. - A mzbjar $enezt eYrr=,?, i~,~-~ed fi~~j "he Ei:iikk &- su~~rccsTechrloiogy SateeUi.ke (EivfS) W!S a syr-t,c~piic vie%\i of large areas taken in four sepsrzie wave&ernds from more than 550 miles in space. BWTS k-11agery p~~~~des?he land maaag.i;r 21 up-to-date plxoto iyap of an 95,000-acre 2rea ai diflsreet ldmes (seasons) of i..ile year. ~e!~er'reporeed that "' '- enia imagery ~firs promise in forest rr.,a,~ag--ment inveatory work over extensi~~ziyforested areas, althou& results to date are experklentai and not yeady k: im1ne&atr: US?.

q-7, A his expedmental satellite was launched or.1 $.sly 23, 1972, by the 'U.S, Natioi%a] Aeronautic. and Space AdarzmstratEor:. . {NASA). B"crecrj& scerle in-

_',miL~ion. 1-,j ,.i.-:-.i.banr '2-r a. mu'itispectra! f.-anrer and ieiays ei.;r;lionic signals to gronna. ;acili'&s.- The signxis are cn:?x:erf.ed coauentio2si; photographic liI"itr~ imagss in -the brim of positive 78-rrnz-1, irans- pzrencies by an electrsi~bsz~ iecorder. p'-n5m:.rwuyiCa illad$---,, from the archhe%ty~~n~par@:?ciei .- 7- - be ,oiaLnedq7 l-~ horn IdASB in the for:-:~ o[ third- f Ai;bszr~:t: jL 11:~Cnod I;gc, beer1 6s::ised p;onacmg<. i genertitioa "I-~III.~?.'c;la~d;,-afld-1'.~?1itc: pesitives and I liig;-l-qkalit:; b~eck-l.,;x~-wrhi.,G;-,egat*-s QnjcE,; ail< 1-1- ' \ . . r fiega"t;irs. 1~i~;;cstof the positives been of good ! ficiencly koj:? dense .t;anspaancie~ o?;ransti:?g Tzoc? 1 i qdity, but the negatives h8,!7$ bean exrrejlleiw deese. 1 Earth Resources -lechnolog!i Sate%", imager)?. Trcns- 1

J -qrp..~e:E eiia:cateeall a stand arc^ light sour.ce ic 1 'Clonsequectly, the negat':rss have a high fog le.;rei, a 1I dete:raIin::+ ''L A erposu::e and processing information 1 reduced Bil~.~bt~range 6:' the gay scde, an8 a loss of 1 r;eded ior 111akng negaii1.e~.A "2:istenn baSA Eatinn" 1' image contrast. T?.ie gray scale on eacll 'T~-;II~. 1 was develop&. b;i &stir.$ si6 selecting combinclbo:?~ j irar?spa:e~:;?cy i~n_zs$9 steps, but ~~lyseven or eip&t car; I 3f 31j39light SO;J~~S~a>-,, devi.,louj:. chal:,p in Cjb9~. 1 . . ,,. r.fc,.,,,-- ..; 1 be diccri.ninate& on -the ieme negatphies. 1 density and c~~~;..~si,S .lligc3bv~ L liiijg iri :pl~,-il) s&, TI- A of i e?f:c:s are. CCI;~L.SILG~jy ~a]c~latit~.g2djustm3nt~ in ex- I llrc remot,$ sensing reeesrch 5nit th; Pacigc 1 posw;~ deveic~nren", .?'i;e metbod desc$oed czn I: Souih~~leskForest acd Range B::perime;c.t Statio;~ie , . --. 1 be used in: ~eiaiiaelysnag da;lcrooms withmi sipen- I using bRTS &~24~..geryto stad)/ foract fespjrces. The s>re eqrripm:r.r. Iis ns.,'F.i~u~al~r.s '-,---, ?i,ras ciernoms:ralec in a 1 I u~~l'i'sph-otographic sta-ff hzs fo~~~dit &~.~cIL;&, how- / Ngh-al'liludc plvoio mission s.i-;r ehe Black Hi& 1 eici, lilaie ji!i~fa~toq5$&ig~m,$n:i (lox 30x) j :ii;tiomal Faresil S~T.J,"~I Eakata. 1 - I irom '.,ASA-prodzced ;legzt&es for ze]d and Long exposure is needed to rtilake enlargen~ents Table 1-Steps lo be used for compeasati~~gfor reciprocity eeffect z'o from the dense nega";ves. A 4X enlargement, for ex- processing fln2 " ample, requires an exposure of 10 to 15 Klinutes. Even hi&er magnification requires unreasonably long exposure-and this can have adverse effects on the finished print, such as loss of critical detail. I have developed a teclznique for producing high- quality black-and-white negatives from ERTS trans- parencies. This method insures that the same quality is mainbined frorn one pass (orbit) to the next as well as frorn season to season. It can also be used to make negatives from any transparencies-black and white or color. The method can be followed in a small darkroom without any large investment of l~ource:film data sheet for Kodak Ektapan Film-4162, March 1969. money. '~ppl~the percent adjustment to correct the developing time selected in fable 2. MATERIALS AND METHOD Each ERTS transparency is evaluated on a light source to determine the correct exposure and process- exposed film and the positive transparency are placed ing information. I use either channel 5 (0.6 to 0.7 on the enlarger base and held Rat with a piece of pm) or channel 7 (0.8 to 1.1 pm) for making copy optically flat glass. negatives. Through a series of tests, a "System ASA Processing the exposed sheet can be handled Rating" was derived for a particular filrn emulsion. in either a tray or a tank, depending on the number This was done in conjunction with both the illumina- of sheets to be liandled at one time. tion provided by the evaluating light source as well as Fgms, Developers the exposing light source. Once these light sources have been established they should remain as stan- Several films and developers were tested for use in dards. Changes in film density and contrast, due to making negatives from ERTS transparencies. I found the reciprocity characteristics of the emulsion, are that Kodak Ektapan Film (Type 4162)~was the best controlled by use of the Reciprocity Effect Compen- for this task. Ektapan film is a medium-speed (ASA sation Table (table I). Use of the table helps elimi- loo), very fine grain, extremely stable (Estar base), nate all preliminary testing. panchromatic film. A hi&-quality negative was pro- duced by processing Ektapan film in Kodak Microdol- Equipment X filrn developer. Microdol-X Developer has the Any light meter can be used to read the over-all characteristics of low graininess coupled with maxi- density (light value) of the tes"cransparency. The mum sharpness and renders a low fog level. light source used to evaluate the test transparency is the standard to which all transparencies will be com- ""Sstem ASA Rating" pared in the future. This standard can be a light table, To use the light meter, a light standard, an enlarger transparency illuminator or viewer, contact printer, elluminator), Ektapan filrn, and Microdol-X or even a homemade light box consisting of a lamp Developer in the right combination, I had to first find and a diffusion screen. But the standard must remain a usable ASA rating. This was done by a series of test unchanged. exposures. The film exposure time was kept constant An enlarger was used as a source of illumination to and the enlarger lens aperture bf stop) setting changed contact expose the negative image from the ERTS (e.g., 10 sec @ f.8, 10 sec @ f.11, 10 sec @ f.16). Tl?? transparency. The selection of an enlarger over other test film sheets were notch-coded for identification, printing equipment was due to its versatility. De- and all exposure variables were recorded. They in- sirable features of an enlarger permit variations in ex- cluded: exposure time and f stop; lens used; distance posure time, aperture opening (f stop), distance from lens to base (easel); diameter of light beam on between lamphousing and easel, and the use of neu- easel (focus control); variable enlarger settings; and tral density filters. Neutral density filtration of 100 neutral density filtration-if used. (color compensating filters-cyan, magenta, and Before developing the test exposures, it is neces- yellow) was used to control exposure time. The .un- sary to compensate for reciprocity effect. Reciprocity Table 2-Developitzg hime,!? hsed on I/POOsecond Ektapan The tecl~niqareclassified here is unique in that it is Si'i eet FiIm and hficrodol-X Film Developer, QY solution composed of specific pieces of equipment and one teml_leratuve particular film type. Others using it must go through this procedure with their own equipment to arrive at their own stem" rating. A different ""$stem ASA Rating" was established for mahng enlarged negatives . ERTS transparencies.

STEP-BY-STEP PROCEDURE With the new ""$s"tem ASA Ra"cngWknow~i, a fast, efficient method is available for producing nega- l~ustadjust for reciprocity effect by using adjustment tives from ERTS transparencies by follo~ngthese figures in fable I, column 4. steps: 2~odakEktapan Film-4162 data sheet, March 1969. 3~ostoften used temperature. 1. Obtain a light meter reading for the trans- parency on a standard li&t source. failure can occur at exposure times exceeding 1/10 second because of the characteristics of the emulsion. To compensate for changes in density and con"crat, use fable I and table 2. Table 1 shows that the 10- second test exposures required 35 percent less devel- opment. The tray method (temperature of developer -68"~) requires a developing time of 10 minutes f&ble 2). Because of the long exposure, however, the adjusted developing time for the test exposures processed under these conditions was 6% minutes (i.e., 35 percent of 10 minutes = 3.5 minutes; there- fore, 10 minutes less 3.5 minutes = 6.5 minutes). After the film was processed and dried, the nega- tives were examined for over-all density, contrast, gray scale, fog level, and detail. Contact prints were also made from the test negatives and evaluated. A negative was selected that. had a good range of gray levels, a minimum fog level, and "ce sharpes"Eeta8. After the test and the evaluation were completed, these hown values were used to deterrmine the "*stem ASA Rating": (a) exposure time (seconds); (6) aperture setting (f stop); (c) lens aperture adjust- ment (column 2 of table 2); and (d) light vdue of "Iansparency (obtained with meter, transparency, and standard light source). By using a li&t meter, we can calculate the "@stem ASA Rating." For example, the best test negative selected was exposed at f.8 for 10 seconds. Since table 1 showed a lens aperture ad- justment of 2 stops more, the calculated exposure used in wor&ng backwards to arrive at a Tim speed computes to be f.16 for 10 seconds. Wi-tln the light mekr set on a light value of 9 (measured from the transparency on the standard light source), the &al was rohted until f.16 was aligned with 10 seconds. The number that appeared in the ASA window of the computer was the new ""P;stem ASA Rating." ASA 2 was the rating arrived at for this particular system. 2. Find an exposure setting (f stop and time) with 9. Process the fPlm accordhg "E the inskuctions the light value and ""%s"Eem ASA Rating.'9 received in the film package, except for adjusted 3. Use table d for adjusting exposure for Reci- developing time. procity Compensation-adjtkst aperture or time, but not both. Enlargements 4. Set enlarger in the same configuration as the one used when test exposures were made, If extreme enlargements are required, portions of 5. Expose negatives according to the adjusted ex- the EWTS transparency can be enlarged onto Ektapan posure settings (from step 3). film. This metllod wdl permit larger blowps over 6. Set up for processing by either tank or tray thahattainaMle with a contac"cega"cve. Tl~eadvantage method and prepare chemicds (developer, stop bath, of an enlarged negative (2X or 3X) over a contact and fixer). negative is a reduction in the noticeaue granularity 7. Just be-fore processing, take temperature read- (the graininess of developed image) in the find en- ing of developer and find developing time in table 2. larged print. A different ""Sstem ASA Rating" will 8. Reduce "ce developing time (table 2) by the need "6 be determined for making the enlarged nega- percent development adjustment called for in table 1. tives.

Figure I-Prints made from a Forest Sewice-produced negative: A, contact print (1 :I); B, 10X enlargement; C, 20X enlargement; D, 30X enlargement. The nega- tive was made from an E RTS "cansparency (ID 1291-18182-5) that shows the San Francisco Bay area. Scan lines become more noticeable as magnification increases. Imagery is from Multispectral Scanner band 5 (red, 0.6 to 0.7 ,Urn), May 10,1973. Figure 2-Top: conventional photography at a scale of 1 : 110,000 over the Black Hills National Forest, South Dakota. Bottom: ERTS image (ID 1172-17123-7) enlarged about 30X for compari- son; ERTS image is channel 4 (0.8 to 1.1 pm),January 11, 1973. Prints recent high-altitude photo mission over the Black Hills National Fores"cin South Dakota. Existing Enlargemenb can be made on variable contrast Forest Service maps at a scale of % inch = 1 mae photo paper and the over-all contrast controlled by (1 : 126,700) lack the type of detail and information means of filters. Polyconkrat Paper or Polycontrast that is helpful for photo navigation. An ERTS image Rapid Paper developed in Dektol Developer is a good was enlarged and scaled to the National Forest map combination. and flight lines transl'erred to the photos. The photo With a good negative, prints can be made ranging crew found these photos to be far superior to the in size from contact (1 :1) to 30X or even beyond maps that had been used in the past. (a.I). iir;@re 2 2lustrates 30X enlargement made from a negative produced by the method described and shows how it compares with conventional photography taken by high-flying aircraft. A variety I~eller,Robert C. ERTS imagery-problems and promises of scales can be achieved by enlarging the negative to for foresters. 1973. (Paper presented at Meeting of Remote match existing maps, aeronau"ccal charts, or high- Sensing Subject Group, Intern. Union of Forest Research altitude aerial photography. The particular scale Organizations, Freiburg, West Germany, Sept. 19, 1973.) desired can be produced by superimposing the nega- 2~.~.National Aeronautics and Space Administration. Pro- tive image (in enlarger) onto the mag, chart, or aerial cessing methods for ER TS negatives. ERTS Investigators' Bull. A(13): 1-4. 1973. photo placed on tl~eeasel. 3~radenames and commercial products and enterprises are A practical use of prints made from the negatives mentioned solely for information. No endorsement by the produced by this method was demonstrated on a U.S. Department of Agriculture is implied.

The Author

RICHARD J. MYHRE is assigned to the Station's remote sensing research unit headquartered in Berkeley, Calif. He operates the unit's photo labora- tory and also serves as its aerial photographer. Native of Tacoma, Wash., he joined the Station in 1965 after 3 years at the U.S. Forest Service's Forest Insect Laboratory, Beltsville, Md.