Anda menginginkan matematika, jadi begini:
Anda perlu mengetahui CoC kamera Anda, sensor berukuran Canon APS-C angka ini adalah 0,018, untuk Nikon APS-C 0,019, untuk sensor bingkai penuh dan film 35mm jumlahnya adalah 0,029.
Rumusnya adalah untuk kelengkapan:
CoC (mm) = viewing distance (cm) / desired final-image resolution (lp/mm) for a 25 cm viewing distance / enlargement / 25
Cara lain untuk melakukan ini adalah rumus Zeiss :
c = d/1730
Di mana d adalah ukuran diagonal dari sensor, dan c adalah CoC maksimum yang dapat diterima. Ini menghasilkan angka yang sedikit berbeda.
Anda harus menghitung terlebih dahulu jarak hyperfocal untuk lensa dan kamera Anda (rumus ini tidak akurat dengan jarak yang dekat dengan panjang fokus, misalnya makro ekstrim):
HyperFocal[mm] = (FocalLength * FocalLength) / (Aperture * CoC)
misalnya:
50mm lens @ f/1.4 on a full frame: 61576mm (201.7 feet)
50mm lens @ f/2.8 on a full frame: 30788mm (101 feet)
50mm lens @ f/1.4 on a Canon APS frame: 99206mm (325.4 feet)
50mm lens @ f/2.8 on a Canon APS frame: 49600mm (162.7 feet)
Selanjutnya Anda perlu menghitung titik dekat yang merupakan jarak terdekat yang akan menjadi fokus mengingat jarak antara kamera dan subjek:
NearPoint[mm] = (HyperFocal * distance) / (HyperFocal + (distance – focal))
misalnya:
50mm lens @ f/1.4 on a full frame with a subject at 1m distance: 0.984m (~16mm in front of target)
50mm lens @ f/1.4 on a full frame with a subject at 3m distance: 2.862m (~137mm in front of target)
50mm lens @ f/2.8 on a full frame with a subject at 1m distance: 0.970m (~30mm in front of target)
50mm lens @ f/2.8 on a full frame with a subject at 3m distance: 2.737m (~263mm in front of target)
50mm lens @ f/1.4 on a Canon APS frame with a subject at 1m distance: 0.990m (~10mm in front of target)
50mm lens @ f/1.4 on a Canon APS frame with a subject at 3m distance: 2.913m (~86mm in front of target)
50mm lens @ f/2.8 on a Canon APS frame with a subject at 1m distance: 0.981m (~19mm in front of target)
50mm lens @ f/2.8 on a Canon APS frame with a subject at 3m distance: 2.831m (~168mm in front of target)
Selanjutnya Anda perlu menghitung titik jauh yang merupakan jarak terjauh yang akan menjadi fokus mengingat jarak antara kamera dan subjek:
FarPoint[mm] = (HyperFocal * distance) / (HyperFocal – (distance – focal))
misalnya:
50mm lens @ f/1.4 on a full frame with a subject at 1m distance: 1.015m (~15mm behind of target)
50mm lens @ f/1.4 on a full frame with a subject at 3m distance: 3.150m (~150mm behind of target)
50mm lens @ f/2.8 on a full frame with a subject at 1m distance: 1.031m (~31mm behind of target)
50mm lens @ f/2.8 on a full frame with a subject at 3m distance: 3.317m (~317mm behind of target)
50mm lens @ f/1.4 on a Canon APS frame with a subject at 1m distance: 1.009m (~9mm behind of target)
50mm lens @ f/1.4 on a Canon APS frame with a subject at 3m distance: 3.091m (~91mm behind of target)
50mm lens @ f/2.8 on a Canon APS frame with a subject at 1m distance: 1.019m (~19mm behind of target)
50mm lens @ f/2.8 on a Canon APS frame with a subject at 3m distance: 3.189m (~189mm behind of target)
Sekarang Anda dapat menghitung total jarak fokus:
TotalDoF = FarPoint - NearPoint
misalnya:
50mm lens @ f/1.4 on a full frame with a subject at 1m distance: 31mm
50mm lens @ f/1.4 on a full frame with a subject at 3m distance: 228mm
50mm lens @ f/2.8 on a full frame with a subject at 1m distance: 61mm
50mm lens @ f/2.8 on a full frame with a subject at 3m distance: 580mm
50mm lens @ f/1.4 on a Canon APS frame with a subject at 1m distance: 19mm
50mm lens @ f/1.4 on a Canon APS frame with a subject at 3m distance: 178mm
50mm lens @ f/2.8 on a Canon APS frame with a subject at 1m distance: 38mm
50mm lens @ f/2.8 on a Canon APS frame with a subject at 3m distance: 358mm
Jadi rumus lengkapnya w / CoC dan HyperFocal yang dihitung sebelumnya:
TotalDoF[mm] = ((HyperFocal * distance) / (HyperFocal – (distance – focal))) -(HyperFocal * distance) / (HyperFocal + (distance – focal))
Atau disederhanakan:
TotalDoF[mm] = (2 * HyperFocal * distance * (distance - focal)) / (( HyperFocal + distance - focal) * (HyperFocal + focal - distance))
Dengan CoC precalulated: Saya telah berupaya untuk menyederhanakan persamaan berikut dengan substitusi berikut: a = jarak pandang (cm) b = resolusi gambar akhir yang diinginkan (lp / mm) untuk jarak pandang 25 cm c = pembesaran d = Panjang Fokus e = Bukaan f = jarak X = CoC
TotalDoF = ((((d * d) / (e * X)) * f) / (((d * d) / (e * X)) – (f – d))) - ((((d * d) / (e * X)) * f) / (((d * d) / (e * X)) + (f – d)))
Sederhana:
TotalDoF = (2*X*d^2*f*e(d-f))/((d^2 - X*d*e + X*f*e)*(d^2 + X*d*e - X*f*e))
Lebih jauh disederhanakan dengan WolframAlpha:
TotalDoF = (2 * d^2 * e * (d - f) * f * X)/(d^4 - e^2 * (d - f)^2 * X^2)
Atau jika tidak ada yang dihitung, Anda mendapatkan monster ini, yang tidak dapat digunakan:
TotalDoF = ((FocalLength * FocalLength) / (Aperture * (viewing distance (cm) / desired final-image resolution (lp/mm) for a 25 cm viewing distance / enlargement / 25)) * distance) / ((FocalLength * FocalLength) / (Aperture * (viewing distance (cm) / desired final-image resolution (lp/mm) for a 25 cm viewing distance / enlargement / 25)) – (distance – focal)) - ((FocalLength * FocalLength) / (Aperture * (viewing distance (cm) / desired final-image resolution (lp/mm) for a 25 cm viewing distance / enlargement / 25)) * distance) / ((FocalLength * FocalLength) / (Aperture * (viewing distance (cm) / desired final-image resolution (lp/mm) for a 25 cm viewing distance / enlargement / 25)) + (distance – focal))
Sederhana:
(50*a*b*c*d^2*f*e*(d-f))/((25*b*c*d^2 - a*d*e + a*f*e)*(25*b*c*d^2 + a*d*e - a*f*e)
Jadi pada dasarnya gunakan CoC dan HyperFocal :) yang dihitung ulang