Tuesday, January 5, 2010

Meter Sub-Ranging and Its Effects

The Pocket Spot Light Meter sub-ranges between 5 and 6 EV. This means that at less than about 6 EV, the meter changes from 1 degree to 3 degree reading. (To judge 3 degrees is the same as 1 degree, but use the thickness of the case. Remember that the actual spot is mostly square, not round as the site implies.)

To optimize meter sensitivity over the widest range, the Pocket Spot Light Meter subranges in two places: at the low end and the high end. For various reasons, the high end sub-ranging is not an issue and will probably never be noticed. But because we photographers are so interested in the shadows, there are times when the EV 5 to 6 range is very important. It is in this range that the meter sub-ranges, i.e. it changes from 1 degree to 3 degrees to gather more light.

So, what happens if the one degree shadow is surrounded by something slightly brighter and the meter sub-ranges? If it isn't that much brighter, the meter will meter the 3 degrees and that is that, but if it is several stops brighter, it will go between 1 degree and 3 degrees displaying a reading that oscillates between the brightness of the 1 degree and the 3 degree. This can be confusing, but knowing what the meter is doing can clarify the reading.

4 comments:

Stephen Schaub said...

This is very good info to know...

suspire said...

Do you guys have these in stock?

Unknown said...
This comment has been removed by the author.
Unknown said...
This comment has been removed by the author.

Pocket Spot

Pocket Spot
Metering in the Office, 10 2/3 EVs

Pocket Spot

Pocket Spot
Metering in the Office, 4 1/3 EVs

Pocket Spot Spec Sheet

Pocket Spot Digital Light Meter Specs

Display: 2-digit Red LED with 1/3, 2/3 LED indicators

Dial: White, laser-engraved on Meter's anodized color background. Intermost dial is ISO with f/# on the outside. f/1.0 to f/128. Outer dial is shutter speeds from 8 minutes to 1/4000 sec on the inside and EV on the outside. EVs from -1 to 20. Body is marked with Zones from Zero to X (10). [Romans didn't have a zero, but what are you going to do? ]

ISO: 3 to 12800 ISO, marked in 1/3 stops

EV range: -1 2/3 to 23 at 100 ISO

Spectral Sensitivity: Compensated for "typical" B&W film, i.e. HP5+ or Tri-X

Angle of View: approximately 1 degree, smaller at very high EVs and 3 degrees at lower EVs

Viewing: Bore-sight through the hole the length of the chassis. Meter is held about 12" or 300mm from the eye (length of strap)

Linearity: about 1% from low to high.

Calibration: Not required. No adjustments inside.

Finish: Black anodized over a solid block of machined aluminum. Texture is random tumble over stones before anodize. Other colors in consideration at extra cost are RED and BLUE.

Battery: 6V PX28 or equivalent, Supplied

Dimensions: 2.25" x 2" x 3/4" (L x W x T) 57 x 50 x 19 mm
Dial on top is 1/8" thick, 3 mm

Weight: 4 1/8 oz (117 grams) with strap and battery, both included.


specifications subject to change

More pictures on page two near bottom.