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12-25-2010, 03:40 PM   #226
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QuoteOriginally posted by dgaies Quote
For what it's worth, I just ran a quick series of tests to try and quantify the threshold of tungsten color light at which the front focus manifests itself. I used a room with three overhead 60 watt regular tungsten light bulbs. The lights are controlled on a dimmer and I reduced the light level gradually until the focus problem presented itself. I started with the blinds open using natural light around 5 EV and the focus was fine. I closed the blinds and turned the dimmer up to 6EV and the focus was fine. I tried a light level of 5 EV and it was fine. 4 EV was fine was well. 3 EV, however, was front focused. So I tried 4EV again and the focus was fine again. Down to 3EV, the focus was off. I repeated this a few times and have concluded (that at least for this particular combination of K-5 and FA43), at around 3EV there is front focus.

So I would conclude that at low levels of artificial, tungsten colored light (3-4 EV and below) is where the FF issue begins. I haven't had any major issues in actual use, but I suspect that is because my shots were either above 3-4 EV or were in light that was low enough that the AF-assist light kicked on and mitigated the problem.
Thank you very much for this information. This gives a good feel about how this would or would not affect me, should I get a K-5.

12-25-2010, 04:25 PM   #227
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QuoteOriginally posted by dgaies Quote
For what it's worth, I just ran a quick series of tests to try and quantify the threshold of tungsten color light at which the front focus manifests itself. I used a room with three overhead 60 watt regular tungsten light bulbs. The lights are controlled on a dimmer and I reduced the light level gradually until the focus problem presented itself. I started with the blinds open using natural light around 5 EV and the focus was fine. I closed the blinds and turned the dimmer up to 6EV and the focus was fine. I tried a light level of 5 EV and it was fine. 4 EV was fine was well. 3 EV, however, was front focused. So I tried 4EV again and the focus was fine again. Down to 3EV, the focus was off. I repeated this a few times and have concluded (that at least for this particular combination of K-5 and FA43), at around 3EV there is front focus.

So I would conclude that at low levels of artificial, tungsten colored light (3-4 EV and below) is where the FF issue begins. I haven't had any major issues in actual use, but I suspect that is because my shots were either above 3-4 EV or were in light that was low enough that the AF-assist light kicked on and mitigated the problem.
Thanks for checking that. It confirms what I posted a couple of pages back with something more scientific than what I was referencing from.
To put this in perspective then, the K5 would appear to be ~4 stops optimistic regarding AF operation.
There was a post much earlier that seemed to hint that the problem wasn't a tungsten light problem per se, but a general illumination problem, with the AF going wonky in dim light no matter what the source.
It's already dark here, but I might get a chance to confirm this in a day or two.
It's probably something goofy like they have the gain turned down to far in the sensor or some such.
12-25-2010, 04:31 PM   #228
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QuoteOriginally posted by bjan Quote
Janneman is the second person in the world that has a good working K5 in respect of AF under artificial light condition (with given DOF that shows the issue ) !
CONGRATULATIONS janneman !
Thank you

QuoteOriginally posted by bjan Quote
But...... I bet with you that your camera is faulty too ! Just do the right test with the right lens and aperture / distance combo. Make shots of your mother in law under artificial light this evening . Head shoulder portrait from a 1 metre distance with a aperture of 2.8 or faster. Not wider than 35mm lens . You will see blurry eyes before the first glass of wine is taken by her. (asssumed you put AF on the eyes ) A sharp nose she might have in the end result but that she had anyway right ?
well, as I don't have a mother in law, proper testing was impossible but the moment I got my new K-5 yesterday I wanted to test but as it cam out of a freezing delivery van I decided to let it warm up again befroe removing any caps and so...

So I tested, just one low light bulb 40W.
Lenses used DA*50-135 and FA*80-200/2.8, both at f2.8.

Looked more than okay to me,the FA*80-20 even had some back focus (as is had on all my digital dslr's but correctable with the new AF adjust)
Then I aimed a t the sky.... second batch, just a habit, after all we were told all cameras on the market were stain free...and will you excuse me for no further testing, I had the string again...
12-25-2010, 05:20 PM   #229
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QuoteOriginally posted by Fer Quote
Ok, so this is basically how this thread has evolved:

1. There's no issue with AF, works perfectly fine. You guys post some samples showing the supposed problem
2. Those samples show a problem indeed, but I have found no such thing with any of my lenses
3. Care to quantify the problem in EV terms? I'm just saying, but you guys are probably trying to use your K5 in pitch dark in a medieval cave (which btw shouldn't matter that much, since the AF is confirming focus anyway; if light is below what the AF can handle, why would the camera confirm focus without even hunting for a second?)
(4. Wait, I might have these problems too. Not too serious, though)
5. Yep, those EV values are a little on the verge of what the AF can handle, based on K5 specs
6. Wait, they aren't
7. Alright, so I have the problem too, and it's probably serious, but I trust Pentax to fix it, even though they have not shown the basic decency to tell their customers that they know about the issue and are working on it (which even as we speak, we cannot be 100% sure of)

I find it a little disappointing that some people get so defensive and need over 200 posts in the thread to grudglingy admit that there is a problem. No one here is out to put Pentax or the K5 down for spurious reasons.

Other than this, the K5 is a great camera, and I really want to keep it, but I won't unless this serious problem is fixed. It's not a mere bug, and it's not minor.

Above all, I'd like Pentax to treat me as their partner (as Wheatfield suggested), and change their stupid policy of not communicating at all with their customers whenever there is a problem. I've already shown my willingness to be their partner by shelling out the cash to buy their product above others from competitors, so let's see some reciprocity here.
I don't know which business/marketing school these guys got their MBAs or whatever qualifications in, it's disrespectful for your customers and awful business practice, no matter how you view it. And please, enough with the "it's the way they do things in Japan, we must accept it". I don't care if a company is headqueartered in Japan, Albania or Minnesota, they need to understand that we are now living in a globalized world, so they have to manage their clients' expectations everywhere.

And it is fair to say that, generally speaking, most of us don't care that much that there is a problem (after all, it's a fact of life), as long as we're kept informed in due time of the steps the company/service provider is taking to sort it out. I don't understand the kind of complacency that goes: "that's just the way they are, I don't care that they have not made an announcement, because traditionally they fix the issues anyway". Well, of course they do, otherwise they would be out of business. It doesn't change the fact that they should grow up as company and start communicating with their clients in a mature way.

End of rant, sorry if I got too carried away.
Merry Christmas everybody!

nice post mate..I think you have sumed it up well.....not a rant..just facts well done

Id like to thank Bjan too...he's bashed us over the head with this problem..and basicly made us go test our K5, some didn't agree with his proposals..but in the end we have all fell in line , as we have all the same issue...all bar Jannerman that is ...so cheers Bjan for pushing the issue



Wheatfield

I suggested that its a problem not in just artificial light..but low light in general..be nice if you could do the test too mate..just to conform or not if Im dreaming it..


My work around last night at a Christmas party was to use live View...what a pain in the arse that was..LV is now pretty good on a tripod..but hand held..I dont like it at all..IMO anyway..

obviously.. it don't matter if you use flash either...as out of focus is out of focus whether its exposed correctly or not..


Last edited by Tommot1965; 12-26-2010 at 02:51 AM.
12-25-2010, 05:24 PM   #230
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QuoteOriginally posted by janneman Quote
Thank you



well, as I don't have a mother in law, proper testing was impossible but the moment I got my new K-5 yesterday I wanted to test but as it cam out of a freezing delivery van I decided to let it warm up again befroe removing any caps and so...

So I tested, just one low light bulb 40W.
Lenses used DA*50-135 and FA*80-200/2.8, both at f2.8.

Looked more than okay to me,the FA*80-20 even had some back focus (as is had on all my digital dslr's but correctable with the new AF adjust)
Then I aimed a t the sky.... second batch, just a habit, after all we were told all cameras on the market were stain free...and will you excuse me for no further testing,

I had the string again.



mate. thats a right bummer for you..what yer gonna do now...will you try another K5 ?
12-25-2010, 05:27 PM   #231
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QuoteOriginally posted by dgaies Quote
For what it's worth, I just ran a quick series of tests to try and quantify the threshold of tungsten color light at which the front focus manifests itself. I used a room with three overhead 60 watt regular tungsten light bulbs. The lights are controlled on a dimmer and I reduced the light level gradually until the focus problem presented itself. I started with the blinds open using natural light around 5 EV and the focus was fine. I closed the blinds and turned the dimmer up to 6EV and the focus was fine. I tried a light level of 5 EV and it was fine. 4 EV was fine was well. 3 EV, however, was front focused. So I tried 4EV again and the focus was fine again. Down to 3EV, the focus was off. I repeated this a few times and have concluded (that at least for this particular combination of K-5 and FA43), at around 3EV there is front focus.

So I would conclude that at low levels of artificial, tungsten colored light (3-4 EV and below) is where the FF issue begins. I haven't had any major issues in actual use, but I suspect that is because my shots were either above 3-4 EV or were in light that was low enough that the AF-assist light kicked on and mitigated the problem.
mate..your a legend for doing that...I reckon the problem is all low light shooting could you test that too...just to either back up or dismiss my claim..i asked wheatfield to try it too...be intrested in both your results ...
12-25-2010, 05:34 PM   #232
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QuoteOriginally posted by Tommot1965 Quote
...all bar Jannerman that is ...so cheers Bjan for pushing the issue ..
maybe they solved the low light issue in my camera before sending it to me but forgot to check for stains...

Anyways, very annoyed that either Pentax Benelux or the store sent me a bad copy...
(Ans there are more reports of people NOT having the AF issue, just that there were many people without stains...
So there is an issue but it may be that not evreynody has that issue.
I did not say that thare is no issue with AF, I just reported I did not have an issue.
12-25-2010, 05:38 PM   #233
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QuoteOriginally posted by Tommot1965 Quote
mate. thats a right bummer for you..what yer gonna do now...will you try another K5 ?
From a different store, I think I will cancel this order. Only prblem is that it is about the only store in NL which carries the 18-135. I ordered the kit but they are not available as such yet so all "kits"are individual lenses and bodies put together. Will try to return the body but keep the lens. If I cannot return I will definately ask for a lower price as I orderwd in october and had to pay full price and they now dropped about 120,00. If they don't do that i will send in all and ask for refund. + shipping.

12-25-2010, 06:46 PM   #234
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I found this video on youtube - an easy test of AF (in)consistency under different light conditions:
12-25-2010, 07:14 PM   #235
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Nice find. Pretty telling, eh?

I wonder how many firmware updates will be required to fix this mess.

QuoteOriginally posted by tibor Quote
I found this video on youtube - an easy test of AF (in)consistency under different light conditions:
http://www.youtube.com/watch?v=d2W5gwTtLqc
12-25-2010, 08:49 PM   #236
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QuoteOriginally posted by Tommot1965 Quote
mate..your a legend for doing that...I reckon the problem is all low light shooting could you test that too...just to either back up or dismiss my claim..i asked wheatfield to try it too...be intrested in both your results ...
You're welcome. I'll give a try tomorrow once the sun comes back up
12-25-2010, 11:40 PM   #237
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good find tibor. ill try that later ..onya mate
12-26-2010, 12:02 AM   #238
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Just now I do adjust my focusing with a 50mm f1.9 manual lens and focus on the chart. My best result is -8 in AF adjustment. I am apply this figure for all. Now my focusing in tungsten light seems a lot more better and my kit lens now working great in focusing.

hope this help.

Tom
12-26-2010, 02:11 AM   #239
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Ok that video sums it up pretty well. The tricky part is that the camera is confident and confirms focus equally quick in both situations.
12-26-2010, 02:39 AM   #240
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QuoteOriginally posted by Tommot1965 Quote
Id like to thank Bjan too...he's bashed over the head with this problem..and basicly made us go test our K5, some didn't agree with his proposals..but in the end we have all fell in line , as we have all the same issue...all bar Jannerman that is ...so cheers Bjan for pushing the issue

Thanks TOMMOT you are exactly understanding my " sharp edges" here and there. I want the issue to be solved as bad or more than anyone else and that is why I want as many people as possible to stand up with one voice towards PENTAX and make them feel their responsibility for the product and the end users. I am even thinking about sending the content of this thread to all leading Photo magazines worldwide to make them aware and carefull with their "GOLDEN AWARDS " ! Low light AF testing should from now on be part of any serious camera test .
However many problems are the start of a bettter world and let`s hope this is the case also here.
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