TOOLS
Фотометрическая программа просмотра IES/LDT
See how a light distributes its output. Compare files side by side and save the results.
Your files
Drag IES or LDT files here
Up to 4 files · 5 MiB each · Files stay on your device. No upload. No sign-in.
Illustrative samples only. These are synthetic distributions, not product measurements.
Supported formats: IES LM-63, LDT EULUMDAT. Open the file list below to see basic header values.
Understanding photometry
A photometric file (IES or LDT) describes how much light a luminaire sends in each direction. The candela distribution lets you predict illuminance on any surface before you install anything. Reading it comes down to three ideas: luminous flux (total light), luminous intensity (light per direction) and the beam shape that emerges from the intensity curve.
Illuminance (lx) = intensity (cd) ÷ distance² (m²) · Luminous efficacy (lm/W) = flux ÷ input power
Candela vs lumens
Candela (cd) is intensity in one direction; lumens (lm) is the total light emitted in all directions. The polar curve plots cd against angle – 0° straight down, 180° straight up.
C-planes
C0–C180 and C90–C270 are two vertical planes through the fixture. Comparing both reveals if the beam is symmetric or tilted.
Beam and field angle
Beam angle is the full width where intensity stays at or above 50% of the plane’s peak. Field angle is the 10% width. A narrow beam throws light far; a wide beam floods an area evenly.
Efficacy
Flux divided by input power gives lm/W. It tells you how efficiently the fixture turns electricity into light – a key number when comparing products.
Example at 30°: focused 787.5 cd, wide 562.9 cd – the focused beam keeps more intensity near centre, the wide beam spreads it.
Light distribution
Inspect vertical angle 30°
A C0/C180: 787.5 / 787.5 cd · C90/C270: 743.5 / 743.5 cd
Compare the files
Photometric quantities for the visible files. Values describe the complete tested source.
| Параметр | А | Б |
|---|
An offline copy includes your files and view settings. Send it to a colleague to open the same comparison.
Good to know
Should I compare intensity or shape?
Intensity in candela shows absolute output at each angle and is the fair scale when two products run similar powers. Shape in percent normalises each file to its own peak, which isolates the beam pattern from overall brightness.
Are the lumens and watts for one metre of LED strip?
Yes – LED strip photometry is always per metre. The luminous flux, input power and efficacy values describe the tested length, so compare products at the same length.
Why can source lumens differ from calculated output?
The IES/LDT file stores the source flux from integration of the candela curve. The delivered lumens of the strip itself can differ because of temperature, binning and how the value was measured. Always ask the manufacturer how a number was obtained.
Can this tell me if a room is bright enough?
Not by itself. It shows the distribution of one fixture. Room brightness also depends on the number of fixtures, mounting height and reflectances. Use this with a layout or a lighting calculation.
How do I send this comparison to someone?
Use Save offline copy to keep the files and view settings together, Export CSV for a spreadsheet summary, or Save chart for a shareable image of the curves.
How are results calculated, and what is checked?
Flux comes from the candela curve, efficacy is flux ÷ power, and beam/field angles are measured at 50% and 10% of the plane peak. Values are marked “–” when a number is unavailable or there is no single bounded lobe.
Tell us the model, tested length, power and CCT you need.
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