixels wide, in JPEG, PNG, TIFF or AVIF - that is 89 px/°, comfortably above what a 4K screen needs.

What about upscaling?

It exists, it works, and it has a narrow domain of use. Doubling the resolution of an 8,000-pixel source takes it from 22 to 44 px/°: within a point of what a retina laptop needs. Doubling a 16,000-pixel source produces nothing but weight - the requirement was already covered.

The takeaway

Divide the width of your panorama by 360. If the result is above 45 px/°, your tour will hold up to zoom on a desktop screen. Below 21, it will be sharp on opening and soft the moment the visitor moves in, phone included - which is precisely the moment they have become interested in something.