Zitsanzo ziwiri za mafunso okhudza zida zowunikira za kamera
1. Kamera ya analog ya lenzi imodzi imakhala ndi kutalika kwa 10 cm. Poyamba, kamerayo imakonzedwa kuti ijambule chinthu pa nthawi yosatha. Ngati wina akufuna kugwiritsa ntchito kamera kujambula chinthu chomwe chili pamtunda wa mamita 5, werengerani:
(a) Mtunda pakati pa filimu ndi lenzi pamene kamera yayikidwa kuti ijambule chinthu chosatha,
(b) Mtunda pakati pa filimu ndi lenzi pamene kamera yayikidwa kuti ijambule chinthu chomwe chili pamtunda wa mamita 100,
(c) Sinthani malo a lenzi kuchokera pa malo osatha kupita pa malo okwana mamita 100. Kodi lenziyo yasunthidwa kutali ndi filimuyo kapena ili pafupi ndi filimuyo?
Zokambirana
Amadziwika kuti:
Utali wa lenzi (f) = 10 cm = 100 mm
Yankho:
(a) Mtunda pakati pa filimu ndi lenzi pamene kamera yayikidwa kuti ijambule chinthu chosatha.
Mtunda pakati pa lenzi ndi filimu = mtunda wa chithunzi (s')
Chinthu chakutali kwambiri chimatanthauza kuti mtunda wa chinthucho ndi wopanda malire.
Kamera ikakonzedwa kuti ijambule chinthu, mtunda pakati pa lenzi ndi filimuyo umasinthidwa kuti kuwala kochokera ku chinthucho kuyang'anitsidwe ndi lenziyo kuti ipange chithunzi cholondola pa filimuyo.
Ponena za magalasi ozungulira, zafotokozedwa kuti ngati mtunda wa chinthu (s) = wopanda malire ndiye mtunda mthunzi (s') = kutalika kwa lenzi (f).
Mtunda pakati pa lenzi ndi filimu = mtunda wa chithunzi (s') = kutalika kwa focal (f) kwa lenzi = 100 millimeters.
(b) Mtunda pakati pa filimu ndi lenzi pamene kamera yayikidwa kuti ijambule chinthu chomwe chili pamtunda wa mamita 5.
Mtunda wa chinthu = 5 m = 5000 mm
Utali wa lenzi (f) = 100 mm
Mtunda pakati pa filimu ndi lenzi = mtunda wa chithunzi, wowerengedwa pogwiritsa ntchito njira ya lenzi yozungulira chifukwa lenzi ya kamera ndi lenzi yozungulira:
1/s' = 1/f – 1/s = 1/100 – 1/5000 = 50/5000 – 1/5000 = 49/5000
s' = 5000/49 = 102 mamilimita
(c) Kusintha kwa malo a lenzi kuchokera pa malo osatha kupita pa malo okhazikika a mamita 100
Mukayiyika kuti ijambule chinthu pa nthawi yosatha, mtunda pakati pa lenzi ndi filimu ndi mamilimita 100. Mukayiyika kuti ijambule chinthu chomwe chili pamtunda wa mamita 5, mtunda pakati pa lenzi ndi filimu ndi mamilimita 102. Motero, kusintha kwa mtunda wa lenzi kuchokera ku filimu ndi 102 mm - 100 mm = 2 mm.
Kodi lenzi yasunthidwa kutali ndi filimu kapena pafupi nayo? Zachidziwikire, lenziyo imasunthidwa kutali ndi filimuyo chifukwa pa nthawi yopanda malire, mtunda pakati pa lenzi ndi filimuyo = kutalika kwa lenziyo. Ngati lenziyo yasunthidwa pafupi ndi filimuyo, mtunda pakati pa lenzi ndi filimuyo ndi wochepera 100 mm.
2. Magalasi awiri ozungulira, aliwonse okhala ndi kutalika kwa 40 mm ndi 20 mm. Magalasi onsewa amagwiritsidwa ntchito mu kamera ya analogi kujambula chinthu chomwe chili pamtunda wa mamita 10. Dziwani:
(a) Mtunda pakati pa filimu ndi lenzi ndi kutalika kwa 40 mm pamene kamera yayikidwa kuti ijambule chinthucho. Komanso werengani kukula kwa mzere.
(b) Mtunda pakati pa filimu ndi lenzi ndi kutalika kwa 20 mm pamene kamera yayikidwa kuti ijambule chinthucho. Komanso werengani kukula kwa mzere.
Zokambirana
Amadziwika kuti:
Utali wa lenzi yozungulira ndi 1 (f)1) = 40 mm
Utali wa lenzi yozungulira ndi 2 (f)2) = 20 mm
Mtunda wa chinthu = 10 m = 10.000 mm
Yankho:
(a) Mtunda pakati pa filimu ndi lenzi ndi kutalika kwa 40 mm pamene kamera yayikidwa kuti ijambule chinthu
Mtunda pakati pa filimu ndi lenzi = mtunda wa chithunzi (s'), wowerengedwa pogwiritsa ntchito njira ya lenzi yozungulira chifukwa lenzi ya kamera ndi lenzi yozungulira:
1/s' = 1/f – 1/s = 1/40 – 1/10.000 = 250/10.000 – 1/10.000 = 249/10.000
s' = 10.000/249 = 40,2 mm
Kukula kwa mzere (m):
m = s'/s = 40,2/10.000 = 0,004 nthawi
(b) Mtunda pakati pa filimu ndi lenzi ndi kutalika kwa 20 mm pamene kamera yayikidwa kuti ijambule chinthu
Mtunda pakati pa filimu ndi lenzi = mtunda wa chithunzi (s'), wowerengedwa pogwiritsa ntchito njira ya lenzi yozungulira chifukwa lenzi ya kamera ndi lenzi yozungulira:
1/s' = 1/f – 1/s = 1/20 – 1/10.000 = 500/10.000 – 1/10.000 = 499/10.000
s' = 10.000/499 = 20,0 mm
Kukula kwa mzere (m):
m = 20,0/10.000 = nthawi 0,002
Yerekezerani kukula kwa mzere mu kuwerengera uku ndi kwapitako. Kutengera ndi kukula kwa mzere kawiri kumeneku, zitha kutsimikizika kuti kukula kwa mzere kumawonjezeka ndi kutalika kwa lenzi. Chifukwa chake, posankha lenzi ya kamera, muyeneranso kuganizira kutalika kwake. Pazinthu zakutali, lenzi yokhala ndi kutalika kwa mzere wautali iyenera kugwiritsidwa ntchito kukulitsa chithunzi chopangidwa ndi lenzi ndikujambulidwa pafilimu.
Ngati tijambula chinthu chakutali pogwiritsa ntchito kamera yokhala ndi lenzi yowonera zinthu, timakulitsa chithunzi chomwe chimapangidwa posintha ma lenzi ndikugwiritsa ntchito lenzi yokhala ndi kutalika kwakutali kwa focal. Tikhoza kusintha ma lenzi chifukwa lenzi yowonera zinthu imapangidwa ndi ma lenzi angapo okhala ndi kutalika kosiyana kwa focal.
Mukamajambula zithunzi za zinthu zakutali pogwiritsa ntchito kamera ya lenzi imodzi, ndi bwino kugwiritsa ntchito lenzi yokhala ndi kutalika kwakutali. Lenzi iyi ili ndi mawonekedwe osalala.
