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12-23-2010, 12:49 PM   #151
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QuoteOriginally posted by Sparkle Quote
Buyer's Remorse adds to such problem(s) and vice versa.
Interesting!...so, and I tested your hypothesis



It was taken with the 16-45, and the focus was on the K-7 box, and the Porsche emblem and even the front lights are in better focus...I wonder whether your hyposthesis still holds true?

12-23-2010, 12:51 PM   #152
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The fact that you cannot take a properly focussed picture in a living room under artificial light is not a dealbreaking problem for some of the people it seems Fer. What can you expect from a 1000 Dollar plus camera .......? Don`t be so childish.
12-23-2010, 12:54 PM   #153
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What is your problem PCARFAN ? You can see very well it is a box you focussed on isn`t it ? The sharp Porsche emblem and front lights are a bonus I would say !
12-23-2010, 01:11 PM   #154
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QuoteOriginally posted by bjan Quote
You are absolutely right Dgaies ! That is why I would never say such silly thing indeed and never did.
What I have said is that the AF of the K-5 does not work under artificial light and this only being visible in the end result in case the DOF involved let you notice this. And believe me that is not very silly to say in this case. The fact that you have more succes in respect of frontfocussing in dim tungsten light with your K5 than with your Kx or K7 does not mean al lot to to anyone of us as we cannot judge your results from here from any of those camera`s you made those pictures with. I would say you seem to use the right compositions and setttings to avoid the issue come into effect more than I would without being aware of the issue all the time. Again I don`t understand that people try to defend a serious fault in the K5 rather than smashing the problem in PENTAX face.
Perhaps I was not clear enough. To say that the AF of the K-5 does not work under artificial light is misleading. There is obviously a threshold which may be light temperature dependent, under which the AF system does not perform well. Pentax may be able to improve on this shortcoming or they may not. I'm not denying that under certain conditions there is an issue. But I don't believe that those conditions have been fully quantified yet so it's hard to know if this is an actual bug/problem or just of trying to use AF at the edge of it's useful range.

And, FWIW, I am fully aware of the overall issue of BF/FF under tungsten light and how to check for it. I used to own both a K10D and K20D, both of which had significantly more issues focusing under tungsten light than my K-5. My results have nothing to do with composition as I can replicate them with focus charts as well. Again, I am not suggesting there isn't an issue here. At the moment, however, I suspect the issue has more to do with pushing up against the light level limit of the AF system more than the K-5's ability to deal with low to moderate levels of artificial light. I, as much as anyone, would like to see this improved via firmware or a hardware fix.

Furthermore, your logic is flawed in the statement that you don't understand why people "try to defend a serious fault in the K5 rather than smashing the problem in PENTAX face". The flaw is that you presume there is a serious flaw and that if there is one, that Pentax won't address it. I fail to see how "smashing the problem in PENTAX face" is helpful to any K-5 owners at the moment.

12-23-2010, 01:16 PM   #155
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QuoteOriginally posted by dgaies Quote

....it's hard to know if this is an actual bug/problem or just of trying to use AF at the edge of it's useful range.

..., I suspect the issue has more to do with pushing up against the light level limit of the AF system more than the K-5's ability to deal with low to moderate levels of artificial light.

...
Well, if that were the case, then the K5 AF system has a less useful range than the Kx.

That doesn't make sense, and I think there's enough data, information and samples in this thread to conclude there is a genuine issue, and a major one at that. Maybe it hasn't been "quantified" enough for your taste, but the problem occurs in fairly normal lighting conditions and I can't see why anyone would insist on looking for alternative explanations that would mean the K5 is a lesser camera than we all think it is.
12-23-2010, 01:17 PM   #156
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ok

I just did a candle light test. on AFC...tripod with remote shutter release..perfect ....did it in AFS with green light enabled..perfect again { as I would expect}

also did it in AFC in near darkness..and this thing still managed focus.. perfect again

sorry to say that in my house we don't have any tungsten light sources...but i will try again once i do

Lens was a 16-45 F4...so may not be wide enough to induce the problem

im getting a 17-50 2.8 tomorrow..so ill try with that
12-23-2010, 01:19 PM   #157
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QuoteOriginally posted by pcarfan Quote
Interesting!...so, and I tested your hypothesis



It was taken with the 16-45, and the focus was on the K-7 box, and the Porsche emblem and even the front lights are in better focus...I wonder whether your hyposthesis still holds true?

LMAO

thats a good post mate..love the German car...
12-23-2010, 01:19 PM   #158
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QuoteOriginally posted by Wheatfield Quote
The exposures you are listing are around EV5 or thereabouts. The K5 AF is rated to EV-1, but that would be, I expect, a full spectrum daylight rating. I've had good results myself as low as EV3 in artificial light, with colour temp in the 3000K range, and no problems at all in higher light levels (EV 8-10) with tungsten.
I'm thinking what we are seeing is a combination of colour failure of the sensor at low light levels combined with a loss of the double check that Pentax dropped to pick up the AF speed.
Hopefully they can do a firmware fix that will mask the deficiency in the sensor, or at least program the assist light to come on at higher EV values, perhaps 5 or 6 rather than the present level of 3 or 4.
Time will tell, but in the meantime, I would venture to say that in very low light levels, manual focus might be the best approach.
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.

12-23-2010, 01:20 PM   #159
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I wonder whether the AF problem might be related to fluorescent lights, especially those tungsten bulb replacements which seem to be more common than actual tungsten bulbs these days. I suppose the light coming from these is really a mix of a few distinct wavelengths converted from the two distinct uv wavelengths by the fluorescent coating (?), whereas the hot tungsten filament produces a continuous spectrum. While this mix is good enough for the eye as a tungsten light replacement the AF sensor(s) and/or the related color temperature sensor might not see it that way.
12-23-2010, 01:22 PM   #160
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First shot is in artificial (tungsten) light, EV is about 4, I think (1/40s, f/1.4, iso400). Second shot is about 3 stops more light, next to a window with no artificial light (1/320s, f/1.4, iso400). Both were taken with the K-5 + FA*85 and no AF adjustments in the custom menu.




12-23-2010, 01:22 PM   #161
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QuoteOriginally posted by Tommot1965 Quote
ok

I just did a candle light test. on AFC...tripod with remote shutter release..perfect ....did it in AFS with green light enabled..perfect again { as I would expect}

also did it in AFC in near darkness..and this thing still managed focus.. perfect again

sorry to say that in my house we don't have any tungsten light sources...but i will try again once i do

Lens was a 16-45 F4...so may not be wide enough to induce the problem

im getting a 17-50 2.8 tomorrow..so ill try with that
Yes, I don't think those conditions would show the problem. In the test I showed a few pages back, the assist light would never come on, so in principle your test was not conducted in the same lighting conditions. I have no doubt that the K5 focuses perfectly well in any light if the assist light is helping.
12-23-2010, 01:25 PM   #162
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QuoteOriginally posted by Fer Quote
znieh, while the fact that many users are not complaining about the AF issue would suggest it might be a hardware issue, it is quite clear now that it is a firmware issue, and people who don't have it are simply not shooting in low tungsten light, or not looking at their images close enough.
Oh, I hope so... What I heard about possibe HW issue was that some unit on the pcba was not activated. But I don't think this was more than a hypothesis.

QuoteOriginally posted by bjan Quote
Adjusting FF or BF with microadjustments is very risky with ZOOMLENSES . You will get from one problem into an other .
Yes, I am aware of that. It's just less than a mediocre workaround. If normal mode gives me FF -> try USER1-TUNGSTEN. If this does not match -> use the LV contrast AF or do a quick AF adjustment ...

Somehow I should step aside and look at myself while I am doing that ... so ... firmware 1.02! firmware 1.02! firmware 1.02! ... Come on guys, start yelling together, maybe this is being heard over there in Japan...
12-23-2010, 01:32 PM   #163
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QuoteOriginally posted by dgaies Quote
First shot is in artificial (tungsten) light, EV is about 4, I think (1/40s, f/1.4, iso400). Second shot is about 3 stops more light, next to a window with no artificial light (1/320s, f/1.4, iso400). Both were taken with the K-5 + FA*85 and no AF adjustments in the custom menu.



Seems alright, assuming you were focusing on the Orange-Miso Glaze line.

The color temperature of that tungsten light source seems much cooler than the ones I'm having problems with, though, assuming you took these with AWB or non-adjusted Tungsten WB.
12-23-2010, 01:37 PM   #164
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QuoteOriginally posted by dgaies Quote
First shot is in artificial (tungsten) light, EV is about 4, I think (1/40s, f/1.4, iso400). Second shot is about 3 stops more light, next to a window with no artificial light (1/320s, f/1.4, iso400). Both were taken with the K-5 + FA*85 and no AF adjustments in the custom menu.
That`s very nice Dgaies.... The clocks on the second picture do indicate the time 12 hours later than in the first pic.
If this is not what you want to show then it can only be that your camera is the only one that does not show the frontfocus issue under Artificial light. Congratulations !
12-23-2010, 01:37 PM   #165
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QuoteOriginally posted by Fer Quote
Seems alright, assuming you were focusing on the Orange-Miso Glaze line.

The color temperature of that tungsten light source seems much cooler than the ones I'm having problems with, though, assuming you took these with AWB or non-adjusted Tungsten WB.
Yes, that's the line I was aiming for. No major FF issues in this example anyway.

I wouldn't read much into the color of the image as I think I adjusted it after the fact. The light source on the first one was a regular incandescent light bulb. I have the raw files, so I can take a look at those a little later and give you a better idea of the true temp of the light.
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