Test of the E-M5 IBIS at long focal lengths...

Started Nov 26, 2013 | Discussions thread
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Beach Bum Senior Member • Posts: 1,055
Test of the E-M5 IBIS at long focal lengths...

So, after some searching, I found the first test of the E-M5 IBIS at long focal lengths.


Now, I've maintained all along that IBIS is entirely incapable of coping with long focal lengths. And, in fact, the longer the focal length, the worse its performance is going to be. I've been accused of making "novel" claims with this line of reasoning, when, in fact, this is the conventional wisdom on the topic. Sure, the E-M5 IBIS is very effective at short focal lengths, measured at 3 stops at 45mm.

The first thing I'll say about this is that Panasonic has lenses that have tested better than this, notably the 12-35 with 3.5 stops and the 35-100 with 3.8 stops. So, IBIS isn't exactly the best available.

The second thing I'll say is that I believe that the performance of IBIS will drop as the focal length increases. Please read this sub-thread, and read it carefully, even though it's inordinately boring and excruciatingly long.


Now, on to the results provided in the first link I posted above utilizing the E-M5, a 300mm Nikon lens, and a 1.4x extender. Note that this doesn't appear to be a comprehensive test, but some information can be gleaned from this.

At 300mm (600mm eq.), he estimated that he would need 1/500s to get a tack sharp shot with IBIS off. But, at 1/80s, he was unable to get a sharp shot with IBIS on. Note that this would have been 2.64 stops improvement, had he been able to get a sharp shot at 1/80s. But, since he didn't, it seems 2.64 stops is not plausible at 300mm.

He further went on to say that he needed 1/200s to get a sharp shot at 300mm, which is about 1.32 stops. IMO, this is not exact, but a rough guide about what to expect. Based on his findings, I would have to say that he's getting less than 2 stops at 300mm.

Okay, not completely convincing yet about a drop in performance. Now, let's go to his results with the 1.4x extender, making it 420mm (840mm eq.).

Here's a direct quote:

"After shooting dozens of shots with this combo, I find the minimum shutter speed to tame the shake in this whopping 840mm (equiv) is 1/640 sec!"

1/640s, really? He took dozens of shots and needed 1/640s. This isn't anywhere near a 3 stop improvement. In fact, it isn't anywhere near a 2 stop improvement. I can't say for certain what the improvement is, but, if we were to assume that he would have needed 1/840s without IS, then the improvement is only 0.4 stops. If we were to assume that he needed 1/1000s without IS, then the improvement is only 0.64 stops.

Noticing a pattern yet? The improvement, while probably still there, is getting less and less as the focal length increases, gradually winding its way to zero stops (at a high enough focal length). This is simply common sense, and something I've observed repeatedly with IBIS. The effectiveness drops precipitously at higher focal lengths.

OIS, OTOH, is tailored to the lens and can maintain its effectiveness throughout its focal length range. This has been proven time and time again with lenses from many manufacturers, including Panasonic and CaNikon.

This, as I've stated many times, is the reason high end compacts and long zoom compacts ALL use OIS. Because of their crop factor and long equivalent focal lengths, sensor shift stabilization is ill-equipped to do the job.

Lens shift is a lot more expensive than sensor shift, yet all the best compacts use lens shift, because it works. Don't think for a second that they wouldn't switch to a cheaper alternative (even to save a few pennies, literally) if it actually worked at these focal lengths.

My point? OIS is necessary for any system to be complete. It's absolutely, unequivocally needed for longer focal lengths. And, on the premium short lenses, you can expect it to beat IBIS.

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