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02-15-2011, 04:33 PM   #571
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QuoteOriginally posted by jolepp Quote

It is possible that some copies of the K-5 do not suffer from tungsten/low light FF at all, but I cannot recall posted test photos supporting this (?)

Sorry - should have posted this - FA 43mm Ltd, ISO 100, f1.9, T 2sec (EV less than 1) - the AF assist light came on, as it should:


Under these conditions, my K10D either fails to focus, or has slight FF.

02-15-2011, 04:53 PM   #572
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QuoteOriginally posted by Christine Tham Quote
the AF assist light came on, as it should
yeah, with auxiliary beam everything seemes to be ok as at the day light does....
02-15-2011, 04:58 PM   #573
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QuoteOriginally posted by filorp Quote
yeah, with auxiliary beam everything seemes to be ok as at the day light does....
Apparently according to Falk his K-5 still FF when the AF light comes on, as the AF light switches off BEFORE the camera has completed focusing.

But his K-5 and my K-5 have identical firmware and model number, so it seems the issue is not related to firmware (or if it is, it is not related to the DSP/CPU firmware revisions but something far deeper within the camera ...)

My camera does FF around EV1-2 but only very slightly, same as my K10D. This problem it appears is not just limited to the K-5 (and indeed, not just to Pentax cameras, as I posted videos of similar behaviour on a Sony).
02-15-2011, 05:03 PM   #574
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QuoteOriginally posted by Christine Tham Quote
My camera does FF around EV1-2 but only very slightly, same as my K10D.
Just a short note that one expects the K10D to FF under Tungsten light. That's why the "+" in SAFOX has been introduced (a colour temperature sensor for the AF module). Ideally, the K-7/K-5 should be immune to colour temperature when it comes to AF accuracy.

02-15-2011, 05:07 PM   #575
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QuoteOriginally posted by Class A Quote
Just a short note that one expects the K10D to FF under Tungsten light. That's why the "+" in SAFOX has been introduced (a colour temperature sensor for the AF module). Ideally, the K-7/K-5 should be immune to colour temperature when it comes to AF accuracy.
I think the real issue is that cameras generally have problems AF in low light regardless of colour temperature.

Under those exact conditions, the Canon EOS 1D Mk III refuses to lock focus, period.
02-15-2011, 05:11 PM   #576
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QuoteOriginally posted by Christine Tham Quote
I think the real issue is that cameras generally have problems AF in low light regardless of colour temperature.

Under those exact conditions, the Canon EOS 1D Mk III refuses to lock focus, period.

Just curious, what does the Pentax Specifications on the K5 say about the AF abilities? Can you post it here? I haven't seen it, but it must exist?
Regards
02-15-2011, 05:17 PM   #577
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QuoteOriginally posted by Rupert Quote
Just curious, what does the Pentax Specifications on the K5 say about the AF abilities? Can you post it here? I haven't seen it, but it must exist?
Regards
I think the manual says the K-5 should be able to focus down to EV -1, but that's assuming the AF assist light comes on and is working correctly.

What I am finding is that there is a narrow band (around EV1-2) where the AF assist light may not come on, resulting in the camera exhibiting slight FF.

This seems to be a very specific problem under very specific circumstances which I am unlikely to encounter (and indeed, it is an issue I have yet to encounter in "real world" shooting conditions).

It does seem the problem is more severe for other units out there - I am only commenting on the behaviour of my specific unit.
02-15-2011, 06:23 PM   #578
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QuoteOriginally posted by Christine Tham Quote
I think the real issue is that cameras generally have problems AF in low light regardless of colour temperature.
Isn't it true that the K-5 consistently produces FF, as opposed to ending up with some erratic focus choice?

If we were dealing with the latter, your assumption would have merit. If we are dealing with consistent amounts of FF, there should be a cure, given that the camera should have a means to detect the colour temperature. Maybe the colour temperature sensor cops out at such low light levels?


QuoteOriginally posted by Christine Tham Quote
Under those exact conditions, the Canon EOS 1D Mk III refuses to lock focus, period.
That's noteworthy in a way, but given that other Pentax products manage to produce less FF than the K-5 under the same circumstances, it is somewhat irrelevant as far as the K-5's potential is concerned, isn't it?

02-15-2011, 06:54 PM   #579
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QuoteOriginally posted by Class A Quote
That's noteworthy in a way, but given that other Pentax products manage to produce less FF than the K-5 under the same circumstances, it is somewhat irrelevant as far as the K-5's potential is concerned, isn't it?

With all due respect, we don't have any evidence of this, only anecdotal reports based on specific units - not statistically valid.

And my anecdotal experience based on my units suggests about the same level of FF between the K10D and the K-5.

As far as the K-5's "potential" is concerned, obviously from my test shot it is potentially able to focus at EV well below 1 (note that the test shot is underexposed, suggesting the real EV is significantly less than the image parameters would suggest).

At this stage, I would hesitate to assume that there is a consistent problem. Clearly there are problems with some units, however the problems are not consistent (some are reporting minor FF, some are reporting severe FF, at least one is reporting BF, some are reporting no problems) and it also seems that units with exactly the same firmware are exhibiting different behaviour.
02-15-2011, 08:12 PM   #580
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QuoteOriginally posted by Class A Quote
Isn't it true that the K-5 consistently produces FF, as opposed to ending up with some erratic focus choice?
I don't think this is true in every case. My findings on my camera, and I just did it again to be sure, is that it is somewhat erratic. DA 35mm Ltd @ 2.8 and 4 seconds, EV 1, tungsten/incandescent light, I tried 5 more times. 3x spot on, 1x front focused, 1x kinda front focused. At EV3, shutter speed to one second, I got 1x spot on, 1x back focused and 2x front focused. The fifth time at EV3 the focus assist light came on and consequently the camera got it right.

I can't explain how this fits in with the others that can consistently produce FF in low light other than to say that there appears to be inconsistency among units and we cannot definitively say there is a problem with *ALL* units.
02-15-2011, 08:53 PM   #581
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I think I have covered this before, but I never got a definitive answer...or I forgot it? Why can't the assist light be turned on at will? This would eliminate the problem for me, since I shoot little very low light shots. Looks like it would be easy to make it available via one of the buttons? I know it is a workaround, but for me it is one that would seem to be just fine?
Regards
02-15-2011, 09:11 PM   #582
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QuoteOriginally posted by GregK8 Quote
I don't think this is true in every case. My findings on my camera, and I just did it again to be sure, is that it is somewhat erratic. DA 35mm Ltd @ 2.8 and 4 seconds, EV 1, tungsten/incandescent light, I tried 5 more times. 3x spot on, 1x front focused, 1x kinda front focused. At EV3, shutter speed to one second, I got 1x spot on, 1x back focused and 2x front focused. The fifth time at EV3 the focus assist light came on and consequently the camera got it right.

I can't explain how this fits in with the others that can consistently produce FF in low light other than to say that there appears to be inconsistency among units and we cannot definitively say there is a problem with *ALL* units.
I'm not disputing the inconsistency. I'm sure its real. But I am reporting that MY K-5, which is a replacement, gives me consistent FF on my DA 40 at the same EV. Under EV3.5 it FF and increases its FF as light decreases until the assist lamp comes on (then its fine). But the FF is relatively slight (the focus point is at the boundary of what is in focus at EV2).

BUT my FA 50 DOESN'T FF at all, even at light levels of 1.7 EV (without assist lamp) and is consistent. My DA 40 is my worst lens tested so far.

I tried this with different focus charts with same results. Two foot distance to target. Camera on tripod to ensure it was stable once focus lock achieved. EV measured with Sekonic light meter. Light was from halogen light on dimmer.

So are people experiencing different results with different lenses?
02-16-2011, 02:19 AM   #583
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JRforman, this does not really surprise me, as the AF module will receive less light with your DA40 at EV3.5 than with your FA50 at EV1.7...

Secondly I've found out that focus chart, with their nice, contrasty targets, are somehow not really representative... My K5 does not FF much with my FA50 on focus targets, even down to EV0.5, but as soon as I'm shooting my kids in poor light (no contrasty lines to lock on), I end up with some huge FF (about 10cm, depends on the light/distance)...

Christine, I think all the uproar about this is that the K7 does not suffer from FF at all, its '+' sensor doing its job perfectly, even with the AF assist lamp disabled. I know, I had one, as I had a K10, K20 and Kx (and they suffered from FF).
And you can search here, there was no such report at its time...
02-16-2011, 05:24 AM   #584
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QuoteOriginally posted by Christine Tham Quote
With all due respect, we don't have any evidence of this, only anecdotal reports based on specific units - not statistically valid.
That's true and this is why I write my report. The whole thing is a bit complicated (no simple truth here after 250 test shots) which is why it takes me a couple days to write it up. Actually, the focus problems are neither erratic nor following a very simple rule. However, a fuzzy rule exists which I am writing down and which may help to avoid the problem.
02-16-2011, 05:42 AM   #585
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QuoteOriginally posted by jrforman Quote
BUT my FA 50 DOESN'T FF at all, even at light levels of 1.7 EV (without assist lamp) and is consistent. My DA 40 is my worst lens tested so far.
I tested for FF with my FA31, FA43, FA50 & FA77. The FA31, 43 & 77 all had FF issues between 1 and 4 EV (I didn't test ant lower) while the FA50 seemed to hold in there fairly well. The FA43 needed almost -10 fine AF adjust in good light whereas on my K100DS it was perfect.

So I saw similar results to what you are seeing. I don't own any of the DA primes.
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