Konica Minolta LS-150 Luminance Photometer

Konica Minolta LS-150 Overview

The portable LS-150 employs a silicon photocell that is spectrally matched to the CIE V(λ) photopic observer function. The single lens reflex (SLR) optical design allows the operator to conveniently view a display or light source through the eyepiece and then focus and align a central black measurement spot within the target object. The LS-150 features a fixed 1° measurement field-of-view that corresponds to a minimum measurement spot size of 14.4mm at the minimum working distance of 1012mm. The LS-150 reports luminance in units of candelas per square meter (cd/m²), or in imperial units of foot Lamberts (fL).

Measurement Range & Accuracy

The LS-150 provides luminance measurements over the range from 0.001 to 999,900 cd/m². As a point of reference, the brightness of a typical flat panel display (LCD) will be about 500 cd/m². The silicon photocell is spectrally filtered to match the CIE V(λ) photopic observer function and satisfies the criteria for a class B photometer per DIN 5032 part 7.

Measurement Spot Size

Luminance meters are often referred to as “spot photometers” due to the fact that the measurement of luminance is made from a defined spot or area on a light source or display. When making luminance measurements it is vital that the measurement spot (as denoted by the central black spot viewed through the eyepiece) is located well within the target area on the object. If the measurement spot only just fits within the lit area, or overlaps any of the surrounding unlit area, the resultant luminance measurement will be erroneous, possibly to a significant degree.

As standard, the LS-150 has a minimum measurement spot of 14.4mm diameter at a working distance of 1012mm. Four accessory close-up lenses are available that attach to the input to the LS-150 and result in smaller measurement spot sizes (down to 1.3mm diameter). For even smaller measurement spot sizes, consider the related LS-160 photometer that features a 1/3° field-of-view.

Low Flare SLR Optics

The LS-150 employs flare-less SLR optics for the highest possible accuracy. The degree to which light outside of the defined measurement field-of-view can influence the measurement is an important factor in the design of luminance meters. In the design of the LS-150, Konica Minolta kept the lens flare factor below 1.5%. So even if there is a very high luminance object just outside the LS-150’s 1° field-of-view, it will not contribute to the readings.

Other Important Information

Basic operation of the LS-150 gives you readings of the target object’s luminance in cd/m² (or you can select foot Lamberts if you prefer). Advanced operation allows you to hold a reference reading in memory and compute a luminance ratio for the currently measured luminance. You may also enter a colour correction factor specific to the type of light source under test. The LS-150 features an LCD display located on the side of the main body, while a secondary display illuminates within the eyepiece field-of-view after the measurement trigger has been pressed and once a measurement has been recorded. The LS-160 operates from two AA-sized batteries, while an AC mains adaptor is optional.

The LS-150 is available with several useful options. You can convert the measurement mode from spot luminance to illuminance (units of lux) using the model CS-A15 illuminance adaptor. For remote measurements, the CS-A14 C-mount lens adaptor can be attached to the LS-150 eyepiece. This allows a commercially available CCD camera to be attached to the luminance meter.