I use an F-Stop timer and I feel that I would be unable to work without one now. To be able to exposed test strips at fixed stops and then select the best one for your main print is a joy. Any burning in or holding back will be fractions of your chosen time. This carries through should you wish to make a larger or smaller version of your original print. All you have to do is establish the main exposure and everything else drops into place.
I started out on this form of printing by using rounded up exposures from Gene Nocon's chart. From there several years later, I invested in a F-Stop timer and never looked back.
To print in any other fashion in my opinion truly leaves you in the darkroom.
Vincent brings up a good point which is the basic reason for using F/stop printing. The human eye can see shifts in tonal values in approximately 1/4 stop increments. So, when doing test prints of test strips, exposing by f/stops gives a reliable and repeatable increment that corresponds with what the eye can detect.
Once you get the exposure nailed down to the nearest 1/4 stop, you can fiddle with it even more. I seldom see the need for further refinement, but sometimes there is and others will and often do.
Dodging/burning, split-grade printing, changing print size, all greatly facilitated using the F/stop exposure method.
I use a calculator. For each range of paper grade there will be a deta-exposure that produces an image that is 'just a little brigher' or 'just a little darker' to my eye. So in my case I have tested to find that at the low contrast end the multiplier is 1.4 and at the high contrast range it is 1.1, and around 1.3 for the mid range.
Likewise if a f-stop timer is used, the 'stop-value' needed for a given degree of change will be different depending on end of the contrast range you are using, so an f-stop timer its not necessarily a panacea. Ideally I would like to have a "D-stop" timer. DENSITY-stop, which would be programmed to produce a uniform density change per increment, depending on which contrast grade I am using.
I feel the same. Of course, I could print without one, but after using an f-stop timer, I would never want to do without.
Originally Posted by TEX
There are many threads on this topic. Search Darkroom Automation F-stop timer and RH Designs Stopclock timer.
I have the latter and consider it indispensable. Someone gave a link to its manual which can be a bit challenging until you have a timer in hand and start using it. I have the same feeling for the DA timer's manual which I have read also.
With a regular timer, you typically use 3s or 5s test strips which are fine except that the zone difference between each strip decreases the exposure time increases. With an f-stop timer, the zone difference between each stop is the same. I set mine for 1/6 stop difference between each step. The time has a test strip mode so I keep adding as many 1/6 stop strips as I want. Now I tend to see the print tones in stops and that make dodging and burning more intuitive.
For burning, the timer has numerous memories so you an easily program many steps for burns. It is easy for me to make a print with half a dozen burns of various times without having to remember seconds. On my printing notes, I include the base exposure and each burn is in stops, e.g. +1/6, +11/6. For the +11/6 burn, I just push the program button to enter "Program 1" and then punch the up button 11 times.
The timer has two channels so it works great for split grade printing. It has a function to tie the two channels together so that if you adjust the base exposure in one channel, it adjusts the exposures on the other channel as well to maintain the same contrast grade (I don't use that one).
It has a drydown mode so that you can program in a drydown percentage when you are ready to expose final prints. You click the "Compensate" button and it automatically reduces the programmed exposure times by the drydown percentage.
I believe it has a metronome function built in but I don't use that either. While I appreciate the simplicity of a metronome, I don't have the attention to count to 38, then 7, then 12, then 22, etc.
Some of the timers are compatible with exposure and contrast meters.
Mine has a probe that can be fitted to a cold light to adjust the timer to any variations in light output.
Even if you like a very low tech darkroom, you will appreciate an f-stop timer because its technology truly simplifies the process once you get the hang of it.
Regarding the use of the metronome, Michael Smith and Paul Chamlee of Azo/Amidol fame usually use nothing other than the metronome. To see Michael print is fun....the "printing light" is never off...cardboard over the paper until the exposure is made, then the cardboard is off while the metronome beats.... Michael "dances" about listening to the beats until the exposure is over, cardboard flips back over the printing frame. Burns and dodges are also done with the metronome....the cardboard comes off, the burn is done for a few beats ( seconds of course ) the cardboard goes over the printing frame again while the "printing light" stays on. Not having to turn off the light source makes the workflow faster. Obviously such an approach would be difficult with conventional silver enlarging printing....but now that I think of it though, I wonder.
By the way, I use the DA timer....great. I am sure the RH timer is great as well.
I'll bet a case of beer you wouldn't like such a timer if indeed you had one.
Originally Posted by ic-racer
A little bit of time perusing a step tablet will tell the tale: look a the difference between 0.1 OD and 0.2 OD, now look at the difference between 1.8 OD and 1.9 OD - it's just not the same visual difference although it is the same same density difference.
Now, if you had this "D-Stop feature" in a timer you would have to tell the timer just where you wanted the density incremented. The same density increment takes a different time increment depending where on the HD curve you are sitting. And of course, it varies again with the paper and the developing and toning.
I find, in my printing, that a grey scale 'step tablet' made at around 10 equal stop intervals from white to black (ie, the zone system tones for the paper and developer I am using) is a very useful thing to have at hand when deciding on print exposure. It also shows me what will happen to the highlights if I move the shadow tones and gives a quick indication of how much to burn and dodge. With the meter and timer the strip lets me make close to perfect prints on the first try without any test strips - the scale makes it much easier to see what I am asking for, because, unfortunately, the system gives me what I ask for and not what I want.
I think making zone-system/grey-scale 'step tablet' should be the first lesson in darkroom printing. Takes only a half hour to make, prevents a lifetime of pulled-out hair loss.
I have the RH Designs Analyser for my Ilford head. While it doesn't have a uniform density adjustment, it does show what each change will do to the printed density, both in exposure and contrast. It's also an f/stop timer. I would really hate to go back.
Originally Posted by Nicholas Lindan
My other enlarger is for color and has a ZBE head where you can leave the time constant and it adjusts the density (in 1/30th of a stop increments). It is another excellent way of printing.
Either way thinking about adjustments in relative stops sure beats thinking in terms of seconds.
Actually the way it would work is that the exposure difference required to produce the same density difference for a middle gray across all contrast grades would be standardized. So when in the Yellow/Green range, a "d-stop" would be defined as say 1/2 stop. When in the Magenta/Blue range a "d-stop" may be defined as say 1/8th stop.
Originally Posted by Nicholas Lindan
The timer would have a peculiar function in that as you altered the contrast the indicated time in "d-stops" would change, though the actual time would stay the same. So, any time I want the mid tones 'just a little lighter' I would increase the exposure by one "d-stop" and the mid tones will get 'just noticeably lighter' whether I am in the Yellow/Green area or the Magenta/Blue area. If I used regular f-stops, a one-half stop change is going to darken the image printed with Magenta/Blue way, way more than a one-half stop change in the Yellow/Green end (which would be barely noticeable).
I learned and used f/stop printing and split grade printing before I purchased my Stop Clock Pro, using an f/stop chart that I got from Ralph Lambrecht's web site. I believe that I could print just as well with a standard timer and the chart. But the timer makes my darkroom sessions more productive: if I decide, for example, that the highlights need to be just a little darker I can easily and quickly add 1/4 stop to channel 1, for instance. Or if I decide the picture needs a little less contrast I can quickly add 1/3 stop to the highlights on channel 1, and subtract 1/3 stop from the shadows on channel 2. The times for any burns that I have previously worked out are automatically recalculated to the new base times.
The timer is simply a tool that makes me a more efficient printer, reduces math errors, and lets me think more about the product than the process. That said, you would have a fight on your hands if you tried to take it from me!