How Many Lumens Do You Need to Project in Daylight?

Working out how many lumens you need to project in daylight will depend on many, many factors.  If you are trying to project an image outside when the projector screen is bathed in daylight then you will need a projector that is approximately capable of emitting at 110,000 lumens.

Clearly, there aren’t any projectors capable of projecting with this kind of luminosity.  However, this article will discuss the ways in which you can adjust the surrounding environment to begin to put the odds in your favor if you wish to project images outside, in the daytime.

How bright is daylight?

First of all, we need to know what we are up against when it comes to daylight.  How many lumens does the sun emit in relation to lighting up a surface?  The illumination of a surface is measured in a unit called Lux.

Lux is the measurement of lumens applied to a surface with an area of 1 meter squared.  Therefore, 1 lux is equal to 1 lumen applied to a single 1 meter squared surface.

A lux meter can be used to measure the illuminance of a light source such as the sun or a projector.

Usually, on a sunny day, the sun would illuminate a surface somewhere between 90,000 to 100,000 lux.

Obviously, other factors would decrease the amount of lux within the outdoor environment such as cloud cover, the position of the sun in the sky, shade from buildings or trees etc.  Therefore, the ambient light can vary.

Can a projector project outside in daylight?

Yes, a projector can project outside in daylight however, the resultant image will differ in quality depending on a large array of variables.

A projector projecting onto a surface within direct sunlight will likely result in an image completely washed out of color so therefore no text, colors or shapes will be discernible.

A high powered projector with a luminosity of 20,000 lumens should be able to project a washed out but viewable image outside, in daylight but with a large amount of shade covering the projector screen or surface.

That said, a low powered projector of 2000 lumens or below will be completely washed out as it wouldn’t be able to compete with the ambient light in the surrounding environment.

Given all of the above, it is no wonder that drive-in cinemas only show movies during dusk and nighttime hours.

Another way of improving your chances of successfully viewing your movie, TV show, or sports show outside is by using an Ambient Light Rejecting (ALR) screen.  These screens reduce the amount of ambient light reflected back to the viewer.

Ambient Light Rejecting (ALR) screens work by reflecting light back in the direction from which it came.  That means that a projector should be positioned perpendicular to the ALR screen with the audience in a similar viewpoint too.  This will result in the projected image being bounced back to the audience but the ambient light being bounced away as it is coming from a different angle.

If there is a lot of ambient light coming from the same direction as the projector itself, an ALR will not be effective.

Can a projector project inside a room in daylight?

Given that there is little to no chance of being able to view an image outside in daylight, it begs the question, can a projector project inside a room in daylight?  The answer to this is a definite yes.

This is because the ambient environmental light is far lower than outside, even in the shade, however, there are still variables at play here that will determine how well you can view any given projected image indoors within the daylight.

If the projector screen is close to an outside window, a projector with a luminosity of approximately 6000 lumens will probably be required to display the image.

Being able to move the projector screen away from the outdoor light source as well as any internal electrical light source will mean that a projector more in the range of 3000 lumens will be sufficient.

As long as there are no direct light sources other than the projector shining on the projector screen surface, a projector delivering 3000 lumens will be sufficient to view a crisp, colorful image.  Text, photos, and videos will be viewable with ease.

Another consideration to make is how far away the projector will be from the screen.  For example, lux is a measurement of lumens when applied to a surface area of 1 meter squared.  Therefore, the amount of lux will diminish for every additional 1 meter we apply the light source to.

We can all observe this effect for example by applying a torch to a surface and then slowly moving the torch away from the surface.  When the torch is close to the surface, the light appears bright (as the amount of lux is high) whereas when you move the torch further away, the light appears dimmer.  This is because the amount of lumens has remained the same but is spread over a wider area.  This results in a lower lux value.

Another consideration to make is what you are intending to project while indoors within the daylight.  For example, projecting a movie that may contain scenes that are in the night time will be harder to view due to the high amount of ambient light in the environment.

A projector projecting a pale PowerPoint presentation just containing text in a large font will be viewable in a much lighter situation.

Another way of improving your chances of successfully viewing your movie, TV show, or sports show inside is by using an Ambient Light Rejecting (ALR) screen.  These screens reduce the amount of ambient light reflected back to the viewer.

Ambient Light Rejecting (ALR) screens work by reflecting light back in the direction from which it came.  That means that a projector should be positioned perpendicular to the ALR screen with the audience in a similar viewpoint too.  This will result in the projected image being bounced back to the audience but the ambient light being bounced away as it is coming from a different angle.

If there is a lot of ambient light coming from the same direction as the projector itself, an ALR will not be effective.

Best practices for using projectors outdoors

To cut a long story short, the best way to obtain the best image from a projector outdoors in the daytime is by reducing the amount of competing light in the environment.  The other way is to increase the value of lux from the projector.

We will explore this below.

First of all, it doesn’t matter if your projector itself is located in the sun.  The sun shining on the projector and its beam of light will not diminish the overall luminosity of the resultant image.  The projector will still emit the same amount of lumens regardless.

What does need to be in the shade is the surface of the projector screen.  There isn’t a projector in existence that will be able to compete with the intensity of light, or lux applied to any surface, by the sun itself.  The sun will apply anywhere between 32,000 and 100,000 lux to a surface.

Place the projector screen in the shade with as wide a shady canopy around the surrounding area.  This will reduce the amount of ambient light that the projector is having to compete with.

Choose a projector capable of projecting as many lumens as possible.  Even a projector with 6000 lumens will likely struggle to compete with an outdoor environment on a sunny day.  A projector more in the region of 20,000 lumens would probably be required.

Next, choose an overcast day to watch your movie.   Cloud cover will reduce the ambient light levels quite significantly.

The position of the sun in the sky will also affect the ambient light levels too.  Essentially, try to watch your film or TV show during dusk or, better still, the night time.

Finally, try to position your projector as close to the screen as you possibly can without the image being too small.  This will increase the amount of lux as lux is the value of lumens applied to any given surface area.

As the amount of lumens is a constant i.e. 6000 lumens, if these 6000 lumens are spread over a 2 meter squared area, the resultant lux value will be lower than the same amount of lumens being applied to a smaller, 1 meter squared surface.

Conclusion

Attempting to use a projector in daylight is fraught with issues.  Projecting onto a surface that is bathed in direct sunlight is next to impossible given the capabilities of today’s projectors.  Being able to lower the ambient light levels outside is going to help but is still bound to be difficult.

Projecting indoors in daylight is much easier as you can control the ambient light levels much more.  For instance, you can reduce the amount of daylight by drawing the blinds or curtains.  You can also lower or remove artificial lighting by lowering the dimmer switch or switching off the lights altogether.

Essentially, for this to work lower the lux levels from competing light sources on the projector screen. 

Glossary

Flux – Flux, otherwise known as luminous flux is the measure of the power of light emitted from a source.  The SI unit of flux is known as a lumen.

Lumen – A lumen is the SI unit or numerical value given to the entire power of a light source at any given moment in time.

Lux – Lux is the SI unit for the total luminance of any given surface area.  For example, one lux is equal to the illumination of 1 meter squared when applied with a light source of 1 lumen.

Candela – Candela is the SI unit for the luminous intensity of a light radiated in a single direction.

Nit – Nit is the SI unit for the luminous intensity of a surface area in accordance with light emitted in a single direction.  For example, one nit is equal to the illumination of 1 meter squared when emitted from a light source of 1 candela in value.

Below are some example lux readings as stated on Wikipedia.  https://en.wikipedia.org/wiki/Lux

Moonless, overcast night sky= 0.0001 lux

Full moon on a clear night = 0.05–0.3  lux  

Family living room lights= 50 lux

Very dark overcast day = 100 lux

Office lighting = 320–500 lux

Sunrise or sunset on a clear day = 400 lux

Overcast day = 1000 lux

Full daylight = 10,000–25,000 lux

Direct sunlight = 32,000–100,000 lux