(b) Fees for the regular services described in these sche are listed in Part 8 of this publication. Fees for z items and services have not been fixed and charges will be made for actual incurred. Upon request, estimates will be furnished for specific which should provide a close approximation of actual cost. Item 212.111a 212.111 Miscellaneous photometric measurements and tests. Description Determination of luminous transmittance of neutral or col filter, one sample. 212.111z Special measurements not covered by this schedule. Item 212.112 Incandescent electric lamps. Description 12.112a Standards of spherical candlepower, set of three type 51 lamp 12.112z Special measurements not covered by this schedule. Image Optics and Photography 212.130 General. Direct inquiries to, and mark shipments for the mage Optics and attention B214, National Burea tandards, Washington, DC 20234. Telephone: 301-921-2182. 212.131 Visual measurements of optical characteristics. (a) Test 212.131a is applied to photographic objectives mou n a lens barrel or shutter. The back focal distance determines the osition with respect to the focal plane for a camera focused on a dis bject. The equivalent focal length determines the scale facto agnification for small field angles. ing cameras. The information is used in calibrating the camera scales to position the lens, object plane, and image plane for any desired ification without visual focusing. (c) 212.131c and d are tests of objectives used in precision ing cameras where there is a need to have the relative proportions of image not significantly different from those of the object. The 1ts include the information obtained in 212.131b and information on ortion. Since distortion changes with magnification, it is advisable pecify, for test, the magnification most commonly used. (d) 212.131f and h are general evaluations of a photographic ctive for precise applications. The results include the information ained in 212.131b and information on resolution. 131a 131b 131c 131d 131e Cost of fabricating new devices needed to adapt test items to our equipment will be added to the fees indicated below: Determination of back equivalent focal length and back focal distance. Determination of equivalent focal length, back focal distance, separation of nodal points, and lens thickness. Determination of equivalent focal length, back focal distance, Determination of equivalent focal length, back focal distance Fee for each additional ratio. 131f Determination of equivalent focal length, back focal distance nodal point point separation, lens thickness, and resolution at 5° intervals from center to edge of field for parallel light at one aperture. 131g 131h Fee for items 212.131c and 212.131f when performed at the same time on one lens. Determination of equivalent focal length, back focal distance 131i Fee for each additional ratio. 131j Fee for items 212.131d and 212.131h when performed at the same time on one lens. 212.131k 212.131z Determination of single radius of curvature. Fee determined the nature of the work required. Minimum fee. Special measurements not covered by this schedule. 212.132 Photogrammetry. (a) and (b) This is a test of the definition characteristics a lens. It is performed photographically. In general, if a lens yie satisfactory results when subjected to this test, it is probable that additional test for lateral chromatic aberration is necessary. (c) This is a qualifying test for photographic objectives aerial mapping cameras. It is a photographic test and the determinati are made for the plane of best average definition. (d) and (e) The f-number is the ratio of the equivalent fo length of the lens to the diameter of the effective aperture. (f) This is a test of the platen of a precision aerial mapp camera which is the surface against which the film is held during exposu It is a test to determine conformance to specifications requiring that platen shall not depart from a true plane by more than +12 microns (+0.0 in.). (g) This is a test of a photographic objective mounted in camera. It gives the same information as test 212.132c except for ba focal distance. It is preferable that these lens characteristics determined for the lens as mounted in a barrel shutter but occasionally is desirable to determine these quantities for the lens mounted in camera. The shutter should be open when the camera is submitted for tes (h) This is a test of a lens-camera combination for pho grammetric mapping. It gives the departure of the principal point of au collimation from the center of collimation which is the intersection of lines joining opposite pairs of collimation index markers. The rad distortion is determined with respect to the calibrated focal length of lens. This test cannot be performed on a camera having a detacha magazine which bears the collimation index markers. This is the p liminary test on a precision type camera to determine compliance W specification. If no provision has been made for ready adjustment of collimation index markers and they are not aligned at 90°, the camera returned for adjustments. If the 90° condition is satisfied but provision has been made for ready adjustment of the principal point W respect to the center of collimation, the camera is returned for adju ments. (i) If the principal point can be positioned properly W respect to the center of collimation by ready adjustment of the lens i transverse direction or by ready movement of the collimation index marke this is done in the course of the test. Following adjustment, pins are to preserve the setting. pins, a proper sized drill and reamer, and a sufficient number of pins to perform the doweling must accompany the camera. It is desired that roll pins be submitted for this task. Item 212.132a 212.132b 212.132c 212.132d Description Determination of resolving power at 5° intervals from center to edge of field for collimated light at one aperture. Fee for each additional aperture. Determination of back-focal distance, equivalent focal length, distortion, and resolving power at 5° intervals from the center to edge of the field. This is the test usually required for lenses that are to be mounted in precision aerial cameras. Determination of equivalent focal length and true geometric fnumber for one marked stop. 212.132e Fee for each additional stop. 212.132f 212.132g 212.132h 212.132i Determination of compliance of camera platen with flatness Determination of calibrated focal length, radial and tangential distortion, and resolving power at 7.5° intervals from center to edge of field for lens mounted in camera. of Location of the principal point of auto-collimation, check of 90° Setting the principal point of auto-collimation and 90° 212.132z Special measurements not covered by this schedule. 212.133 Refractive index. (a) The index of refraction of a solid, transparent optical material is measured at visible wavelengths of calibrated emission lines of cadmium, helium, and mercury. Ordinarily measurements are made at room temperature, near 22 °C. Specimens submitted for test must be in one of the geometrical forms described below: (1) Test specimen in the form of a prism, with two rectangular surfaces polished optically flat within one-eighth wavelength. The minimum linear requirements for these surfaces are approximately 25 mm (length) x mm (height). The optimum The optimum refracting angle varies from 70° for index = 1.4 to 50° for index na (2) Test specimen in the form of a rectangular slab approximately 25 mm x 13 mm x 5 mm, such as is commonly used for the adjustment of an Abbé refractometer. Two surfaces must be polished optically flat within edge. Index of specimen should not exceed na = 1.8. (b) Refractive index values and accuracy given to as many figures as are considered significant. able accuracy lies in the range +0.000005 to +0.0001. (c) Generally tests are based on correspondence regarding the exact nature of the requirements. Do not ship materials to the Bureau until arrangements for test have been completed. 212.133z Determination of index of refraction of solid optical media for visible spectral lines. 212.134 Modulation transfer function measurements of lenses. When submitting lenses for modulation transfer function measurements the focal plane, f-number, off-axis position, and target line orientation (radial or tangential) must be specified. Each lens submitted for test must be accompanied by a mounting plate 1/16 inch thick, 5 5/8 inches in diameter, with four body drill holes, for No. 8 screws, spaced 90° apart on a center circle of 5 1/4 inches in diameter. 212.134a 212.134b 212.134z Determination of data necessary for plotting one modulation transfer function curve, on axis, at one fixed set of parameters. Fee for each additional curve based on original focal plane. 212.135 Photography (step tablet density, residual thiosulfate concentration, etc.). When photographic step tablets are submitted for calibration, the type of density, printing or visual, must be stated. Diffuse Transmission Density is measured in accordance with United States of America Standards Institute standard PH2.19-1959. (a) USA Standard Printing Transmission Density, Type P2-b, is measured on step tablets of 21 steps or less. Densities greater than 4.10 are not calibrated as part of this test but must be ordered separately under item 212.135z. The densities of tablets of high quality are measured with a precision such that three times the standard deviation of the mean is 0.01 or 1 percent, whichever is greater. Defective tablets cannot be measured with this precision. Tablets submitted for calibration must be free of scratches, fingerprints, abrasions, and foreign matter and must have steps of uniform density. Tablets not suitable as standards are not accepted for calibration. |