Stouffer TP35-21, 21 step transmission projection step wedge, increment 0.15
Stouffer TP35-21, 21-step transmission projection step wedge
21 steps, increment 0.15, 35 mm, Dmax 3.05
TP35-21 data
21 steps, increment 0.15, Dmax 3.05
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The Stouffer TP Transmission Projection step wedges . A conversion chart indicates the proper exposure in seconds
Transmission Projection (TP) Step Wedges are most commonly used in the enlarger to establish exposure and processing adjustments and to determine the speed and contrast of photographic papers. The grey scale is to be used in the negative holder and projected onto the paper.
RoHS-Compatibility:
Products manufactured and sold by Stouffer Industries are RoHS compliant. All step wedges, step tablets, gray scales, and any other photosensitive quality control device made contain no or less than agreed levels of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE) flame retardants.
Longlivety:
Stouffer Step Tablets and Gray Scales are made under controlled conditions to meet or exceed the requirements for archival permanence following procedures recommended by the manufacturers of the materials. Archival permanence is usually defined up to 10 years or more. Studies at the National Institute of Science and Technology have shown that the densities of this kind of step tablet will remain stable for at least four years when handled and stored with care.The primary causes of degradation are use, followed by ( in no particular order) heat, humidity, fingerprints, splashes including spittle, chemical fumes and vapors, attempts to clean the emulsion with anything other than a soft camelhair brush, and abuse.A quality control device that is handled 40 times a day will degrade faster than one that is handled once a week. The user should set a routine to determine the frequency of replacement based upon factors occurring in-house and the foregoing discussion.We recommend to change the step wedge after 3-6 months and immediately at visual damage
Calibration:
This step wedge is also availabe in calibrated version. Please allow extra charge and lead time of about 4 weeks.
How to use the Stouffer TP (Transparent Projection) Scales?
The TP guides are designed to help determine paper grades, exposure consistency, and Zone System techniques. It can be used by contact printing or by projecting the image onto the paper surface. Once you have a base exposure for your testing it will help you determine your density range by showing how many steps are visible. Each step has an optical density of .15 which equals 1/2 F-stops of exposure (for the 21 step) and density of .10 - 1/3 F-Stop for the 31-step scales.For example, if your test shows 10 steps of density from Dmin to Dmax you are achieving a 5 F-stop range of density from that particular paper/negative combination.
To use the TP guide for Zone system work you will have to pick a subject in the image to be printed and decide which Zone you want it to fall into. Refer to the test strip from the TP guide to determine which step falls into the same printed Zone and adjust your exposure accordingly for the negative exposure.
Of course the best way to become comfortable with using the TP guide is by testing. Knowing that the steps of the 21 step represent 1/2 F-stop increment and the 31 step represent 1/3 F-Stop increment values will help in calculating your various tests and exposures.