Calculating f-stop Timing in Enlarging

[pentaxuser]

Just pull out your school days log tables from that drawer and you can easily do the calculations on paper too!

Log tables are for Canadian Lumberjacks. Nothing wrong with the abacus is what say

pentaxuser

 

[Pieter12]

I am probably oversimplifying, but I just estimate the amount of burning or dodging necessary as a fraction of the base time for either filter. My timer displays the actual exposure in seconds and I use the closest number to the amount I have determined. The timer sounds a metronome and I use that to count out my doging and burning. Not precise, but I find it works for me and slight variations don't seem to be apparent in the final prints. No charts, no calculators, nothing to set, and so far it is scaleable when I make larger prints.

 

[pentaxuser]

Tapping the "^" key on an f-stop timer is something I can manage.

Just a pity for me that the exponential key on the scientific calculator I was bequeathed didn't have a key marked "^"

I had to Google "^" and none of the symbols tables it came up with had a "^" with an explanation that it was the exponential key so good job you were kind enough to reply so thanks for that

pentaxuser

 

[MattKing]

That symbol is one of the most intuitive around - it means "raised to" and it looks like "raised to".
If only many of the other shorthand symbols were that clear!
In case it isn't obvious, the reason you need things like that is because most text based systems of notation lack the ability to easily show superscript or subscript text - you are stuck with a single line of display.

 

[Nicholas Lindan]

Just a pity for me that the exponential key on the scientific calculator I was bequeathed didn't have a key marked "^"

I was using it as the up-arrow/raise key on a timer. Regular 'ole ASCII doesn't have an up-arrow. I suppose I could use ▲ or the up arrow from some symbol/dingbat font.

 

[Kilgallb]

I have an app on my iPhone call Fstop printing calculator. Enter the time of the last print then it calculates new times for 1/4-stop, 1/2-stop and 3/4-stop. The app has a mode that makes the screen all RED to prevent fogging.

I also have a table on my darkroom wall of 1 stop, 1/2 stop and 1/4 stops. find your base exposure on the 1/4 stop table and adjust up or down as desired. Yes, I know it is not exact.

 

[Chan Tran]

Log tables are for Canadian Lumberjacks. Nothing wrong with the abacus is what say

pentaxuser

Abacus is great for adding and substracting but not good for other kind of calculation. However, to use the log table or the slide rule you have to do the addition and subtraction yourself.

 

[Chan Tran]

That symbol is one of the most intuitive around - it means "raised to" and it looks like "raised to".
If only many of the other shorthand symbols were that clear!
In case it isn't obvious, the reason you need things like that is because most text based systems of notation lack the ability to easily show superscript or subscript text - you are stuck with a single line of display.

The symbol ^ was used when people started using computer and old computer couldn't print or display superscript or subscript. When you write 2 to the 1.33 power it should be written as 21.33.
On the calculator the key to raise to the power would generally be labelled as yx and thus you don't find the ^ key on a calculator.

 

[MattKing]

As is probably already apparent, I've been a devotee of f-stop Timing for quite a while.
With all due respect to @Ian C , the problem with this thread is that some may gain from it the impression that it is the calculations that matter the most.
And that really isn't the case.
What matters the most is the behavior of the materials we use - in particular the photographic paper - in combination with how we see things in prints. Ideally, we want those materials and our vision to vary predictably and intuitively when we make changes.
As it turns out, those behaviors respond logarithmically, so using controls (lens apertures and exposure times) that also vary logarithmically work really well with those materials and how our vision works.
Lens aperture controls on lenses are already set up to work logarithmically. F-stop timing ensures that the exposure times work that way too.
When you work that way, it becomes really easy to visualize (in fractional stops) what changes are desirable, and then to make them happen easily and predictably.
With a bit of practice, it becomes easy to look at something and visualize whether what you need is a 1 stop change, a 1/2 stop change, a 1/3 stop change, a 1/4 stop change, a 1/6 stop change or even, if it is a printing day where everything is going well, a 1/12 stop change.
Once practiced, that ability to visualize becomes instinctive.
And with all due respect to Doremus, I don't enjoy the same intuitive visual linkage when I employ percentage changes instead.
The logarithmic/F-stop approach scales extremely naturally - a printing plan expressed in fractions of stops works equally well with all sorts of different magnifications or base exposure times.
And with a bit of familiarization, it also works well with different papers and different contrast settings/grades.

This thread supplies an approach for coming up with/calculating the necessary times in order to make those desired and predictable fractional stop changes. Others have chimed in with other ways to arrive at the times. There are timers that do it easily for you. There are also tables that make it easy to look those times up - which is what I do, using the excellent table in @RalphLambrecht 's "Way Beyond Monochrome". If Ralph would like me to, I'd be happy to post that table again here on Photrio. Ralph has posted it here before, and the pdf version I have came from that. I have it in book form, as I have the first edition of his book on my shelf.

 

[Doremus Scudder]

Matt,
1/12 stop - 5% - whatever. It's all the same. It's just what you get used to. If I had an f-stop timer, I'd likely use it. I like math and physics, but I just don't see the point in doing needless calculations in the darkroom. For me, percentages are easier than calculating fractions of an f-stop. Even easier than consulting f-stop tables.

Really, it's the results that matter. How we get there is highly individual.

Best,

Doremus

 

[RalphLambrecht]

There seems to be confusion between the math behind f-stop printing (logs and exponents) and f-stop printing itself.

f-stop printing with an f-stop timer requires no math whatsoever. Nada, zilch, kein, net, non, nei....

There is no more math involved in f-stop printing than there is in setting the shutter speed and aperture on a camera.

* * *
​

I'm sorry to say, but percentages just introduce unneeded complication.

Taking 15% of 17 seconds is not something I am going to do in my head in the middle of a printing session. Tapping the "^" key on an f-stop timer is something I can manage.

exactly right!

 

[RalphLambrecht]

As is probably already apparent, I've been a devotee of f-stop Timing for quite a while.
With all due respect to @Ian C , the problem with this thread is that some may gain from it the impression that it is the calculations that matter the most.
And that really isn't the case.
What matters the most is the behavior of the materials we use - in particular the photographic paper - in combination with how we see things in prints. Ideally, we want those materials and our vision to vary predictably and intuitively when we make changes.
As it turns out, those behaviors respond logarithmically, so using controls (lens apertures and exposure times) that also vary logarithmically work really well with those materials and how our vision works.
Lens aperture controls on lenses are already set up to work logarithmically. F-stop timing ensures that the exposure times work that way too.
When you work that way, it becomes really easy to visualize (in fractional stops) what changes are desirable, and then to make them happen easily and predictably.
With a bit of practice, it becomes easy to look at something and visualize whether what you need is a 1 stop change, a 1/2 stop change, a 1/3 stop change, a 1/4 stop change, a 1/6 stop change or even, if it is a printing day where everything is going well, a 1/12 stop change.
Once practiced, that ability to visualize becomes instinctive.
And with all due respect to Doremus, I don't enjoy the same intuitive visual linkage when I employ percentage changes instead.
The logarithmic/F-stop approach scales extremely naturally - a printing plan expressed in fractions of stops works equally well with all sorts of different magnifications or base exposure times.
And with a bit of familiarization, it also works well with different papers and different contrast settings/grades.

This thread supplies an approach for coming up with/calculating the necessary times in order to make those desired and predictable fractional stop changes. Others have chimed in with other ways to arrive at the times. There are timers that do it easily for you. There are also tables that make it easy to look those times up - which is what I do, using the excellent table in @RalphLambrecht 's "Way Beyond Monochrome". If Ralph would like me to, I'd be happy to post that table again here on Photrio. Ralph has posted it here before, and the pdf version I have came from that. I have it in book form, as I have the first edition of his book on my shelf.

Matt feel free to post it here or anywhere. I prepared it for the darkroom community to help, but I need to stress that an f/stop timer is a precious investment, making the process much simpler and more enjoyable (and no, I'm not being paid to say this).

 

[Alex Benjamin]

Matt feel free to post it here or anywhere. I prepared it for the darkroom community to help, but I need to stress that an f/stop timer is a precious investment, making the process much simpler and more enjoyable (and no, I'm not being paid to say this).

+1

I spent a year working from Ralph's table pinned right next to the enlarger, with the added time calculations penciled in. Worked quickly and wonderfully, as after a while you have the amount of time to add at each interval memorized.

Finally got an f/stop timer. Not only did it simplify the process, it made it much more precise. Even the usually dreary task of making contact prints is now a breeze, and I always quickly nail the perfect exposure for them.

 

[Chuck_P]

Matt feel free to post it here or anywhere. I prepared it for the darkroom community to help, but I need to stress that an f/stop timer is a precious investment, making the process much simpler and more enjoyable (and no, I'm not being paid to say this).

I would have to concur. When I finally learned about f-stop timing and ultimately bought one, my thought processes on print exposure manipulations began, rather quickly, to be uniquely linked to the one-stop zone changes that define the exposure scale from solid black to solid white, as well as those fractional changes in print tones. It played out for me just as @MattKing indicated in his post. Whereas before, I knew I wanted an area to be lighter or darker and I would dodge a few seconds then burn here and there a few seconds to try and get what I wanted by just estimating how long a manipulation I should give. I have to give DA a shout out for their f-stop timer..........and no, I'm not being paid to say this either, it's just a fact. I understand the percentage approach, but it doesn't carry with it.....for me.....that mental link between stopping down and opening up of the aperture and the action of setting, say, a one stop more or less change of print exposure on the f-stop timer.

 

[MattKing]

Matt feel free to post it here or anywhere. I prepared it for the darkroom community to help, but I need to stress that an f/stop timer is a precious investment, making the process much simpler and more enjoyable (and no, I'm not being paid to say this).

Happy to do so. Both as a graphic in the thread, and an attached pdf.

 

[MattKing]

Matt,
1/12 stop - 5% - whatever. It's all the same. It's just what you get used to. If I had an f-stop timer, I'd likely use it. I like math and physics, but I just don't see the point in doing needless calculations in the darkroom. For me, percentages are easier than calculating fractions of an f-stop. Even easier than consulting f-stop tables.

Really, it's the results that matter. How we get there is highly individual.

Best,

Doremus

Functionally, the percentage approach works fine.
The difference is that, unless you use a logarithmic progression of percentages - 2.8%, 4%, 5.6%, 8%, 11%, 16% as a relatively coarse, half stop progression example - you don't get the same visual identification of the progression of tones.

 

[Doremus Scudder]

Functionally, the percentage approach works fine.
The difference is that, unless you use a logarithmic progression of percentages - 2.8%, 4%, 5.6%, 8%, 11%, 16% as a relatively coarse, half stop progression example - you don't get the same visual identification of the progression of tones.

Matt,

Yes, percentages don't always come out evenly at exposure doublings like f-stops do, Then again, there are no pesky fractions of a second. And, it's close enough and easy.

Here's a 20% test strip exposure starting at 10 sec. - roughly 1/4-stop change: 10 - 12 - 14.4 (round to 14) - 17.28 (round to 17) - 20.736 (round to 20 for the doubling) - 24 - 28.8 (round to 29) - 34.6 (round to 35) - 41.4 (round to 41 - really close to two doublings).

So, with rounding, the finished test strip would have 10 sec. - 12 sec. - 14 sec. - 17 sec. - 20 sec. - 24 sec. - 29 sec. - 35 sec. - 41 sec. You see the 1/4 stop progression clearly. And, as far as accuracy goes, it's got no more error than the modern shutter-speed sequence.

Like 1/3-stops better? Use 25%: 10 - 13 - 16 - 20 - 26 - 32 - 40. these are rounded values of course, but that looks a lot like f-stop timing to me without the timer or the hassle.

And making test strips is the only thing that requires any calculation at all. If I have a print that I want a half-stop more exposure on, I'll increase exposure 50% EZPZ. 1/3-stop? 25% is close enough, etc. Those values are easy to figure in my head; no chart, no fancy timer needed.

Again, I'll go back to the main flaw in all of this: visualizing a stop of density change in a print, or fraction thereof, is not a constant. A stop exposure difference at a high contrast setting makes a lot more difference than the same exposure difference at a low contrast setting, whether you use f-stop timing or percentages. If you guys can visualize all those different changes for all those different contrast grades, my hat's off to you. I don't think it's possible.

Either method is just getting in the ballpark. An expressive fine print often needs very small changes and refinements; another couple seconds of exposure here or there, another 15 seconds in the developer, blending that burn just right, etc. At that point, no one is using either f-stop timing or percentages.

Best,

Doremus

 

[Chan Tran]

Happy to do so. Both as a graphic in the thread, and an attached pdf.

View attachment 381646

Any way it works but for me the calculator is easier than the chart. Not that I don't use chart as I was one who stole the Log table but that was before I had calculator.

 

[GregY]

Matt,

Yes, percentages don't always come out evenly at exposure doublings like f-stops do, Then again, there are no pesky fractions of a second. And, it's close enough and easy.

Here's a 20% test strip exposure starting at 10 sec. - roughly 1/4-stop change: 10 - 12 - 14.4 (round to 14) - 17.28 (round to 17) - 20.736 (round to 20 for the doubling) - 24 - 28.8 (round to 29) - 34.6 (round to 35) - 41.4 (round to 41 - really close to two doublings).

So, with rounding, the finished test strip would have 10 sec. - 12 sec. - 14 sec. - 17 sec. - 20 sec. - 24 sec. - 29 sec. - 35 sec. - 41 sec. You see the 1/4 stop progression clearly. And, as far as accuracy goes, it's got no more error than the modern shutter-speed sequence.

Like 1/3-stops better? Use 25%: 10 - 13 - 16 - 20 - 26 - 32 - 40. these are rounded values of course, but that looks a lot like f-stop timing to me without the timer or the hassle.

And making test strips is the only thing that requires any calculation at all. If I have a print that I want a half-stop more exposure on, I'll increase exposure 50% EZPZ. 1/3-stop? 25% is close enough, etc. Those values are easy to figure in my head; no chart, no fancy timer needed.

Again, I'll go back to the main flaw in all of this: visualizing a stop of density change in a print, or fraction thereof, is not a constant. A stop exposure difference at a high contrast setting makes a lot more difference than the same exposure difference at a low contrast setting, whether you use f-stop timing or percentages. If you guys can visualize all those different changes for all those different contrast grades, my hat's off to you. I don't think it's possible.

Either method is just getting in the ballpark. An expressive fine print often needs very small changes and refinements; another couple seconds of exposure here or there, another 15 seconds in the developer, blending that burn just right, etc. At that point, no one is using either f-stop timing or percentages.

Best,

Doremus

Thank you DS!

 

[pentaxuser]

That symbol is one of the most intuitive around - it means "raised to" and it looks like "raised to".
If only many of the other shorthand symbols were that clear!
In case it isn't obvious, the reason you need things like that is because most text based systems of notation lack the ability to easily show superscript or subscript text - you are stuck with a single line of display.

It doesn't appear to be intuitive to Google either as I said in an earlier reply It might be intuitive to those who know what it means but not to those who do not or are not intuitive and do not deal with such symbols in their everyday lives

pentaxuser

 

[Erik L]

IMO whatever method that is convenient and logical for the way your brain works is the way to go. I admit that I wouldn’t use f stop printing if I had to look at a table and enter fractional numbers on my timer. However since I have an f stop timer I couldn’t imagine printing any other way. I save time by using it. Just the simple act of making test strips in whatever f stop increments you want saves time with the f stop timer. There is no physical changing of the seconds on the timer, just set to test strip mode and step on the foot switch, move card over print, step on foot switch, move card, step on foot switch etc. The timer automatically calculates the times, no messing with changing seconds by hand on the timer. It seems trivial but is a big time saver for me. It’s my favorite darkroom accessory. It’s not for everyone as seen by many posters who do things differently but after years of using an f stop timer I would be disappointed if my timer broke and I had to train my old brain to think differently.

 

[Chan Tran]

It doesn't appear to be intuitive to Google either as I said in an earlier reply It might be intuitive to those who know what it means but not to those who do not or are not intuitive and do not deal with such symbols in their everyday lives

pentaxuser

As I said in the earlier post the ^ isn't mathematically correct for raising to the power. They only started to use that symbol when they started using computer and old computer can't print or display superscript. For example 2 to the 1.33 isn't 2^1.33 but rather 21.33 and on a caculator the key for that should be labelled yx.

 

[RalphLambrecht]

+1

I spent a year working from Ralph's table pinned right next to the enlarger, with the added time calculations penciled in. Worked quickly and wonderfully, as after a while you have the amount of time to add at each interval memorized.

Finally got an f/stop timer. Not only did it simplify the process, it made it much more precise. Even the usually dreary task of making contact prints is now a breeze, and I always quickly nail the perfect exposure for them.

more than glad o hear that.

 

[Luckless]

I find the easiest way to avoid having to deal with fractions of a second is to just round to the nearest millisecond instead.

Also, letting a computer deal with the actual math. And letting it flip the switch on the enlarger... A digital enlarger timer running on an f/stop scale is simple and reliable, and you don't even need to track down some fancy or expensive rare device.

I built my own from student's Arduino kit, and added a project box and suitable plugs and wiring, and a few afternoons tailoring some basic tutorial content into a custom timer. But that was mostly because I had specific workflows I wanted after I quickly became tired of manually setting a basic timer for each exposure. Which was honestly mostly from the risks of misreading my own notes in near dark or forgetting where I actually was in a sequence.


For dialing in on a print's exposure and contrast I like to use a 4x5 test sheet and stationary exposure patch with a simple cardstock mask. Pick a spot in the image that I want to test that hopefully fits both shadow and highlights into the mask area, load a test sheet and hold things in place with a few magnets. Each exposure covers roughly the same area if I don't bump it too much and gives me a 1:1 comparison for each test segment.

This mostly allows me to deal with accurate visualizations of f/stop changes across contrast grades by the simple method of: I don't.

I estimate and ballpark, and then I test. A digital f/stop timer just makes those tests consistent and even, and makes my notes accurate and easy to read with a consistent 3 digit pattern making up the bulk of what's likely to change.

But I did take it a step further and built the timer itself to do a chunk of the fiddly work for me by adding a Sequence Mode. I set a start 'EV' and dial in a step factor, and for the next 5 times I press the Big Red Button it automatically gives me the correct time I was aiming for for that stage of the test. And I work with 1/12th of a stop notches as that gives me easy 1/3s, 1/4s, and 1/2s.

[Metric is far superior, expect for all the times it isn't.]

Notes from one of my recent sessions:

---

Adjust and focus enlarger for a 5x7 print.

Dial in EV 2-00 @ 0-06 step [Con 3, f/8, High]

Position Mask and Test Sheet, Press Button, pull the test sheet holder to the next notch, Press button, pull to next notch... [It is so easy that even I struggle to mess it up.] process and review test sheet. All far too dark, but the differences in the first two strips gives me an educated guess to dial in. Setup for another sequence.

Dial in EV 1-06 @ 0-03 step [Con 3, f/8, Low]

Position Mask and Test Sheet, Press button... Process and review. Row 4 looks good

Double check focus, Change timer mode to standard exposure, dial in to EV 2-03, put a full sheet in, press button, process print.

Like it as a straight print as is. Go back and cycle through load and button press five more times, develop the little stack of prints, and walk out with a half dozen copies for myself and friends. Easy.

---

I can't easily flub a number. I'm not likely to transpose digits I'm reading off a table. No duplicated times from reading the wrong line before setting my next time in a series. I squared away the annoying math ages ago, and shoved it down into a black box where I don't have to care about it. Changing between paper sizes starts me off in the right ballpark with a quick whole number +/- and my adjustment notes stay in working order.

I'm still on the hook for adjust contrast grades and stuff correctly. But we'll see how long I keep printing for with the current setup before I figure out a pattern I mess up often enough for me to justify finding a way to pull that into a unified control interface...

My timer runs its EV scale backwards, and assumes f/1.0, but that was just for convenience of the notes and interface. My timer doesn't have a link back to the enlarger's aperture, I have no desire to use my enlarger at less than 1 second, and dropping the negative sign saved me a character on the LCD, so it works just fine for a compact time notation that scales easily.

And I'm another user owing thanks to Ralph Lambrecht and their chart. While I'm not directly using the chart anymore I still have a copy next to the enlarger. They helped me put two and two together on the whole 'an enlarger is just an inside out camera', and it just makes sense to work with it by stop values.

 

[snusmumriken]

I’m a scientist, so I’m in favour of precision. But you guys must be incredibly quick getting your hands or dodging tools into place if you are measuring fractions of a stop with a timer. Or maybe you have a foot switch. Myself, if I have to dodge or burn, I use a metronome. It isn’t terribly, but to the eye the result is repeatable. And I use seconds rather than f-stops. I guess I’m just a heretic.