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02-12-2010, 01:14 PM   #16
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Consider the size of the AF point as well

I played with my K100D a long time ago to understand the AF better.

I took a blank piece of paper, drew a black line on it with a marker, then using AF center point only, started to see how far off the line would the camera still focus.

It turns out the focus "point" is a focus "area" that as I recall, overlaps with the adjacent focus "points". Especially the cross type sensors in the middle. the two points at the edge were much less sensitive.

Go try it. Its illuminating.

-k

02-12-2010, 01:29 PM   #17
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QuoteOriginally posted by GeneV Quote
I do understand the the optometrist has narrowed down the possibilities before we get to the "better or worse" part, but I would think that we have done the same narrowing when the camera focuses on the flat surface. The front or back focus part is (hopefully) fine tuning.

What I honestly don't know about the red dot is whether the dot will be off from the point of focus by the same amount and in the same direction always, or whether we are talking about a margin for error. Also, can't the dot just as easily be off from the true point of focus laterally or diagonally as well as just in distance?

For example, if I put the red dot on the tip of a dog's nose to focus on that point, if the camera is actually focusing on a point left or right or diagonally of the nose, I will miss the focus and the photo will appear to have a back focus problem. I'm probably just being dense, but I am not seeing how the inclined scale would help me tell if I am focusing on the wrong point in the scene because the dot is off.
If I read your question correctly, you are interpreting that if the red dot is not at the exact sensor location, using the sloped ruler will make the focus correct by taking into account what ever offset of sensor to red dot there may be, because you will correct for that when making the adjustment.

Unfortunately, that would only be correct if everything you photograph is at the same incline.

I find more that things are usually perpendicular to the axis of the lens than at a defined angle.

Perhaos GoreManX can comment if this is a correct interpretation
02-12-2010, 09:43 PM   #18
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QuoteOriginally posted by GeneV Quote
What I honestly don't know about the red dot is whether the dot will be off from the point of focus by the same amount and in the same direction always
it's not that the dot is "off" - it's just that the actual sensor encompasses the dot but also a lot more. Meaning, you can put the dot on a dog's nose, but if the eye or ear or collar is within range of the much larger AF sensor, the camera might legimitately focus on that that instead. It's not like it always focuses 3mm to the left (or whatever) - it's that it *chooses* where to focus within a larger region whose cneter (more or less) is the dot.

QuoteQuote:
I'm probably just being dense, but I am not seeing how the inclined scale would help me tell if I am focusing on the wrong point in the scene because the dot is off.
I don't understand what you are asking here. The only way to do a controlled focus test is to make the there is one and only one thing for within range of the focus sensor. That means you can't have anything else "near" the dot. Only if managed to set up a test in which this is true do you have any ide where the camera tried to focus, and only then can you then try to compare where it tried to focus with where it actually focused. The point of an inclined plane is to make the latter determination, but you still have to first make sure the camera has focused where you wanted it to. that's why the fnacy chart shown has a vertical component (the actual target) as well as the inclined component (the scale that shows you how the camera did). Other focus tests combine these by making sure there is an area *within* the inclined plane that is larger than the focus sensor but has just one thing to focus on within that area.
12-18-2014, 01:06 PM   #19
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I am aware that this thread is rather old but I still want to make a reply.

I'm having some 'issues' regarding this exactly and have started a thread discussing it. Some people seem to discard it and just assume it's user error.
I consider this thread as a confirmation of what I've been stating, and would like to 'bump' it, so that it's seen/read, and those who say there's no issues with focus inconsistency with the K-5 II, blaming it on user error, might retract, or acknowledge that in fact, there may be some reason other than simple user error...
Thank you for this.

Kind regards.

Paul

12-18-2014, 05:11 PM   #20
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I'm speaking purely from my own experience here and I am going to be blunt.

Pentax AF is not great. It's quirky and takes some learning to get it to work the best it can. Whether that fact makes out of focus shots "user error" or camera error leaves lots of argument room for brand zealots on the internet but it doesn't make the task of getting in focus pictures any easier. Once you know how it works, it works well enough. Until then it's not good. In my experience it's far easier to pick up a canon or nikon dslr for the first time and get in focus shots than it is with a pentax.

Honestly, Nikon and Canon AF, especially on their high end bodies, absolutely destroys Pentax in the AF department.

And a bunch of people here are going to read that and post their amazing once-in-a-life-time shots of a perfectly in focus eagle pick-pocketing a bear while simultaneously catching a salmon and looking generally *awesome* and they will proclaim that there's nothing wrong with Pentax AF because they got that shot once. But one amazing shot, or even a few, doesn't answer the thousands of almost in focus shots that argue against Pentax AF being "fine".

Another thing that clouds the issue is that everyone has a different threshold for what is perfect, good enough, and just not good enough. People post shots here all the time that they are perfectly happy with that I would never show anyone because they are so imperfectly focused. I'm sure there are people that look at my shots and think the same thing.

If you don't want to spend a long afternoon learning how the AF system works and a few months honing that knowledge I can hardly blame you. I can tell you that, if there's nothing wrong with your hardware, after some practice you'll be taking perfectly infocus shots all the time but that won't help you now.

And, in the beginning it's damn near impossible to tell if there *is* a problem with the lens or camera. It took me two weeks of using my new FA 31 before I was able to grasp exactly what sort of adjustment it needed and I've been shooting my K5ii for 18 months or so. If I had got the camera and lens new together I would have had no idea what was going on and I would have been extremely frustrated.

The thing is that no camera or system is perfect, you have to pick the system whose strengths align with your needs. If perfect like 90% of the time autofocus is a non-negotiable thing for you then Pentax probably isn't a good choice. The Pentax system has a lot of strengths going for it but sadly AF isn't one of them at this time. They know it and have been working on it, as witnessed by the K3's improved AF. Hopefully that will continue to develop and in a few years AF will be fine or even a brand strength.
12-18-2014, 05:35 PM   #21
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QuoteOriginally posted by Homo_erectus Quote
Honestly, Nikon and Canon AF, especially on their high end bodies, absolutely destroys Pentax in the AF department.
Nikon AF is far ahead of the rest of the pack and current Pentax (K-3) is equivalent to Canon. At least according to the complaints I get from my Canon shooter friends. Canon is quick to lock but lacks precision. Pentax is slower, but more accurate.
QuoteOriginally posted by Flugelbinder Quote
those who say there's no issues with focus inconsistency with the K-5 II, blaming it on user error, might retract, or acknowledge that in fact, there may be some reason other than simple user error...
I am familiar with the zombie thread you have bumped and I doubt that it will provide the effect you desire. It discusses some of the same factors that were brought up on your other thread. I don't believe your focus issues are user error per se, though I do believe you choose to ignore the best counsel the more senior users of this site can offer you on the limitations of AF in general, reasonable expectations, and how to troubleshoot and tune your camera.

At one point you indicated that your K-5 IIs may be a poor match for you. I would grant that. You may want to consider purchase of a Nikon D5300 instead, then you will have the benefit of best-in-class AF at a similar price point to your Pentax.


Steve
12-18-2014, 05:46 PM   #22
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Thank you!
For two days now I've been pulling hairs out... This afternoon, thinking it might have been the extremely low light I was (purposely) working on, I popped the in camera flash.
Oh my lord, what a mess... Front focus, back focus, a few inches off, almost a mile off, it's just completely unpredictable, for me at this stage, as you mention, but it's just all over the place...
A quick example, with a +1 adjustment, wont bother anyone with the 100 + shots wasted...
Focus on the closet, facing the camera, underneath the exhaust fan, how does the camera "chooses" to focus on the fr*#ng faucet?!? Also use error???

---------- Post added 12-18-14 at 05:49 PM ----------

QuoteOriginally posted by stevebrot Quote

At one point you indicated that your K-5 IIs may be a poor match for you. I would grant that. You may want to consider purchase of a Nikon D5300 instead, then you will have the benefit of best-in-class AF at a similar price point to your Pentax.


Steve

Very kind of you...



By the way, I'm not such a newbie, although not a very experienced one, I've been doing this for two and a half years and it's the first time/camera that has this kind of behavior... Nikon 3100-D90-D7000-Fuji X-E1-Pentax K-5 II
Attached Images
View Picture EXIF
PENTAX K-5 II  Photo 

Last edited by Flugelbinder; 12-18-2014 at 05:57 PM.
12-18-2014, 06:30 PM   #23
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QuoteOriginally posted by Flugelbinder Quote
how does the camera "chooses" to focus on the fr*#ng faucet?!?
Exif indicates center point fixed with focus attained at the center (vertical) point. That would be the center of the wood-grained rectangle visible below the bottom edge of the range hood. Despite this the plane of focus includes the faucet handle at left and the paper bag at right. Assuming you did not take a half step back after locking focus, the system is obviously severely front-focusing. The +1 adjustment may be partially to blame, though it is hard to tell. Exif also indicates tungsten lighting in the room which may also contribute to front focus.*

Have you been in conversation with your dealer or with Ricoh/Pentax in regards to these issues?


Steve

* The AF system in the K-5 II/IIs (SAFOX X as in the K-3) is not supposed to be affected by tungsten light.


Last edited by stevebrot; 12-18-2014 at 06:45 PM.
12-18-2014, 06:43 PM   #24
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QuoteOriginally posted by stevebrot Quote

Have you been in conversation with your dealer or with Ricoh/Pentax in regards to these issues?


Steve
Steve, unfortunately, that is my biggest problem. Since I'm working with a very limited/strict budget, to save a little over 100 bucks, I bought the camera used, to a forum user (RAART). I have asked him twice, very politely, and explained the situation even referring the threads started about the matter, but he's been unresponsive...
12-18-2014, 06:47 PM   #25
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QuoteOriginally posted by Flugelbinder Quote
This afternoon, thinking it might have been the extremely low light I was (purposely) working on, I popped the in camera flash.
Whether you use flash or not does not affect how well the AF system works.


Steve
12-18-2014, 06:48 PM   #26
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QuoteOriginally posted by stevebrot Quote

...The system is obviously severely front-focusing...

...The +1 adjustment may be partially to blame, though it is hard to tell..




Steve

* The AF system in the K-5 II/IIs (SAFOX X as in the K-3) is not supposed to be affected by tungsten light.
I've been saying this for the past 2 days. Sometimes (also have examples) it back focuses, sometimes focuses closer, sometimes further... It's almost like the camera is in auto instead of single....... It's becoming really frustrating...

*Yes, I have read all about it and certainly did not expect this... At all!!!
12-18-2014, 06:53 PM   #27
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QuoteOriginally posted by Flugelbinder Quote
I bought the camera used, to a forum user (RAART)
That user was browsing this thread a few minutes ago. Perhaps you will get a response.


Steve
12-18-2014, 07:09 PM   #28
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I'm sure he's aware of my 'problems'... I have asked him the same day I bought the camera... Would love to see some etiquette from his end...
Have never had an issue with used equipment before, until now. Bought a lens the same day, didn't like the way it was not sharp (actually thought the problem would be the lens, but am not sure anymore), called the seller and he was happy to take it back... Etiquette...


---------- Post added 12-18-14 at 07:39 PM ----------

Still regarding the 'tests', the shot after that, I turned to the living room, focus on my baby girl - half press the shutter twice to ensure it's properly locked - and it back focuses on the window...
Should I just throw it out the window?

I have no idea what type of human being he might be, nut in the spirit of the season at least, I truly hope he reconsiders.

---------- Post added 12-18-14 at 07:50 PM ----------

Wish I had another lens to be able to confirm if the problem is indeed the lens, as posted above by a couple of users...

Last edited by Flugelbinder; 12-18-2014 at 07:39 PM.
12-18-2014, 08:34 PM   #29
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I have already contacted B&H, inquiring about returning the 35...
Paul, if you're reading this, please acknowledge my request and do the right thing...
12-21-2014, 09:38 AM   #30
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QuoteOriginally posted by Homo_erectus Quote
I'm speaking purely from my own experience here and I am going to be blunt.

Pentax AF is not great. It's quirky and takes some learning to get it to work the best it can. Whether that fact makes out of focus shots "user error" or camera error leaves lots of argument room for brand zealots on the internet but it doesn't make the task of getting in focus pictures any easier. Once you know how it works, it works well enough. Until then it's not good. In my experience it's far easier to pick up a canon or nikon dslr for the first time and get in focus shots than it is with a pentax.

Honestly, Nikon and Canon AF, especially on their high end bodies, absolutely destroys Pentax in the AF department.
Speaking from my not really big experience, I get in/out focus ratio on moving subjects pretty much the same with either camera I use: Canon SL1, Pentax K200D, or K5IIs. Manual, or AF does not make much difference in ratio. So, I assume it's not the camera's issue, but mine.
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