LV Lightvalues Exposure Calculator

Schrausser, D. G. (2025). LV Lightvalues Exposure Calculator. https://doi.org/10.5281/zenodo.17037428 1 LV Lightvalues Exposure Calculator Dietmar G. Schrausser orcid.org/0000-0002-4924-8280 Correspondence: [email protected] Karl-Franzens University, Graz, Austria Overview Android application Lightvalues LV 1 for calculating aperture values 𝐴𝑣 corresponding to light values 2 by shifting the time value 𝑇𝑣 = 𝑠−1 or arithmetic 𝐼𝑆𝑂 speed value 𝑆 in steps 𝑘 according to the common classification (s. Fig. 1), where 𝑇𝑣𝑛−𝑘 = 𝑇𝑣𝑛⋅ 2𝑘, 𝑆𝑛+𝑘 = 𝑆𝑛⋅√2𝑘, 𝑇𝑣𝑛+𝑘 =𝑇𝑣𝑛 2𝑘, 𝑆𝑛−𝑘 =𝑆𝑛 √2𝑘 and 𝐴𝑣(𝑇𝑣𝑛)= 𝐴𝑣(𝑇𝑣𝑛+𝑘)⋅√2𝑘=𝐴𝑣(𝑇𝑣𝑛−𝑘) √2𝑘, 𝐴𝑣(𝑆𝑛)= 𝐴𝑣(𝑆𝑛−𝑘)⋅√2𝑘=𝐴𝑣(𝑆𝑛+𝑘) √2𝑘. Therefore 𝐴𝑣 is calculated from 𝑇𝑣 or 𝑆 as 𝐴𝑣𝑇𝑣 = 𝐴𝑣𝑇𝑣0⋅ 𝑎𝑇𝑣, 𝐴𝑣𝑆= 𝐴𝑣𝑆0⋅ 𝑎𝑆 with 𝑎𝑇𝑣 = 21 2⋅log2𝑇𝑣0 𝑇𝑣 = e1 2⋅log(𝑇𝑣0) 𝑇𝑣 , 𝑎𝑆= 21 2⋅log2𝑆 𝑆0= e1 2⋅log 𝑆 𝑆0. The shutter speed is set in the range between 𝑇𝑣 = 32000 and 2 hours, 𝑇𝑣 = 0.000138, aperture ranges from 𝐴𝑣 = 0.5 to 𝐴𝑣 =152 and speed 𝑆 is set to range between 𝐼𝑆𝑂 0.4 and 𝐼𝑆𝑂 102400. On aperture, shutter speed and exposure see e.g. Roberts (1995), Beaver (2018), Bernacki (2020) and Simon et al. (2022). Logarithmic speed 𝑆° (s. Allbright, 1991) is transformed from arithmetic speed 𝑆 by 𝑆° = 10 ⋅ log10(𝑆)+ 1 = 10 ⋅ log(𝑆) log(10)+ 1, 𝑆 = 10𝑆°−1 10 . 1 https://github.com/Schrausser/LV 2 Light level for incident or reflected light on a logarithmic scale. Creative Commons Attribution 4.0 International (1) (2) (3) (4) (5) (6) (7) (8) (9) Schrausser, D. G. (2025). LV Lightvalues Exposure Calculator. https://doi.org/10.5281/zenodo.17037428 2 The exposure value 𝐸𝑣 is calculated from 𝑇𝑣 and 𝐴𝑣, where 𝐸𝑣 = log2 𝐴𝑣2 𝑇𝑣−1 =log(𝑇𝑣 ⋅Av2) log(2),𝑇𝑣 =2𝐸𝑣 𝐴𝑣2,𝐴𝑣 =√2𝐸𝑣 ⋅𝑇𝑣 𝑇𝑣 . The total luminous flux or illuminance 𝐸𝑉 in lux 𝑙𝑥, where 𝑙𝑥 =𝑙𝑚 𝑚2 results from 𝐸𝑣 and 𝑆 by 𝐸𝑉=250 ⋅2𝐸𝑣 𝑆. For logarithmic functions in general see e.g. Marsden & Weinstein (1985), Howie (2001) and Sobot (2021). Presets for time and aperture combinations at 𝐼𝑆𝑂 100/21° (8) are given (s. Tab. 1), with aperture values 𝐴𝑣 are rounded to one decimal place. Custom time-aperture-ISO combinations for exposure values 𝐸𝑣 (10) or illuminance 𝐸𝑉 (11) can be achieved by shifting 𝐴𝑣 itself (s. Fig. 1). Table 1. Exposure presets for 𝑇v, 𝐴𝑣 and 𝐸𝑣 (10) at 𝐼𝑆𝑂 100/21° by condition cnd. cnd 𝑇𝑣 𝐴𝑣 𝐸𝑣 Sun 125 11 14 Cloud 125 8 13 Overcast 60 5.6 11 Dawn 15 4 8 Indoors 15 2.8 7 In addition, direct calculations (5) of aperture 𝐴𝑣 from shutter speed 𝑇𝑣 (6) and 𝑆 (7) can be performed (c.f. Schrausser, 2025). This should be used when shutter speeds outside the usual steps (1) (2) are present or when only one shutter speed is available, as in the case of the socalled mechanical emergency shutter speed (s. Tab. 2). Table 2. 𝐴𝑣 for 𝑇𝑣 (5) (6) at 𝐼𝑆𝑂 100/21° and 𝐼𝑆𝑂 400/27° with 𝐸𝑣 (10) by condition cnd. cnd 𝑇𝑣 𝐸𝑣 250 100 60 45 ISO 100/21° Sun 7.8 12.3 15.9 18.3 13.9 Cloud 5.7 9.0 11.6 13.3 13.0 Overcast 2.8 4.3 5.6 6.5 10.9 Dawn 1.0 1.6 2.0 2.3 7.9 Indoors 0.7 1.1 1.4 1.6 6.9 ISO 400/27° Sun 15.6 24.6 32.0 36.7 15.9 Cloud 11.4 18.0 23.2 26.6 15.0 Overcast 5.6 8.6 11.2 13.0 12.9 Dawn 2.0 3.1 4.0 4.6 9.9 Indoors 1.4 2.2 2.8 3.2 8.9 (10) (11) Schrausser, D. G. (2025). LV Lightvalues Exposure Calculator. https://doi.org/10.5281/zenodo.17037428 3 Further manuals or introductory literature on photography are given by e.g. Hedgecoe (1977, 2009) and Jacobson et al. (2000), see also Kenneth Mees (1931), Cannon & Hunt (1981), Hitchcock (1989), Current et al. (2000), Friedman & Ross (2003) or Pavlidis (2022). Figure 1. Screenshots from LV Application. Source ! /////////////////////////////////////////////////////////////////////////////////// ! // LV Lightvalues ! // Exposure calculator ! // by Dietmar G. Schrausser © 2025 ! // _name$=”LV” _ver$=”3.8.2” CONSOLE.TITLE _name$ INCLUDE strg.inc INCLUDE lv.inc GOSUB values sw=-3 % // color switch // insw=1 % // input switch // tv=10 av=18 av1=18 iso=18:iso$=”100” ! m1: IF sw=1 :r=255:g=255:b=255:ENDIF IF sw=0 :r=0 :g=0 :b=0 :ENDIF IF sw=-1:r=80 :g=30 :b=30 :ENDIF IF sw=-2:r=30 :g=80 :b=30 :ENDIF IF sw=-3:r=80 :g=90 :b=180:ENDIF GR.OPEN 255,r,g,b,0,1 GR.SCREEN sx,sy dy=sy/3/4 txz0=sx/10 txz1=sx/2.5 txz2=sx/3.5 GR.TEXT.BOLD 1 IF insw=1 THEN GOSUB inpt ! DO ! insw=1 GOSUB col ! % // AV shift // GR.BOUNDED.TOUCH swavp,0,sy/3,sx/3,sy*2/3 IF swavp=1 IF av>1:av=av-1:rav=av:rtv=tv:ENDIF GOSUB sub1 Schrausser, D. G. (2025). LV Lightvalues Exposure Calculator. https://doi.org/10.5281/zenodo.17037428 4 ENDIF GR.BOUNDED.TOUCH swavm,sx*2/3,sy/3,sx,sy*2/3 IF swavm=1 IF av<36:av=av+1:rav=av:rtv=tv:ENDIF GOSUB sub1 ENDIF ! % // menue // GR.BOUNDED.TOUCH swin,sx/3,sy/3,sx*2/3,sy*2/3 IF swin=1 GOSUB inpt:GR.CLS ENDIF ! % // TV shift // GR.BOUNDED.TOUCH swtvp,0,0,sx/3,sy/3 IF swtvp=1 IF tv>1:tv=tv-1:av=av-2:ENDIF GOSUB sub1 ENDIF GR.BOUNDED.TOUCH swtvm,sx*2/3,0,sx,sy/3 IF swtvm=1 IF tv<31:tv=tv+1:av=av+2:ENDIF GOSUB sub1 ENDIF ! % // iso shift // GR.BOUNDED.TOUCH swisop,sx*2/3,sy*2/3,sx,sy IF swisop=1 IF iso<39:iso=iso+1 av=av+1 % // // GOSUB sub1 ENDIF ENDIF GR.BOUNDED.TOUCH swisom,0,sy*2/3,sx/3,sy IF swisom=1 IF iso>1:iso=iso-1 av=av-1 GOSUB sub1 ENDIF ENDIF ! % // text TV // iso$=iso$[iso] IF sw>-1 IF tv=rtv THEN GR.COLOR 255,255/2,0,0,1 ENDIF IF tv<1 THEN GR.TEXT.DRAW tx,sx/2,sy/3-dy,Tv$[1] IF tv>31 THEN GR.TEXT.DRAW tx,sx/2,sy/3-dy,Tv$[29] IF tv>0 & tv<32 GR.TEXT.SIZE txz0 GR.TEXT.ALIGN 1 GR.TEXT.DRAW tx,0,dy,”Tv” IF tv<17 GR.TEXT.DRAW tx,0,sy*3/12,” 1/” ENDIF GR.TEXT.SIZE txz2 GR.TEXT.ALIGN 2 GR.TEXT.DRAW tx,sx/2,sy/3-dy,Tv$[tv] ENDIF GOSUB col ! % // text AV // IF sw>-1 IF rav=av THEN GR.COLOR 255,255/2,0,0,1 ENDIF IF av<1 THEN GR.TEXT.DRAW tx,sx/2,sy*2/3-dy,Av$[1] IF av>36 THEN GR.TEXT.DRAW tx,sx/2,sy*2/3-dy,Av$[36] IF av>0 & av<37 av1=av GR.TEXT.SIZE txz0 GR.TEXT.ALIGN 1 GR.TEXT.DRAW tx,0,sy/2+dy/2,”Av” GR.TEXT.SIZE txz1 GR.TEXT.ALIGN 2 GR.TEXT.DRAW tx,sx/2,sy*2/3-dy,Av$[av1] ENDIF GOSUB col ! % // text iso // GR.TEXT.SIZE txz0 GR.TEXT.ALIGN 1 GR.TEXT.DRAW tx,0,sy-dy/3,”ISO” GR.TEXT.SIZE txz2 GR.TEXT.ALIGN 2 GR.TEXT.DRAW tx,sx/2,sy-dy,iso$ Schrausser, D. G. (2025). LV Lightvalues Exposure Calculator. https://doi.org/10.5281/zenodo.17037428 5 ! % // Color switch // GR.BOUNDED.TOUCH t1,sx/3,sy*2/3,sx*2/3,sy IF t1 insw=0 sw=sw+1:IF sw=2 THEN sw=-3 GR.CLOSE:GOTO m1 ENDIF ! GR.TEXT.SIZE txz0 GR.TEXT.ALIGN 3 IF dlg<>6 GR.TEXT.DRAW tx,sx,sy/20,lv$[dlg] ELSE IF tv<31 & av1<35 & tv>1 & av>1 & iso>1 & iso<39 GOSUB v0: GOSUB EV ENDIF GR.TEXT.DRAW tx,sx,sy/20,ev$+” Ev” GOSUB E_V GR.TEXT.SIZE sx/15 GR.TEXT.DRAW tx,sx,sy-sy/100,e_v$+” lx” ENDIF GOSUB ln GR.RENDER ! UNTIL 0 ! ONERROR: ONBACKKEY: GOSUB fin END ! ! // sub //////////////////////////////////////////////////////////////////////////// ! values: ARRAY.LOAD tv$[], “+”, “32000”,”16000”,”8000”,”4000”,”2000”,”1000”,”500”,”250”,”125”,”60”,”30”,”15”,”8”,”4”, ”2”,”1”+i$,”2”+i$,”4”+i$,”8”+i$,”15”+i$,”30”+i$,”1’”,”2’”,”4’”,”8’”,”15’”,”30’”,”1h”, ”2h”,”-“ ARRAY.LOAD av$[], “- “,”0.5”,”0.6”,”0.7”,”0.8”,”1.0”,”1.2”,”1.4”,”1.7”,”2.0”,”2.4”,”2.8”,”3.4”,”4.0”,”4.8” ,”5.6”,”6.7”,”8.0”,”9.5”,”11”,”13.5”,”16”,”19”,”22”,”27”,”32”,”38”,”44”,”54”,”64”,”76 ”,”88”,”108”,”128”,”152”,”+” ARRAY.LOAD iso$[], “- “,”0.4”,”0.6”,”0.8”,”1.1”,”1.5”,”2.2”,”3”,”4.4”,”6”,”8.8”,”12.5”,”18”,”25”,”35”,”50”, ”71”,”100”,”141”,”200”,”283”,”400”,”566”,”800”,”1131”,”1600”,”2263”,”3200”,”4526”,”64 00”,”9051”,”12800”,”18102”,”25600”,”36204”,”51200”,”72408”,”102400”,”+” RETURN ! col: IF sw=1 THEN GR.COLOR 255,30 ,30 ,30 ,1 IF sw=0 THEN GR.COLOR 255,180,180,180,1 IF sw=-1 THEN GR.COLOR 255,255,30 ,30 ,1 IF sw=-2 THEN GR.COLOR 255,30 ,255,30 ,1 IF sw=-3 THEN GR.COLOR 255,240,240,240,1 RETURN ! ln: GR.LINE l1,0,sy*1/3,sx,sy*1/3 GR.LINE l2,0,sy*2/3,sx,sy*2/3 GR.TEXT.ALIGN 1 GR.TEXT.DRAW tx,0,sy*1/6,” -“ GR.TEXT.DRAW tx,0,sy*5/6,” -“ GR.TEXT.ALIGN 3 GR.TEXT.DRAW tx,sx,sy*1/6,”+ “ GR.TEXT.DRAW tx,sx,sy*5/6,”+ “ RETURN ! sub1: PAUSE 100:GR.CLS RETURN ! inpt: ARRAY.LOAD lv$[],m1$+” Sun”,m2$+” Cloud”,m3$+” Overcast”,m4$+” Dawn”,m5$+” Indoors”,m6$+” EV”,m7$+” Calculate”,_ex$+” Exit” DIALOG.SELECT dlg, lv$[],_name$+” “+_ver$+” – ISO@100 …” IF dlg=5:tv=13:av=12:iso=18:ENDIF IF dlg=4:tv=13:av=14:iso=18:ENDIF IF dlg=3:tv=11:av=16:iso=18:ENDIF IF dlg=2:tv=10:av=18:iso=18:ENDIF Schrausser, D. G. (2025). LV Lightvalues Exposure Calculator. https://doi.org/10.5281/zenodo.17037428 6 IF dlg=1:tv=10:av=20:iso=18:ENDIF IF dlg=7 IF tv<31 & av1<35 & tv>1 & av>1 & iso>1 & iso<39 GOSUB v0 GOSUB calc ENDIF ENDIF IF dlg=8:GOSUB fin:END:ENDIF rtv=tv rav=av RETURN ! calc: GOSUB EV:GOSUB E_V ARRAY.LOAD calc$[],”Tv= 1/”+tv0$+” (“+tv1$+”)s”,”Av= “+av0$,”ISO= “+iso0$+”/”+din$+”°”,”Ev: “+ev$,e_v$+” lx”,”Ok” DIALOG.SELECT dlg2, calc$[],m7$+” Calculate…” IF dlg2=1 INPUT “Tv=…”,tv01,VAL(tv0$) GOSUB AvTv GOTO calc ENDIF IF dlg2=2 INPUT "Av=...",av01,VAL(av0$) av0$=STR$(av01) tv01=VAL(tv0$) GOSUB AvTv GOTO calc ENDIF IF dlg2=3 INPUT “ISO=…”,iso01,VAL(iso0$) GOSUB Aviso GOTO calc ENDIF IF dlg2=6 THEN GOTO inpt RETURN ! v0: % // conversions // IF tv<17 % // Tv < 1sec // tv0$=Tv$[tv] tv1$=STR$(ROUND(1/VAL(tv0$),5)) ENDIF IF tv>16 % // Tv >= 1sec // SW.BEGIN tv SW.CASE 17:tv0$=”1” :tv1$=”1” :SW.BREAK SW.CASE 18:tv0$=”0.5” :tv1$=”2” :SW.BREAK SW.CASE 19:tv0$=”0.25” :tv1$=”4” :SW.BREAK SW.CASE 20:tv0$=”0.125” :tv1$=”8” :SW.BREAK SW.CASE 21:tv0$=”0.0667” :tv1$=”15” :SW.BREAK SW.CASE 22:tv0$=”0.0333” :tv1$=”30” :SW.BREAK SW.CASE 23:tv0$=”0.0167” :tv1$=”60” :SW.BREAK SW.CASE 24:tv0$=”0.0083” :tv1$=”120” :SW.BREAK SW.CASE 25:tv0$=”0.0042” :tv1$=”240” :SW.BREAK SW.CASE 26:tv0$=”0.0021” :tv1$=”480” :SW.BREAK SW.CASE 27:tv0$=”0.0011” :tv1$=”900” :SW.BREAK SW.CASE 28:tv0$=”0.00056”:tv1$=”1800”:SW.BREAK SW.CASE 29:tv0$=”0.00028”:tv1$=”3600”:SW.BREAK SW.CASE 30:tv0$=”0.00014”:tv1$=”7200”:SW.BREAK SW.END ENDIF av0$=Av$[av1] iso0$=iso$ din$=INT$(INT(10*LOG10(VAL(iso0$))+1)) % // DIN // RETURN ! AvTv: % // calc Av Tv // av0$=STR$(VAL(av0$)*EXP((0.5*LOG(VAL(tv0$)/tv01))) ) av0$=STR$(ROUND(VAL(av0$),2)) tv0$=STR$(tv01) tv1$=STR$(ROUND(1/tv01,5)) RETURN ! Aviso: % // calc Av iso // av0$=STR$(VAL(av0$)*EXP((0.5*LOG(iso01/VAL(iso0$)))) ) av0$=STR$(ROUND(VAL(av0$),2)) iso0$=STR$(iso01) din$=STR$(ROUND(10*LOG10(iso01)+1,1)) RETURN ! Schrausser, D. G. (2025). LV Lightvalues Exposure Calculator. https://doi.org/10.5281/zenodo.17037428 7 EV: % // calc Ev // ev$=STR$(ROUND(1/LOG(2)*LOG((VAL(av0$))^2/(VAL(tv0$))^-1),2)) RETURN ! E_V: % // calc E_V // e_v$=STR$(ROUND(250*(2^VAL(ev$)/VAL(iso0$)),2)) RETURN ! fin: PRINT _name$+” Lightvalues “+_ver$ PRINT ”Copyright “+_cr$+” 2025 by Dietmar Gerald Schrausser” PRINT "https://github.com/Schrausser/LV" PRINT "DOI:10.5281/zenodo.16502602" RETURN ! // END // ! // References Allbright, G. S. (1991). Emulsion Speed Rating Systems. The Journal of Photographic Science 39 (2): 95–99. https://doi.org/ 10.1080/00223638.1991.11737126 Beaver, J. (2018). 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Foundations of Photography: A Treatise on the Technical Aspects of Digital Photography. Cham: Springer International Publishing. https://doi.org/ 10.1007/978-3-031-06252-0 Roberts, G. (1995). Exposure. In Mastering Photography, 76–87. London: Macmillan Education UK. https://doi.org/10.1007/ 978-1-349-13506-6_5 Schrausser, D. G. (2025). HP_Prime_MATH: Manual. Zenodo. June 2025. https://doi.org/10. 5281/zenodo.15713317 Simon, G., Vakulya, G., & Rátosi, M. (2022). The Way to Modern Shutter Speed Measurement Methods: A Historical Overview. Sensors 22 (5): 1871. https://doi.org/10.3390/ s22051871 Sobot, R. (2021). Exponential and Logarithmic Functions. In Engineering Mathematics by Example, 51–66. Cham: Springer International Publishing. https://doi.org/10. 1007/978-3-030-79545-0_4