[Class A]

No, it sounded from this guy like it was all of them, possibly to varying degrees.

Just to clarify, the intention of my earlier post was to say that the idea that "not all K-5 are affected and that Falk may only have measured problems pertaining to his copy only" has very little merit. I'm completely with you on the notion that Pentax is facing a systematic problem and is working on it.

That is my suspicion too - that the problem is more or less present on all Pentax cameras, not just the K-5.

That's a misinterpretation of what Erik posted, since he was specifically talking about the K-5. It has been suggested more than once that the K-5's problem is far worse than previously seen on any Pentax DSLR.

Christine, please excuse me if I don't respond to your earlier post and may not respond to future posts either. I don't think it would be very productive.

I think this particular thread is valuable and it should not take the same course as the previous K-5 front focusing thread that was closed. I think we all should try to keep it as focused as possible and abstain from personal "battles" with other forum members. Every contribution to the topic is of course more than welcome no matter who the poster is.

[Christine Tham]

Unfortuately, the place of purchase has a bad reputation for being very hard to get money back out of. MediaMarkt, huge European heartless home electronics chain. Sweden has all kinds of consumer protection though so I will probably be able to get my money back, but it might take a lot of time and effort.

I know what you mean, that's why I decided to buy my K-5 from a local family owned store, rather than buying online. In the end, I got them to match an online price - they said they weren't happy because they have higher costs than an online store, but they were very good to me - they allowed me to check in store that the K-5 did not have any stains, and allowed me to take test shots and browse on their store computer - they also said if I found any other problems just take it back to them and money back no questions asked.

I am worried that if you wait one month, it will make things a lot more difficult to get your money back. They will say if you weren't happy why did you not return immediately? Maybe you broke it and now trying to cheat us ... The fact that you were waiting for a fix may or may not carry any weight, because you were dealing with a third party rather than a store employee.

[Erik]

I am worried that if you wait one month, it will make things a lot more difficult to get your money back. They will say if you weren't happy why did you not return immediately? Maybe you broke it and now trying to cheat us ... The fact that you were waiting for a fix may or may not carry any weight, because you were dealing with a third party rather than a store employee.

Hey, I bought it in November, but I didn't take a lot of indoors pictures, and when I did, I wasn't convinced this wasn't user error until I realized no amount of futzing around with the compensation would help me, and that a lot of other people had the same problem. Falk's study was the final straw that caused me to finally send it in.

So yeah. November. I'm already in trouble If I can demonstrate that the product is faulty and not fit for its intended purpose, though, I should still be able to get my money back.



and maybe I'll buy an X100

[Christine Tham]

That's a misinterpretation of what Erik posted, since he was specifically talking about the K-5. It has been suggested more than once that the K-5's problem is far worse than previously seen on any Pentax DSLR.

No, I didn't misinterpret what Erik posted (even though it was ambiguous - he said the repair man said "all of them" not "all of the K-5s") - I however deliberately generalised the problem to potentially include all Pentax DSLRs and said so in my reply to him.

Yes, it has been suggested that the K-5 problem is worse than previous DSLRs. That suggestion has also been countered by other posters (not me) claiming they have seen the problem before.

I am not trying to take a position, but in the absence of a confirmed cause it's safer to be inclusive and say the problem may have affected multiple models. At the end of the day whether the problem is exclusive to the K-5 or not is neither here nor there - we still have to decide whether to live with it or not.

[Class A]

Instead the problem seems to be worse.

Yes, but note that it hasn't been worse for the K-7. Judging from user reports, the K-7 has been an improvement regarding front focusing under Tungston lighting. The K-5 issue is a new one. I am fairly confident that the K-5's AF module has been tweaked (aren't the focus areas at slightly different locations as well?) and that an issue was introduced that needs ironing out.

[When originally replying to this I probably clicked the edit button by mistake and so I ended up messing up your post. I tried to put it back as it was. I'm sorry about the goof-up .

Not to worry. I'm afraid I cannot give you a lot of marks for your restoration efforts since you missed about two thirds of the content , but I have restored the post to its original state. All the best, Jolepp, your contributions to this forum are highly appreciated.

[Christine Tham]

So yeah. November. I'm already in trouble If I can demonstrate that the product is faulty and not fit for its intended purpose, though, I should still be able to get my money back.

Let's hope for both our sakes that there is a fix then. Or failing that, you will be able to get your money back. I do agree that something like this can certainly leave a "sour taste" in one's mind regarding future purchases.

Come to think of it, every camera Pentax has released has had it's share of problems. My K10D has focusing problems with my DA21mm, but I learnt to live with them. Same with my K-5 - I learnt within two days of purchasing that I had a slight FF issue - but I decided it was acceptable to me. I'm sorry to hear that your issues appear to be more pervasive and impacting the shots you are taking - I am certainly not suggesting that you need to "live with it" - but hope that you will get a satisfactory end result.

[newarts]

Nice, in depth work and analysis as usual.

Thank you,
Dave

[the swede]

Hey, I bought it in November, but I didn't take a lot of indoors pictures, and when I did, I wasn't convinced this wasn't user error until I realized no amount of futzing around with the compensation would help me, and that a lot of other people had the same problem. Falk's study was the final straw that caused me to finally send it in.

So yeah. November. I'm already in trouble If I can demonstrate that the product is faulty and not fit for its intended purpose, though, I should still be able to get my money back.
and maybe I'll buy an X100

I returned my K-5 to Cyberphoto today on refund (ånger rätt), told them i didnt want to get caught in the waranty wheel. The guy understood and sighed. He didnt tell me but from the tone of the conversation it sounded like they're having a few K-5 coming back to them....

I will do the waiting game now, perfectly happy with my K-7 in the meantime.

[Erik]

I returned my K-5 to Cyberphoto today on refund (ånger rätt), told them i didnt want to get caught in the waranty wheel. The guy understood and sighed. He didnt tell me but from the tone of the conversation it sounded like they're having a few K-5 coming back to them....

I will do the waiting game now, perfectly happy with my K-7 in the meantime.

I even live in Umeå, where Cyberphoto is, and I know they're good to deal with, but I was so anxious to get a K-5 that I had to go to MediaMarkt (because Cyberphoto hadn't gotten any in stock yet)... Stupid me.

[jolepp]

I'm in a similar situation with a brick and mortar shop: after waiting for a while for the firmware fix to turn up I'm in the process of sending emails back and forth with the seller. I might end up sending the K-5 to repair so that there has been a change to fix it and then having the trouble of making an issue of it with the consumer protection authorities (or at least telling the seller that this would be the next step). I guess this means I'll prefer online mail-order from now on as this has a 14 day return-for-a-refund without giving a specific reason mandated by law over here (physical shops do not have to do this).

[falconeye]

I can definitely confirm this. The camera is able to focus on a weak LED light (first photo), but misfocuses on a relatively strong yellow light, as you can see from my second photo.
[...]
What do you think of the theory proposed by dlacouture that the behaviour of the AF assist light may also be lens dependent?

So do you think that scenario [(led vs. tungsten, ed.)] isn't covered by the three lightbulbs you used?
Should we not see bright (x-axis) red dots with high defocus and dim blue dots with low defocus in your graph then? As you say, I think Fig. 4 (and others) seem to provide evidence to the contrary.

Actually, if you look at Fig.4, then you'll see that blue and magenta focusses correctly down to -1 EV while red "jumps" at 0 EV. Additionally, the way I measure LV weights red with 30% making it appear -1.7EV darker than a light meter's reading which must avoid channel clipping. Combined, this would give a, say 2.5 EV advantage to an LED light, compared to a tungsten light, based on automatic exposure readings.

Therefore, I think the study, Christine's observations and Class A's reasoning are all compatible statements.

The only thing I am less sure about is halogen. I've seen enough anecdotical evidence that halogen may be a special case. On the other hand, halogen spectrum is not special and I would have a hard time to understand why. So, for the time being, I classify the halogen case as mythical.


@Christine: Your spherical aberration theory is good. But I fear that we have some evidence against it like the dependency on light color or that stopping down doesn't help (beyond a proportional reduction of the confusion circle of course). Maybe, an extension of your theory to include CA or Bokeh-CA would be required. It still wouldn't explain the strong dependency on luminosity though.

We can all speculate (and I did it as well). But at the end of the day, we don't know what makes the lens dependency. That would require a very elaborate study in itself. BTW, I agree that the AF assist light behaviour could be lens dependent too.

2) Does the 645D show this behavior as well since it (presumably) shares the same focusing system?

I would be rather surprised to learn that 645D and K-5 share the very same physical module. It would cover maybe less than the inner third of the 645D frame only.

[Aristophanes]

This situation illustrates something I've noticed in various forums over the years (primarily Nikon/Pentax,) and that is:

When an issue like this pops up, for every person actually experiencing 'user error', there is probably another who actually has a problem with their equipment - but that problem is masked by a lower standard of expected performance.

"My camera/lens has no problem" often really means "I'm OK with it's performance - problem or not."

However, once people become aware of a legitimate issue that is generally observed, they wonder if they got their money's worth compared to another brand. User error still becomes the manufacturers fault because there is a deficiency.

The big questions here are: Why does Pentax have this issue and why does Nikon or Canon not? Is there better value elsewhere?

[dadipentak]

Thanks for a very competent piece of technical analysis, Falk. This is not an issue which impairs my use of, or dampens my enthusiasm for, my K-5. However, I can appreciate that it may be a deal-breaker for some. It seems to me that Pentax has a lot riding on the K-5 as a break-out in terms of market position so I think there's room for hope that they will deliver improvement via firmware.

[Class A]

Actually, if you look at Fig.4, then you'll see that blue and magenta focusses correctly down to -1 EV while red "jumps" at 0 EV.

Sure, but with "bright" red I meant much more than 0 EV. I just checked an exposure that I recently did with studio modelling lights (just the modelling light (probably Tungsten, small chance for halogen but I doubt it), without the strobes firing) and the data suggests the camera had at least 7 EV available.

[WerTicus]

Despite the K-5 locking focus incorrectly i never got the impression that the k20d or k-x i had could manage to do it reliably in similar light conditions anyway.