f/stop timers: Darkroom Automation or RH Designs?

[wrench]

Thank you Nicholas for your insight. You cleared up a lot of things for me. Now just one more question.
I noticed that the RH timer can compensate for enlarger height while keeping all the burn/doge/base exposure sequences proportional. This would be fabulous for printing the same image at different sizes. Can the DA timer do this as well? If I had to guess, I think the answer would be yes, but I would have to use the adjustment or drydown compensation feature for this and just figure out the percentage of additional exposure for a given height. Is that correct?

 

[RH Designs]

Hello Nicholas

Thanks for the useful post, but may I clarify a couple of points?

At the system level the DA system uses a seperate meter and timer, while the RH Designs units integrate the timer and meter.

Not strictly true; we offer a combined unit with a less sophisticated timer, the Analyser Pro, or separate units - the StopClock Professional timer which has two channels and programmable sequences, and the ZoneMaster II meter which has identical metering functions to the Analyser.

DA system gives greater control in placing print tones where you want them and allows precise control of midtones and midtone contrast; obviously this takes more time and effort than the RH approach of scanning for the brightest and darkest points and letting the timer pick the paper grade and exposure.

We don't use a scanning technique. You pick the areas you want to measure, highlight, shadow, midtone (up to 8) and the meter shows you on the grey scale where those tones will be placed for the grade you've chosen. Then you can adjust the time and grade setting to move those tones around if you want. The grey scale display helps you identify any areas which may require dodging or burning in, and the meter can then calculate the amount required. You may have been thinking of the Heiland Splitgrade units we represent in the UK which are much more automated. Our meters were specifically designed NOT to be automatic! I generally liken the Heiland to an auto-exposure camera with manual override, and the Analyser/ZoneMaster to a hand-held spot meter. A densitometer function is included in both.

The DA timer has more memories, assuming you buy the model with memories.

True.

Lastly we chose to display times in true seconds because most people are familiar with that, and it gives an indication of how much time remains during the exposure. Both systems are indeed equally valid.

 

[Tim Gray]

Thank you Nicholas for your insight. You cleared up a lot of things for me. Now just one more question.
I noticed that the RH timer can compensate for enlarger height while keeping all the burn/doge/base exposure sequences proportional. This would be fabulous for printing the same image at different sizes. Can the DA timer do this as well? If I had to guess, I think the answer would be yes, but I would have to use the adjustment or drydown compensation feature for this and just figure out the percentage of additional exposure for a given height. Is that correct?

Both timers will do this. This is due to the way both timers reference subsequent exposures for dodging and burning (and split grade) back to the original exposure.

So basically, with either timer, you make a print at one size and get all the details down. If you change print sizes, all you have to do is figure out your base exposure again. Whether you do that with math, a meter, or test strips, once you plug in the new base exposure, all the subsequent exposures are automatically changed as well.

 

[Mahler_one]

"Kudoes" to both Nicholas and Richard for their civilized, informative, and measured discussion of the merits and differences of their respective units. Refreshing, and very much welcomed. Simply confirms the positive opinions posted here about both gentlemen. And yes, both systems are great.

Ed

 

[Nicholas Lindan]

I noticed that the RH timer can compensate for enlarger height while keeping all the burn/dodge/base exposure sequences proportional.

Yes, both RH and DA timers have the dodge and burn exposures as stops +/- the base exposure. If you want to burn in the sky for 2 stops you would set the burn to 'B 2.0' on the DA timer. This would create the same burn all the way from wallet size to mural. The same is true of the burns programmed into the RH timer's channels.

The RH timers perform dodging as a sort of inside out burn. The DA timers have a dedicated dodging mode that is a bit easier to use and accommodates multiple dodges by splitting the dodge exposures so that you don't run out of time in which to dodge. Dodging is much less popular than burning because up till now there hasn't been a timer that handled it well. Quite often a magazine's how-to-make-a-print column shows someone using six burns to make an image that could have been made with 3 dodges instead. If you find yourself burning in the area of interest you are doing it wrong.

You have to determine for yourself the actual amount of base exposure adjustment you need when changing magnification. There is a special ruler on the DA support page that indicates how much exposure change is required - it can be used with any f-stop or seconds timer. It, of course, works most conveniently with the DA timer. The ruler method has been found to work to 1/30th of a stop of accuracy.

The DA Precision Enlarging Meter will directly indicate the exposure change required when changing exposure:

1. Zero the meter at the original magnification;
2. Change the magnification;
3. Read the change in illumination level from the meter;
4. Adjust the timer's base exposure by the same amount,

The meter reading + the timer setting = the total exposure. As long at the meter and timer sum to the same value the same total exposure will be given to the paper - this works very much like the EV system on a camera where any shutter speed and f-stop that sum to the same EV number produce the same exposure.

I am sure the RH Designs systems have a similar mechanism with the probe on their analyzer models.

You can also use an Ilford EM-10 meter for this purpose - actually what this meter was designed for. With the EM-10 you zero the meter at the original magnification, change the magnification and then adjust the lens aperture so the illumination is brought to it's prior level. The problem with this technique is that you can't keep the lens set at it's optimum f-stop. OTOH, if printing with color it is important to keep the exposure time constant and so the aperture change method is preferred.

 

[Mahler_one]

Nicholas: I have read and reread the following and I admit to not being completely able to understand what you are saying. Sorry to be such a dunce. Can you explain the concept in just a bit more depth? I promise to try to understand!

<It is easy to control local contrast with the negative contrast index in stops of scene luminance to stops of negative density and the paper contrast in stops of negative density (the same thing as stops of paper exposure) to stops of print luminance.>



Ed

 

[Nicholas Lindan]

And yes, both systems are great.

I only know of one man who can make that statement with confidence as he owns and uses both systems. I think it would drive me nuts - like alternating between driving on the left and driving on the right.

P. J. O'Rourke suggested a very good way to remember how to drive in Great Britain: It's a socialist country: keep left and look for danger from the right. Reverse if crossing the pond the other way.

 

[Mahler_one]

Well Nicholas, I have HEARD that both systems are great. Both you and Richard I'm sure think that each of your respective systems are great, and have not said that the other system is not great...so, not meaning to think in syllogisms, both systems are great.

 

[Nicholas Lindan]

Nicholas: I have read and reread the following and I admit to not being completely able to understand what you are saying.

<It is easy to control local contrast with the negative contrast index in stops of scene luminance to stops of negative density and the paper contrast in stops of negative density (the same thing as stops of paper exposure) to stops of print luminance.>

Reading assignment: Meese, The Theory of the Photographic Process, revised edition 1954, Chapter 5. Quiz on Friday.

On page 162 he plots the typical 'S' HD curve and along with it the curve of the derivative of density to exposure dD/dE. The derivative is the local contrast of the film or paper and is the change in negative density for a given change in scene illumination.

If one stylizes the HD curve as a perfect 'S' it turns out that the curve of local contrast is a bell-shaped curve reminiscent of a standard distribution.

Although people talk of a straight-line portion of the HD curve, in reality the HD curve hasn't got a flat spot on it. Ditto the local contrast curve. The local contrast changes throughout.

Plot the local contrast for a VC paper and you are in for a shock, an application note on this is in process and will be posted on the DA web site in the next few weeks.

That asside, a decent approximation can be had by confining oneself to the standard Zones. At each zone the constant change in exposure results in a different change in negative density or print reflectance.

If you have information on the film's response and on the paper's response (available in the Darkroom Automation 'Paper Seed Charts') you can transfer the range in scene illuminance to the range in print tone.

As an example:

You are taking a picture of a snow scene where the interest is in the shadows on the snow.

Metering the bright snow and the shadowed snow you measure a 1 stop difference.

In the highlight zones you know the film (from your prior testing) produces a 0.3 stop change in density for a one stop change in exposure.

Unfortunately, the VC paper you want to use also has low contrast in the highlights of, again, about a 0.3 stop change in print tone for a 1 stop change in exposure.

As a result the one stop change in scene brightness becomes a 0.3 stop change in the negative which then becomes a 0.1 stop change in the print tone.

Obviously, this isn't going to work - well it will work, producing the same disappointing snow scene you have been battling with all your life.

The solution is to move the 1 stop difference in snow brightness to the middle of the film curve where the local contrast is at it's highest by placing the snow where zone VI would normally sit at a local contrast of 1.2 stops/stop. By increasing development time, safe to do as the highlights are down on the curve, you can get a local contrast of 1.6 stops/stop.

By going from a VC paper which has very low highlight contrast to a graded paper you can get a local contrast in the highlights of .6 stops/stop by printing the highlights down a bit.

The resulting contrast in the print will then be 1.6 * .6 = 1 stop.

So the snow scene you metered at 1 stop of contrast will have a 1 stop contrast range in the print and look as pretty as it did in real life.

Shadow detail will be a problem, of course, so you may want to reflect light into the interesting shadows if you can and think about using a dilute developer to help bring up the shadows.

The highlights may lack a bit of sparkle because they have been printed down, and you will probably have to use an overall slight bleaching in a cutting dilution of Farmer's Reducer.

If you had to do the above using conventional OD units for negative and print density you will be forever converting from OD to stops of exposure and back again.

By using stops throughout, stops of scene brightness can translate directly to stops of print brightness.

Disclamer: All the numbers above are from the top of my head (or pulled from my ....) and are for illustrative purposes only.

 

[Mahler_one]

I will definitely fail the test, and will need an excused absence.

Thanks. A good deal of reading and thinking is now in order....gee whiz Nick, won't test strips work? How about split grade printing? What did photographers do in real life before the meters were available...surely they were able to print a scene such as you described?

 

[timbo10ca]

I chose the RHD Stopclock Pro because I wanted the power of the Zonemaster 2. I'm not sure if DA has an exposure meter available. Zonemaster for quick proofing and playing to see what the neg is capable of, Stopclock for honing in on the fine print. IIRC, the RHD just needs you to purchase an extension cord for the enlarger and safelight, cut the end off and wire on a the plugs they send (when I bought mine, anyway) because the timer power inputs are those crazy Brit ones-No biggie.

Tim

 

[Chazzy]

This thread has so confused me that I'm quite sure I have no business using either product.

 

[RH Designs]

IIRC, the RHD just needs you to purchase an extension cord for the enlarger and safelight, cut the end off and wire on a the plugs they send (when I bought mine, anyway) because the timer power inputs are those crazy Brit ones-No biggie.

Tim

They're not the crazy Brit ones Tim, they're the same international standard you'll find on your computer . We supply plugs for you to wire onto your enlarger and safelight, or you can buy adaptors locally which save you the trouble. It's not practical for us to produce a unit with sockets tailored for each individual country, there are too many variations. That's also why IBM chose the international standard IEC connectors for the original PC.

 

[Nicholas Lindan]

gee whiz Nick, won't test strips work?

Not if the negative has too little contrast in the highlights (negative shoulder) to deal with the lessened contrast available in the paper's toe/highlight regions.

Lots of paper contrast in the highlights is very hard to achieve, impossible with VC paper.

How about split grade printing?

Won't do anything for you. Well, it will allow a natural opportunity to try and burn in the highlights with a #5 filter, but as VC paper doesn't have highlight contrast worth diddly, it is a rather futile effort. But remember, if you find yourself dodging or burning the area of interest something is seriously wrong.

What did photographers do in real life before the meters were available...surely they were able to print a scene such as you described?

Trial and error, experience, reading chapters 5 and 23 in Meese...

See, it can get worse. This isn't modern technology or anything, the graph above was originally developed by Jones in 1934.

How did people cross the ocean before 747 sleeper seats were invented? In less comfort. And it doesn't mean you can't take a sailboat across the Atlantic.

Time goes on, you get better tools, and you can produce more and better in the limited time you have available. The old tools still work as well as ever - and new tools are nice to have, you don't have to use every bell and whistle.

 

[timbo10ca]

They're not the crazy Brit ones Tim, they're the same international standard you'll find on your computer . We supply plugs for you to wire onto your enlarger and safelight, or you can buy adaptors locally which save you the trouble. It's not practical for us to produce a unit with sockets tailored for each individual country, there are too many variations. That's also why IBM chose the international standard IEC connectors for the original PC.

Oh yeah- they're those crazy computer ones.... Been a while since I did the set-up.

 

[Mahler_one]

Great stuff Nick! I did not know about the "difficulty" with highlight contrast and VC paper...reference? You are telling us that VC paper cannot provide prints that adequately provide the highlight contrast that is captured by the negative? So, will our printing results generally improve if graded paper is used? Of course, with the use of graded papers the techniques that one uses to expose and properly develop film assume greater importance, adn there is much less latitude for error. Moreover, subtle changes in contrast depend upon changes in developers ( and other techniques ) rather then simply using another combination of filters.

Thus, the negatives obviously must capture the highlights correctly for them to be printed on graded paper. As a corollary, to repeat your assertion, even IF the highlights ARE captured correctly on film such highlights will not print properly on VC paper. Right? Do Pyro developed negatives ( in discussion on another thread already ) aid one in capturing highlight contrast on the enlarging paper? Indeed, do Pyro developed negatives capture greater highlight contrast at all?

Can the Meese text still be found? I do have that wonderful Richard Henry book on Controls in Black and White Photography...a great introduction to the technical aspect of film and paper, but understandable even by non physicists and engineers.

Should the discussion of VC paper and highlight resolution be moved to another thread?

 

[Ken N]

This thread has so confused me that I'm quite sure I have no business using either product.

They both have very simplified "PHD" (Push Here Dummy) functionality.

But you do bring up a good point. The idea behind F-stop printing is to simplify our lives. Following this thread, it seems like F-stop printing is one of the most complex and laborious things you can do.

The reality is, figuring these timers out is pretty easy, but the manuals are necessary at first.

 

[Nicholas Lindan]

The idea behind F-stop printing is to simplify our lives. Following this thread, it seems like F-stop printing is one of the most complex and laborious things you can do.

Hmmm...

But an f-stop timer has simplified your life, hasn't it?

An understanding of tone reproduction isn't required to use either timer. They carry through the original 'push the button and we do the rest' paradigm that started modern photography. It's the discussion of what the rest is that gets done behind the scenes that scares people.

All of the gory digressions, of which I am most guilty, also apply without f-stop printing. If tone reproduction doesn't interest you then skip the whole wretched mess - the physics of it are independent of how you set the exposure. If tone reproduction does interest you, then working in stops from beginning to end makes life simpler.

Even pursuing photography on a strictly 'artistic' plane is easier if you use stops all the way through. After all, you are already using stops for exposure time every time you click the shutter speed dial - to use stops when timing a print simply requires forgetting.

It's like everything in life: You can cook a duck without any understanding of Maillard reactions; OTOH, a perusal of them shows just why it is a good idea to apply a sweet glaze before cooking if your goal is a lovely crisp browned skin.

 

[Mahler_one]

Now Nick...you are having fun with this group...the Maillard reaction to cook the Mallard...the amino and the carbonyl, groupies in taste. Enough of this thread.

To repeat, both timers are great....

 

[Ken N]

Nicholas wrote:
"But an f-stop timer has simplified your life, hasn't it?"

I'm not so sure about that. Simplified? No. Made more productive with fewer errors? Yes.

 

[wrench]

Well, I got my DA timer in the mail yesterday. I was so excited I popped it out of the box, plugged it in, and started fiddling around with it. BAD IDEA. I am not a patient person, but I finally sat down and read the manual (even though I already did about 5 times before I got it). I have about 50 contact prints to catch up on, so I set to work, and by about the 5th print I had the test strip printing all sorted out. Once I figured it out, the timer was a dream. I really like the buttons on it too, they're fun to push. The display can be a little cryptic at times, but I kept the manual right next to the timer and honestly now that I know what is what, I don't really need it anymore. So all in all, I'm very happy, making 50 contact prints is a lot less daunting now because everything goes so much faster and smoother. I haven't gotten into any fancy split grade printing or dodging and burning yet, but it doesn't seem like it will be too difficult.
Best, Laura