Focal length equivalents between formats

Introduction

The table below lists the focal length equivalents between formats, keeping track of aspect ratios, such that every format can fit into any target format. In other words the equivalent format is strictly wider.

Focal lens equivalents

APS-C

APS-C

Focal length	Horizontal FOV	Vertical FOV	APS-C	35mm	GFX	H5D	4x5	6x17	8x10
10mm	102.9	79.7	10	14	17	21	48	36	101
14mm	83.7	61.6	14	20	24	30	67	50	142
16mm	76.2	55.1	16	23	28	34	77	57	162
18mm	69.8	49.8	18	26	31	39	87	65	182
35mm	39.5	26.8	35	50	61	75	169	126	354
50mm	28.2	19.0	50	72	87	107	241	180	506
55mm	25.7	17.3	55	79	96	118	265	198	557
56mm	25.3	17.0	56	80	98	120	270	201	567
60mm	23.6	15.8	60	86	105	128	289	216	607
80mm	17.8	11.9	80	115	140	171	386	287	810
90mm	15.9	10.6	90	129	157	193	434	323	911
200mm	7.2	4.8	200	287	349	428	964	719	2024

35mm full frame

35mm full frame

Focal length	Horizontal FOV	Vertical FOV	APS-C	35mm	GFX	H5D	4x5	6x17	8x10
14mm	104.3	81.2	10	14	17	21	47	35	99
16mm	96.7	73.7	11	16	19	24	54	40	113
17mm	93.3	70.4	12	17	21	25	57	42	120
19mm	86.9	64.6	13	19	23	28	64	48	134
20mm	84.0	61.9	14	20	24	30	67	50	141
24mm	73.7	53.1	17	24	29	36	81	60	169
28mm	65.5	46.4	19	28	34	42	94	70	198
35mm	54.4	37.8	24	35	43	52	118	88	247
45mm	43.6	29.9	31	45	55	67	151	112	318
50mm	39.6	27.0	35	50	61	75	168	125	353
85mm	23.9	16.1	59	85	103	127	286	212	600
105mm	19.5	13.0	73	105	128	157	353	262	741
120mm	17.1	11.4	84	120	146	179	403	300	847
200mm	10.3	6.9	139	200	243	298	672	500	1411

Fuji GFX

Fuji GFX

Focal length	Horizontal FOV	Vertical FOV	APS-C	35mm	GFX	H5D	4x5	6x17	8x10
23mm	87.2	71.0	12	17	23	28	64	42	133
32mm	68.8	54.3	16	23	32	39	88	59	186
45mm	51.9	40.0	23	33	45	55	124	82	261
50mm	47.3	36.3	25	37	50	61	138	91	290
63mm	38.3	29.2	32	46	63	77	174	115	365
100mm	24.7	18.6	51	73	100	123	276	183	580
110mm	22.5	17.0	56	80	110	135	304	201	638
200mm	12.5	9.4	102	146	200	245	553	366	1160
250mm	10.0	7.5	127	183	250	306	691	457	1450
Hasselblad 24mm	84.8	68.7	12	18	24	29	66	44	139
Hasselblad 28mm	76.1	60.7	14	20	28	34	77	51	162
Hasselblad 35mm	64.1	50.2	18	26	35	43	97	64	203
Hasselblad 50mm	47.3	36.3	25	37	50	61	138	91	290
Hasselblad 80mm	30.6	23.2	41	59	80	98	221	146	464
Hasselblad 90mm	27.4	20.7	46	66	90	110	249	165	522
Hasselblad 110mm	22.5	17.0	56	80	110	135	304	201	638
Hasselblad 150mm	16.6	12.5	76	110	150	184	414	274	870
Hasselblad 210mm	11.9	8.9	107	154	210	257	580	384	1218
Hasselblad 300mm	8.4	6.3	153	220	300	368	829	549	1740
Hasselblad 24mm (1.5)	62.6	49.0	18	26	36	44	99	66	209
Hasselblad 28mm (1.5)	55.1	42.7	21	31	42	51	116	77	244
Hasselblad 35mm (1.5)	45.3	34.7	27	38	52	64	145	96	304
Hasselblad 50mm (1.5)	32.6	24.7	38	55	75	92	207	137	435
Hasselblad 80mm (1.5)	20.7	15.6	61	88	120	147	332	220	696
Hasselblad 90mm (1.5)	18.4	13.9	69	99	135	165	373	247	783
Hasselblad 110mm (1.5)	15.1	11.4	84	121	165	202	456	302	957
Hasselblad 150mm (1.5)	11.1	8.3	115	165	225	276	622	412	1305
Hasselblad 210mm (1.5)	8.0	6.0	160	230	315	386	870	576	1827
Hasselblad 300mm (1.5)	5.6	4.2	229	329	450	552	1243	823	2610

Pentax 645

Pentax 645

Focal length	Horizontal FOV	Vertical FOV	APS-C	35mm	GFX	H5D	4x5	6x17	8x10
25mm	82.4	66.5	13	18	25	31	69	46	145
28mm	76.1	60.7	14	20	28	34	77	51	162
33mm	67.1	52.9	17	24	33	40	91	60	191
45mm	51.9	40.0	23	33	45	55	124	82	261
55mm	43.4	33.2	28	40	55	67	152	101	319
80mm	30.6	23.2	41	59	80	98	221	146	464
85mm	28.9	21.8	43	62	85	104	235	155	493
110mm	22.5	17.0	56	80	110	135	304	201	638
150mm	16.6	12.5	76	110	150	184	414	274	870
160mm	15.6	11.7	81	117	160	196	442	293	928
300mm	8.4	6.3	153	220	300	368	829	549	1740

Hasselblad H5D-60

Hasselblad H5D-60

Focal length	Horizontal FOV	Vertical FOV	APS-C	35mm	GFX	H5D	4x5	6x17	8x10
24mm	96.4	79.9	10	14	20	24	54	36	114
28mm	87.6	71.3	12	17	23	28	63	42	132
35mm	75.0	59.7	15	21	29	35	79	52	166
50mm	56.5	43.8	21	30	41	50	113	75	236
80mm	37.1	28.2	33	48	65	80	180	119	378
90mm	33.2	25.2	37	54	73	90	203	134	426
110mm	27.4	20.7	46	66	90	110	248	164	520
150mm	20.3	15.3	62	90	122	150	338	224	709
210mm	14.6	10.9	87	125	171	210	473	313	993
300mm	10.2	7.7	125	179	245	300	676	448	1419
24mm (1.5)	73.4	58.4	15	21	29	36	81	54	170
28mm (1.5)	65.2	51.1	17	25	34	42	95	63	199
35mm (1.5)	54.2	41.9	22	31	43	52	118	78	248
50mm (1.5)	39.4	30.0	31	45	61	75	169	112	355
80mm (1.5)	25.2	19.0	50	72	98	120	270	179	568
90mm (1.5)	22.5	16.9	56	81	110	135	304	201	639
110mm (1.5)	18.5	13.9	69	99	135	165	372	246	780
150mm (1.5)	13.6	10.2	93	134	184	225	507	336	1064
210mm (1.5)	9.7	7.3	131	188	257	315	710	470	1490
300mm (1.5)	6.8	5.1	187	269	367	450	1014	672	2128

LF (4x5)

LF (4x5)

Focal length	Horizontal FOV	Vertical FOV	APS-C	35mm	GFX	H5D	4x5	6x17	8x10
72mm	80.1	67.9	12	18	24	30	72	45	151
90mm	67.8	56.6	15	22	30	37	90	56	188
150mm	43.9	35.8	26	37	51	62	150	93	314
240mm	28.3	22.8	41	59	81	99	240	148	502
300mm	22.8	18.4	52	74	101	124	300	186	628

LF (6x17)

LF (6x17)

Focal length	Horizontal FOV	Vertical FOV	APS-C	35mm	GFX	H5D	4x5	6x17	8x10
72mm	99.5	45.2	11	15	19	23	51	72	108
90mm	86.7	36.9	13	19	23	28	64	90	134
150mm	59.1	22.6	22	32	39	47	107	150	224
240mm	39.0	14.3	35	51	62	76	171	240	359
300mm	31.6	11.4	44	64	77	95	214	300	448

LF (8x10)

LF (8x10)

Focal length	Horizontal FOV	Vertical FOV	APS-C	35mm	GFX	H5D	4x5	6x17	8x10
150mm	80.5	68.2	12	18	24	30	71	44	150
240mm	55.8	45.8	20	28	39	48	114	71	240
300mm	45.9	37.4	25	35	48	59	143	89	300
450mm	31.5	25.4	37	53	73	89	214	133	450
600mm	23.9	19.2	49	71	97	119	286	177	600

Code

The table above was generated by the program below.

package main

import (
	"fmt"
	"math"
)

type Medium struct {
	h, v float64
	name string
}

func (m Medium) AspectRatio() float64 {
	return m.h/m.v
}

var (
	MediumAPSC  = Medium{25.1, 16.7, "APS-C"}
	MediumFF    = Medium{36, 24, "35mm"}
	MediumMFF   = Medium{43.8, 32.8, "GFX"}
	MediumMFH   = Medium{53.7, 40.2, "H5D"}
	MediumLF45  = Medium{121, 97, "4x5"}
	MediumLF617 = Medium{170, 60, "6x17"}
	MediumLF810 = Medium{254, 203, "8x10"}
)

var Mediums = []Medium {
	MediumAPSC,
	MediumFF,
	MediumMFF,
	MediumLF45,
	MediumLF617,
	MediumLF810,
}

type Lens struct {
	focal float64
	tc float64
	mfg string
}

func (l Lens) String() string {
	var s string
	if l.mfg != "" {
		s = l.mfg + " "
	}
	s += fmt.Sprintf("%.0fmm", l.focal)
	if l.tc == 1.0 {
		return s
	}
	return s + fmt.Sprintf(" (%.1f)", l.tc)
}

func (l Lens) Focal() float64 {
	return l.focal * l.tc
}

var LensesAPSC = []Lens {
	{10, 1.0, ""},
	{14, 1.0, ""},
	{16, 1.0, ""},
	{18, 1.0, ""},
	{35, 1.0, ""},
	{50, 1.0, ""},
	{55, 1.0, ""},
	{56, 1.0, ""},
	{60, 1.0, ""},
	{80, 1.0, ""},
	{90, 1.0, ""},
	{200, 1.0, ""},
}

var LensesFF = []Lens{
	{14, 1.0, ""},
	{16, 1.0, ""},
	{17, 1.0, ""},
	{19, 1.0, ""},
	{20, 1.0, ""},
	{24, 1.0, ""},
	{28, 1.0, ""},
	{35, 1.0, ""},
	{45, 1.0, ""},
	{50, 1.0, ""},
	{85, 1.0, ""},
	{105, 1.0, ""},
	{120, 1.0, ""},
	{200, 1.0, ""},
}

var LensesGFX = []Lens{
	{23, 1.0, ""},
	{32, 1.0, ""},
	{45, 1.0, ""},
	{50, 1.0, ""},
	{63, 1.0, ""},
	{100, 1.0, ""},
	{110, 1.0, ""},
	{200, 1.0, ""},
	{250, 1.0, ""},
}

var LensesPentax = []Lens {
	{25, 1.0, ""},
	{28, 1.0, ""},
	{33, 1.0, ""},
	{45, 1.0, ""},
	{55, 1.0, ""},
	{80, 1.0, ""},
	{85, 1.0, ""},
	{110, 1.0, ""},
	{150, 1.0, ""},
	{160, 1.0, ""},
	{300, 1.0, ""},
}

var LensesHasselblad = []Lens {
	{24, 1.0, ""},
	{28, 1.0, ""},
	{35, 1.0, ""},
	{50, 1.0, ""},
	{80, 1.0, ""},
	{90, 1.0, ""},
	{110, 1.0, ""},
	{150, 1.0, ""},
	{210, 1.0, ""},
	{300, 1.0, ""},
}

func init() {
	for _, v := range LensesHasselblad {
		v1 := v
		v1.tc = 1.5
		LensesHasselblad = append(LensesHasselblad, v1)
	}
}

func init() {
	for _, v := range LensesHasselblad {
		v1 := v
		v1.mfg = "Hasselblad"
		LensesGFX = append(LensesGFX, v1)
	}
}

var LensesLF = []Lens {
	{72, 1.0, ""},
	{90, 1.0, ""},
	{150, 1.0, ""},
	{240, 1.0, ""},
	{300, 1.0, ""},
}

var LensesLF810 = []Lens {
	{150, 1.0, ""},
	{240, 1.0, ""},
	{300, 1.0, ""},
	{450, 1.0, ""},
	{600, 1.0, ""},
}

type System struct {
	Medium
	Lenses *[]Lens
	Name string
}

var (
	SystemAPSC = System{MediumAPSC, &LensesAPSC, "APS-C"}
	SystemFF = System{MediumFF, &LensesFF, "35mm full frame"}
	SystemGFX = System{MediumMFF, &LensesGFX, "Fuji GFX"}
	SystemPentax = System{MediumMFF, &LensesPentax, "Pentax 645"}
	SystemHasselblad = System{MediumMFH, &LensesHasselblad, "Hasselblad H5D-60"}
	SystemLF45 = System{MediumLF45, &LensesLF, "LF (4x5)"}
	SystemLF617 = System{MediumLF617, &LensesLF, "LF (6x17)"}
	SystemLF810 = System{MediumLF810, &LensesLF810, "LF (8x10)"}
)

var Systems = []System {
	SystemAPSC,
	SystemFF,
	SystemGFX,
	SystemPentax,
	SystemHasselblad,
	SystemLF45,
	SystemLF617,
	SystemLF810,
}

func fov(ssize, focal float64) float64 {
	return 2 * math.Atan(ssize/(2*focal)) * 180 / math.Pi
}

type LensAll struct {
	Lens
	HFoV float64
	VFoV float64
	Eq map[Medium]float64
}

func (la LensAll) String() string {
	var s string
	s = fmt.Sprintf("|%v\n|%.1f\n|%.1f", la.Lens, la.HFoV, la.VFoV)
	for _, m := range Mediums {
		s += fmt.Sprintf("\n|%.0f", la.Eq[m])
	}
	return s
}

func Equivalent(l Lens, m Medium, mtarg Medium) float64 {
	if m.AspectRatio() <= mtarg.AspectRatio() {
		return l.Focal() * mtarg.v/m.v
	}
	return l.Focal() * mtarg.h/m.h
}

type SystemEquiv struct {
	System
	Lenses []LensAll
}

func (se SystemEquiv) String() string {
	s := fmt.Sprintf("=== %s ===\n", se.Name)

	s += `{| class="wikitable"` + "\n"
 	s += "|+"+se.Name + "\n"

	s += fmt.Sprintf("|-\n")
	s += fmt.Sprintf("|Focal length\n")
	s += fmt.Sprintf("|Horizontal FOV\n")
	s += fmt.Sprintf("|Vertical FOV\n")
 	for _, m := range Mediums {
 		s += fmt.Sprintf("|%s\n", m.name)
 	}
 	for _, l := range se.Lenses {
 		s += fmt.Sprintf("|-\n%s\n", l)
 	}
 
 	s += "|}"
 
	return s
}

func main() {
	for _, system := range Systems {
		se := SystemEquiv{system, nil}
		lenses := []LensAll{}
		for _, lens := range *system.Lenses {
			la := LensAll{Lens: lens}
			la.HFoV = fov(system.Medium.h, lens.Focal())
			la.VFoV = fov(system.Medium.v, lens.Focal())

			la.Eq = make(map [Medium]float64)
			for _, m := range Mediums {
				la.Eq[m] = Equivalent(lens, system.Medium, m)
			}

			lenses = append(lenses, la)
		}
		se.Lenses = lenses
		fmt.Println(se)
	}
}