bpulv Loc: Buena Park, CA

A step tablet is a device used to calibrate a densitometer. It is usually a negative that has been exposed and developed and contains shades of grey ranging from the clear film base to the blackest black. The shades of grey are arranged in ascending white to black sequential adjacent rectangular steps with each step of a know transmission density. The most common step tabler has 21 steps of white, grey and black with an increase in density of each step of 0.15 (0.05 to 3.05). The step tablets come either pre-calibrated or uncalibrated. Pre-calibrated step tablets are used to calibrate the densitometer. It is often easier and cheaper to use an uncalibrated step tablet and use a calibrated densitometer to calibrate the steps of the uncalibrated step tablet by making a table (on paper) showing the density measurement of each step and using those measurements when using the step tablet for its final intended use. I will give you an example, however I will not go into all the details and it can sound very confusing (especially the way I write things) if you have never done it before.

Let's say you buy a new box of negative film of a lot number you have never used before. By placing your step tablet on top of a sheet of the film and exposing and developing it using time and temperature you would read the densities on that film with a densitometer and plot the results on logarithmic graph paper or in a computer program. You could then do the same thing with a sheet of the paper you intended to use for your prints and plot those results on the same graph against the densities of the steps on the step tabler. Note that since the paper yields a positive image you will be plotting the dark area densities on the step table against the corresponding white areas on the paper. The net result is that by carefully using the appropriate exposures and processing your negatives and film exactly the same as the step tablet images, the results will consistently be top quality full tone prints.

Bipod

That's it! Eastman Kodak Photographic Step Tablet #2:
http://i.ebayimg.com/images/i/350674644610-0-1/s-l1000.jpg
.
Kodak was a wonderful resource. I treasure my 1945 edition of the Kodak Reference Handbook --
it was one of the last editions to list the formulas for Kodak developers. Right down to the 2000s
Kodak was putting out good technical manuals.

The biggest unknowns in mechanical cameras were actual shutter speeds and amount of flare in the
lens. But it was possible to measure both (either directly or as the "personal film speed" of a given
camera and film).

Both these uncertainties are still with us. Brand new mirrorless cameras still have a focal
plane shutter--of unknown calibration. PCs make it really easy to measure shutter speed,
but digital cameras make it very difficult: there's no simple way to get behind the shutter to
measure its speeds. Maybe the program itself measures the speeed and somehow compensates,
maybe it doesn't. But the shutter is still a mechanical device--with all that entails.

And this is the golden age of flare: a typical "pro" zoom might have 20 elements in 15 groups: that's
30 surfaces in one lens! No matter how good the coatings, it's going to lose some contast.
extremely expensive, sharp lenses that aren't contrasty.

Folks who won't use a filter because it adds two surfaces will use a zoom lens containing
30+ surfaces--go figure! Extremely expensive, reasonably sharp at most focal setting,
but not contrasty. That's the "new normal".

But now there is a huge, new uncertainty that cannot be measured or elminated: firmware.
There is no being sure what the camera will do in a particular situation: it's controlled
by a computer program. It was tough enough understanding center-weighted metering,
but now we've got multi-zone metering, highlight weigthed metering, etc. and a program
that tries to guess what the photographer wants.

So we just give up, and let the camera make the decisions: focus, exposure, etc. Maybe,
if we are really daring, we add some exposure compensation.

Of course, cameras are no better at undrstanding what they are looking at, or at reading
the photographer's mind, then they were in the days of Daguerre.

Take three close ups a of a white horse, a grey horse, and and a black horse, and they
camera will still give you three grey horses. And it doesn't know that lemons are really
yellow, or that a background is confusion, etc. As a photographer, the camera is a
very good computer.

Fortunately, we have a methodology: "shoot lots and cull" followed by "fix it in PhotoSlop".

Despite the limitation that a properly white-balanced digital camera gives accurate color,
the latter makes it easy to achive those gaudy, saturated colors that used to only be available
in dimestore postcard lithography. Thanks to modern technology, you no longer have to pay
ten cents for a red red sunset over blue blue water: you can make your own! And tens of
thosands of PhotoSloppes do.

And how do we print? With another embedded system: the computer printer. More secret
firmware, plus secret formula inks and toners of dubious permance. Honest grain has been
replaced by pixellation: worse than litho dots because they create digital artifacts (a do
PhotoSlop "filters" -- really proprietary algorithms).

Kodak's Filter Manual lists the absorbption curves (by wavelength) for all of its fiters.
But a digital filter algorithm does whatever it does--only the programmer knows for sure.

That's what photography is today: an algorithm contained in secret firmware. The person
holding the camera serves three functions: buyer, scene-selector, and bipod. The camera is
in charge of getting the shot, so it is the photographer.

User ID

So then, you have no excuse ?


`

selmslie Loc: Fernandina Beach, FL, USA

It is worse with leaf shutters but most mechanical focal plane shutters can be slow by more than 1/3 stop at the highest speeds. Electronic shutters are more precise.

It's the number of groups that are the worst offenders because they represent air-glass transitions. You are right that it's pretty silly to fret over the addition of a single UV filter for front surface protection.

Yet another reason to not meter at all. I have become accustomed to shooting 1/3 stop darker than Sunny 16 (e.g., ISO 400 and 1/1000 @ f/11) and opening the aperture a stop or two for partly cloudy or overcast. It works very well and shadows are easily recovered.

You make a clear case for taking control and becoming a thinking photographer.

selmslie Loc: Fernandina Beach, FL, USA

You have no excuse for rude and insulting posts.

Hawkowl Loc: Ithaca, NY

Bipod, I rather enjoyed your pithy analysis of modern photography! I think it helps me to understand why I have found myself buying like six old film cameras in the past two years. And I will chuckle to myself (and perhaps even tell others) that I am just a button-pushing, scene-selecting bipod, in the service of unfathomable algorithms contained in secret firmware. Like a good movie, it sounds important, naughty, and terrifying all at the same time! (Rather like life itself, one might say). I just wish all the dealing with algorithms and firmware wasn't so hard! I mean, we spend years (eagerly) slaving away learning the details, salivating at the thought of the next round of algorithms and firmware and lenses...and in the process, the algorithms are shaping our brains to accept it all, and it gives us just enough reinforcement to crave even more. Will this eventually change our DNA? Will it affect human evolution? I can't even imagine what the future holds. Supposedly Caesar once said, "Give them bread and circuses"! I think now he might say, "Give them algorithms and firmware"! Will the algorithms ever run out? Will they get so good that they start turning on each other? Will the best algorithm win? Or maybe they've already won, they're just using us to snap all the portraits and scenes they need for their nefarious purposes?

Maybe I really should switch to decaf...!

bpulv Loc: Buena Park, CA

How did we get from a discussion about step tablets to a discussion of personal philosophies about photography and equipment, A 100% TOTALLY UNRELATED SUBJECT? When people want to discuss a subject that is unrelated to the stated subject of the thread they are on, they should start a new thread rather than hijack a thread from those who are interested in its original subject.

selmslie Loc: Fernandina Beach, FL, USA

I think you can forgive us for assuming that your question had been answered back on page one when you said, "Thank you, that is all I needed to know."

If you want to get the thread back on track, maybe you can clarify a couple of your own posts.

You later correctly stated that, "A step tablet is a device used to calibrate a densitometer." So far, so good.

But in the next paragraph you described a method of using it with film, "By placing your step tablet on top of a sheet of the film and exposing and developing it using time and temperature you would read the densities on that film with a densitometer and plot the results on logarithmic graph paper or in a computer program. ...by carefully using the appropriate exposures and processing your negatives and film exactly the same as the step tablet images ..." Perhaps you would like to explain how that film gets exposed "exactly the same as the step tablet images". It sounds more like something we might do with photographic paper, not film.

Most of us have found more practical ways to narrow down the correct exposure and development for film without using a step tablet, for example, trial and error. That's the reasoning behind the practical recommendation to stick with one film and developer combination. You can learn from a variety of your chosen subject matter how to make it all work.

So there is a connection between this and the apparent digression. The reliance on camera automation or on laboratory testing of film with a step tablet are both flawed - disconnected from reality.

bpulv Loc: Buena Park, CA

Of course, the exposure and the contrast range of a given scene will never be exactly the same. The purpose is to adjust your exposure, film processing and paper processing so that you can consistently produce a negative that will produce a full tone print. The tonal range of a film is generally wider than that of the paper. If you expose a film with a step table and process it, you can count the number of unique steps that can be resolved without the use of a densitometer. If you do the same with the paper you intend to use, you will usually find that it will resolve a different number of steps then the film, usually less. The trick to consistant full tone images is to align the tonal range of the film so that it is centered on and matched the tonal range of the paper.

To take it a step further, when taking the picture you measure the LR (light ratio) or SBR (Scene Brightness Range) using an incident light meter (the easiest way) or a reflective reading with a grey card. Then, knowing the LR or SBR adjust the film developing time according to the graph you developed for that film and paper combination using the step tablet and densitometer readings of the film and paper step tablet tests. For low contrast scene, you expand the film's contrast to match the paper through longer development and for high contrast scenes, you compress the film's contrast to match the paper (assuming the paper has a lower tonal range then the film). Since everything is done mathematically, the results will always be consistent providing that the exposure, exposure information including LR or SBR of the scene and processing including chemistry and chemistry potency (maintained with replisher for high volume) and temperature are always the same.

User ID

You can definitely use a step tablet/wedge to expose film
[at a standard consistent lumen level] and then check the
resulting densities on the film to plot the the characteristic
curve of the film-batch-and-process-variables combination.

You can also plot curves by shooting a reflection tablet with
a camera, which will then take into account the effect the
lens has on contrast at various apertures. This should be
done with a controllable light source to avoid the shutter's
mechanical variability.

-----------------------------------------------------------

The [complete] "Zone System" is just a pragmatic way of
doing all this without step wedges and densitometers. The
claims made by those who attempt to impose the Zone
System on digital photography are questionable. The test
methods they use do produce useful info, but to call it the
"Zone System" is just click bait/marketing. The work may
be quite useful, but Zone System is cannot be.


`

bpulv Loc: Buena Park, CA

Wrong! I have Kodak #2 step tablets that I bought in the 60's.

selmslie Loc: Fernandina Beach, FL, USA

Really? You have done this? How do you accomplish a "standard consistent lumen level" to match a camera exposure and get the film speed?

It can't be done because any film exposed for more than one second will end up with reciprocity failure. Reciprocity failure will mess up both your film speed and your contrast results. Only Fuji Across can be exposed for more than one second.

A transparent step wedge can be used to calibrate a densitometer or you can use it to test paper exposure and contrast. It's useless for exposing film.

I used this approach thirty years ago with a Macbeth Color Checker (now made by X-Rite) which provided range from +2 to-2.5 stops (a 4.5 stop range). To get a full 10 step range I needed three overlapping exposures. It was a difficult to execute and the results needed to be measured carefully and adjusted to get the overlapping squares to match.

That's why I developed a more pragmatic approach to testing A Practical Guide to Film Characteristic Curves that anyone with an Epson scanner can use. It provides a way to determine both development time and film speed at the same time using your own camera(s).

Hardly anyone uses the Zone System rigorously as defined by Adams and Archer, even when they are working with sheet film. But understanding the principles of densitometry is useful for all forms of film development.

(Download)

selmslie Loc: Fernandina Beach, FL, USA

As I explained in my response to User Id, there is no practical way to expose film through a step wedge with an exposure time of less than 1 second to avoid reciprocity.

Since you have not provided us with a methodology for exposing the film, it's probably safe to assume you are speaking theoretically and have never actually done it.

User ID

`



Gravity shutter. Gravity is very reliable.
Device is so super simple mechanically
that, for any practical application, it is
99% consistent. In case it's unobvious
to anyone, this is done in a darkroom.


`

selmslie Loc: Fernandina Beach, FL, USA

That's pretty far-fetched. Did you just Google it? You don't even credit the person you quoted.

Can you show us a picture of your setup using one or are you just bluffing?

At http://www.casedimage.com/2009/09/29/gravity-shutter/ I see the claim that, " At the T setting though its quicker and more accurate that pulling on and off the lens cap with no danger of shoving it out of focus (my exposure times outside on a sunny day are around 1 to 4 secs)." Hardly a precise shutter.