F stop printing

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Nicholas Lindan

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Personally, I use percentages...
That is all "f-Stop" timing is. If you use 7% steps it equates to the 1/10 of a stop of modern f-Stop timers. 25% steps are .32 stops apart (1/3 of a stop for all intents and purposes) - a convenient interval for a test strip.

f-Stop timing is a really bad name for the technique. I confess to promulgating the name - I should have thought up something better. In using the DA and other 'pure' timers you never see the f-stop sequence, just 2.0, 2.1, 2.2...

I imagine it all started with someone taping a lens f-stop chart to the wall and using the sequence as exposure times. The standard lens f-stops yield 1/2 stop changes in time, 1/2 stop intervals yield 1/4 time stops, and 1/3 stop intervals for a lens (f2.8, f3.2, f3.5, f4.0) yield 1/6 time stop intervals.

If I didn't have an f-Stop timer handy I would have looked at the technique and said "Hey, pretty cool, I guess" and then I would have promptly gone back to seconds. But as I do have an f-Stop timer handy I would never consider plugging my enlarger into a linear timer. And I think that goes for all f-Stop timer owners.
 
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Pieter12

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Different strokes for different folks. I use an f-stop timer and split-grade printing. I would almost have to go back to darkroom 101 to print otherwise.
 

albada

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f-Stop timing is a really bad name for the technique.

+1!
I think Gene Nocon coined that (poor) name in his book and for his timer.
An aside: If you search for his timer on the internet, you'll see that it has 26 buttons. Wow! I guess the rotary encoder hadn't been invented yet.
 

nmp

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For those who do not have an F-stop timer, there is a nifty Excel sheet provided by Gerard Smeets where you can calculate the step times based on a number of input variables:


:Niranjan.
 

Nicholas Lindan

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I think Gene Nocon coined that (poor) name in his book and for his timer.
An aside: If you search for his timer on the internet, you'll see that it has 26 buttons. Wow! I guess the rotary encoder hadn't been invented yet.
If you Google "Gene Nocon patent" you will get the patent showing a block diagram of the timer and a description of operation that defeats my powers of understanding.

It actually had 31 keys - a key below each display digit for adjusting the base time. After that had been entered it could be changed by stop increments with a 20 key pad.

From the patent it looks like it was made from discrete TTL logic - but in 1985 I can't believe that was how it was implemented. The block diagram may be there to show the functional units of the software.
 

jnk

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Not clairvoyant. He asked vague and nonsensical questions like "I just built my darkroom and I am looking for the basic "dummies" book on enlargement." I am suspicious of any new person who is asking questions without giving details and contexts of what they are looking for. And then once the well meaning members as they are on this forum come back with their recommendations, OP shows little or no follow-up interest. I think members can do a better job early on to make the OP divulge more information and clarifications before jumping on to interpret their take on it.

:Niranjan.

he wanted basic information not a thesis sorry just an observation
 

albada

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An f-Stop timer becomes really, really useful if you also have an enlarging meter that works in stops.

Thinking about this posting made me realize that I overlooked this advantage of f-stop timing in terms of eliminating test-strips. For example:

Suppose you know that to print skin-tone with a time of 4 stops (16-seconds), your f-stop meter must read 3.8.
A skin-spot on your easel reads 3.2. So you need 0.6 more stops of exposure. Add 0.6 to the time on the f-stop timer, making it 4.6 stops of time.
Done. No complex calculations or test-strip needed. Or for precise work, you can start with a fine test-strip, eliminating a coarse strip.
 

albada

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Terminology itself is rather confusing. There is no "f" involved here since you are not changing the aperture of the enlarging lens. It is simply "stop" printing [...]

How about calling it "stop-based"? As in "stop-based timing" using a "stop-based timer". And the "stop-based meter" that I bought from DarkroomAutomation is helpful. Like nmp, I dislike the "f" because it's unrelated to the f-stops on the lens.
 

RalphLambrecht

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If the best exposure is between 22 and 32 seconds, I do another strip in between. For me, it is easy to use a 1/12 stop progression within that range, but 2 second intervals within the range will yield useful results as well.

I find that when one tests with logarithmic/geometric (f-stop) progressions, and makes logarithmic/geometric (f-stop) adjustments, it is easier to see what needs to be changed, and how much one needs to change. So I think that f-stop printing helps one "learn how to judge and make a good print".

very true!
 

koraks

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I think members can do a better job early on to make the OP divulge more information and clarifications before jumping on to interpret their take on it.

Just be careful not to create the photographic equivalent of the Arduino forum. I'll leave it at this for now; anyone interested in details is free to contact me about this.
 

Mick Fagan

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How about calling it "stop-based"? As in "stop-based timing" using a "stop-based timer". And the "stop-based meter" that I bought from DarkroomAutomation is helpful. Like nmp, I dislike the "f" because it's unrelated to the f-stops on the lens.

Unless my memory is gone (very probable) the "F" in f stop is an abbreviated, or shortened version of "mathematical Factor", it is generally shortened to "f/5.6" or a slightly longer "factor/5.6"

Pretty much everything to do with film photography, including printing, is governed by mathematical factors that we undertake to obtain correct exposure. Whether that be done by looking up charts, using a specially designed darkroom timer or other methods, such as working out the mathematical factor ourselves to obtain the correct exposure to light sensitive materials. All of these methods use a factor derived from a mathematical calculation to give us the desired result.

Using f/stop timing one could reduce the exposure by 1 whole stop by changing the lens by half a stop and and by changing the exposure by half a stop to get the desired result.
 

Buzz-01

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Good for you! Did you use an Arduino? I've used both an Arduino and an evaluation board for the PIC18 (I built two controllers).
I programmed the test-strip feature to put the base exposure at the left, center, or right-end of the test-strip. I usually use "center". "Left" is good for determining how much to burn, and "right" is good for deciding a dodge.
One feature I really like is turning off the safelight when the enlarger is on for any reason (focusing or exposing). I used a relay, but a triac should work equally well.
To conserve space on the LCD, I use tenths of stops for everything, which works well for exposure arithmetic, but it can't represent third or quarter stops. For those, I must use steps of 0.2 or 0.3 stops instead.

I used an STM32F4 for mine, but it could just as easily have been a PIC18/24 or any of the AVR/Arduino devices. The STM32 was simply what I had in stock.

Mine also switches off the safelight (and I can set the safelight brightness on it, dimming the 12V LED safelight bulb I use). For simplicity I also use a relay to switch the enlarger bulb on and off.
I've never thought of placing the base exposure elswhere than on the right-hand side of the paper (I'm right handed so that's most convenient to start for me). Your method of left-middle-right sound very useful though, you might have motivated me there to update my software a little... 😁

The reason I built this timer is to make most of a darkroom session. There's only a few hours available in an evening and it takes some time to set things up in my makeshift darkroom, so I want to be as productive as possible.
For me, that's (f-)stop printing using an automated timer.
But without one, it's easy to just follow the aperture numbers on any vintage lens and use those as your exposure times for a test strip (2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, ...). As someone said before, that will give you a half-stop incremental test strip, which is what I use most as a first (and quite often the only needed) test strip. A cheat sheet of the incremental exposure times would be useful ofcourse. Hence the reason for me to build my timer...

Unless my memory is gone (very probable) the "F" in f stop is an abbreviated, or shortened version of "mathematical Factor", it is generally shortened to "f/5.6" or a slightly longer "factor/5.6"

Pretty much everything to do with film photography, including printing, is governed by mathematical factors that we undertake to obtain correct exposure. Whether that be done by looking up charts, using a specially designed darkroom timer or other methods, such as working out the mathematical factor ourselves to obtain the correct exposure to light sensitive materials. All of these methods use a factor derived from a mathematical calculation to give us the desired result.

Using f/stop timing one could reduce the exposure by 1 whole stop by changing the lens by half a stop and and by changing the exposure by half a stop to get the desired result.
I always assumed that F was short for Focal length; e.g. aperture diameter in mm = focal length / aperture number?
But still, I think naming it factor makes sense in a way here (and could very well be valid as well, as my knowledge is purely gathered on a hobbyist-basis 😇)
 
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Sirius Glass

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If the best exposure is between 22 and 32 seconds, I do another strip in between. For me, it is easy to use a 1/12 stop progression within that range, but 2 second intervals within the range will yield useful results as well.

I find that when one tests with logarithmic/geometric (f-stop) progressions, and makes logarithmic/geometric (f-stop) adjustments, it is easier to see what needs to be changed, and how much one needs to change. So I think that f-stop printing helps one "learn how to judge and make a good print".

Which is way I will switch back and forth between methods.
 

Nicholas Lindan

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For me, it is easy to use a 1/12 stop progression within that range, but 2 second intervals within the range will yield useful results as well.

For small increments, like 1/12 stop, there isn't much if any difference between a linear progression and a logarithmic progression. The smaller the stop increment the more linear the progression - the basis of differential calculus, really.

A 1/12 stop 5-strip test would start out at a 6% step and finish at a 7% step: 10 seconds, 10.6 seconds, 11.2 seconds, 11.9 seconds, 12.6 seconds. Without an f-Stop timer one might as well set the timer to 0.6 seconds (or 6% of the base exposure (though 5% / 10% are easier on the grey matter)) and be done with it.

A 1/12 of a stop change in print exposure is roughly equivalent to a 1/6 of a zone / stop change in negative exposure (midtones, regular development, #2 paper). Control over exposure can be far more precise when printing than when shooting. Printing can deliver what the Zone System only promises.
 

MattKing

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@Nicholas Lindan
I was looking through your website, and couldn't find anything that might be referred to as an "introduction to f/stop printing".
Do you have such a reference you could refer to, and might be linked to here?
Perhaps @RalphLambrecht would be willing to share an excerpt from his book?
 

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doesn't f-stop printing change the depth of focus?
 

MattKing

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doesn't f-stop printing change the depth of focus?

No, because it doesn't involve changing the aperture.
It involves changing the exposure time, in increments of (fractions) of f/stops.
Some are more comfortable with referring to is as "stop" printing, but that can add even more confusion for the uninitiated.
Logarithmic printing would also be accurate, but that would scare away even more people :smile:.
 

albada

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@Nicholas Lindan
I was looking through your website, and couldn't find anything that might be referred to as an "introduction to f/stop printing".
Do you have such a reference you could refer to, and might be linked to here?
Perhaps @RalphLambrecht would be willing to share an excerpt from his book?

For those who own a copy of Way Beyond Monochrome (2nd ed.), the chapter of interest is "Timing Print Exposures" on pages 23-27. Here's an interesting quote:

Some experienced printers have adopted the practice of using percentages of the base exposure time for all dodging and burning procedures. This approach is not as consistent but very similar to f/stop timing, and these printers should have little or no trouble switching to f/stop printing, because they are already halfway there.​

The author summarizes the advantages of f/stop timing thusly: "It provides any darkroom practitioner with robust print control and the ability to predict repeatable results with confidence." He expands and justifies this statement through the remainder of the chapter.

BTW, this is by far the most thorough book I have on darkroom printing.
 

Mick Fagan

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For those who own a copy of Way Beyond Monochrome (2nd ed.), the chapter of interest is "Timing Print Exposures" on pages 23-27. Here's an interesting quote:

Some experienced printers have adopted the practice of using percentages of the base exposure time for all dodging and burning procedures. This approach is not as consistent but very similar to f/stop timing, and these printers should have little or no trouble switching to f/stop printing, because they are already halfway there.​

The author summarizes the advantages of f/stop timing thusly: "It provides any darkroom practitioner with robust print control and the ability to predict repeatable results with confidence." He expands and justifies this statement through the remainder of the chapter.

BTW, this is by far the most thorough book I have on darkroom printing.

I agree that it is the best book on darkroom techniques, with the original version being a close second to the second edition; I have both versions.

In the first edition pages 19 to 23 are the relevant ones.

I thought Ansell Adams trio of books were good, but for darkroom work, Way Beyond Monochrome, either version, leave Ansell Adam's books in the dust.

Wonderful legacy Ralph, many thanks for those books.
 

Bill Burk

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That's true at a given grade (contrast). But a boost of 1/2 stop will look much different at grade 1 versus grade 5, although with enough experience (which I lack), I suppose one will develop that intuition across a range of grades.

Oh what a great timer we could create if we worked in Delta-E as they do in the graphic arts (e.g., monitor calibration) where 1 dDelta-E is the difference someone can see.

I find a “third-stop” at grade 2 (yes it’s different at grade 4 as you hinted albada) gives me a difference I can see in a test strip. And by that, I mean it’s enough for me to prefer one test strip section over the next adjacent.

The dots at 4, 5, 6, 8, 10, 13, 16, 20, 25, 32, 40, 50 (and 60+28) are all I use to implement “third-stop” timing. All there is to it… memorize the differences in short-term memory for the test strip you are making and it’s a piece of cake.

So I often set the timer at 50, and count clicks; 10, 8, 7, 5, 4, 3 covers the range of 13 to 50 seconds and I can tell on the resulting test strip which is which because every step looks different.
 

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albada

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Oh what a great timer we could create if we worked in Delta-E as they do in the graphic arts (e.g., monitor calibration) where 1 dDelta-E is the difference someone can see.

I find a “third-stop” at grade 2 (yes it’s different at grade 4 as you hinted albada) gives me a difference I can see in a test strip. And by that, I mean it’s enough for me to prefer one test strip section over the next adjacent.

The dots at 4, 5, 6, 8, 10, 13, 16, 20, 25, 32, 40, 50 (and 60+28) are all I use to implement “third-stop” timing. All there is to it… memorize the differences in short-term memory for the test strip you are making and it’s a piece of cake.

So I often set the timer at 50, and count clicks; 10, 8, 7, 5, 4, 3 covers the range of 13 to 50 seconds and I can tell on the resulting test strip which is which because every step looks different.

Bill, you might be flashing your paper -- with that bright green backlit timer-dial. I've never seen a back-lit Time-O-Lite before, but that Omega-rebadged thing is bright! They could have at least used red light. Have you had any problem with it fogging paper? I ask because many LCDs have black characters on a back-lit background, similar to your timer, and if yours is no problem, then those LCDs should be ok too.

Anyway, that's a clever way to make a test-strip using f-stop timing with a conventional timer, and 13-50 seconds is a most useful range.
 

RalphLambrecht

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That is all "f-Stop" timing is. If you use 7% steps it equates to the 1/10 of a stop of modern f-Stop timers. 25% steps are .32 stops apart (1/3 of a stop for all intents and purposes) - a convenient interval for a test strip.

f-Stop timing is a really bad name for the technique. I confess to promulgating the name - I should have thought up something better. In using the DA and other 'pure' timers you never see the f-stop sequence, just 2.0, 2.1, 2.2...

I imagine it all started with someone taping a lens f-stop chart to the wall and using the sequence as exposure times. The standard lens f-stops yield 1/2 stop changes in time, 1/2 stop intervals yield 1/4 time stops, and 1/3 stop intervals for a lens (f2.8, f3.2, f3.5, f4.0) yield 1/6 time stop intervals.

If I didn't have an f-Stop timer handy I would have looked at the technique and said "Hey, pretty cool, I guess" and then I would have promptly gone back to seconds. But as I do have an f-Stop timer handy I would never consider plugging my enlarger into a linear timer. And I think that goes for all f-Stop timer owners.

before I had an f/stop timer, I taped an f/stop timing clock face to my Gralab 300 in 1/3 stops.
 

Bill Burk

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Bill, you might be flashing your paper -- with that bright green backlit timer-dial. I've never seen a back-lit Time-O-Lite before, but that Omega-rebadged thing is bright! They could have at least used red light. Have you had any problem with it fogging paper? I ask because many LCDs have black characters on a back-lit background, similar to your timer, and if yours is no problem, then those LCDs should be ok too.

Anyway, that's a clever way to make a test-strip using f-stop timing with a conventional timer, and 13-50 seconds is a most useful range.

It's not that bright, I held a bright flashlight to it for a few seconds before taking the picture.
 

tomatojoe

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before I had an f/stop timer, I taped an f/stop timing clock face to my Gralab 300 in 1/3 stops.

Mr Lambrect:

Did this modification help much? I have been just using a regular timer and 5 second intervals for my first "test strip" for a long time. When I learned the "close time" I then shortened my interval. My gray lab was broken after a long while and I just worked by intuition, it worked OK
 
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