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02-17-2011, 09:29 PM - 1 Like   #661
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QuoteOriginally posted by creampuff Quote
Seriously I wonder why you don't take positive steps and have a refund or an exchange. In another post you indicated that you discovered the focus issue on your camera body within a few hours of getting it. So what is stopping you from getting your presumably defective camera swopped for another one or sending it in for service? It seems the most logical step would be to replace your dud copy rather than hope for a supposedly rumored firmware fix.

Please read the posts before replying... My post you replied to had the following ,...

"I've been holding off sending my K-5 back for replacement/Repair becuase of the alleged FW fix."


I'll say it again .... there is rumour of a firmware fix that is imminent.

There is nothing "presumably defective" about my K-5. It IS defective in terms of focussing in low light.

The reputable shop that sold me the camera has stated that a firmware fix is on the way.

As I've said before I am waiting for this fix. if it does turn out to be NOT forthcoming I will send the camera back for replacement/repair.

It is Pentax's slowness in responding to this issue that is causing hesitation, not a lack of positivity on my part.

02-17-2011, 11:35 PM   #662
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QuoteOriginally posted by Rupert Quote
I could be wrong......but I can't seem to find any K5 shooter here that has sent his camera to Pentax Service with a focus issue and received it back repaired/not repaired? There may indeed be a repair for this, I see that on the Nikon D7K Forum there are several reports of focus issues like the K5 that were repaired by Nikon, and the shooters were well satisfied.

Surely someone is going to try this instead of just going for a new body every time they get a bad focusing camera? Before I give up on the K5, I would like to hear from some that have actually given Pentax a shot at making a repair. We are assuming firmware, but it could be that all that is needed is some hardware fix or some tweaking at a Certified Service Center?
Regards
I think this will happen if the next firmware update doesn't fix the problem...at that point Id expect a few K5 owners will be getting a service
02-18-2011, 07:48 AM   #663
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Read This

QuoteOriginally posted by dcmsox2004 Quote
for falk......... please indulge my ignorance as well as my desire for a k-5........

every time i read about this i think i need to enroll in a class at MIT or cal polytech.... i find the nuts and bolts of the focus and it's related camera components most interesting, but what a brain drain.... i hope i'm not interpreting these posts as a 'how to' guide for an end user in overcoming the flaws of the k-5..... to be frank, this is why i add the k-5 to my b+h cart and then walk away from it..... scares the bloody hell out of me... either the k-5 will focus properly in low light, be it natural of man made, or it won't..... seems like all the manipulation with the settings for the k-5 still can't overcome it's inherent failings...
but... other k-5 owners state they have NO problems whatsoever... how can this be.... is it a software issue or mechanical problem only affecting a few random bodies?????
i'm even willing to have my wife kill me if i order the new silver surfer version about to be released... i'd be stunned if this 1699 beauty also exhibits ff................
just trying to assimilate this info so i can make an informed decision....
is that possible for a guy who studied fortran in college in 1974 ?????
dave m
Autofocus: phase detection

Nice applet there as well.

In addition, you can click the link to information on cross correlation.

Ray
02-18-2011, 08:10 AM   #664
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QuoteOriginally posted by Rupert Quote
I could be wrong......but I can't seem to find any K5 shooter here that has sent his camera to Pentax Service with a focus issue and received it back repaired/not repaired? There may indeed be a repair for this, I see that on the Nikon D7K Forum there are several reports of focus issues like the K5 that were repaired by Nikon, and the shooters were well satisfied.

Surely someone is going to try this instead of just going for a new body every time they get a bad focusing camera? Before I give up on the K5, I would like to hear from some that have actually given Pentax a shot at making a repair. We are assuming firmware, but it could be that all that is needed is some hardware fix or some tweaking at a Certified Service Center?
Regards

I still think this is a valid question and I still don't see a single soul that has given Pentax a chance to make a repair. It has happened with Nikon users, and they are now happy. It may not be a firmware fixable problem, and if so it will be necessary to send in your K5. Will someone please try this! It might be the Magic Bullet everyone seeks?
Regards!

02-18-2011, 09:01 AM   #665
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QuoteOriginally posted by Rupert Quote
and I still don't see a single soul that has given Pentax a chance to make a repair
i did give pentax a chance to repair my camera.... three months ago. Last week, finally i was promised free of faults replacement... free of stains, free of flash issue, free of tungsteen ff. I feel slightly cheeked, bought a camera with preorder - instead of taking a pictures i await solution.... and i read this forum hoping for some answers....
02-18-2011, 10:17 AM   #666
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QuoteOriginally posted by filorp Quote
i did give pentax a chance to repair my camera.... three months ago. Last week, finally i was promised free of faults replacement... free of stains, free of flash issue, free of tungsteen ff. I feel slightly cheeked, bought a camera with preorder - instead of taking a pictures i await solution.... and i read this forum hoping for some answers....
So what was the outcome of your experience? Did they just give you a new camera or make a repair? Tell us more specifics of your return?
Regards
02-18-2011, 10:30 AM   #667
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QuoteOriginally posted by Rupert Quote
So what was the outcome of your experience? Did they just give you a new camera or make a repair? Tell us more specifics of your return?
Regards
neither of what you mention.... im still waiting for replacement.... pentax uk service still awaits for replacement units to arrive.... as far as i know they did try to fix my camera - ordered the parts from Japan but apparently it was in vain. Technician manager who i tried to speak to, told me at first time that my camera connected via service terminal to diagnostic computer doesnt show any fault any deviation from specification everything is by the book. So i got into conclusion that ff under dimm light is up to specification
02-18-2011, 11:56 AM   #668
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QuoteOriginally posted by Ray Pulley Quote
Autofocus: phase detection

Nice applet there as well.

In addition, you can click the link to information on cross correlation.

Ray
Thank you for posting this. It greatly enhanced my understanding of the issues.

02-18-2011, 01:11 PM   #669
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QuoteOriginally posted by Ray Pulley Quote
Autofocus: phase detection

Nice applet there as well.

In addition, you can click the link to information on cross correlation.

Ray
Yup cheers for this. very informative !
02-18-2011, 05:06 PM   #670
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The Stanford applet is nice and entertaining. But IMHO lacks some fundamental details. Esp. when it comes to understanding limitations and what may go wrong.

In my own work, I prefer to cite Doug Kerr's classic 2005 paper for photographers:
http://dougkerr.net/pumpkin/articles/Split_Prism.pdf
(esp. Fig. 13 on p. 13).
02-18-2011, 05:32 PM   #671
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QuoteOriginally posted by Ray Pulley Quote
Thanks for sharing.
Falk already pointed to the real McCoy.

Did everyone notice the link to the "SynthCam" application for the iPhone? I started another thread about it.
02-18-2011, 05:52 PM   #672
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Yes, but...

QuoteOriginally posted by falconeye Quote
The Stanford applet is nice and entertaining. But IMHO lacks some fundamental details. Esp. when it comes to understanding limitations and what may go wrong.

In my own work, I prefer to cite Doug Kerr's classic 2005 paper for photographers:
http://dougkerr.net/pumpkin/articles/Split_Prism.pdf
(esp. Fig. 13 on p. 13).
Doug's paper is indeed informative, but you have to have used that funny thing called a split prism, which many newer photographers of the digital age have never seen...

The Stanford link will take you as deep as you want to go by following various links, and also includes the nice image of the typical PDAF light path in the camera box which is helpful for people to see why LVAF and PDAF may not agree. I think that you have posted a similar image of a split K7 but with regards to the sensor stain issue.

At the end of the day, I find it interesting that every digital Pentax body I have owned (all but the K7 and original IstD), tend to move towards FF in lower light.

You can search any forum and the internet in general and you will see much evidence of this being the case.

There has been lots of speculation about IR effects, and Pentax did incorporate a color sensor in the K7 and K5 for some reason, perhaps to try and sense when the light source contains more IR? However, I find it hard to believe that it would be cheaper and more effective to put a complete color-sensing sub-system in just to know when you might have high IR content rather than simply placing a good IR cut filter in the PDAF light path. I think that this system is mainly aimed at improving AWB.

Others have speculated that the issue is related to CA in the PDAF lensing elements, which, if true, is a different problem, but I am not sure why this would be so consistent as the light is reduced?

There is more to this than we know, but I am quite sure that Pentax and the other manufacturers do know whatever it is we are guessing about. What makes little sense to me is the fact that the slide to FF on all of my Pentax bodies has been consistent low light behavior. This is also a pretty well documented effect in other brands. Therefore it seems like adding some sort of offset table based upon meter reading and/or AWB setting would at least get us within the DOF in almost all cases where the lens itself did not start out in a heavy FF position in normal lighting (which would mean the lens would need adjustment).

Ray
02-18-2011, 06:27 PM   #673
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QuoteOriginally posted by Ray Pulley Quote
However, I find it hard to believe that it would be cheaper and more effective to put a complete color-sensing sub-system in just to know when you might have high IR content rather than simply placing a good IR cut filter in the PDAF light path.
Have you seen my post in which I explain why the AF system may "think" it obtained focus, while the image (the photographer is interested in) is not focused on the sensor?

The issue is that with real lenses you can have the green component of the image in focus while the red component is not or visa versa. I understand colour blind AF modules have their peak sensitivity within "green", hence the mismatch when the main image content is very red.

I'm also curious as to why low light would provoke a tendency to FF. Is that really the case?
02-18-2011, 07:37 PM   #674
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Yes - Not my Experience

QuoteOriginally posted by Class A Quote
Have you seen my post in which I explain why the AF system may "think" it obtained focus, while the image (the photographer is interested in) is not focused on the sensor?

The issue is that with real lenses you can have the green component of the image in focus while the red component is not or visa versa. I understand colour blind AF modules have their peak sensitivity within "green", hence the mismatch when the main image content is very red.

I'm also curious as to why low light would provoke a tendency to FF. Is that really the case?
I have owned at least 2 copies of all but 2 of the Pentax DSLRs (IstD and K7). All tend to move to FF as the light is reduced. You can search for this and you will find many posts about it going back to before this forum even existed, but the cause has always been thought to be tungsten lighting, which just so happens to also be the lighting used in many indoor low-light situations.

There has been a lot of speculation about the causes over the years, and fixes like adding a hot mirror IR cut filter have been tried, but the issue remains and seems worse in the K5 and the Kr.

What you are describing is simply CA, or chromatic aberration, and that cause has also been speculated upon over the years.

CA in the lens would not seem to me to be so consistent as all lenses have differing amounts and types of CA (I have more than a dozen lenses, mostly Pentax, but Tamron and Sigma as well and they ALL move to FF as the light is reduced).

CA in the PDAF optics would be consistent, however, and there is one very persistent advocate of this cause over at the other forums.

In my case, I tested many lenses in different light, reduced both daylight and tungsten light with ND filters on the lenses, used 3 different color filters over the lenses, used a LED light where I reduced the output of the light with the same lens using ND filters, and the only consistent result was a shift to FF at EV 3-4 with any color light.

For me, after all of this wasted time testing 3 K5s, I do not need any more convincing that the K5 has a consistent problem with FF at EV 3-4 or so. BTW, so does my K20, but it is a gradual shift and it stays just barely in the DOF at this light level, which works for most all of my indoor shooting situations, which are generally f5.6 and no lower than EV 2-4.

As for why? We may never know for sure.

Ray
02-18-2011, 08:18 PM   #675
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QuoteOriginally posted by Ray Pulley Quote
I have owned at least 2 copies of all but 2 of the Pentax DSLRs (IstD and K7). All tend to move to FF as the light is reduced.
So what are the chances of pentax fixing the FF on this model...?
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