Fstop timing

[Alan Townsend]

Been reading on Bruce Tanners website again, stupid idea of f stop timing is actually starting to make sense. Perhaps its just the sleep deprivation.

At least the way bruce tanner describes the process makes it seem very simple.. do a test strip and instead of a linear 2-4,-6 or 5-10-15 second time differenctial sequence. You do it by a scientific "stops". And when you develop the test strip and let it dry you have a strip with far superior differences between each of the stops.

Then you can take your prefered stop number in the test strip and break it down by 1/4 and 1/3 and so forth to get a more accurate and enhanced accuracy versus the old "20 seconds is to dark, 10 is to light, but do i need to break down the 15 second section into 10-11-12-13-14-15 test strip sequence"


But then I hit a wee snag, in times past some of my convential test strips dictated I set the gralab 300 to 5 seconds, and using the dark room automation handy dandy fstop chart..


And doing some quick math, how the hell does a person deal with a 1 or 2 minute, or even 80 minute long expsure time without worring about heat buildup in the negtive itself causing defects?

Mono,

To deal with heat effects, replace tungsten with LED bulbs if possible.

Get some neutral density filters to lengthen exposure if needed to replace fractional seconds with even seconds.

Or spend big bucks on an fstop timer that you don't really need otherwise.

Alan Townsend

[flamberge]

Hi.

I think this is my first post here, and for the fist time IMHO I may be able to contribute something.

please forgive my english, I was raised speaking spanish and german.

I have been using the f-stop method for my enlarging from some 10 years ago, and I will try to explain some misunderstandings.

If a good print takes some 28 seconds of exposure, it doesn’t matter if you calculate it in f-stops or seconds. The final exposure will always be the same 28 seconds.

There is no way that using the f-stop method will take you to 80 plus seconds exposure times.

What the f-stop method gives you, is a more rational way of thinking about increasing/decreasing a given exposure time because the increment in density (within limits) of the paper picture is ruled by the same law of physics as the exposure of a negative. In simple, is’t just not linear.

so, if you have a given density achieved at an exposure of 4 seconds, and now you want to double it, the time you will need to do it will be 8 seconds.

But if the same density was achieved at an exposure of 16 seconds, now you will need 32 seconds of exposure to double the density of your print.

A test strip exposed in linear increments of the same amount of time ( say, 5 seconds), will lead to a decreasing difference in density between exposures as time goes on.

That’s why the linear method of thinking exposure fails. Sure, you can get perfect prints that way, (I did it for almost 40 years) but it takes longer and is not as intuitive as the f-stop method, who in its roots is the same way as we expose negatives.

You get a lot more meaningful increments in density using f-stops.

During the pandemic I was sent home. Im a pediatric surgeon with a history of a mild hearth attack. I spent my time among other things, to my hobby in electronics. I designed and made an arduino f-stop timer , You can see it (in spanish) in the spanish Nikonistas forum, here: https://www.nikonistas.com/digital/f...ra-ampliadora/

[Renato Tonelli]

Flamberge: excellent explanation. Your f-stop timer looks great.

Welcome to the Forum.

[ic-racer]

You can easily get into really long exposure times with f-stop timing. For example if you need to increase a one-second exposure by 60 stops, your exposure will be longer than the estimated history of the universe.

log2(436117076600000000) = 58

[Vaughn]

One way is just as good as another way. There is nothing that makes one method 'superior' or "more intuitive" than the other...other than how the individual wants to think about it and what they are use to.

Thankfully my exposure unit has no f/stops so it is a non-issue for me.

[aduncanson]

I found Darkroom Automation's f-stop dial for the graylab timers to be very helpful.

https://www.darkroomautomation.com/support/grastops.pdf

[Pieter]

One way is just as good as another way. There is nothing that makes one method 'superior' or "more intuitive" than the other...other than how the individual wants to think about it and what they are use to.

Thankfully my exposure unit has no f/stops so it is a non-issue for me.

We already think in terms of f-stops for exposure, so doing the same for printing is more intuitive for me. Plus, it is about a stop difference moving from 8x10 to 11x14, all my times including dodging and burning can be easily applied without starting over.

[Vaughn]

We already think in terms of f-stops for exposure, so doing the same for printing is more intuitive for me. Plus, it is about a stop difference moving from 8x10 to 11x14, all my times including dodging and burning can be easily applied without starting over.

That's cool...and, right, wrong, or otherwise, working in seconds is intuitive for me (back in my silver printing days).

As an aside, I would rarely have a goal of making a 16x20 print to look just like an 8x10 print from the same negative. I tended to see them as two different images...considering how print size can affect our viewing of an image. I preferred 'starting over'......plus my method of burning/dodging was too complicated (too crazy perhaps) to keep track of and record.

[nolindan]

... plus my method of burning/dodging was too complicated (too crazy perhaps) ...

You like "Crazy complicated"? - why you are just the man for f-stop printing with all of its accoutrements.

Well, maybe not, it does have the danger of simplifying things for some people. They find "sanely simplified" to be just too boring for words, and, after all, it can become a trap that is hard to escape from.

[Vaughn]

You like "Crazy complicated"? - why you are just the man for f-stop printing with all of its accoutrements.......

Most likely!

Instead of any significant dodging, I made the base exposure a little light, then burnt the print down selectively until I saw what I wanted. I used the base exposure to burn in areas with a hole in a piece of cardboard. An area of the image might get burned in by hitting the timer hit 4 times with the hole this size, moved this way...and so forth. I'd look at the wet print and might decide to give that area 5 hits, but move the hole this way this time. The timer might get hit 30 or more times before I am done. Chiseling away with light. Lots of fun, especially having so much space to work with making 16x20s.

This is a ~7x16 silver gelatin print from 4x5. Actually - not a great reproduction of the print, but a lot of fun working with it.