Calculating f-stop Timing in Enlarging

[Alex Benjamin]

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.

Actually, for short times, you work with an f-stop timer exactly as you would with any other method: you stop down the lens one or two stops and double or triple the time. With longer times, fractions of a second becomes irrelevant. What is practical with the F-stop method is that if you do stop down, the calculations are made for you, i.e., 1/3 or 3/4 stop is 1/3 or 2/3 stop no matter if your lens is at f/5.6, f/8 or f/11. It's just the time that's longer; the proportions are the same. It's not better, it's just simpler, quicker and more precise.

 

[Doremus Scudder]

I use a metronome too, or at least the metronome function on my GraLab 450 timer. The timer itself is set to 99 seconds, the highest it will go. I begin and end exposures by revealing/blocking the light with a card; hold the card over the lens, step on the footswitch, remove card and begin counting. I count up to my target exposure like a musician counts beats: 1 - 2 - 3 - 4 - ... - 15 - 16 - OFF, so I never lose track of where I am in the sequence. I can reliably count half and even quarter seconds that way (eight or sixteenth notes in quarter-note = 60 bpm), but don't usually need such precision.

Making a test strip that way is EZPZ; just cover consecutive stripes on the strip with a card while counting. Example using my 25% test strip numbers above: Count 10 seconds, move card on the beginning of second 11, but start over with 1, count three seconds, move card at beginning of next second but starting over with 1, count 3 seconds, etc.

The sequence looks like: - 10 -- 3 -- 3 --- 4 -- 6 --- 6 -- 8 (and OFF).
That gets me my desired: 10 - 13 - 16 - 20 - 26 - 32 - 40 seconds, which I find a good range of exposure times and easy to remember.

Voilà, a progressively spaced test strip in approximate 25% (= ~1/3 stop) increments. No charts or calculators and minimal figuring of percentages.

I like simple tools. Why spend money on technology if it doesn't give you an advantage? Carlton Watkins prints aren't worse because he didn't have an f-stop timer

Best,

Doremus

 

[Pieter12]

Actually, for short times, you work with an f-stop timer exactly as you would with any other method: you stop down the lens one or two stops and double or triple the time. With longer times, fractions of a second becomes irrelevant. What is practical with the F-stop method is that if you do stop down, the calculations are made for you, i.e., 1/3 or 3/4 stop is 1/3 or 2/3 stop no matter if your lens is at f/5.6, f/8 or f/11. It's just the time that's longer; the proportions are the same. It's not better, it's just simpler, quicker and more precise.

On some lenses, focus can change with the f stop. I always just change the time.

 

[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.

Thanks That remark of mine was meant as a joke The clue was in log tables being for Canadian lumberjacks

pentaxuser

 

[Chan Tran]

Thanks That remark of mine was meant as a joke The clue was in log tables being for Canadian lumberjacks

pentaxuser

You said you don't find the ^ key on your scientific calculator because no calculator has it. Your calculator should have the function but it's not labelled as ^.

 

[RalphLambrecht]

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.

not necessarily a heretic but apparently fact-resistant; not a desirable scientist trade.BYW.:Metromomes are incredibly annoying, and foot switches are too easily stepped on by accident, messing up the print.

 

[MattKing]

Foot switch user here, and here is my 1/2 stop progression test strip guide:

And yes, 6 is a round-off of 5.6.

 

[Doremus Scudder]

I couldn't live without my footswitches anymore. They are indispensable for burning! I guess I like the steady beat-beat-beat of the metronome (beeps in my case now ) So many years practicing music gets one used to that.

Doremus

 

[Chuck_P]

I would be hearing that metronome in my head when I'm not even printing.........couldn't stand it.

 

[Pieter12]

I would be hearing that metronome in my head when I'm not even printing.........couldn't stand it.

Kind of distracts me from the tinnitus. Plus, when the voices in my head choose to sing, it helps them keep in time.

 

[Alex Benjamin]

I guess I like the steady beat-beat-beat of the metronome (beeps in my case now ) So many years practicing music gets one used to that.

So THAT'S why I never made it to Carnegie Hall !!!

 

[Chuck_P]

Kind of distracts me from the tinnitus. Plus, when the voices in my head choose to sing, it helps them keep in time.

I'm a tinnitus sufferer too I wear a hearing aid that plays white noise, I find the hum of my LPL enlarger during a printing session rather soothing as well.

 

[Doremus Scudder]

I would be hearing that metronome in my head when I'm not even printing.........couldn't stand it.

The metronome isn't constant. It's only on when I'm exposing a print; it goes on and off when I step on the footswitch.

Now, developing film for 14 minutes in total darkness with nothing but the metronome to keep time as well as time your agitations (so you're counting 840 seconds total as well as making sure you shuffle through the six-sheet stack every 30 seconds), that's something that would drive you crazy!

Doremus

 

[MattKing]

We probably have a number of different threads here that talk about things that drive us crazy!

 

[Nicholas Lindan]

Now, developing film for 14 minutes in total darkness with nothing but the metronome ... would drive you crazy!

That's why God invented the GraLab timer.

There is no one timer that fills every need in the darkroom, though if I had to pick only one it would probably be a GraLab.

"A jack-of-all-trades is master of none."

 

[snusmumriken]

not necessarily a heretic but apparently fact-resistant; not a desirable scientist trade.BYW.:Metromomes are incredibly annoying, and foot switches are too easily stepped on by accident, messing up the print.

I’d prefer you not to be insulting, but I’m interested to know what fact you think I am resisting?

 

[Rmaydana]

I did the calculations for the most common factors, then use a simple calculator.

1/2 stop multiply or divide by 1.4
1/3 stop multiply or divide by 1.26
1/4 stop multiply or divide by 1.18

I wanted to share a simple design I put together using modern tools. The paper might be basic, but this e-paper display is absolutely awesome for the darkroom! Right now, I’ve set it up with f-stop increments for 1/4, 1/3, and 1/6. The rest is super easy to calculate, and I even added a button to switch between (+/-).

It’s all based on a starting time, and everything calculates from there. I’ve compared it to the tables, and it’s spot on. I’m really excited about how well it’s working!

 

[Chuck_P]

.......................and foot switches are too easily stepped on by accident, messing up the print.

I definitely like the footswitch that operates my DA F-stop timer. I've never stepped on it by accident but I have, inadvertently, activated it before I'm ready. This is because with my shoes on it's hard for me to sense the pressure of my shoe in the switch. My solution is to print in my sock feet so I have a much better feeling for the switch beneath my foot.