SKU: RHSCP-1 Category:

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

Two channel f-stop enlarger timer with dry-down compensation, 1/24th stop resolution and enhanced split-grade mode.

Easy to use if you’re beginning yet versatile and powerful enough for professional printers, the legendary StopClock Professional really will save you time and paper. Using our F-Stop exposure system in conjunction with a built-in automatic test strip generator and ten exposure memories per channel, you can set up a complete printing sequence quickly and easily, often with reference to just a single test strip! Once the paper’s on the easel and the lights are switched off, making the print becomes a simple matter of pressing the start button and shading the relevant areas of the print. No times to remember, no fiddling with timer settings in the dark. The two channels make split-grade printing a breeze, and there’s even a special mode which effectively allows the exposure and contrast of variable contrast paper to be controlled separately. And if the base exposure is changed, the StopClock recalculates all the burn-in exposures to maintain the correct density relationships! A special compensation mode alters exposure times to allow for the effects of “dry-down”, the change in apparent print brightness as the paper dries. It can also be used to compensate for the effects of toning.

StopClock Professional 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.
  • All exposure times are set in coarse and fine steps of actual exposure rather than simple seconds, producing consistent changes on the paper. 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 is changed, 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 exposures 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.
  • Can be connected to our ZoneMaster for exposure metering.
  • 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 footswitch.

Video Presentations

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

Please note that the flickering visible on the display in these videos is a result of the recording process and is NOT representative of the product – the display looks steady to the eye.

StopClock Professional 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.). Suitable for cold light enlargers.
  • Display type: Yellow LED, three levels of dimming, 590nm LEDs are safe for colour as well as b+w 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.

Please Note: The StopClock Professional is designed to control enlargers in which the lamp can be switched on and off simply by applying mains power – this covers the great majority of enlargers but excludes some which have closed-loop control systems such as the Durst Autocolor, Fujimoto, etc.

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