# G1X maximum shutter speed question . . .

Started Aug 10, 2013 | Questions thread
Re: G1X maximum shutter speed ANSWER: IS LIMITED BY SHUTTER TRANSIT SPEED...

mike1783 wrote:

The fastest shutter speed is supposed to be 1/4000. When in manual exposure, it seems that this value can only be reached at F11 or higher. Same in TV mode. (At least on my G1X.) Any way to get the highest shutter speed at, say, F5.6? . . . my camera stops at 1/2500 at this aperture, and the rest of the speeds are grayed out.

Thanks.

your question was interesting, so I did some basic math of speed of leaf shutter leading edge speeds...

if you do the math

you'll discover the shutter edge need only move laterally (transit across lens opening aperture)19 times SLOWER (343 nm/s) at narrowest aperture diameters (f11-f16) @ 15.1mm WA focal length for 1/4000s (covers only 1.37mm diameter) than the widest aperture diameters (f2.8) @ 60.4mm TA focal length for 1/1600s (covers 10.41 mm diameter, which is 7.6 times farther)... moving much FASTER (6509 nm/s)

If you wanted the mfr to offer the fastest shutter edge speeds to run for the narrower apertures:

you would get uselessly underexposed shots at max ~ 1/76,000s for f11 with WA 15.1mm FL!!!

key is, the shutter mechanical speeds hit their max physical speeds for the largest aperture diameters requiring covering greater oepning aperture distances.

so, the max limitations of shutter speeds (edge transit times) are actually calculated from the largest aperture diameters involved

e.g.

Canon PowerShot G1X:

15.1 - 60.4 mm f2.8/ f5.8 lens

mechanical shutter lateral transit speeds covering aperture diameter distances:

@ 15.1 mm WA:

1/4000s max f11 = 15.1/11 = 1.37mm or 1372727 nm in 1/4000s = 0.3432 um/s or 343.2 nm/s

1/3200s max f8 = 15.1/8 = 1.89mm or 1887500 nm in 1/3200s = 0.5898 um/s or 589.8 nm/s

1/2500s max f5.6 = 15.1/5.6 = 2.70mm or 2696428 nm in 1/2500s = 1.0786 um/s or 1078.6 nm/s

1/2000s max f4 = 15.1/4 = 3.78mm or 3775000 nm in 1/2000s = 1.8875 um/s or 1887.5 nm/s

1/1600s max f2.8 = 15.1/2.8 = 5.39mm or 5392857 nm in 1/1600s = 3.3705 um/s or 3370.5 nm/s

@ 60.4 mm TA:

1/1600s max f5.8 = 60.4/5.8 = 10.41mm or 10413793 nm in 1/1600s = 6.5086 um/s or 6508.6 nm/s

shutter transit speeds: 18.96 times (or 19x) faster at widest aperture diameter (10.41 mm) than narrowest aperture diameter (1.37 mm)

I realize the calculations assume simple hypothetical shutter speed mechanics, so I ignore the design specifics just to get at the bare numbers of an imaginary leaf shutter edge passing across an aperture hole of a certain size (open/close action in one lateral move) to illustrate how the values look like in different speed-aperture scenarios

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SDaniella
(formerly: sdyue)

shutter transit speeds: 18.96 times (or 19x) faster at widest aperture diameter (10.41 mm) than narrowest aperture diameter (1.37 mm)

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