SKU: RHSCV Category:

Product videos on all the RH units are on the RH Designs YouTube channel.

Two Channel Compensating Enlarger Timer with light sensor,
dry-down compensation, 1/24 stop resolution
and enhanced Split Grade mode

Based on the StopClock Professional this Vario version incorporates a light monitoring system which can compensate for variations in the enlarger’s light output during an exposure. Cold light (or cold cathode) enlargers use one or more fluorescent tubes rather than incandescent bulbs as a light source. As these tubes warm up their light output increases, sometimes very significantly, and this can lead to difficulties in matching the final print to the test strip and inconsistencies between prints made at the same nominal exposure. The StopClock Vario’s light sensor measures the light level continuously and if it increases, the timer speeds up to shorten the exposure time. If the light level decreases, the timer slows down. This maintains the total volume of light, and hence the exposure of the paper, constant. Result – predictable prints!

Two versions are available. For Zone VI cold lights which have a light sensor factory fitted, a connecting cable is included. For other cold lights which don’t have a sensor, we provide a light sensor and cable assembly which you can fit to your lamphouse yourself – full instructions and a fitting kit are included.

The Vario incorporates all the features of the standard Professional model with the exception that it cannot be connected to a ZoneMaster II exposure meter. You can of course use the meter separately and transfer the time manually but please read the note below.

If the light sensor is disconnected, the Vario behaves just like a standard StopClock Professional, meaning that if you have a second enlarger using a standard light source, you can use the Vario with that as well.

StopClock Vario Features

  • Base exposure time 1.0 seconds to 240 seconds, in steps of 1/24th to 1/2 f-stop (or of 0.1 or 1.0 seconds in linear time mode). Time is controlled to 0.01 seconds.
  • Enlarger light monitoring system adjusts the exposure time automatically to compensate for variations in enlarger light output.
  • All exposure times are set in coarse and fine steps. The fine step size is 1/24th f-stop (approx 2%). The coarse step size can be set to 1/2, 1/3, 1/4, 1/6 or 1/12 of a f-stop. Coarse/fine button toggles between 1/24th and the set coarse time step.
  • Nine subsequent exposure times can be programmed, each calculated either relative to the base exposure or the total exposure time thus far. Burn-in exposures are set in steps of 1/12th to 1/2 f-stop. If the base exposure changes, the burn-in exposures are recalculated to maintain the density relationships.
  • Two completely independent channels, each having separate base and burn-in exposure times.
  • Split-grade mode, in which exposure can be controlled using one channel while the second can be used to adjust contrast. Equivalent contrast is displayed in steps of 0.1 grade.
  • Automatic test strip mode, for quickly producing test strips with 1/12th to 1/2 stop increments either as an incremental exposure or separate complete exposures.
  • Exposure Compensation of +/-20% to allow for dry-down or and/or toning with respect to a test print.
  • The clear yellow LED display brightness can be set to one of three levels. The display colour has been chosen to be safe for both colour and black and white printing.
  • Audible beep at the end of each exposure, and optional seconds tick whilst the enlarger is switched on.
  • Rugged steel enclosure and high quality components for reliability. Illuminated control buttons.
  • Automatic safelight switching; manual (focus) mode; 750 watts (500 watts in 115v versions) switching capacity
  • A footswitch is available as an optional extra for hands-free operation – see the accessories page.
  • Exceptionally easy to use! All timing, including switching between channels, can be controlled from the foot switch.

StopClock Vario Specification

  • Timing accuracy: Better than 1%
  • Timing repeatability: Better than 0.1%
  • Exposure setting accuracy: Better than 1%; resolution 1/24th stop.
  • Timing range: 1.0 to 240 seconds per step, up to ten steps per channel, two channels.
  • Timing resolution: 0.01 sec.
  • Switching capacity: 750W per outlet, 750W total (230V only; 500W total for 115V version.). Designed especially for cold light enlargers.
  • Display type: Yellow LED, three levels of dimming, 590nm LEDs are safe for colour papers (Safe except for direct exposure – dimmer than the filtration control lighting on most enlargers).
  • Size: WHD 200mm x 65mm x 160mm (7.8 x 2.5 x 6.3 inches)
  • Weight: 2200g approx as shipped.
  • Input voltage: 200-250V AC 50Hz (100-125V 50/60Hz optional)
  • Accessories supplied: Mains lead, enlarger/safelight connectors, instructions.
  • Full two year guarantee, plus 14 day refund if you are not completely satisfied.

Note on the use of exposure meters

Because any changes in light level are compensated for during exposure only, small errors may occur when using an exposure meter with an enlarger controlled by a compensating timer. For best results ensure the enlarger is well warmed up and ensure that the exposure is made as quickly as possible after the measurements are taken.

Enlarger Type

Zone VI 220v, Zone VI 110v, Other Makes 220v, Other makes 110V