Another option might be to incrementally pull the dark slide to pre-marked spots, essentially making a "test strip" on one sheet of film through multiple exposures of a white wall. I haven't tried this, so I can't attest to its usefulness, but it should work. The cumulative total exposure should place the wall at the desired zone (VIII or IX), if my thinking is correct. The strip at the right Zone V density should tell you the speed, and multiple sheets could be used to zero in on "N" development.
[COLOR=SlateGray]"You can't depend on your eyes if your imagination is out of focus." -Mark Twain[/COLOR]
Rio Rancho, NM
See noiseoil's article: http://www.apug.org/forums/article.php?a=104 for a writeup on testing for film speed and development changes with a Stouffer wedge. He uses the 1/2 stop per step model.
Incrementally pulling a dark slide could do the same job, but it would be hard to crowd as many steps as the Stouffer has in two rows into a single row. The Stouffer wedge is just a labor and materials saver. I figure it also keeps me from making the human error that creeps into making so many multiple exposures on one sheet, pulling the dark slide in increments... Did I slide the slide after cocking and shooting strip 13 and 14? But it could certainly be done that way by a careful worker.
The problem with doing the darkslide method revolves around the number of exposures that must be made as well as the fact that shutter errors will be multiplied and an intermittency effect occurs. (A series of cumulative exposures does not equal the effect of an instantaneous exposure which should be otherwise equivalent.)
To do the darkslide method it is probably easier to do two sheets: one using a zone I exposure (= 1 unit of exposure) as the unit and a second sheet based on a zone V exposure (= 16 units of exposure). What you want to achieve is a series of stripes representing zones 0 through zone X or in other words, a series of stripes each one stop/zone apart with the following units of exposure in the sequence: 0, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512.
To get this the darkslide is withdrawn almost all the way so that only a bit of the film is covered. This will give the film-base +fog or zone 0 density. The film is exposed to a zone I exposure (-4 stops from the indicated meter reading) and the darkslide is inserted a little further. The film is given a second zone I exposure to bring the uncovered film up to a cumulative exposure equal to zone II. (You would now have zones 0, I & II represented if the film was developed at this point.) The darkslide is inserted a bit more and the zone I exposure is repeated TWICE (to get an area of cumulative zone III). The darkslide is inserted a bit more and the zone I exposure repeated FOUR times (to get up to zone IV). The series of exposures on this sheet now goes from zone 0 through zone IV or 0 through 8 units of exposure.
The method is repeated on the second sheet except now the film is exposed using zone V (the indicated meter reading) as the unit. This will result in zones V through X on the film or exposures representing 16, 32, 64, 128, 256 & 512 units on the second sheet.
A simpler way to do the test on sheet film is using the Stouffer wedge placed above the film inside the holder and giving an exposure equal to zone X. This gets all the densities on the film at once and eliminates the multiple exposure and intermittency effects.
A third way to do this involves using 5 darkslides with holes punched in different locations. The film holder is loaded as usual with a standard darkslide in place. Once in the camera, that darkslide is withdrawn and replaced with one of the darkslides having a small hole punched through it. An exposure is made for zone I and then the darkslide is flipped and an exposure is made for zone II. That darkslide is then replaced with another having the hole somewhere else and a zone III exposure is given. The darkslide is flipped, zone IV exposure given, darkslide replaced with another, zone V exposure given, darkslide flipped, zone VI exposure given... until the zone X exposure has been made. The regular darkslide is then replaced so the holder can be removed from the camera and the film processed. The result of such a test can be seen in the example image which I hope will be found below. This is a test I did using an HP5+ sheet and testing for a van dyke brown print emulsion exposure. (Note that a Stouffer wedge has been placed on the film when making the contact sheet to help calibrate the print emulsion response. It is not part of the zone test described above.)
Well, that takes care of it in one frame - one click! But it
Originally Posted by Lee L
won't do in my case; a 6 x 4.5 and two 6 x 7s.
I have tested 9 zones with 10 frames; 2 zone 5s at aperature
change. The 9 are nice to have and I've a splendid Tobias TB+
which will read any and all zones it sees. All I really need are 5
zones. It is zones 3, 4, 5, 6, and 7 that make a print. Zones
2 and 8 can be guestimated. Zone 1, while a speed point
for most, prints black, and zone 9 white.
I think I'll make that trip to the paint store. A five zone
2 x 2 foot should be easy enough. I'd like to remove any
vignetting and even development issues by shooting
center of frame. Dan
Try Gordon Hutchings' Zone board, described in _The Book of Pyro_.
The basic technique is this--You make a long board with a lamp in a reflector on top aimed down the board (you could also just use a lamp or a light on a light stand and an evenly colored wall). The intensity of the light will fall off proportionally to the inverse square of the distance, so place the dark end on Zone I and label it, say with a large Post-It note and a marker. Then use a spot meter to see where Zone II falls and label that, and then Zone III, etc. Photograph the board, and the labels will tell you where to take your densitometer readings from.
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OK. I have a better idea what you're up against now, and I appreciate the wish to get away from lens falloff.
First, you could try a Kodak Q-13, reflection step wedge and color control patches that smieglitz mentioned. The gray scale there is 20 steps in 0.10 density increments between 0.0 and 1.90, but it's smaller than you want.
Second, I too have thought about using paint color samples and countertop laminate samples for DIY step wedges. The laminate has the advantage of performing well in the field. I actually picked up samples of both about 2 weeks ago, but haven't had time to calibrate them. I have some laminates that would do well, but I'm sure you can pick some out at your local store. The most neutral set of paint samples I found locally was the Behr brand at the local Home Depot, series 780E for the lighter patches and 780F for the darker patches. These come with four dark grays and three light grays on two cards that are 5" x 6", and would make a decent target. Estimating visually from the Kodak Q-13 scale, they appear to be about the followng reflection densities: 0.0, .05, .1, .3, .5, .8, and one about 1.3 or 1.4. You could also find a darker black I'm sure.
You used to see larger samples of some laminates that would make a good larger target, about 5" x 6" each, but I haven't seen those lately. My local Home Depot doesn't carry laminate samples in any size anymore, but Lowes has a good selection of small ones.
The Hutchings Zone Board sounds good too. I haven't read the book. I'll have to calculate some practical dimensions for that.
Hope this helps.
Why not a pint of flat white and flat black.
I may even 'print' five maybe 7 zones. I think
my Sekonic L-228 analog good to .03; not bad
Black paint; I've read of 2.08. Probably nothing
very special. Dan
Flat white and flat black paint would work well. Some places do a custom computer match to an existing color, so you could take in a gray card and try to get a matching pint of that as well for a three zone setup. I have no idea how close they could come to an exact match.
There are sheets of felt in craft shops sized 9x12 or so. A white, black, and a gray or two might work for a larger target. How about high brightness office paper, a gray card, and some black felt for a three zone target? You could use multiple pieces of each for a larger target. How about a few pieces of appropriately chosen matt board? These options would make a nice larger target. The possibilities are pretty much endless if you don't need calibration to exact values.
Has anyone tried half-tone style scales produced on a laser printer? With certain computer graphics programs, you could produce your own custom scale. Print a bunch of different densities and measure, then make a scale that works for you. For a large target, you could do full sheets of single tones and put them together on a backer board.
Lots of ways to get there.
No, no. Mix the paint. A really good white and black may
be zones 1 and 9 or close. The five middle zones would need
to be mixed. I think 7 zones possible.
The linearity of my Sekonic L-228 may be a problem. Do you
know of any way to check a light meter's linearity? Dan
I wouldnt think that any reflective surface would provide enough difference to cover more than 2 or 3 zones. Remember that in a photography setting, you are trying to capture areas that are brightly lit verses shaded.