Originally posted by Fer As far as I'm concerned, I'm sorry, it is very much a sky is falling issue, and if it's not resolved by firmware (fingers crossed) enough of a deal breaker for me to return my K5 as defective. I cannot for the life of me take a properly focused shot in my living room with my K5, whereas I have no problems at all in the same light with my Kx. I don't even have such AF problems with my LX3 wide open (I know, smaller sensor, but still)
Sounds pretty serious to me, and that's before even considering the price gap between the K5 and the other two. The thing cannot focus, it does not get much worse than that for a semi-pro DSLR, or does it?
The LX3 isn't using the same focus technology. It's AF is more akin to LiveView AF than phase focus AF.
The K5 apparently has problems focusing under certain conditions. Do you live in a medieval cave under 24 hours of perpetual darkness? Where do you figure the K5 cannot focus?
Read what you are writing, please.
I recall some high end Canon from a little while back couldn't focus either. Was it the 1D MkIII that wouldn't focus? It was a camera way beyond semi pro though.
Originally posted by philbaum Wheatfield,
thanks for the insight.
Could it be that Pentax chose a new autofocus sensor for the K5 to improve autofocus performance in general, but it came with this weakness at the tungsten temperature?
Even if they can turn on the green light for higher EV levels, it won't have significant range, is that correct? The good news with the K5, is that the camera's great iso performance can be used to mitigate the low lite autofocus weakness by using a smaller aperture/larger DOF. Even with the K20's lower iso performance, i use that same technique to cover up any AF weakness by a larger DOF that covers more of the theatre stage. works quite well.
This is a case where Pentax coming out with an official announcement about the situation would be more useful than a ton of explanation and rumours.
What some people don't realize is that most design decisions come with intrinsic advantages/disadvantages. thats the real world. Manufacturers don't want to talk about them because any announced weaknesses may be offputting to sales, but they are there in any product, e.g. better water resistance=higher cost, lens based vibration reduction=better viewfinder image=higher cost and more bulk, etc.
Don't look for more explanation than a firmware update. They are pretty tight lipped about this sort of stuff.
One of the things I've learned over a 40 year stint as a semi pro photographer is that I need to be more of a partner with my camera company than an adversary.
For me, this means that if I have a defect in a product, either design or manufacture, they get the thing back for repair. That's their end of the deal.
My end of the deal is to treat them as a partner in the problem, I have nothing to gain by shoving a problem down their throat with a stick.
I have yet to have a front line camera that didn't have some quirk. My Oly OM1 had a habit of it's meter needle jamming, hence making the meter useless. My Nikon F2 would sometimes pack up it's meter as well due to a poor contact between the prism and camera body. My Bronica ETRs would pop it's back open, exposing whatever was in it for no apparent reason.
My Nikon F3 had a habit of shedding lenses. All three of my LX bodies were very casual about shutter control in auto, and would sometimes just cycle the shutter at maximum speed no matter what exposure was called for.
Consequently, this is just a shrug moment for me.
I'll watch my focus a bit more carefully in situations where it may fail, figure out what the cutoff seems to be for focus accuracy and keep using my camera.
At some point, sooner rather than later I suspect, Pentax will do what it can to rectify the problem and all will be right in the world again. Birds will sing, flowers will grow and I'll spend my golden years dining on chicken and wine.
Until then, if I have to stop down a little in some situations, or manual focus occasionally, I now have lots of high ISO overhead to allow me to do it.
And were it really a deal ender for me, I would return it for a refund. And if it was such a big deal that I had to switch brands, I'd switch.
I'm not needing to make that decision though. The thing works in most of the light conditions I'm likely to put it in as it is, and still has enough redeeming characteristics to forgive it having a wonky AF near the lower end of it's range.
One thing I have noticed in my look at this is that the imaging sensor can continue to make pretty good pictures long after the AF has kakked. I wouldn't be surprised if the EV-1 rating on the AF is a bit optimistic as well.
You are correct that the AF assist coming on sooner would not help at range, it would help close up where AF inaccuracy is going to be a bigger issue. At distance, even wide open, DOF will help mask slight misfocus.
I was at my wife's offices' Christmas dinner the other night. I took my K5 with the 31 attached. Looking at the pictures with an eye to is it possible the mis-focused pictures are caused by this particular deficiency rather than just me running the AF out of range, I discovered that under the tungsten light illuminated room was in the EV 2 range, perhaps a little brighter in places. The AF hit mostly close enough that I would consider it OK for print, with some fails. It didn't do well with dark subjects at low light levels, unsurprisingly.
I think in tungsten illumination, I would want a couple more stops to get some reliability, probably EV 4 or so is the threshold between reliable and a mess. With candle light, I expect this would need to shift another stop or more up because of spectrum loss.
It will be interesting to see what Pentax can do with this. Hopefully, they just need to turn up the gain on the AF multiplier.