Let's Talk Test Strips!
I'm wondering if people could share their methods for making test strips, those key guides to determining your base exposure for every print. For a while, mine have been remarkably poor in quality. At the moment, I cut a piece of 8x10 paper into about four pieces, so that they're 8"x2.5." I hold a piece of cardboard over my strip and expose each strip segment for an additional three seconds (using a digital timer). But I can never hold the cardboard steady or move it a consistent distance along the length of the strip. And if I get to close, I could end up touching the strip, leading to fuzzy double-exposures and ruining it. And even if it weren't ruined, it's hard to be sure you're reading the right time because the regions are so diverse in width!
So, I have a new method that I'm going to try. I bought some 1/2"-wide magnetic tape, which I plan on using to both hold down the edges of the strip and also gradually shield it from exposure. That way, I'll have strips that are pretty darn consistent!
So what method do you use for making test strips? Do you do three seconds per segment, or do you vary your times to make differences based on a logarithmic scale, such as stops of exposure? And finally, what criteria do you personally use to judge the "correct" time?
I place the strip in the easel and place a board on top of the strip for the first exposure, moving the board to the second position and so on. The board does not move the strip if it is placed on top, this is with a two bladed easel. Regarding F stop, I guess after so many years I simply know the starting point, usually F8 or 11. The F stop will largely be determined by the density of your negative, too much-too little you will need to adjust. Tim increments are usually dependent on the size print, but 8x10 to 11x14 usually 3-5 seconds with approximately 2" areas exposed. Then find the closest to what you are looking for and place a strip so that it includes a hilight and deep shadow and expose the entire strip. Adjust accordingly until you have detail in both. Print. Adjust. Print Again. I am sure others will have additional methods for you to try.
I use little strips of paper, about one-inch by two-inch. It is a little slow, but I do them one-at a time. It could take hours to work up a print before a full sheet gets in the easel. There is no way to know what changes need to be made to the next one until the first is dry. Trying some 'method' of exposing multiple little pieces at once just results in a big waste of paper, been there, done that.
I use 5x7 papers with an old Kodak Print template on top of it. The template has a pattern of various dark pie slices that give you timings if you shoot the whole thing for a minute. They I just pick the pie slices I like best and interpolate somewhere in between for my first straight print.
I usually use a whole sheet of paper, and judge the neg by experience and enlargement size. I may use slightly more paper than using strips, but I get to see the entire print and its relationships this way.
Edit: I also wanted to add that using Michael Smith's method (see his site) of outflanking/overshooting is integral to seeing what your neg has to offer.
Last edited by PVia; 01-27-2011 at 11:03 PM. Click to view previous post history.
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Check out "Way beyond monochrome" for a good introduction to making f-stop test strips. I was an eye opening to me.
A few chapters are actually downloadable: http://www.waybeyondmonochrome.com/WBM2/TOC.html
See chapters on "Make your own test stip printer" and "Timing print exposures". Great stuff.
EDIT: anikin beat me to it, so I SECOND his suggestion!
Trust me, I am terrible with woodwork and I was able to build it successfully. It's not perfect, but it has absolutely made making test strips, both continuous and a single section, a piece of cake!
I make test strips from a sheet of 8x10 paper. I use a paper cutter and cut five strips two inches wide by 8 inches long. I set up my enlarger to make an 8x10 print, and from looking at my contact sheet decide where across the image to place the test strip. If its a portrait I'll include the face and background, if a landscape diagonally to get foreground and background and sky, etc. I mark the position on my easel with a piece of masking tape.
I place all of the test strips in a paper safe, and expose them on a time sequence based on the initial exposure of my contact sheet.
I develop all five strips at the same time in a large tray.
Sometimes I dry the strips with a hair dryer, but usually I can spot my exposure while the strips are wet.
Based on the test strip I then make a full size working print.
I'll chime in with a 3rd on the f/stop test strips, it' the way to go, really.
And kudos to Messrs Lambrecht and Woodhouse for a weighty tome for the
I also trust my metering/EI and will usually get a good starting
print by doing a test strip to detemine the minimum time needed
to get the unexposed edge of the film to print 'black'.
Without building 'test strip printer' you can get a fairly good result by
exposing a little more paper with each exposure, shown on the left.
The accumulated exposure will be in the right column, and are 1/2 stops apart.
exp - accumulated
02 - 02
01 - 03
01 - 04
02 - 06
02 - 08
04 - 12
04 - 16
08 - 24
08 - 32
16 - 48
16 - 60
Last edited by dasBlute; 01-27-2011 at 08:32 PM. Click to view previous post history.
FWIW I have made an f-stop template using Neutral Density (ND) gels/filters from a swatch book (either Lee - UK or Roscoe - USA). A .15nd is a half stop of reduced light; .3nd is 1 stop of reduced light; .6 is two; .9 is three and so on. I have a cardboard holder with these swatches mounted and I can "add" additional pieces of ND gel depending on how strong the enlarger light is on the baseboard - the variables being the height of the head and the stop on the lens. I tend to use only a stop of 5.6 as this seems to be my enlarger's lens sweet spot for sharpness. I expose the print thru the template with one base exposure of, for example 30 seconds. If the 1 stop (.3nd) looks to be the best exposure I half the base time while keeping the lens glued to the stop of 5.6. A stop of light reduction is half (-50%) the base time in seconds while a stop of light increase is double (+100%) the base time. Likewise, arithmetically, one can use the .15nd too for half stop increments and use a 50% increase or a 25% reduction. This might seem to be overly complicated but I am a retired motion picture chief lighting technician and have come to use this method over the years to do exactly this on film lights and on motion picture cameras. Hope that this helps.
P.S. FYI you can also use this mathematical relationship when increasing of decreasing the height of the enlarger head if you have a ruler or scale on it's supports. Halving the height of the head increases the light intensity by a stop (or double if you will) and raising the head by doubling the height decreases the light by a stop (or 50%). The relationship holds true for all set heights but becomes a bit hard to calculate sometimes........this is how I calculate expose times for different sized enlargements.
Last edited by samcomet; 01-27-2011 at 11:26 PM. Click to view previous post history.
Reason: forgot to add the P.S.