Just out of interest, how does one find out that 'Pentax is aware' of something like this?

Is there someone at Pentax we can talk to about what, if anything, they're doing about a problem like this?

I must say, the more I think about this, the more stunned I am... is it really conceivable that having built the green button into the camera in the first place, they really didn't stick a couple of M series lenses on the front and have a play with one of the pre-production models?

I'm not an advanced photographer by any means, but it took me all of about five minutes to notice the problem as soon as I stuck my old 135mm lens on the front.

Ok, an update.

The exposure errors seem to be very inconsistent, and depend on how bright the scene is. For this, I used:

- 50mm PKA lens (and for the last test 135mm M series) in manual mode,
- stop down metering to set the shutter,
- viewfinder covered during the metering.
- centre-weighted metering selected
- Option 2 in Custom menu "green button in Tav and M"
- ISO 400

Test 1: Garden scene.

Results (exposures picked by camera on stop down)

F 1.7; 1/500 (Ok)
F 8; 1/8 (very over exposed)
F 22; 1/2 (quite over exposed)

Same in A mode: shutter speeds respectively 1/500, 1/30, 1/4, all Ok.

These results agree with blende8's.

Test 2: Indoor scene, low ambient light

F 1.7; 1/45 (Ok ish)
F 8; 1/5 (Ok ish)
F 22 0.7 (very under)

Same in A mode: shutter speeds respectively 1/45, 1/2, 4 sec, all Ok.

Test 3: Same indoor scene as 2; 135mm M lens

F 3.5; 1/8 (Ok ish)
F 11; 0.3s (quite under)
F 32 0.5s (very under)

Conclusions:

Which way the stop-down metering gets it wrong depends on how much ambient light there is. If there's a lot, it progressively overexposes at high F numbers. If it's a darkish scene, it progressively underexposes at higher F numbers.

Bottom line: stop down metering does not work - unless I (and presumably others) am doing something really daft.

[Rant]If my ME Super can work out the shutter speed in aperture priority, without having to stop down the lens first, why can't the K10D? [/rant]

I suppose I'll just have to stick to A-lenses and newer, and use trial and error with the M-series ones that I've had such great service with, with my ME Super and Super A.

But as I said earlier, I think having a glaring metering problem like this is going to deservedly cost Pentax a lot of credibility. Their claims about old-lens compatibility seem rather hollow to me right now.

Well I've found that at F22 (with both my M-series lenses) it actually picks a shorter exposure than it does at F11.

That can't be right, can it? And unsurprisingly the resulting image is very dark indeed.

I must admit, this has come as a huge disappointment. I find it hard to see how Pentax can make a real success of the camera if the metering doesn't work properly.

Anyone have any more detailed information?

I have some old M-series lenses (135 and 200mm) which I've been playing with. AFAICT their iris mechanisms are working perfectly.

In manual mode, the green button next to the shutter release is fantastic - a quick push at whatever aperture you've selected, and the camera takes a peek through the stopped down lens and sets the shutter speed.

However, I've noticed some inconsistencies in the exposure using this technique:

- with the lens wide open, the resulting shot is quite a bit over exposed
- stopped right down it's very underexposed
- at F11 it's about right.

This seems to be the case whether I use spot, centre-weighted, or multi-segment metering.

I was very careful to cover up the viewfinder completely before setting the shutter speed for a given aperture.

Anyone any ideas why this might be so? Am I doing something wrong, or have I misunderstood something?

In the Feb 07 Issue #4 Digital SLR Usermag there's an 8 page "head to head" review of the K10D vs the GX10.

I'll just quote the concluding paragraph...

"We prefer the balance and look of the Pentax, but it's by no means a straight win. The Samsung has a clearer, less cluttered look to the menu, an additional 12-months warranty to the K10D's 1 year, and you can't overlook the company's improved luminance noise reduction algorithm over that employed by the Pentax."

Interestingly, given the discussion here, they do their resolution comparison with "best-quality JPEGs and default image tone and sharpness settings", and don't mention any significant difference between the cameras in terms of sharpness.

Exactly my experience, except that it was just one horrible big speck.

Bought a Rocket Blower:

http://www.jessops.com/Store/s32860/0/Cleaning--and--Maintenance/Jessops/Rocket-...

which sorted it out a treat.

Thanks for all your replies, guys. Can't say I'm surprised that there's no easy way!

I'll be getting a copy of AP (first for about 15 years) this afternoon!

And I've got about a dozen items on watch in ebay

If I want to buy a second hand car, there are a couple of price guides that list all the makes, models, years, with prices that a buyer might expect to pay.

Is there anything resembling this in the second hand lens market that would give someone recently afflicted with a bad case of LBA a starting point?

TIA

Well, the particular example happened to be a shot of some upside down writing, and I wanted to check the sharpness.

So having shot it, I wanted to zoom in digitally and read it without turning the camera upside down. I could rotate it but not zoom it, since the "press Ok" solution, obvious in retrospect, hadn't occurred to me.

Anyway, to answer your question, not often. As I said, now that I know you can rotate and then zoom, it's a "very minor gripe".
Well if, as someone has said, the jpeg degrades a bit for every saved rotation, then I'd argue, clearly yes.

But I'm not going to lose any sleep over it.

You're quite right. I had misunderstood these two functions. Thanks for that clarification.

At least what I want to do is possible - thanks for drawing my attention to the need to hit Ok to save the orientation manually. But I still think the UI would be slicker if you could quickly rotate and zoom without having to save first.

But I hereby downgrade 'minor gripe' to 'very minor gripe'