PIX 2015

What is the best m43 for focus tracking?

Started Mar 31, 2013 | Questions thread
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Anders W
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Re: See this review..
In reply to clengman, Apr 4, 2013

clengman wrote:

clengman wrote:

Anders W wrote:

clengman wrote:

olliess wrote:

clengman wrote:

olliess wrote:

Anders W wrote:

olliess wrote:

I was asking about that exact post. You state that the system only shifts the sensor in rotation about the horizontal axis (which I take to be the optical axis). So does this system compensate pitch and yaw only using vertical/horizontal translation?

Pitch and yaw are corrected by shifting the sensor up-down and left-right. All in-body IS systems do this and work like that.

Thanks. I understood previous in-body systems to work this way, but I had wondered (from the name?) if the Olympus system actually corrected for multiple rotation axes. It seems not.

I don't think you're understanding correctly.

Sorry, I should have said "corrected using multiple rotation axes." You can see from the previous post that I was talking about pitch/yaw compensation (two of three rotation axes) via sensor translation.

Sorry. My mistake.

I think the biggest misunderstanding of the E-M5 IBIS is that it's the 5-axis part that makes it great. The additional two axes are only valuable in limited circumstances and in fact those corrections can't be applied with most lenses. The lens has to be able to communicate its current focus distance to the camera in order for X and Y-axis translation correction to be done right. None of the m43 lenses that I have do that and obviously no adapted lens will either.

Not disputing your general point that two of the five axes are of pretty limited importance most of the time. The main point is that the new IBIS is very efficient in correcting the other three.

I believe it. I'm looking forward to getting my hands on an E-M5 at some point down the line. It sounds like the improved IBIS will be nice to use.

But I have strong reasons to think you are wrong when you say that all/most native MFT lenses don't report focus distance to the body and therefore can't even enable correction for vertical/horizontal shift. If they don't do that, why would information on focus distance appear in the E-M5 EXIFs, as it does for native, electrically connected lenses (possibly adapted FT lenses too, although I am not sure about that since I don't have any)?

I didn't say anything about all or most of the native lenses. I can only comment on the two native, electronically-coupled lenses I own, the mkI 14-42mm zoom and the non-R version of the 40-150mm zoom. I'm sure that some lenses (maybe most? I don't know.) report this value.

I've looked for the focus distance in the EXIF data for pictures taken with both these lenses and I have not seen a value for subject distance recorded anywhere.

If I'm wrong I don't mind being corrected.

Note that I was talking about the E-M5 here. I am not saying every MFT camera retrieves the info on focus distance from the lens and reports it to the body. But, judging by its EXIFs, the E-M5 does. And the E-M5 is the only camera that needs that information for full IBIS functionality.

It occurred to me after I posted that the E-M5 might record it even if the e-pl1 doesn't. You have the 40-150mm zoom right? Do you see subject distance recorded in EXIF for photos taken with that lens? Just curious now.

OK. So I did check with my 40-150/4-5.6 R, and, yes, focus distance is reported in the EXIF in that case too, just as with all other native MFT Oly and Pany lenses I have looked at.

One additonal thing to note here: There are actually two different measures of focus distance reported in the EXIFs. One is called FocusStepCount and the other FocusDistance. The latter is reported in meters (with up to three decimals). Presumably, the first is what is actually reported/measured and the second just a conversion. But one small mystery here is that whereas I have found the FocusStepCount to behave predictably (e.g., by reporting very similar values on repeated AF trials on the same target and with the mean value changing predictably as you change the focus distance), the FocusDistance value is somewhat suspect. For example, even if the FocusStepCount is unchanged from one shot to another, the FocusDistance value might differ. I have still to understand why this is the case. Perhaps it's just a firmware bug of one kind or another. But when I experiment with the AF system in a way that makes use of this information, it is the FocusStepCount I pay attention to for the time being.

 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
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