Here we are aiming to attain a very shallow depth of field so that just the important features of the face are sharp and the remaining composition is out of focus. Given we are dealing with head and shoulders portraiture, for simplicity, I will assume a telephoto of 100mm in 35mm equiv. terms at 2m from the subject. The figures show calculated DOF range.
*The fill-in flash in sunlight calculations assume exposure is set to over-expose sunlit areas by 0.5 stop eg. ISO 100, f/16, 1/70th sec.
#GN for fill-in flash are for ISO 100 in metres to achieve the exposure at 2m.
|Camera & lens||at wide open||at widest aperture in sunlight with fill-in flash*||at widest aperture in sunlight with fill-in flash* with ND 2 stops filter||at widest aperture in sunlight with fill-in flash* with ND 3 stops filter||at f/8||at smallest aperture|
|6×6 medium format film, 150mm lens, 1/500th x-sync, 100ISO||f/3.5: 6cm DOF range||f/5.6, 1/500th: 10cm #GN 11||f/3.5, 1/300th: 6cm GN 11||f/3.5, 1/150th: 6cm GN 11||14cm||f/22: 40cm f/32: 59cm|
|35mm 1/60th sec x-sync, 100ISO||f/2.8: 6cm||f/16, 1/60th: 37cm GN 32||f/8, 1/60th: 18cm GN 32||f/5.6, 1/60th: 13cm GN 32||18cm||f/22: 51cm|
|Canon 5D, 1/200th x-sync, 50ISO||f/2.8: 6cm||f/6.3, 1/200th: 14cm GN 19||f/3.5, 1/200th: 8cm GN 19||f/2.8, 1/180th: 6cm GN 19||18cm||f/22: 51cm|
|Canon 350D, 1/200th x-sync, 125ISO, EFS 17-85 f/4-5.6||f/5.6: 21cm||f/11, 1/200th: 41cm GN 19||f/5.6, 1/200th: 21cm GN 19||f/5.6, 1/100th: 21cm GN 19||30cm||f/16: 60cm f/22: 85cm|
|Nikon D200, 1/250th x-synx, 100ISO, DX 18-70mm f/3.5-4.5||f/4.5: 16cm||f/8, 1/250th: 28cm GN 16||f/4.5, 1/200th: 16cm GN 16||f/4.5, 1/100th: 16cm GN 16||28cm||f/16: 57cm f/22: 80cm|
|Olympus E series, 1/4000th FP sync, 50mm f/2.0||f/2.0: 10cm||f/2, 1/4000th: 10cm GN 4 in FP ie. need the FL-50||f/2, 1/1000th: 10cm GN 8 in FP N/A||f/2, 1/500th: 10cm GN 11 in FP N/A||39cm||f/16: 81cm f/22: 116cm|
|Olympus E series, 1/180th X sync, 50mm f/2.0||f/2.0: 10cm||f/9.5, 1/180th: 47cm GN 19||f/4.5, 1/180th: 22cm GN 19||f/3.5, 1/180th: 17cm GN 19||39cm||f/16: 81cm f/22: 116cm|
|Olympus E series, 1/4000th FP sync, 14-54mm f/2.8-3.5||f/3.5: 17cm||f/3.5, 1/1500th: 17cm GN 7 in FP ie. need the FL-50||f/3.5, 1/350th: 17cm GN 14 in FP N/A||f/3.5, 1/180th: 17cm GN 19 in FP N/A||39cm||f/16: 81cm f/22: 116cm|
|Olympus C8080, 1/300th X sync, f/2.4-3.5, 50ISO||f/3.0: 29cm||f/5.6, 1/300th: 55cm GN 11||f/3.0, 1/300th: 29cm GN 11||f/3.0, 1/150th: 29cm GN 11||80cm||f/8: 80cm|
|Sony DSC-R1, 1/2000th x-sync, 160ISO||f/4.5: 17cm||f/4.5, 1/2000th: 17cm GN 7||f/4.5, 1/500th: 17cm GN 14||f/4.5, 1/250th: 17cm GN 19||30cm||f/16: 60cm|
|Canon 1DMIII, 1/250th xsync, 85mm f/1.8||f/1.8: 4.5cm||f/8, 1/250th: 20cm GN 16||f/4, 1/250th: 10cm GN 16||f/2.8, 1/250th: 8cm GN 16||20cm|
|Canon 1DMIII, 1/500th xsync PW hypersync or wired, 85mm f/1.2||f/1.2: 3.0cm||f/5.6, 1/500th: 14cm GN 11||f/2.8, 1/500th: 8cm GN 11||f/2.0, 1/500th: 5cm GN 11||20cm|
|Canon 1DMIII, 1/500th xsync PW hypersync or wired, 85mm f/1.2 at ISO 50 (L)||f/1.2: 3.0cm||f/4, 1/500th: 10cm GN 11||f/2.0, 1/500th: 5cm GN 11||f/1.4, 1/500th: 3.5cm GN 11||20cm|
|Olympus E-510, 1/400th sec (with banding), 50mm f/2.0 at 2m||f/2.0: 10cm||f/6.3, 1/400th: 31cm GN 12||f/3.2, 1/400th: 16cm GN 12||f/2.4, 1/400th: 12cm GN 12||39cm||f/16: 81cm f/22: 116cm|
|Olympus E-510, 1/400th sec (with banding), 200mm f/3.5 at 4m||f/3.5: 4cm||f/6.3, 1/400th: 8cm GN 24||f/3.5, 1/400th: 4cm GN 24||n/a||10cm|
Thus, it shows that where daylight flash fill-in is not needed, then the narrowest depth of field is with cameras that have a large sensor (eg. medium format or full frame 35mm) or at least a f/2.0 100mm lens available as with the Olympus E series.
When shooting portraits with fill-in flash in daylight without using filters, the picture changes a little with consideration required for the fastest possible flash sync, the lowest possible ISO, here the medium format leaf shutter cameras again win, but the Olympus E series with super FP mode and a 50mm f/2.0 lens is able to match them, with the Sony DSC-R1 not far behind. To achieve a comparable result with the Canon 5D you would have its special 50ISO mode, while the Nikon D200 and Canon 350D/20D/30D along with older 35mm film cameras with their slow x-syncs lag a considerable way behind. When the Olympus cameras are used without a super FP mode flash, then, given their smaller sensor size not surprisingly come last.
Note that the Olympus FL-50 flash in super FP mode at 1/2000th sec gives a maximum effective GN of about 7 in m at ISO100, which limits is use for group shots or subjects if they are more than 3.5m away.
Note also that the lowest true ISO reading on the Canon 350D and Olympus E330 is really 125 not the indicated 100.
Using a 135mm lens and stepping back to 2.7m does not change your DOF range significantly, but of course, if you stayed at 2m to get a tighter headshot, your DOF range would get narrower but the relative differences between each of the above scenarios would not change appreciably.
The Canon 1D Mark III has x-sync up to 1/300th sec, but if you use a PC sync cable and take the flash off the hot shoe and place both flash and camera in manual mode, you can use faster shutter speeds with 1/400th sec posing no problems at all, but a narrow band at the bottom of the frame appears at 1/500th sec (this can be avoided by using the Pocket Wizard hypersync functionality and you regain full TTL capability).
The Olympus E510 max TTL x-sync is 1/180th sec (you can use higher shutter speeds in super FP sync but at lower flash output). By using a PC sync cable attached to a hotshoe adapter, you can do manual flash at up to 1/320th sec without issues. At 1/400th sec there is a narrow band at the bottom of the frame as with the Canon 1DMIII at 1/500th sec.
The Panasonic GH-1 unfortunately forces the fastest shutter speed to be 1/160th sec when it detects a flash is turned on and attached via a PC sync cable.
|subject at 2m, background at 6m||background at 4m behind subject still but subject magnification the same as at 2m with a 100mm lens|
|Canon 5D 50mm lens||f/1.2: 83mm; f/1.4: 71mm; f/1.8: 56mm; f/2: 50mm; f/2.8: 36mm;||subject at 0.97m f/1.2: 166mm; f/1.4: 142mm; f/1.8: 112mm; f/2: 100mm; f/2.8: 76mm;|
|Canon 5D 85mm lens||f/1.2: 141mm; f/1.4: 121mm; f/1.8: 95mm; f/2: 85mm; f/2.8: 61mm;||subject at 1.7m f/1.2: 166mm; f/1.4: 142mm; f/1.8: 112mm; f/2: 100mm; f/2.8: 76mm;|
|Canon 5D 100mm lens||f/1.2: 166mm; f/1.4: 142mm; f/1.8: 112mm; f/2: 100mm; f/2.8: 76mm;||subject at 2m f/1.2: 166mm; f/1.4: 142mm; f/1.8: 112mm; f/2: 100mm; f/2.8: 76mm;|