On Sat, Sep 21, 2013 at 10:30 PM, <usher99@xxxxxxx> wrote:
> JW writes:
> <<Could you plug in some numbers maybe? An example would help me. Are
> you
> <<proving the old rule that a "safe" shutter speed is 1/f, refining it,
> or
> <<disproving it?
>
> Yes, relevant today chasing Flutterbys. Might have 15min tomorrow for
> one more try.
> The thread is related to refining the 1/f rule of thumb for macro.
> Looking at review of IS lenses with the IS off, it is remarkable that
> on most tests 40-60%
> of shots are sharp or have mild blur at 1/f shutter speed. Depends on
> the lens and operator of course.
>
> With macro many think magnification is the main relevant variable and
> that was my untested view until recently. The geometry and math
> would argue that focal length remains important. It is a gross
> simplification but likely good enough to multiply the 1/f by (1+M)**2
> where M is the magnification. So at 1:1 with a 100mm macro lens one
> would require about 4 times faster shutter speed or 1/400 to get a 50%
> chance of a sharp or mild blur shot. Lateral shake is almost irrelevant
> for low mag but imp't for
> higher mag thus the advantage of the 5 axis IBIS in Oly bodies or the
> hybrid system in the Canyon 100 macro. Tripods even better of course
> but not always feasible.
>
I think I get it now (though I don't understand your equation/formula: 1/f
by (1+M)**2). My experience with my own limitations is that I need
something like 1/400 to handhold shots where a significant amount of
magnification is concerned (though I rarely shoot 1:1). I thought I was
just jittery and over-caffeinated, and certainly I often shoot where I am
very dependent upon a high enough shutter speed to get sharp results. I
have always felt that the 1/f rule is too hopeful. Back in the film days
many of us discovered our limitations shooting Tri-X and I generally try
for 1/250 if I'm handholding a 100mm lens, although I don't have any
problem at 1/60 with 50mm, so maybe that's a bit more anecdotal evidence.
In any case, I certainly sense that magnification is a factor, as I have
made accommodations for it in real shooting for a long time, though I never
thought about why.
If you can prove all this a priori, I am all the more interested, even if I
cannot really evaluate the argument.
It would be important to rule out focus errors in evaluating for movement.
In macro, it is often hard to tell the difference, which is another reason
why a little overkill on shutter speed is OK with me.
Joel W.
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