Started Dec 31, 2011 | Discussions thread
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Note : This post contains some numbers. If numbers are not your "thing", that's fine. There is no need to trumpet that. The algebraic formulas below have been carefully derived. If your calculations may come to a different result, I would be interested in knowing how and why they do. For those interested, the implications of these formulas (for certain cameras and lenses) are summarized in the final two sections of this post.

The origins, the yield-rate, and applicability of the oft repeated "rule of thumb" (of using a Shutter Speed that is equal or greater than the the 35mm equivalent Focal Length) to compacts is murky.

A test I conducted some years ago, photographing leafless trees against a sky, indicated that, using a normal, (50mm) lens on a hand-held camera-The slowest shutter speed that ensured maximum sharpness was 1/250th sec. I found that even with firm body support image sharpness was noticeably degraded at 1/125 second, a speed that many photographers consider safe for hand-holding a camera with normal lens .

- Ansel Adams, Page 116, "The Camera", Little, Brown & Company, 1980

Adams recommended a 5 times higher Shutter Speed than is derived from the "rule of thumb".

I translated Adams' chosen "margin" of 5 times the Focal Length using a 50mm lens with 35mm full-frame film (using Leica's 25 Micron COC at film-plane) to the LX3, LX5, and any M34 camera (with a 14mm lens). I used a 1.0 pixel maximum (peak, not RMS) amount of allowable resulting blur

Minimum Shutter Speed (S) = (1) / ( (16) ( Arctangent ( ( (P) (C) ) / ( (2) (L) ) ) )
.

The so-called "Rule of Thumb Standard" form (5 times more lax than the "Ansel Adams Standard"):

Minimum Shutter Speed (S) = (1) / ( (80) ( Arctangent ( ( (P) (C) ) / ( (2) (L) ) ) )
.

where:

P is the Pixel Pitch [in Meters]; and

C is the Crop Factor; and

L is the (35mm equivalent) Focal Length; and

the argument of the Arctangent function is entered in (and to be interpreted by the computing device in) Radians of arc.
.

The resulting implications (for the Panasonic LX3, LX5, and any M34 camera) are :
.

For the LX3 and LX5 : Multiply the (35mm, 50mm lens) "rule of thumb" by a factor of 2.61 .

If you want to leave the same (equivalent) margin that Ansel Adams chose (with 35mm, 50mm lens), multiply the (35mm, 50mm lens) "rule of thumb" by a factor of 13.0 .
.

For any M43 + 14mm lens : Multiply the (35mm, 50mm lens) "rule of thumb" by a factor of 3.32 .

If you want to leave the same (equivalent) margin that Ansel Adams chose (with 35mm, 50mm lens), multiply the (35mm, 50mm lens) "rule of thumb" by a factor of 16.6 .
.

The sobering results :

To equal the margin that Ansel Adams chose, the OIS has to reliably provide no less than 3.7 "stops" of image-stabilization for the LX3 and the LX5 .

To equal the margin that Ansel Adams chose, the OIS has to reliably provide no less than 4.1 "stops" of image-stabilization for a M43 + 14mm lens.

That's a pretty "tall order". I've seen Panasonic (gingerly) imply that Power OIS (i.e., LX5) can in the best cases meet that, but I've only seen Panasonic (gingerly) imply that Mega OIS (on LX3 and M43 lenses) can in the best cases provide 3 "stops" of image-stabilization (falling around 1 "stop" short). It may be wise to consider doubling the "rule of thumb" Shutter Speed with Mega OIS !

Note: The above does not address any particular camera effects of mechanical shutters inducing internal vibration and/or or long Shutter Times possibly leading to problems when tripod-mounted .

DM ...

Panasonic Lumix DMC-LX3 Panasonic Lumix DMC-LX5
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