Archive 2015 · IBIS settings with alt zooms

ebrandon
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p.1 #1 · p.1 #1 · IBIS settings with alt zooms

Here's a question I've been thinking about a long time ...

If you're using an alt zoom with no electronic communications (like the Contax 35-70mm, or Contax 80-200mm f4) with a camera with IBIS like the A7II or A7RII -- does it make sense to leave the IBIS on & set the IBIS focal length to the shortest end of the zoom?

At the short end, the IBIS will provide correct stabilization, and at the longer focal lengths it will still provide some stabilization, right?

I guess what I'm asking is whether the stabilization set to some focal length X is "correct" just not "strong enough" to fully stabilize the zoom at longer focal lengths.

Am I thinking about this right?

Sep 01, 2015 at 09:02 PM

Matt Grum
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p.1 #2 · p.1 #2 · IBIS settings with alt zooms

I think you're essentially correct, that when the real focal length is longer that what is programmed into the camera then it will move the sensor in the correct direction but a much shorter distance than necessary.

It might be a worthwhile strategy with something like a 80-200mm lens, but for a walkabout zoom (24-70) there doesn't seem much point, you'll get stabilisation at the short end where you don't really need it, and ineffectual stabilisation at the long end...

Edited on Sep 07, 2015 at 05:29 AM · View previous versions

Sep 03, 2015 at 08:06 AM

ytwong
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p.1 #3 · p.1 #3 · IBIS settings with alt zooms

I'm thinking the same...
But anyway, I have assigned a button to change FL so it's so easy to change FL...just click a button and then scroll the wheel to select the correct one.

IMO IBIS is rather effective with alt lens.

Sep 03, 2015 at 08:48 AM

jsv_20
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p.1 #4 · p.1 #4 · IBIS settings with alt zooms

I just tested this on a Series E 75-150. As far as I can tell the image on the screen is shakier when I set the IBIS to the shorter end and zoom to 150mm. However, when I set the IBIS to 150mm the image is way steadier, and it's still steady at the shorter end. I tested this hand-held at 1/30 and ISO 2500 (low light).

I think the best way to work with a zoom would be to just change the FL so IBIS is better matched to the FL.

Sep 03, 2015 at 05:37 PM

ebrandon
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p.1 #5 · p.1 #5 · IBIS settings with alt zooms

jsv_20 wrote:
I just tested this on a Series E 75-150. As far as I can tell the image on the screen is shakier when I set the IBIS to the shorter end and zoom to 150mm. However, when I set the IBIS to 150mm the image is way steadier, and it's still steady at the shorter end. I tested this hand-held at 1/30 and ISO 2500 (low light).

I think the best way to work with a zoom would be to just change the FL so IBIS is better matched to the FL.

I'm surprised that with the IBIS set to 150mm, the image doesn't jump around at 75mm.

What's funny is that it never occurred to me try it! I was just thinking about it theoretically -- what makes sense from first principles.

There's a saying: "In theory, theory and practice are the same. In practice, they're not."

Sep 05, 2015 at 07:24 PM

jsv_20
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p.1 #6 · p.1 #6 · IBIS settings with alt zooms

It didn't seem to jump too badly; it was way worse when I tried this with a 2x TC.

Sep 06, 2015 at 06:19 AM


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