What's the difference between ONEs and TWOs ?

Differences between MetroLux (1) and MetroLux II

I'm asked frequently the difference between the MetroLux ONEs and TWOs.  They do the same thing with equal precision.  TWOs have a few nice extras.

The below assumes that you know the general use and function of MetroLux (generically called an integrator, integrating timer, closed-loop timer, and others)  It monitors the light output of your printing lamp (cold light, LED, the sun) while you print and adjusts the time to get the print's exposure the same every time.  It's auto-exposure for your enlarger.  Cold lights drift considerably as they change temperature.  LEDs can be pretty good, but even they can vary, plus it depends on how they are driven.  The sun (platinum printers) has clouds and haze.

Here are the 6 front panel control buttons.  The description is the top level function.  All the buttons can have secondary functions that control niceties and calibration.  Don't be scared, it's simple.

FOCUS turns the enlarger lamp on/off.
UP/DOWN sets the time.
START (or EXPOSE) initiates the timed exposure.
UNITS (or SETUP) chooses between conventional time (seconds) and lux (counting photons).
MEMORY selects the memory that you are using

ONE is a basic machine.  Making adjustments to sound, brightness, that sort of thing, is awkward.  It can be done, but it is weird and unnecessary.  Just live with the standard setting.

TWO is a 'tricked-out' machine, before that expression existed.  Even today, I don't think I'd make a serious change to the design.  It is easy to operate without going back to school.

Feature                                ONE                   TWO

Closed-loop timer                 yes                      yes
LED display                          yes                      yes
Positive click buttons            yes                      yes
Accept footswitch                 yes, START        yes, FOCUS and EXPOSE
Shutter speed timer               NO                      yes
Time or Lux exposures         yes                      yes
Percent control                      yes                      yes
auto calibration                     NO                       yes
calibration 'channels'             2                           2
'time' memories                     3+1                    3 channels of 3+1
Accounts for decay light       NO                     yes

So, what are the NOs?

Shutter speed timer is exactly that.  There is a sensor on the front panel that will measure the speed of your leaf shutters handily.  I love this.  I check all my shutters every few years and when they are too far off for me, I send them out for CLA.

Auto calibration.  The first time you set up your enlarger with a coldlight, this is a nice feature, but it is not the do-all, end-all by any means.  You should still review the numbers and maybe make adjustments.  If you are using any light source besides cold light, then the auto-cal doesn't do really matter.  Not a deal breaker.

Delay light.  (this is the light that comes from a coldlight, tungsten, or quartz lamp after the electricity quits flowing.  It isn't much, but in test strips, it adds up.  If you exposures are short or you light your test strips to be exact, then this is a wonderful feature.  I really like this one as some of my high-key prints require exact exposures.

Memories.  The TWOs have 3 times more.  If you are using the timer for two different enlargers or whatever/however else you might find to use all those memories, then it is nice.  During normal printing I find the 3 times to be fine; one for the main exposure, one for a test strip exposure, and another for a burn or a bump.  The +1 is the percent with a range from 50% to 200% that applies to all the times in that channel.  You can use the percent for dry-down or as a means to achieve shorter or longer exposures, etc.

As you can see, they are about the same.  I have two TWOs in my darkroom.  I like the TWOs a little better.  Easier to change the beep tone or loudness or duration.  The other thing I like about the TWOs is that you can set the times by either 1/10s, 1/2s, 1s, or 10s.  It still counts down the same, but in the setting of the times, sometimes you just don't need to be thinking in 1/10 second when 1/2 second is fine.

The TWOs were designed to accept a remote sensor, but these are no longer available.  The TWOs chassis box easily hangs on the wall or can be propped up with a little piece of wood that you supply.