Что такое формат файла LDT?
A .ldt file contains photometric data. .ldt files are generally created and supplied by lighting product manufacturers. Each file stores data for a given luminaire, for example:
- light distribution curve,
- luminous intensity,
- physical dimensions of the luminaire,
- lamp and ballast parameters.
.ldt files are used by specialized lighting installation design software such as DIALux evo and Relux Desktop to simulate how a fitting will illuminate a space before installation.
.ldt is a plain ASCII text file following the EULUMDAT specification - a de-facto European standard for luminaire photometric data exchange, proposed by Axel Stockmar (Light Consult Inc., Berlin) in 1990. Unlike the North American .IES format, which opens with a version keyword, EULUMDAT has no file signature: every line has a fixed positional role, and intensity values are stored in candela per 1000 lumens (cd/klm).
Безопасность и защита
РИСК: LOWAn LDT file is plain ASCII text with no executable code, so it is safe to open and cannot carry malware in any meaningful way. The only practical caution is sourcing: download LDT files from the fixture manufacturer or a reputable photometric library so your lighting calculations are based on real measured data rather than an edited or fabricated file.
Детали формата
в двух словахПОЛНОЕ НАЗВАНИЕEULUMDAT Photometric Data Fileтакже известен как EULUMDAT file, LDT light file
РАЗРАБОТЧИКAxel Stockmar (Light Consult Inc., Berlin) - de-facto European industry standard, 1990с 1990 (EULUMDAT, proposed by Axel Stockmar as a European luminaire data exchange format)
КАТЕГОРИЯФайлы данных
MIME-ТИПtext/plain
ТИПPhotometric (luminous-intensity distribution) data; plain ASCII text with fixed line order
СТАНДАРТОткрытый · без роялти
Это расширение также используется в…
- ZEMAX Source EULUMDAT object data - ZEMAX OpticStudio can read EULUMDAT (.ldt) as a non-sequential source's photometry, which is why the database mislabeled the format as a 'ZEMAX source file'.
Программы, открывающие файлы LDT
Windows5 apps
EulumdatTools
Бесплатно Web/desktop EULUMDAT viewer and editor; inspect and edit .ldt fields. Verify the site is live before relying on it. 
Dialux evo
Бесплатно Import the LDT via the luminaire catalogue / 'import luminaire' to run lighting calculations. Free professional lighting-design tool.
Relux Desktop
Бесплатно Import the EULUMDAT file as a luminaire to compute illuminance, glare and energy. Free Swiss lighting-design suite.
IESviewer (Andrey Legotin)
Freemium Open the LDT to visualise its polar / 3D light distribution and read parameters; also converts between EULUMDAT and IES. 
macOS2 apps
Blender
Открытый код Blender's IES texture node reads photometric data; for EULUMDAT convert to .ies first (IESviewer), then load it on a light.
Relux Desktop
Бесплатно Import the EULUMDAT file as a luminaire to compute illuminance, glare and energy. Free Swiss lighting-design suite. 
Linux1 app
Text editor (any)
Встроенная Open the .ldt as plain text to read the EULUMDAT fields; for use as a light, convert to .ies and load it in Blender.
Web1 app
IES/LDT online viewer (ieslibrary.com)
Бесплатно Upload the .ldt to view its polar / 3D light distribution in the browser and download an IES copy. Технические подробности
глубокая спецификация| File encoding | ASCII (7-bit) plain text; CR/LF line endings required by most parsers |
| File structure | Strictly positional line sequence - no field labels or tags; every line's meaning is determined by its position in the file |
| MIME type | text/plain |
| File signature | No magic bytes; the first line is the manufacturer identification string (Ident), typically the company name |
| Intensity unit | Candela per 1000 lumens (cd/klm); parsers scale to actual lamp lumens at calculation time |
| C-plane (horizontal) angles | Count declared by the `Mc` field; step angle `Dc` in degrees; full distribution typically covers 0°-360° in 5° or 10° increments |
| G (vertical) angles | Count declared by the `Ng` field; step angle `Dg` in degrees; spans 0° (nadir) to 90° or 180° depending on luminaire type |
| Symmetry code (Isym) | `Isym` 0 = no symmetry; 1 = rotational; 2 = symmetric about C0-C180 plane; 3 = C90-C270; 4 = quadrant - reduces stored data for symmetric fittings |
| Luminaire type (Itype) | `Itype` 1 = point source; 2 = linear; 3 = rectangular area source - determines how software models near-field luminance |
| Physical dimensions | Luminaire length, width, and height stored in millimetres in dedicated positional fields |
| Lamp and ballast block | Records number of lamps, nominal luminous flux per lamp, colour temperature, wattage, and a free-text ballast description line |
| Tilt correction | Optional section storing tilt angle and per-angle correction factors for luminaires mounted at non-horizontal positions |
| Data integrity | No checksum; the declared `Mc` and `Ng` counts must exactly match the number of data rows present, or parsers reject the file |
| Typical file size | 2 KB - 150 KB, scaling with the number of C-planes and G-angle measurements |
| Выпущен | 1990 (EULUMDAT, proposed by Axel Stockmar as a European luminaire data exchange format) |
| Последняя версия | EULUMDAT (single revision; an unofficial 'EULUMDAT/2' extension exists but is rarely used) |
| Открыть стандартное | Да · без роялти |
| Спецификация | en.wikipedia.org |
Конвертации LDT
Возможно
.LDT .IESРУКОВОДСТВО
Да - загрузите файл LDT в IESviewer (бесплатно) и экспортируйте его как файл IES за считанные секунды.
Как конвертировать
.LDT .JPGРУКОВОДСТВО
Вы не можете конвертировать фотометрические данные в фотографию, но можете получить JPG диаграммы…
Как конвертировать
.LDT .PDFРУКОВОДСТВО
Да, вы можете создать PDF из файла LDT - откройте его в DIALux, Relux или IESviewer, создайте фотометрический…
Как конвертировать
.LDT .LDCРУКОВОДСТВО
Конвертация LDT в LDC возможна через IESviewer, хотя она редко требуется, так как большинство программ для…
Как конвертировать
Вопросы и ответы сообщества
спрошено пользователямиВопросов пока нет - станьте первым, кто спросит о файлах LDT.
Часто задаваемые вопросы
What is an LDT file?
It is a EULUMDAT photometric data file - plain text that describes how one light fixture distributes its intensity in every direction. It is the European equivalent of the American IES (.ies) file, used in lighting design and 3D rendering.
How do I open an LDT file?
To just read it, any text editor works (it's plain text). To see the light distribution, use a free viewer like IESviewer or an online photometric viewer. To use it, import it as a luminaire into DIALux, Relux, AGi32 or a renderer.
What's the difference between LDT and IES?
Both store the same kind of photometric data. LDT (EULUMDAT) is the European standard; IES (ANSI/IES LM-63) is the North American one. Most professional lighting tools read both, and converters move data between them.
How do I convert LDT to IES?
Use a free tool like IESviewer or an online photometric converter - it reads the EULUMDAT file and writes an equivalent IES file (the physical data is the same, only the layout differs).
Where do I get LDT files?
Fixture manufacturers (especially European ones) publish them on product pages, and free libraries host thousands. Always prefer the manufacturer's own file for accurate calculations.
Can I edit an LDT file?
Yes - it's plain ASCII you can open in Notepad++/TextEdit, but EULUMDAT is strictly positional: keep the declared C-plane and angle counts consistent with the data rows or parsers will reject the file. A EULUMDAT editor (IESviewer/EulumdatTools) is safer.
Ссылки
1Wikipedia - EULUMDAT photometric data formaten.wikipedia.org
2DIALux - free lighting design software (reads EULUMDAT/IES)www.dialux.com
