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12-29-2010, 01:50 PM   #1
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645D Electronic Level Display issues

The horizon across Lake Michigan has been hard to come by lately, what with all the short days and bad weather. But I got out this morning for a few shots from the snowy beach at the end of our street. 645D, 45-85 zoom, tripod with a 3-axis gear head, calm lake. What better opportunity to try out the 645D's Electronic Level Display?

I quickly discovered that what looked level in the viewfinder did not jive with what the ELD thought was level. When I used the gear head's fine controls to get the ELD carefully squared up, the horizon looked pretty obviously slanty in the viewfinder. When squared by eye there, the ELD consistently showed a 1-2 degree tilt. Either the viewfinder screen is crooked, or my eyes are, or Lake Michigan is, or the ELD sensor is misaligned (or mis-calibrated). So I shot two ways, figuring I'd sort it out later on the computer.

On the computer it's clear: there's something wrong with the ELD. Images that I squared up with the ELD are consistently tilted counterclockwise. A 1.21 degree clockwise rotation (via PS Lens Correction) is required to fix the problem. The ones where I eyeballed it in the viewfinder are all pretty close to square.

Have any other 645D users noticed anything like this?


Tim
Chicago

12-29-2010, 03:51 PM   #2
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i will test this out on saturday, I am going to do some landscape shots then. I will let you know
12-29-2010, 07:33 PM   #3
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Tim, I have seen this myself the past couple of times I've gone out with the 645D. It is most noticeable for me when I have the camera mounted for vertically framed shots -- then the electronic level very clearly does not jive with reality. I have not yet shot any test frames on a location with a clean horizon to demonstrate this but I'm planning to do so...
12-30-2010, 10:03 AM   #4
rlj
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I have a few bubble and electronic levels that are very, very accurate and used these for reference, not the horizon. I did the measurements in my house, so I did not look to see effects of temperature. It is possible that extreme cold/heat may affect readings. I used RRS brackets for holding the cameras to the tripod and use a leveling base for adjusting the tilts.

My 645D is spot on for left/right tilt when in portrait position and off by 1 in landscape. For tilt down and back (fore/aft), the 645D was spot on in portrait and landscape positions.

The yellow markings on the 645D indicate in landscape it was off by 2, but once I corrected so only green showed, the actual correction applied was 1. This probably means the displayed markings have their own tolerance of 0.5.

I similarly checked my K5. Fore/aft tilt is spot on in all positions, but left/right is off 1 in landscape, and 1.5 in portrait.

My guess is that with the display they've chosen (1 increments), their set accuracy is going to be 1 if one takes into account the actual sensor tolerance and the display increments. Since most people have used bubble levels, this is still better than what we've been used to using.

12-30-2010, 05:32 PM   #5
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Temperature was in the mid-20s (f) and I wasn't out that long, so I don't think temperature should have been a factor. I know 1 doesn't sound like much, but it's enough to render the feature unusable. Here's what 1.2 looks like:



Tim
Chicago
12-30-2010, 09:47 PM   #6
rlj
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Hi Tim,

No I do realize that 1 can be annoying; I've had to correct these amounts in PS before (even 0.5 is noticeable). For stitching, having the body level is important (which is why most built-in bubble levels seem next to useless to me).

But I doubt that the built-in level can be much better than about 0.5.

The one solution, short of having Pentax fiddle with it, is simply to know, as I now do for my 645D, that 1 or 2 yellow marks to left, with the green for fore/aft, is perfectly level in landscape position. I just need to remember (or write down) this adjustment.

If we do this 'self-calibration' and remember to adjust for it, we'll know the camera is level. I would rather do this than ship the body off.
12-31-2010, 08:11 AM   #7
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iPhones running Tiltmeter Pro (or probably any of the dozens of other utility leveling apps) are more accurate, if only because they have user calibration features.

I suspect the accelerometer in the 645D is fine, but is running against erroneous calibration data. I further suspect that calibration calls are probably buried in the firmware somewhere, and are trivial to implement, though not currently implemented in the user interface.

I sent an email to Pentax "Customer Care", hoping there's an undocumented calibration routine that users can run, but expecting that there isn't, and that they'll suggest I send it in. This is way low priority for me, so if it has to go in, it'll have to wait.


Tim Wilson
Chicago
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