On Sharpness, ISO and Shutter Speed

Started Nov 29, 2013 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: isn't it just the IBIS?

tko wrote:

In addition, consider the results for the A7R and the D610 in the OP.

The A7R goes from about 2200 to 2500, a 13% change in sharpness. Nothing like the IBIS 50% change over the same shutter speed range.

So what? First, how do you explain that 13% decline for the A7R, which has no stabilization system? Second, there are lots of other variables that might explain why the effect is is more pronounced for the E-M1 and the A7R aside from IBIS, for example the lens used, the weight, and the shutter type.

If you widen your horizons beyond the particular sample images discussed in this thread, you will find that it is already well established that cameras without a stabilization system suffer from shutter shock problems too.

I can only consider what's been analyzed, and there were a lot of cameras analyzed in this thread. The links you posted lead to opinion and guesswork, not graphs, so I would discount them. Anyone can have an opinion, only in this thread did we have analysis.

Unlike you, I don't discount evidence on the basis of the form they take (e.g., graphs versus photos). That merely risks bias and/or incorrect conclusions about causality.

The data I point to have the advantage over the comparison between the A7R and the E-M1 that you prefer to make that they keep everything but the sensor and its being fixed or not constant or approximately constant: the lens used, the weight of the camera, and the type of shutter used (MFT cameras aside from the GM1 are reportedly using the same type of Copal shutter although its flash sync performance has increased a bit over time).

Those who have their mind open to evidence in the form of photos rather than graphs might also want to have a look at the tests reported here (see point 2)


as well as those reported here (where neither of the two cameras studied, NEX-5N and GF2 have IBIS):


BTW: Only some OIS systems mechanically lock the IS lens group when the system is turned off. Others keep the IS lens group floating even when off. It's just that the input from its sensing devices is no longer considered.

No. How on can you have a lens element "float" with no power?

It has power all the time when the lens is mounted on the camera and the camera is on, regardless of whether OIS is on or off. When the lens is dismounted or when the camera is off, the IS lens group is free to move as it pleases.

And if the lens floats, it must be stabilized, or else the images will have blur. Please document this claim.

It is of course stabilized in the sense of being held in place even when the OIS system is turned off. The IS lens group is in this case "floating" (rather than locked mechanically) in a fixed position instead of moving around in response to the motion sensors.

An example of an OIS system that works like this is that used by Panasonic for their MFT lenses. If you shake the lens lightly when dismounted, you will hear the IS group rattle around. With the lens mounted and the camera on, you will hear a hissing sound from the OIS system regardless of whether it is on or off.

 Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +28 more
Post (hide subjects) Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow