K7 K5 Gross Over Exposure Problem

I'm not supposing anything, just noting behaviour that I wouldn't expect. The battery had just gone down to two bars but I took anothert forty shots after that one and I suspect I'll get another 100 or so. But it's possible. I'll just document any further cases should they arise.

This would appear to be an entirely different scenario. Your first example of two images had exactly the same exposure settings.

What you have now reported is two shots with wildly differing shutter speeds.

Any news from Mattmatic?

I'm still waiting to get my grubby hands on the original DNG files... (too big to email)
Matt

Well, if that's the best excuse you can come up with . . .

Okay dokay...

DR_O4030 = Centre Weighted metering, no AE-L. 11.1LV

DR_O4031 = Centre Weighted metering, AE-L enabled. 14.8LV. The exposure information doesn't tie up with the scene - so I suspect you pointed at a brighter area by mistake and pressed the AE-L button

Both had -0.3EV compensation too.

For macro shots, especially snow-drops, I'd definitely recommend fully Manual mode and make use of the shadow/highlight warning on the preview
White flowers can be a pain - it depends what you're trying to capture, and the specular highlights can cause all kinds of havoc for auto-metering on any camera.


DR_O3852 & DR_O3867:
These both show the same exposure matrix information (within 0.2 LV)
Pattern metering was used.

The only interesting difference is this:

* The overexposed image shows "Number of bits per component 16"
* The normal image shows "Number of bits per component 14"

The other two images both show "14" as the number of bits.
The overexposure looks consistent with a mismatch in the number of bits.

I'm not sure if there are any K5 custom settings for bit depth of RAW? Or whether this was a temporary blip that was reset with a power-cycle (as you mentioned).


Do also check what Custom Options you have enabled. There is one that supposedly links AE and AF points together. I thought this sounded a good idea. However, when I tried this it resorted back to effectively spot-metering in the selected AF point...

Hope this helps
Matt

So the reason for the difference between the 2nd pair of images is actually the same as Billy's (normington4 - the OP), the AE-L button had been pressed, probably accidentally.

First pair ? Dunno, despite the 14/16 bits issue, it still sounds to me as if he lens in use at the time (different lens in the 2nd pair of images) did not stop down properly.

Well done Matt.

Thanks for the information Matt - which is extremely useful. For the snowdrop I was rolling around on the ground and contorted at a strange angle so it was likely that a button was pressed by accident - I may have locked the exposure on the sky for instance.

The first example has happened before. The only custom options I have selected are to enable aperture ring for manual lenses and expanded sensitivity. I'll note your conclusions and post another example should it recur. It's still not an issue that concerns me as long as it remains rare. But if a pattern emerges then I'm sure Pentax technical people would be interested. Your help is much appreciated.

.
could that mean 16 bit !? as opposed to 14 ?? just a thought

easily checked !

just tried it on my K7 ! no difference !! worth a try

Well, if I were you I'd at least upgrade to K5 v1.03 firmware

If it happens in 1.03 as well, then I'll definitely have a look next time it occurs. Also worth checking out if anything else gets it out of that mode - for example, did you find that subsequent shots were overexposed and that only a power off worked?

Matt

Yes on each occasion it happens subsequent shots are overexposed and it is only cured by a power off.

Is there a sticky or a 'how to' thread on upgrading firmware?

Ignore that question. Updated the firmware to 1.03. Now for a sensor clean

Since I posted my last comment on 4 March, I have not been near a computer. However part of the time was in the Lakes, and on a morning walk round Buttermere, with gathering rain clouds split by shafts of light coming through, I have had 2 more white-outs on shots 154 and 157, so 3 shots apart.

Shot 154 White-out t1/30 f4.0 ISO 400
Shot 155 OK t1/350 f8.0 ISO 400 - approx 10 seconds later same scene
Shot 157 White-out t1/8 f3.5 ISO 280 - later than 154/5 & new scene
Shot 158 OK t1/180 f6.7 ISO 400 - approx 10 seconds later same scene

From my K7 experience, this is what I found, and I would get batches of problems, then smooth working. However shot 154 was a demonstration of how a defective shot lost a light situation, over Grasmoor.

I do not accept the hypothesis of the accidental touch on the AE-L button. From July 2005 to July 2010 I put 5735 shots through an ist DS with never a White-out & the AE-L button was in the same place on the camera. Prior to that from March 1992 I put 531 films through a Z1, and never accidentally touched the IF and ML buttons. Indeed I have the Z1, ist DS & K5 infront of me as I write this, and part of my loyalty to Pentax has been continuity of layout of the cameras.

Certainly I want to continue with a top of the range Pentax DSLR, and, from my son's experience with a K7, I know that there is at least one K7 or K5, which has no problems.

I am biding my time till next week, before deciding what to do next - Billy

Billy,
Check the full EXIF data on your shots.

Whether you believe it or not the EXIF definitely shows that the AE-L was engaged for the white-out shot. It may not be the whole explanation, but it's the most obvious thing I can see from the EXIF.

I think you'll find there are plenty of K7 & K5 that do not have this problem (as evidenced on this forum). The trick, though, is systematically working through the problem in a scientific and repeatable way.

Check the EXIF on your shots with: http://www.photome.de/

Matt

The evidence shows that AE-L most definitely was activated. That is irrefutable. Whether that occurred due to an accidental button push or some other reason, we may never know.

I strongly suggest that if, after your deliberations, you determine that the camera is at fault. Return it to where you bought it for repair or replacement together with the images that illustrate the problem.