f/stop printing versus real-time.

Keith Tapscott. · Apr 6, 2009

The use of f/stop timers gets mentioned a lot on various photo forums and having read "Photographic Printing" by Gene Nocon, it seems to be a very logical way to produce enlargements.
I have an enlarger timer that allows me to control the exposure time in 0.1 second increments, but I have never actually used a dedicated f/stop timer and I am very tempted to buy one.
There is a chart in the book for using a regular timer for f/stop printing, but surely an f/stop timer is a better option? Does anyone regularly use an f/stop timer and do you feel that your time and effort in the darkroom has improved compared with using traditional timers?

Alex Hawley · Apr 6, 2009

I don't use an f/stop timer; what I do is count beats from a metronome and time my exposure in beats using 1/4 stop increments. I set the metronome at 72 beats/second so its slightly faster than a second for each beat.

It all accomplishes the same thing as using a dedicated timer. Using the metronome lets me concentrate on dodging/burning without having to take my eyes off the print to read the timer.

Jim Noel · Apr 6, 2009

The Nocon timer is an incredible instrument. It will do things automatically which those even slightly mathematically challenged will find difficult.
That said, the use of a metronome is also a wonderful way to print.
If you use a metronome together with the f-stop printing times in Gene's book you should find your printing improving.

BradS · Apr 6, 2009

What does an f-stop timer do that an ordinary timers doesn't? I guess I shoould read the book but, can somebody give a brief overview?

Keith Tapscott. · Apr 6, 2009

BradS said:
What does an f-stop timer do that an ordinary timers doesn't?

One of the reasons I started this thread Brad. I do find the concept of f/stop timing interesting and I wanted to read the views and opinions of other darkroom users whether they find the use of a dedicated f/stop timer to be worthwhile compared to using a regular enlarger timer.

BradS · Apr 6, 2009

I guess my question is even more basic...I have no idea what an f-stop timer is...and, being monday, my imagination isn't conjuring anything up.

What is an f-stop timer?

How is one used?

[EDIT:] Hmmm, ok. I just checked out the Darkroom Automation website...I see what it is. I guess I can multiply and divide by two reasonably well, so, probably don't need one.

Keith Tapscott. · Apr 6, 2009

BradS said:
I guess my question is even more basic...I have no idea what an f-stop timer is...and, being monday, my imagination isn't conjuring anything up.

What is an f-stop timer?
How is one used?

Hopefully, this will help. http://www.rhdesigns.co.uk/darkroom/html/f-stop_printing.html

Nicholas Lindan · Apr 6, 2009

BradS said:
I guess my question is even more basic...I have no idea what an f-stop timer is...and, being monday, my imagination isn't conjuring anything up.

http://www.darkroomautomation.com/fst-faq.htm
http://www.darkroomautomation.com/support/mfsquicks.pdf

BradS said:
I guess, I can multiply and divide by two reasonably well, so, probably don't need one.

If you only do straight prints, and only worry about getting the exposure right to no better than plus/minus one stop, you are right in feeling you don't need one.

But, it isn't a matter of needing one, nobody needs one, just as nobody needs to take photographs. The question is 'do you want one?'; will it make your life in the darkroom more pleasant and productive?

I don't think that is a question that can be answered by someone who hasn't used one.

Martin Aislabie · Apr 6, 2009

BradS said:
What does an f-stop timer do that an ordinary timers doesn't? I guess I shoould read the book but, can somebody give a brief overview?

I too was very sceptical as to the benefits.

How did counting in parts of stops help you print when with a bit of mental dexterity you can achieve the same results :confused:

After all a timer f-stop or linear just controls how much light falls on you photographic paper

However, after universal endorsement of the StopClock Pro at a UK APUG get together, I was sufficiently swayed to get one.

I remained sceptical if it was money well spent right up to the moment I started using it.

The test strip mode, the programmable subsequent steps, the two alternative timer channels and the dry down capabilities all seemed to answer needs I didn't even know I had.

I am not sure I am really getting the best out of it yet - but thats more to do with my capabilities than those of the machine.

The thing I noticed was how much easier printing was, I was able to concentrate on the print in front of me.

I didn't have to think much about the exposure and how to adjust it.

Its amazing how quickly you get your eye in on what a 1/6th or a 1/12th of a stop looks like

If I had to start again tomorrow, it wouldn't be the first thing I would buy for the darkroom but it would be right up at in the top three items on the list

I am now so glad I bought one

I could not contemplate going back to a linear timer

Keith, it I doubt it will be the best photographic investment you have ever made but it is a great piece of kit and I consider it to be good value for money.

Martin

BradS · Apr 6, 2009

Nicholas Lindan said:
If you only do straight prints, and only worry about getting the exposure right to no better than plus/minus one stop, you are right in feeling you don't need one.

But, it isn't a matter of needing one, nobody needs one, just like nobody needs to take photographs. The question is 'do you want one?'; will it make your life in the darkroom more pleasant and productive?

I don't think that is a question that can be answered by someone who hasn't used one.

well...yes, Of course, I want one!

Looks like a fantastic idea and a very useful technological innovation.

but then.... I can also do...

t = t0 * 2 ^ ( n / 3) -----------------------------(e.g. for 1/3 stop increments)

and...

n = 3 * { log(t/t0) / log(2) }

when I need to too...

Vincent Brady · Apr 6, 2009

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.

Cheers
TEX

Alex Hawley · Apr 6, 2009

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.

ic-racer · Apr 6, 2009

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.

resummerfield · Apr 6, 2009

TEX said:
I use an F-Stop timer and I feel that I would be unable to work without one now.......

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.

jeroldharter · Apr 6, 2009

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.

Mahler_one · Apr 6, 2009

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.

Nicholas Lindan · Apr 6, 2009

ic-racer said:
Ideally I would like to have a "D-stop" timer. DENSITY-stop, which would be programmed to produce a uniform density change per increment

I'll bet a case of beer you wouldn't like such a timer if indeed you had one.

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.

L Gebhardt · Apr 6, 2009

Nicholas Lindan said:
I'll bet a case of beer you wouldn't like one if you had one.

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 how to expose an image. It also shows me what will happen to the highlights if I move the shadow tones, gives a quick indication of how much to burn and dodge. And with the meter and timer 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.

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.

ic-racer · Apr 7, 2009

Nicholas Lindan said:
I'll bet a case of beer ...

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.

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).

Dan Henderson · Apr 7, 2009

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!

sim · Apr 7, 2009

Hallo,

F-Stop printing treats the paper exposure in the same way as exposure with the camera is treated ie in f stops rather than pure linear times e.g. shutter speeds going up in a non-linear sequence - 1 second, 2 sec 4 sec 8 sec 16 sec rather than 1sec, 2 sec, 3 sec, 4 sec etc. This does seem to be a natural way to deal with the darkroom exposure.

I have only recently bought an RH Designs Stopclock Professional, having previously done the mathematical calcualtions in my head/bit of paper for F-Stop printing - it is best not to actually think of times with the timer but densities. If a print looks too light by say half a stop, the timer will calculate the extra time needed to get an extra half stop density from the base exposure. It sounds a bit complicated but the RH Designs timer ( there may be others) takes all the headache out of the calculations - bets bit of kit I have bought.

Density starts to rule the printing process rather than times. I have found it soo much easier to concentrate on the actual print my printing is faster, better (I say so myself ) and more enjoyable.

Simo.

BobNewYork · Apr 7, 2009

I've never used an f-stop timer but with the posts I see in this thread and many others I'm getting very tempted. I've also just acquired an enlarger with the Ilford MG head - and the RH Designs dedicated unit looks very well suited to my needs.

As I'm in the middle of starting again in the darkroom my mission is to standardize and simplify every aspect of the process to make the time spent more productive for my needs. The RH Designs analyzer seems like a perfect fit - even though I just picked up a Colorline 5000!!

Time to do some gardening and earn brownie points with the missus!!

Bob H

Keith Tapscott. · Apr 7, 2009

If I made a series of test strips of 4 seconds, 5 seconds, 6.4 seconds, 8 seconds, 10 seconds, 12.5 seconds and 16 seconds, would that be a two-stop range in one-third stop increments?

BobNewYork · Apr 7, 2009

Keith Tapscott. · Apr 7, 2009

BobNewYork said:
Yep.

Thanks, would simplify matters and I should be able to make a much more refined test strip from there.
I get a feeling from the replies so far that many people are comfortable with f/stop printing while others are skeptical.
Perhaps they find that f/stop printing works fine without the need to buy a dedicated f/stop timer, would that be a fair assumption?

f/stop printing versus real-time.

Keith Tapscott.

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f/stop printing versus real-time.

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