Lindsey Optics T-Stop Evaluation System

Cine lenses must be marked in T-Stops (Transmission Stops) and the accuracy of those marks is paramount.

Whether it is to validate aperture markings following the maintenance of a cine-lens or to measure and engrave the aperture values on a re-housed photographic lens that was originally marked by the manufacturer in f stops, a precise and easy-to-use T-Stop meter is required.

We have developed a new generation of T-Stop tester using recent technologies to make the professional's life easier by removing interpretation. Our T-Stop Evaluation system displays the T-Stop values directly on the screen without the need to convert from exposure values.

The system can be used immediately after power on, there is no warm-up period required. The system is calibrated each time it is turned on using the included Calibration Aperture. It can also be re-calibrated if needed.

The very bright LED light source is aimed up into an integration sphere where the light reflects off the walls of the sphere multiple times to produce a highly uniform source. The high brightness and extreme uniformity of the Integrating Sphere light source on our T-Stop Tester provides high precision at small lens apertures (large T-Stop values). The illumination is stable and will not vary over time.

The counter-weighted integration sphere is moved manually and can be locked in place during measurement.

The vertical configuration with 18 x20" baseboard conserves bench space.  All of the electronic components and display are on the baseboard, there's no external box to sit on the bench and consume more space.

The T-Stop Evaluation System is shipped with an LPL mount and our PL-to-LPL adapter to provide secure mounting of cine-lenses and repeatability of the measurements.

Available adapters to other lens mounts can be used to evaluate and validate T-Stop values. 

Acquisition Software:

Our T-Stop Evaluation System Acquisition Software is connected to the system via a USB port.  The software allows rapid data collection of marked T-Stop values from finished lenses.  It's designed to allow collection of data from closed to open and then from open to closed.  The difference between the measured values shows any lost motion in the iris mechanism.

Data can be exported to a spreadsheet in .csv comma separated format.

The data is still displayed on the system touchscreen when the Acquisition software is being used. 

Specifications:

Light Source

Color temperature approximately 6300K (Daylight)

Approximately 5500 lux @ T 1.0.

Counterweighted 300mm Integrating Sphere.

On/Off switch for the Integrating Sphere.

Electronics

4.3 inch Color Touchscreen interface.

Displays T-stop values directly. No conversion table needed.

Range: T1.0 to T22.0 by 1/6 stop increments.

Exposure value (EV) and illumination (lux) can be displayed.

Resolution – T-Value : 0.1

Resolution – EV : 0.1

Accuracy: +/- 0.05

Lens mount interface

Calibration Aperture included.

LPL mount and PL-to-LPL adapter included.

RED Monstro camera interface used.

Panavision SP70 mount available (option).

Metal PL and LPL Lens Caps are included.

Dimensions

Overall dimensions (W x D x H): 458 mm x 508 mm x 860 mm

Overall dimensions (W x D x H): 18 in x 20 in x 34 in

System mass: 16 kg (36lbs)

Maximum lens length: 650 mm from PL flange (longer lenses available upon request).

Maximum lens front diameter: 136mm.

Mechanical opening of sphere aperture: 138mm.

AC Power Input: 100V-240V ~ 1.6A 50-60Hz

Subject to change.