Calibrating for Zone system by multiple exposures pulling darkslide out

[claes_williamsson1]

Hello all,

 

I've recently bought a Horseman 4x5 view camera, and after a couple

of test shots with it (a couple decent, a couple not-so-good) I'm

planning on making a structured attempt at calibrating my

meter/lens/shutter/film/development combination to see if I can start

to learn how to get predictable results with metering and thinking in

terms of the Zone system.

 

This will obviously take quite some patience and work both in and out

of the lab, so before I start I wanted to hear if anyone had any

ideas or comments w/ regards to my "plan" for this.

 

I plan to make "striped" negatives where each stripe differs in

exposure by one stop from the ones next to it, as follows:

 

1. Focus camera on plain and uniformly lit surface.

 

2. Meter the said surface w/ my spot meter, shutter speed priority,

and find what aperture I need at 1/8 seconds (more on why 1/8 in a

second).

 

3. Insert film holder, close shutter, set aperture to what I metered

above.

 

4. Pull darkslide out 1 cm (3/8 inch)

 

5. Make an exposure for 2 seconds.

 

6. Pull darkslide out another cm.

 

7. Make an exposure for 1 second.

 

...

 

and so on until I've made one at the shortest shutter speed, 1/125.

 

8. Then pull out another cm, make _another_ exposure at 1/125.

 

9. This leaves the last cm or so unexposed at the very end of the

film.

 

10. Push the darkslide all the way in. Finished.

 

Except for possible "reciprocity failure" at the first stripes of the

film which is exposed for 4 and 2 seconds, respectively, this should

(since the exposure is additive) expose the film for 4, 2, 1, 1/2 ...

1/125 and 0 seconds (11 stripes) with the center stripe exposed to

yield a "middle gray" (zone 5) if everything is already calibrated.

At the very ends should be a fully darkened and completely unexposed

stripe, respectively.

 

I plan to evaluate the negatives primarily by contact printing test

strips, both since I don't have a densitometer and since the print is

what I'm ultimately after...

 

I thought the above would be a reasonably economical way to get

different exposures on the same sheet of film in a reproducible way

with my equipment... and by, for example, doing two or three

exposures at the same aperture I can also test to see if my

development is a source of variation.

 

Do you think the above is feasible? What do you think will be the

biggest problems/pitfalls/sources of error in this? Any tips on what

to use as my "uniformly lit surface" (it takes quite a bit of

artificial light, I noticed, so maybe I'll do this in daylight...)?

Any other suggestions?

 

Regards from a frosty Sweden,

 

Claes Williamsson

[ole_tjugen]

I think it's feasible, but I would do it the opposite way so that the shorter exposures are progressively covered. This makes for slightly more tolerance to flare:

 

Pull DS out nealy all the way, expose 1/125.

 

Push DS in a little bit, expose 1/125.

 

In a bit more, expose 1/60.

 

And so on, until you expose the last bit for 2seconds.

 

I use this method of making test strips in the darkroom, and have found that it DOES make a difference if I push or pull.

 

The usefulness also depends on the accuracy of your shutter, of course...

[brian_ellis3]

I guess this procedure will give you a very rough idea of how accurate your shutter speeds are. Is that what you're trying to accomplish? Other than that I don't exactly understand what you expect to learn from this procedure but perhaps I'm missing something.

 

As a relatively minor point, it's my understanding that multiple exposures that add up to a particular shutter speed don't produce the same density as a single exposure at that shutter speed. In other words, if I make four exposures each at 1/4 second, I will get a different density than I would if I made one expousre at one second. If I follow your procedure correctly you plan to get your 4 second exposure, for example, by making a series of shorter exposures. I don't think that what you see on the film will be the same as

the density you would get if you made a single four second exposure (completely apart from possible reciprocity failure, which is another issue with this procedure).

 

All in all this strikes me as a collosal waste of time but, again, perhaps there is something I'm not following about what you're doing or what you will be learning.

[pascal_miele]

The photographic effect of 1+1+1+1+1+1+1+1+1+1 is inferior to 10.

 

If you add this to Reciprocity and shutter errors....

 

Use your film and your camera for photography !

[tim_curry]

This may work well for your needs, but I would be concerned with only 3/8" of travel on the darkslide. You may have light bouncing between the slide and film plane. It might be better to use a larger increment, say 3/4" or 1", to make sure you don't get too much light bleeding from the edge.

[doremus_scudder1]

Claes,

 

I use a similar method often to calibrate new films. This is especially useful for quickly finding proper developing times and making "Zone Rulers" to help visualize with. I always use the "push in" method described above and have found the results to be reliable. I usually use two sheets total, leaving the first stripe on the first sheet unexposed to give me a larger area of fb+f to determine "maximum black" with. Between the two sheet I usually get 10-12 Zones. Although I am aware of the additive effect, i.e. that adding exposures together does not exactly equal on longer exposure for the total time, I find this effect to be negligible in practice and easily fine-tuned with field tests after the initial "down-and-dirty" calibrations have been made. If you get in the ball park with your stripe tests, you are assured of a printable neg, and that is all we can really hope for. Your idea is not only workable, but, in my opinion, one of the best options since it automatically includes not only your camera/lens/shutter/film/processing parameters, but also (assuming you are contact printing with your enlarger) the enlarger/lens/paper/processing parameters as well. Just make sure you have the right exposures to achieve a one-stop increase for each stripe. Have fun.

[jerald_brodkey]

I think an easier method is to get a Kodak Color Separation Guide and Gray Scale. I set it up carefully and spot meter the different patches and in that way make one exposure getting rid of problems like reciprocity factors. It may not have quite the range of densities that your method will have but you can always extend the range with another sheet of film if you think that is necessary....

[Glenn McCreery]

This is interesting. Doremus seems to have the technique sorted out. Another, possibly easier method to accomplish the same result would be to use a 4x5 step tablet transparency inserted in front of a sheet of film (assuming that both will fit in a film holder slot). One exposure of a white background would then give a ten zone range on the negative. Exposure should be, I think, such that zone V on the tablet equals zone V on the negative (perhaps spot metering a white background with the zone V step tablet strip in front of the meter will give the correct exposure?). I have not tried this, nor thought it out for more than a few minutes, but intend to give it a try. Step tablets are available from http://www.viewcamerastore.com/product_info.php?products_id=84

[ken_miller4]

If you want to do film testing, an easy way is as follows:

<p>

Get yourself one of

<a href='http://www.stouffer.net/Photo.htm#Transmission%20Projection'>these</a>,

and contact print it with a negative in your film holder. It may be ae bit snug getting it in the holder, but if you use an older holder, it will probably fit just fine.

<p>

Find a light colored surface, and expose the negative (and step wedge) placing the surface on zone X - you can either use the film's true speed, or make a guess at the real EI of the film - it doen't matter for the purposes of this test. Since the step wedge has 20 different steps, each .15 more/less in density than it's neighbor, you will get 10 zones of exposure on the negative. There are 21 steps, but one of the steps is duplicated (10 and 11, I believe).

<p>

Develop the negative using manufacturers recommendations, stop and fix. Dry the negative, and then inspect it. The first step that shows any real density change above fb+f tells you what your film speed is - that's zone 1. Remember that the clearest step would be zone 0, then 0.5, then 1, 1.5, etc. If the zone 1.5 step had the first perceptible density, it means that you need to decrease your film speed by 1/2 stop. If the zone 1 step was the one, your bang on. If zone 0.5 was the one, you film speed can be increased by 1/2 a stop.

<p>

Now that you know which step on the negative is zone 1, you can now determine if your negative was developed for the correct amount of time. Print the negative (with your enlarger, as you would a print) and try to get zone 1 to print with maximum black. This means that the zone 1 step would print as maximum black, with step 1.5 being slighty lighter. Once you've done that, inspect the step that would correspond with zone 8 (or 9, depending on your choice) - it should be a very light gray, almost pure paper white.

<p>

If the step is too dark, you need to increase development. Too white, decrease development. Adjust accordingly, and try again. You can also use this technique to find +/- development times, but the usual +40%/-30% seems to work pretty well.

<p>

Or, you can skip the previous and just carefully inspect your negatives. Do you have good shadow detail? If so, your film speed it probably ok. Thin shadows? Decrease film speed. Shadows have tons of detail? You *may* want to increase film speed. Are your highlights ok? If they're blown out, reduce development. Too gray, increase development.

<p>

What I do is cut the film EI in half, and expose the shadows on zone IV. The straight line portion of todays film is so long (upwards of zone 14/15, and perhaps even higher) that doing this will not affect the quality of your negatives. If it's good enough for Barnbaum, it's good enough for me!

<p>

Above all, just get out and shoot!

<p>

Hope that helps!

<p>

Cheers!

[martin_miller3]

I use the step-tablet method suggested by Glenn. You can get a 21-step, 4x5 step wedge from www.photoformulary.com for about $25. It is graded in increments of 0.15 density units (1/2 stop) up to about 3.0 I was able to borrow a densitometer to calibrate it. It was off by about 0.1 density units at worst so you could probably skip this procedure. The step wedge/ film sheet sandwich was too thick to fit into a Fidelity holder so I carefully inserted fine-grit sandpaper with a suitable thickness paper backing and sanded the film rails until the sandwich would fit. This method is by far the best that I have tried. I scan my 4x5 negatives with a Polaroid SprintScan 45 Ultra and print with an Epson 7600. The step tablet proved valuable in creating a custom gradation curve in Silverfast (scan software). Now when I scan in a new negative, the first print is as good as my original visualization and zone-system skills allow. I recommend this approach highly.

[billkantor]

Claes,

 

I tried this technique recently on three color films. The only difference is that I did 1/2 stop differences between each strip.

 

I can't explain why but the results were almost worthless... It rated Provia at about 40 -50 ISO but when I actually shoot, I find that 80 to 100 is much more accurate. Found the same ~1/2 ISO ratings issue with Astia and Velvia. The only real value I got out of this is that I could see the dynamic range of each film--there is about a stop lattitude difference between Velvia (~5 stops), Provia (6), and Astia (~7).

 

I'd appreciate it if someone can explain to me why I had this problem. The reciprocity issues are not supposed to kick in for the exposure times I used. Mybe you will have better luck.

[jerald_brodkey]

Bill - I'm not sure which of the above methods you are using, but

if you are using Ken Miller's method, remember he says to place the background on Zone X. Since this is a close-up, there will be a bellows factor involved. Chances are if you did not factor that in your films will be underexposed leading to the suggestion of a slower film speed.

 

I still think it is easier to photograph a gray scale, carefully lit,

and read with a spot meter and to then read the densities on a densitometer. It is closer to the real life situation of metering a subject and developing the film and reading the densities. Besides the Kodak one, Stouffers has a range of gray scales...

[jay_de_fehr]

I am simple minded, and use an accordingly simple approach. I start with the manufacturer's suggested e.i. (say 400) meter for e.i. 200, pull the D/S out 1/2 way, make an exposure, pull out the rest of the way and make another with the same aperture/shutter settings. This gives me e.i.s of 200 and 400. Next I flip the holder, meter for intermediate value of e.i. 300, expose half of the sheet, then the rest of the sheet giving me e.i.s of 200,300,400 and 600. That's always been close enough for me, but as I've said, I'm very simple-minded.

[ed_pierce2]

Claes:

What are you trying to find out? Film speed or development time? You need to determine both, and you need the film speed first.

 

Do the speed tests with full sheets for Zone I and send the negs out to be read with a densitometer. Use full 4x5 sheets. You just bought a Horseman and you don't want to spend $20 on a good speed test? A 16"x20" piece of black mat board taped to the shaded side of your house will work. If you don't already know the test procedure, get a copy of The Zone VI Workshop; they are on ebay all the time.

 

After you get the speed test done, then you can work on the development time. Otherwise it's all guesswork.

 

Or, if you have a certain amount of experience, you may be able to judge whether your speed rating is correct by looking at normal negatives. Low value areas placed on zone I should show detail on the negative but not the print. Still, if you really want predictable results, there are not any shortcuts. Do the speed test but by all means don't stop shooting. Keep making pictures while your tests are ongoing.

[rene_bolduc]

Here is what I�ve been doing for the last 15 years to calibrate 4x5 and 8x10 film with

the minimum waste :

- get a board white on one side black on the other

- go outside on a clear day in open shadow (north side of building)

- -focus at infinity

- -aim camera at black side of board

- -pull darkslide one third out and expose for zone I

- -go back into your darkroom and turn the film 180 degrees

- -go back outside pull darkslide one third out and expose for zone VIII using the

white side of board

 

What you will get is a band of unexposed film (FB+F) in the middle, a zone I

(exposure index) and a zone VIII (developpement time) at both ends. I then cut the

film in two lengtwise and get two 4x10 pieces of film that I develop for different

times.

Rene Bolduc

[smieglitz]

You could also pick up 5 old used (or even cracked/taped) 4x5 darkslides and drill a single 1/4" hole in each of them about one inch in from the edge and progressing upwards about 3/4" or so between slides. Load a holder with a sheet of film and use a good darkslide until the holder is in camera. Pull the good slide and replace it with the drilled slide that has the hole drilled at the lowest position. Make an exposure for Zone I. Flip the slide (not the holder) and make an exposure for zone VI. Pull that slide and insert the next drilled slide which has a hole about 3/4" above the position of the first drilled slide. Expose for zone II, then flip and do zone VII. A third drilled slide gives you zones III & VIII, another IV & IX, and a fifth drilled slide gives V & X. Replace the good slide and remove the holder from the camera. Inside you now have a single sheet of film that when developed will have 1/4" circles representing zones I to X on it with zone 0 fbf surrounding them. This procedure eliminates the intermittency effect.

[patrick_mckay]

Whew!!! No shortage of responses on this one. No yet mentioned, is using a (self-constructed) "Zone Board" that Gordon Hutchings describes in his "Book of Pyro". It's very easy to build, and one exposure provides you with 11 zones of exposure data. The only catch is that you will need to have access to a transmission densitometer. Many better labs, or pre-press operations will do this service for you, if you ask.

 

Using this zone board, I'm able to peg down all of my N, +/- times, for a given film/dev. combo within a few hours.

 

Good luck