Stouffer T2115 21 Step Wedge that is used for determining correct exposure times.
The Stouffer Step Wedge is used with contact positives, silk screen printing, printed circuit boards, silk screen stencils and most other photographic applications for judging results, determining speed and contrast for emulsions, and hardness of coatings.
The Stouffer step wedge also serves as a gauge to evaluate the variables encountered in the exposure and processing of lithographic plates and photographic materials by contact. It indicates the direction and magnitude of exposure or processing adjustments necessary to achieve the desired results. Supplied with instruction sheet for how to use.
|Part Number||Steps||Density Increment||F-Stop Equiv.||Dmax||Size|
|T2115||21||.15||1/2||3.05||1/2 x 5″|
How to use a T2115 21 step
Instructions for Photo – Lithography
Set the contact printer / vacuum frame to make several trial exposures on separate pieces of film, with each exposure for a different length of time.
Make three exposures: one determined by past experience or the exposure normally used in daily production, one for less, and then one for more. It may be necessary to repeat this testing procedure using different exposure times.
Process the test negative for the time and temperature recommended by the film manufacturer. It is important to keep processing consistent.
Examine the step tablet/wedge image on each of the negatives. Select as the best the negative in which step 7(on a 21 step wedge) is developed to a dense black, with step 8 only slightly dense. Step 7 will be the aim point for normal copy.
There are many different ways for exposing plates. There are an abundance of different exposure systems and processing techniques. The one constant is the step tablet/wedge. Use the step tablet/wedge as a benchmark for all exposures to achieve accuracy and repeatability.
To find the exposure factor to hold more or less on the Stouffer 21 Step Platemaker Sensitivity guide, follow the chart below.
To Change Exposure 1 Step 2 Steps 3 Steps 4 Steps
To Increase Exposure 1.41x 2.00x 2.82x 4.00x
To Decrease Exposure .71 .50 .35 .25