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02-04-2012, 04:07 AM - 1 Like   #166
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Finally!!! A camera that actually focuses accurately and reliably! *happydance*











Hand held 1/4 sec with SR on:


02-04-2012, 06:23 AM   #167
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I find the camera-ground interface to be the biggest problem with my photography. but it's easier to blame the gear. 40k+ shots on my k-5 bought this summer, no focus issues with the camera... just with the user =)
02-04-2012, 08:38 AM   #168
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I returned my K5 over a year ago due to its inability to AF in low light. I was hoping the new K-01 would be my next camera but the lack of a evf is a deal breaker for me. So, I come here to see how the K5 is doing and find the same complaints and issues still plague the K5 over its AF. Whats the real deal here? Is this camera worth a second look, or should I continue to pass on it? Can it focus in low light (ie- indoor birthday parties ect) or not?
02-04-2012, 08:48 AM   #169
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I got the K5 about a month ago. I had AF issues with Tamron 17-50 so I decided to try another lens. Now with DA 17-70 the AF is spot on even in very low light. No DSLR camera has 100% AF accuracy.

02-04-2012, 10:00 AM   #170
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QuoteOriginally posted by Zugzwang Quote
I returned my K5 over a year ago due to its inability to AF in low light. I was hoping the new K-01 would be my next camera but the lack of a evf is a deal breaker for me. So, I come here to see how the K5 is doing and find the same complaints and issues still plague the K5 over its AF. Whats the real deal here? Is this camera worth a second look, or should I continue to pass on it? Can it focus in low light (ie- indoor birthday parties ect) or not?
I have no problem focusing in low light; bought my k-5 in November last year.
02-04-2012, 03:13 PM   #171
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QuoteOriginally posted by Zugzwang Quote
I returned my K5 over a year ago due to its inability to AF in low light. I was hoping the new K-01 would be my next camera but the lack of a evf is a deal breaker for me. So, I come here to see how the K5 is doing and find the same complaints and issues still plague the K5 over its AF. Whats the real deal here? Is this camera worth a second look, or should I continue to pass on it? Can it focus in low light (ie- indoor birthday parties ect) or not?
I have no issues in shooting my K5 in low light, bought it in Feb 2011. Of course there have been some firmware changes issued since you bought.
02-04-2012, 03:54 PM   #172
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QuoteOriginally posted by philbaum Quote
I have no issues in shooting my K5 in low light, bought it in Feb 2011. Of course there have been some firmware changes issued since you bought.
Not directed at you specifically, but everyone has different expectations of good vs poor AF performance, which makes it difficult on forums like these.

For example, you previously stated that "AF on the middle of a back bear is not a reasonable expectation, etc." - from this I would suggest you have low expectations for AF - the K-5 works just fine on bears (and even possums in the night).

Of course, high expectations could also be unrealistic, and its true that user error can result in misfocus.

Given my K-5 met my expectations when I first purchased it, and then I noticed problems a few months ago and now that Pentax has fixed it the AF performance is back to being acceptable, it seems AF performance can degrade over time and with frequent use and therefore I would probably need to budget for periodic recalibrations in the future (if I keep the camera).
02-04-2012, 05:29 PM   #173
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Christine, I have been following this thread with interest. So now that the situation appears to be resolved I would like to know if you were informed about or if there is anything on the Work Order stating what exactly was fixed/replaced/calibrated etc...?

02-04-2012, 06:59 PM   #174
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QuoteOriginally posted by gda13 Quote
Christine, I have been following this thread with interest. So now that the situation appears to be resolved I would like to know if you were informed about or if there is anything on the Work Order stating what exactly was fixed/replaced/calibrated etc...?
Sorry, didn't pick up the camera - and the camera was sent to Pentax via the shop I purchased from, so I didn't deal with Pentax directly (apart from messages on Facebook).
02-04-2012, 07:37 PM   #175
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Looks like the focus issue is gone.
02-04-2012, 07:40 PM   #176
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My K-5 has been spot on with no lens adjustments needed. So far I am very impressed with the improvements over the K-7.
02-04-2012, 07:41 PM   #177
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I deal directly with CR Kennedy, the Australian distributor. They have repaired my K-5 by replacing the rear focus mode lever module and currently have my DA* 50-135 in for repairs. They have told me that the technicians don't itemize what they do to any of the gear they fix. It's a bit unusual and disappointing because I really want to know why my several-months-old zoom lens that cost $1500 needs new parts. Every repair I've had done to any of my recording studio gear has always been itemized in every detail so I don't see why camera/lens repair should be any different. I also asked if they check other things about the camera/lens other than the issue's in question and they said no. But I'm sure they would do anything that was required if you said it was faulty though. So if you are having focus issues then maybe just tell them it's not focusing properly and see what they say.
02-04-2012, 08:47 PM   #178
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QuoteOriginally posted by Christine Tham Quote
Sorry, didn't pick up the camera - and the camera was sent to Pentax via the shop I purchased from, so I didn't deal with Pentax directly (apart from messages on Facebook).
No worries...just curious about what could be the cause of your specific issue. I have "yet" to experience any problems of this sort, but it is always good to know for future reference what worked in a situation such as this after all if the AF accuracy declined over time in your case it could potentially happen to others as well. Thanks for sharing.
02-05-2012, 09:10 AM   #179
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Is it Just Me?

QuoteOriginally posted by Christine Tham Quote
Finally!!! A camera that actually focuses accurately and reliably! *happydance
Christine,

I am glad that you are happy with the service on your camera and the resuting performance.

However, and presuming the images above are after repair shots, color me confused.

I do not see an example of a good sharp image in those shots. They all look pretty soft to me, and the lady with baby and lady in the last shot do show what looks to me like FF.

There are spots in both of these images where details look sharp somewhat in front of the subject:

Lady's front shoulder on the tee shirt in the image with baby looks to be in focus

A little less clear, but the earring and front shoulder on last lady also looks to be sharper than anything else.

Did the lens go in with the body?

If not, your lens might need a bit of focus adjust.

Ray
02-05-2012, 12:10 PM - 2 Likes   #180
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I went through several stages of AF doubts with a K10D. First I thought the AF was a bit wonky "sometimes", then I thought there were mirror alignment issues, because I had problems with MF too. Then I figured eyesight/dioptre issues, and, finally, I got around to noting whether the SR was on or off when shooting. Whenever I've tried to check for basic focus accuracy at around one to two metres, though, it's seemed spot on.

Since first noting problems, I've learned that the viewfinder system has its own effective aperture, making fast lenses look like they have more DoF than they do. Moreover, noting my technique and trying to find variables, I've discovered that with the K10D VF at least, my eye being off-axis also affects my impression of focus. All other things being equal, I find focus is pretty well always reliable and good with long lenses, even fast ones, the most trouble I've had has been with a 20mm f/1.8, results seem a bit variable with 50/1.4.

My suspicions have also fallen on the SR from time to time, not because the shots are motion-blurred rather than OOF (I know the difference) but because I thought I was seeing inconstencies even with an old MF lens which hadn't moved between shots. The wider & faster the lens, the worse it is.

To be able to move for shake-reduction, the sensor has to be free to move, obviously, and with SR on, it must be free to move during the exposure. Which implies that there's some play in it, however slight. Moreover, depth of focus (i.e. the depth in focus at the sensor plane, behind the lens) is tighter for wider apertures, obviously, but also tighter (at short distances) for wide angle lenses than for longer lenses (sounds paradoxical, but it's the opposite way around from depth of field in front of the lens - less relevant for distant subjects though.)

So wondered, could the focus accuracy of these moving-sensor cameras be determined somewhat by where, exactly the sensor is, and how sloppy it is in its sliding mountings, if it has sliding mountings? Is it magnetically clamped in place when SR is turned off? Does it wear and become sloppier with age? I have no idea, but I do *seem* to get more consistent (focus) results with SR off. I'm not sure whether it's changing between times if I switch SR on and back off again, though. At 20mm and f/1.8 and 12ft focal distance, I make the depth of focus at the film plane of the order of a thousandth of an inch, so the sensor hasn't got to be too loose to be problematic, but then I'd expect a lot less that 1/1000" play for all that. So, more tests needed :-)

If things are overall simply inconsistent then it's kind of hard to pin down, when testing stuff, whether whatever you're changing from shot to shot is having any effect.

I think for AF, there are other effects which might be creeping in below the radar, as it were - the colour and brightness thing has been mentioned, the focus detect does seem to be sensitive to light level (unsurprisingly) and also colour temperature, then there's the business of the VF indicators not necessarily being aligned with the actual effective focal points - I can see that this could quite easily be very different from lens to lens, and could in itself account for a lot of the inconsistencies seen in real-life situations. And I wonder how the focus sensors are sampled, and how often, because many light sources are changing brightness and colour quite dramatically at various frequencies. Old-style striplights, TVs and CRT screens, for example, flicker at a fairly low frequency and I wouldn't be entirely astonished to find that the AF system could be upset by this kind of thing.

As I understand it (which isn't very much) phase detect AF works in effect like a rangefinder with the lens diameter as its baseline, using linear CCDs to compare images from either side for coincidence (see this, for example: Autofocus: phase detection ) - seems to me that if the light has changed somewhat between when the camera's CPU "looks" at the one AF sensor and the other, then it's not necessarily going to come up with the right answer. If there's this kind of effect going on, then "cross" type sensors (with pixels in two directions) are probably going to behave differently to "line" type ones. Moreover, if the focus system's optics suffer from any kind of chromatic aberration, then light (and subject) colour will, I imagine, be highly significant, and I further imagine that this will be affected by any lens chromatic aberration, which tends to be worse the further off-axis one gets, and worse with wideangles.

After pondering this for some time and imagining all the things which could affect image focus or confuse the focus detect system, I've kind of come around to thinking that its not too far short of miraculous that it works at all, and that I get more decent sharp pictures than I used to, and nothing's perfect, so perhaps I should stop worrying too much about it and just take photos :-)
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