K10D Stop down metering exposure problem

Hi all,

Auto WB on the DL with manual lenses almost always results (in my case) with at least a stop, if not more, under-exposure. My example lenses being a 70-210 f3.5 Macro (Soligor) and a 300 5.6 (can't remember the brand, and I'm off out now.. suffice to say, not a Pentax). I don't the technical reason for this though.

Shoot RAW, and pick pretty much any WB and just adjust later.. obviously picking the right one will save a second or two..

HTH

Cheers

Liam

Liam

Is this only with manual lenses? The earlier istD/S/L bodies were known for 1/2 - 1 stop underexposure, perhaps to preserve highlight detail.

Hi smc,

I think you may be right about a little under-exposure with most lenses, I'd never really thought about it, but setting WB and taking the shot with manual lenses ups it by a stop or more; bringing it into line with what I'd normally get from the AF lenses. In which case the manuals could be 2 stops or more underexposed with auto WB.

Cheers

Liam

Erm, How about using Manual mode and a seperate light meter?


(Runs away and hides under a rock)

I have a nice Weston Master (original) still in its box that would do the trick...

It's a pretty fair idea though I would prefer a Pentax Spotmeter.

My Sekonic L-358 seems to take care of the problem just fine!

Or even meter in one of the non-manual modes, and do the math to work out what the exposure should be at whatever aperture you want.

Of course there are work-arounds, but it's just not acceptable in 2007 to have to work around such a fundamental problem as the camera's metering sytem simply not working right - and the weaselly-worded ambiguities in the K10D manual don't let Pentax off the hook, AFAIC.

Anyway, just to muddy the waters still further, there seems to be evidence that the problem doesn't affect all K10Ds.

http://www.pentaxforums.com/forums/pentax-dslr-discussion/3188-k-m-lenses-manual...

... for instance, has a couple of guys reporting no problems.

Is there anyone here with a K10D that's done some careful measurements and found that their camera is getting the exposure right?

I updated my lenses over a period of time and now have no K or M series lenses in use. This was simply because it is much more convenient to use A series or later lenses with the DSLRs, which is of course what they are primarily designed for.

We are talking lenses over 20 years old if we go pre-A and we can't expect total compatibility for ever can we? As it is, there are ways and means to make even screw thread lenses work, but I just feel it's really the difficult path to take, relatively speaking.

If we think the Pentax compatibility isn't perfect (and they say as much in the manual to be fair - "an exposure error may occur" is pretty clear) then the Olympus OM adapter is much worse. It can only be used with limited aperture ranges, and is very expensive as well.

If there is a perceived problem, I would suggest using A series or later lenses.

The main point is that it worked (almost) perfectly with the older Pentax DSLRs.
It's only the K10D that has this specific Problem.

Agreed. I have just two pre-A lenses - the M-series 135 F3.5 and 200 F4. With the kit 18-55 DA, your 75-300 FAJ and then various A lenses from 28 up to 400, I'm pretty well sorted.

However, it's not just the two primes that are a pain to use in stop-down mode. Sticking anything between the lens and the camera, for instance a teleconverter or an extension tube straight away makes it into a manual lens, with all the metering issues we've been talking about. So I now have to think about replacing my other non-auto accessories.

Are you referring to the "Notes on using aperture ring" on p210 where they talk about the restrictions with using the aperture ring.

This reference to exposure errors is in relation to aperture priority mode, not manual.

Under manual mode (all lenses), it just says "exposure check is possible", with no reference to metering errors.

And I'd restate the point I made earlier, namely that it's clear they intended it to work, otherwise they'd never have bothered to use the green button to stop the lens down and set the exposure at all.

Yes, we can't expect complete backwards compatibility for ever, but the vagueness in the manual, taken with the clear intended behaviour just smacks of a cock-up.

And although I agree with all those that have eulogised the camera with A and post-A lenses (and I still don't regret buying it), it has that whiff of spoiling the ship for a ha'p'orth of tar about it. Which for a company that seems poised to make something of a return from the doldrums (if you'll forgive another nautical metaphor), just seems a shame.

Agreed, it is a shame. It seems that some users don't have a problem though, from other forums, so I wonder why there is an inconsistency, and whether it depends on which lenses or accessories are being used. Or whether it's the camera.

I also agree the manual on many pages is, well, shall we say slightly obscure? I wonder if the original Japanese is clearer.

Hello All

Although I must first state that I DO NOT yet own the K10D but I am an interested reader of this thread (and similar threads on different Forums) because one day I hope to upgrade from my *ist Ds. The only reason for me sticking my nose in here is that I have only seen mention of exposure problems when people are using the Green Button method of metering to automatically select the correct shutter speed and I am wondering if a different method would work.

I frequently use Pentax K manual lenses on my Ds but rarely use the AE-L button (my green button equivalent?) to automatically set the shutter speed. Instead (in M focus and M mode) I preselect the aperature ring setting on the lens, then while holding the depth of field preview button I turn the thumbwheel to select the appropriate shutter speed. The exposure compensation reading in the viewfinder acts as an old fashioned "match-needle" indicator to set the correct exposure with +/- exposure compensation if desired. The table on page 210 of the K10D manual is identical to that of the Notes on Using Aperature Ring in the *ist Ds manual and that is the only method that is shown for manual lenses that doesn't say "an exposure error may occur". As a Ds user, of course, the whole green button thing is a mystery to me and I found it contradictory to the above mentioned table in the K10D manual, but I certainly would be interested to know if this method gives the correct exposure with manual lenses on the K10D.

Note: I'm not sure if you would have to select the Optical Preview option for this to work. In fact...not sure if it will work at all because I don't have a K10D to try it on

Cheers

Drew

Wow, nobody here in Canada ever got THAT excited about Pentax.

i have only one M lens, the SMC 135/3.5, and I have had a limited play with it on the K10D. Stop-down metering I have found to be reasonably accurate, but I have not tried it wide-open or fully stopped down. I would not expect to get accurate exposure fully stopped down because of the very limited amount of light hitting the meter. I think that if I were using these lenses consistently I would very quickly know whether the indicated exposure was correct and compensate if it wasn't. However, there seems to me to be a wider issue here - I really didn't spend a large sum of money on a state-of-the-art digital camera to use 30 year-old manual lenses and fiddle about trying to get the correct exposure. If I want to take pictures at 135mm I stick the DA50-200 on the camera and fire away. I cannot see any practical use for the 135/3.5 and will certainly not be looking for any other M lenses. 'A' lenses are of course a different matter, and I use my 50/1.7 regularly with no exposure problems - it is one very sharp lens.

Alan

Hmm. Very different from my experiences. Maybe not all K10Ds are the same?

I've heard this argument before, and I think it's something of a red herring.

I've taken some night time shots now in automatic mode, where the exposure it's calculated is 30 seconds (sic). There can't be much light hitting the meter, even though the lens is wide open when it's doing it, and the shots have been beautifully exposed.

So unless there's something very different going on with stopped-down metering, I can't believe the "insufficient light" argument holds any water at all - except in exceptionally dark conditions, in which case all bets would be off anyway.