What is Diffused Light in Greenhouse Film?
- 3 hours ago
- 4 min read
Why High Diffusion Doesn't Mean Lower Transmission.
Understanding Light Diffusion
When choosing greenhouse film, one of the most misunderstood terms is light diffusion.
Many growers believe that a greenhouse film with a whiter or more “milky” appearance must block more sunlight. Others assume that the higher the diffusion, the lower the light transmission.
Neither assumption is necessarily correct.
In reality, light transmission and light diffusion measure two completely different properties of greenhouse film.
Understanding the difference is one of the keys to choosing the right film for your greenhouse.
The Science
Light Transmission.
Light transmission simply measures how much sunlight passes through the greenhouse film.
For example, if a greenhouse film has a light transmission of 90%, approximately 90% of the available sunlight enters the greenhouse.
It tells us how much light gets through.
Light Diffusion
Light diffusion measures how evenly that transmitted light is distributed after passing through the film.
Rather than travelling in a single direction, diffused light is scattered into many different directions. The total amount of light may remain very similar, but the way the light reaches the crop changes dramatically.
In simple terms:
Light Transmission = How much light enters
Light Diffusion = How the light is distributed
These two characteristics work together, but they are not the same.
Why Does Diffused Light Matter?
Imagine shining a torch through a completely clear sheet of plastic. Most of the light continues in the same direction, creating a concentrated beam. This produces bright hotspots where a large amount of light energy is focused onto a relatively small area.
Now imagine shining the same torch through a high-quality diffused greenhouse film.
The same amount of light still passes through the film, but instead of remaining concentrated, it spreads across a much wider area. The light becomes softer, more even and reaches more of the crop canopy.
The amount of light has not changed, only the direction of the light has changed.
This is the true purpose of diffusion.
Common Misconceptions
“A More Milky Film Means Better Diffusion”
Not necessarily.
Many people judge greenhouse film simply by appearance. A film that looks cloudier is often assumed to have better diffusion performance. However, visual haze and optical diffusion are not the same thing.
A poorly designed film may appear cloudy because it reduces clarity, while providing little improvement in light distribution. True optical diffusion is achieved through carefully engineered additives that scatter sunlight efficiently while maintaining high overall light transmission.
In other words:
A cloudier-looking film is not automatically a better diffused film.
“Higher Diffusion Means Less Light”
This is another common misconception.
High-quality diffused greenhouse films are designed to redistribute sunlight, not block it. Their purpose is to improve light uniformity while maintaining excellent light transmission.
Good diffusion changes where the light goes, not necessarily how much light enters.
Real World Example
To better demonstrate the difference, we compared two greenhouse films using the same green laser source under identical testing conditions.
The purpose of this demonstration is not to measure light transmission, but to visualise how each film redistributes incoming light.
What we observe:
The light spreads across a much larger area.
No strong central hotspot is visible.
The energy is distributed more evenly.
What we observe:
Most of the light remains concentrated in the centre.
A bright hotspot is still clearly visible.
Light redistribution is less effective.
What This Means:
Although both films allow the laser to pass through, the way the light is distributed is significantly different. This simple demonstration helps illustrate one of the key principles of greenhouse film performance:
High-quality diffusion doesn’t reduce sunlight, it redistributes it.
Or, more simply:
Diffusion changes the direction of light, not the amount of light.
Why This Matters for Australian Growers
Australia experiences some of the highest solar radiation levels in the world.
During summer, excessive light intensity can increase leaf temperature and create localised hotspots within the crop canopy.
A well-designed diffused greenhouse film can help by:
Creating a more uniform light environment
Reducing concentrated hotspots
Lowering the risk of leaf scorch and sunburn
Improving light penetration into the lower canopy
Supporting more even crop growth
Improving crop consistency across the greenhouse
While every crop and growing region is different, improving light distribution can be an important part of greenhouse climate management.
Frequently Asked Questions
Does higher diffusion reduce light transmission?
Not necessarily.
A high-quality diffused greenhouse film is engineered to redistribute sunlight while maintaining high overall light transmission. The objective is to improve light uniformity rather than reduce the amount of usable light entering the greenhouse.
Why does one diffused film look whiter than another?
The appearance of a greenhouse film does not always reflect its optical performance.
Some films appear cloudy because of reduced clarity, while others achieve effective diffusion through advanced optical additives without unnecessarily sacrificing transmission.
Is the highest diffusion always the best choice?
Not always.
The ideal diffusion level depends on the crop, greenhouse design, local climate and production goals.
Selecting the right greenhouse film should involve considering transmission, diffusion, durability and the specific growing environment together.
Aus Crop Cover Insight
At Aus Crop Cover, we believe choosing greenhouse film should be based on understanding how light behaves, not simply comparing specifications or judging the appearance of the film.
Our goal is to help Australian growers make informed decisions by explaining the science behind greenhouse materials and how they perform under real Australian conditions.
Because successful crop production isn’t just about how much light enters the greenhouse.
It’s about how effectively that light reaches every plant.
If you would like to learn more or find out pricing, please feel free to contact our friendly team!
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