F-stop timer steps, any preferences?

I am building a homemade f-stop timer. I think I've figured out the basics but one question I have is whether the steps between f-stops should be in tenths, twelfths or even sixteenths. It seems that tenths may be too coarse since some say that prints that differ in exposure by a twelfth stop are noticeably different when placed side by side. Then what about sixteenths? Is that overkill? Thanks.

My F-stop timer is set for tenths as the shortest increment. I do test strips in .5 stop increments. Then use 10 ths at a specific stop for super fine tuning.

I have the same timing sequence every time, and I've made them the same as the f/stops on my light meter.

2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45, 64, 90

In the darkroom I use a metronome, because then I have both hands free at all times.

I usually start with f/5.6 (35mm), f/8 (80mm), and f/11 (150mm), and if I have to open up or stop down from there I will.

My print times are always in the 30-60 second range, which allows me to work with full seconds. In turn this gives me plenty of opportunity to do very smooth dodging and burning sequences.

That's my approach. I don't really need finer adjustments.

The one I built is adjustable in .01 increments, but I have a knob that adjusts them by .05, or 1/20th of a stop. I have yet to find that I need more precision than that.

My color head uses density units, 30 per stop. I find that .05 is usually sufficient there for color, but not for black and white. So keep in mind that there may be more need for fine steps if you are doing black and white vs color. But either way 1/30th of a stop is more than enough.

I tried a metronome after hearing such great things bout them from others. I realized it just won't work for me since I lose track of the time in the middle of any long exposure (I can't seem to count and focus on the dodging or burning at the same time). To keep both hands free I use a foot switch. I suspect the metronomes work great for people with musical abilities, of which I have none.

Also, have you seen Polyglot's f-stop timer? I built one of his design (using his board). Then I used the code as a starting point and built a LED head system. Even if you want to build your own you might want to check it out for some ideas.

http://www.brodie-tyrrell.org/fstoptimer/

I use 1/4 stops. But, what do I know?

cardiomac
the answedepends ,of course, on what one is used to or used to work with.from my long-time experience and love with f-stoptiming


]iwould only consider the folloing:
1. 1/3 stop for rough test strips and significant changes in exposure
2.1/6 stop for closing-in test strips and clear changes in exposure
3.1/12 for fine-tuningtest strips and slight changes in exposure
finer increments might be useful for hard paper grades, but I 'd stay away from1/4,1/8,1/16 an so onand stick to 1/3as used on LFlenses
alsi important is the starting point.I recommend a base of 16s and work up and down from there. How do you intent to handle dodging and burning?

Have a look at the timer in my signature (as posted by Larry above) and feel free to use the source as-is or modify it to suit yourself. It supports 1/100th stops because that was the simplest way of building in drydown correction with sufficient accuracy.

I find when printing that 1/8 stop is quite good enough at moderate grades but if you're printing with hard paper and on your final adjustments, you will sometimes want about 1/20 of a stop adjustment. I do test strips at 1/2 or 1/4 stop intervals and often just guess an exposure to within 0.1 or 0.2 from there and it's good enough.

I use electronic timer that goes 1/10 of a second and use Ralf's f-stop table which I stick to the wall. Works for me...

Hope some one pull a Raspberry pi project soon...

Rpi is not realtime and not therefore not really suitable for high-precision timing with good repeatability. It's also pretty expensive and power-hungry.

polyglot said:

Have a look at the timer in my signature (as posted by Larry above) and feel free to use the source as-is or modify it to suit yourself. It supports 1/100th stops because that was the simplest way of building in drydown correction with sufficient accuracy.

Click to expand...

Thanks for the link to your timer. Very nice work and very generous making it open-source.

It seems that a minimum of 1/12 stop is the required and maybe even 1/20 stop. I'll start with 1/12 and see how it goes.

Thanks everyone for taking the time to reply.

1/12 stop is a reasonable minimum.very hard grades may need less,but if you allow a switch to linear timing,one can always deduct0.1s.