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04-28-2008, 09:37 AM   #1
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Backfocus/frontfocus on K10d?

I became the proud owner of a Pentax K10d in Janurary, my first DIGITALL SLR. Being experienced in regular SLRs but totally new to digital photography I just can't tell which "quirks" are due to the camera and which are due to my inexperience (or even to "unrealistic" expectations)

That being said, I would like to know if there is a good and standard way to TEST for back/front focusing problems. Tho I am sure experience will tell, I would like to be certain while I still have the chance to get it taken care of under the Pentax warranty.

I have heard that some of the earlier K10d revisions had back focusing problems; checking the revision # on my camera I found it to be 2.1 ( which is newer than rev.1.1 which was reported to have the backfocus problem, but much older than the current revision 8.1)

NOTE: If I do have any focusing issues, they don't seem obvious (or at least obvious to me), and I admit the way I've been testing the camera is often worse case scenario: aperture fully open, or close to it..sometimes,but not often, and trying to focus on a specific detail.. Such as a lose thread of yarn, a wick, the beak of a mounted bird, etc.

Again, I really haven't had any obvious misfocusings, but sometimes when I try to "test the envelope" as mentioned above I just cant measure the results consistently. If I am focusing on a candle wick that's a couple inches in front of a birthday card (or other high contrast object) and I hear the "beep" an see the focus indicator light up... I take the picture and sometimes I get the WICK in perfect focus sometimes it's the card...again.. Am working with a very small DOF here ON PURPOSE.

As always, thanks advance for sharing your Pentax wisdom

04-28-2008, 12:14 PM   #2
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Nikon D70 Focus Chart

It will answer your questions.
04-28-2008, 10:21 PM   #3
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Geekybiker...

Thanks for the link. The test was very helpful and it seems I may have somewhat of a front focus issue.

It only seems to occur on my SMC-A 50/f2.0 prime lens tho, but this may be because my other lenses don't me to get such shallow DOF. Or Could it be because the k10d doest work that well with old manual lenses. A friend of mine said something about digital SLR not liking lenses NOT made specifically for digital cameras ( she uses a



After running the test ... I did a modified test of my own... these are my results:



04-28-2008, 10:42 PM   #4
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You have a mirror, prism, or focusing screen problem if that was shot with an A series lens. Front/Back focus is an AF problem. The K mount specification doesn't allow for variance in the flange to focal plane distance, so it is a camera body quality control problem, not an "it doesn't like manual focus lens" problem.
These cameras are not built accurately enough to withstand the scrutiny that people put the images to, if they were, they would cost a whole bunch more money.

04-29-2008, 06:34 AM   #5
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QuoteOriginally posted by Wheatfield Quote
You have a mirror, prism, or focusing screen problem if that was shot with an A series lens. Front/Back focus is an AF problem.

dresden_phoenix, that is what I tried to tell you in your other thread. I dont think the BF/FF issue actually applies to manual focusing, unless you are strictly following the BEEP signal, i believe.



Either you could have a focusing screen problem OR you are not focusing correctly. Hopefully your camera is fine and you just need to learn how to manually focus.

I do have 3 manual lens and only the Kit lens as AF. I am planning on buying a split screen to facilitate the manual focusing task.


Later


BB
04-29-2008, 09:25 AM   #6
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QuoteOriginally posted by Wheatfield Quote
You have a mirror, prism, or focusing screen problem if that was shot with an A series lens. Front/Back focus is an AF problem. The K mount specification doesn't allow for variance in the flange to focal plane distance, so it is a camera body quality control problem, not an "it doesn't like manual focus lens" problem.
These cameras are not built accurately enough to withstand the scrutiny that people put the images to, if they were, they would cost a whole bunch more money.
That is the lens i first noticed my problem with, the A50. I focused by my eye and ignored the beep.

Pentax has not returned any of my messages re the mirrior or focus screen concerns.

BTW welcome aboard.
WW

Dave
04-29-2008, 10:21 AM   #7
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BBear.. yeah this thread got split ... sorry.

So what you are saying is that I need to adjust the diopter?
I tried that a while ago, when it seemed that when things looked focused through the lens ( when i was using purely manual focusing) yet it would take blurry picture. I played around with the diopter settings and all that happenned was that the image through the viewfinder would ALWAYS seem out of focus and so would the read out info in the view finder. So I figured it wasnt the dioter for sure.

I dunno why , but it seems dificult to gauge focus with this digital by eye( as oposed to my film camera) .. it just doesnt seem like either A) I can see clearly enough OR B) that what seems fairly in focus is actually slightly blurred at 100% enlagement on the screen. Anyway, that's why I am using the "beep"/ focus indicator to improve the focus in my pics.

Thats why i started looking into BF/FF issues. I can get some what decent exposures, by COMPENSATING for the focus distance error . I would just hope I would be able to TRUST the read outsof my equiptment. I mean if this is how a digital camera operates , fine. If it's my error.. I would like to know what I AM doing wrong ( what I have to do different from film) .. BUT if it's the camera... I would like it taken care of, since it still under warranty.
04-29-2008, 11:05 AM   #8
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QuoteOriginally posted by dresden_phoenix Quote
Anyway, that's why I am using the "beep"/ focus indicator to improve the focus in my pics.

I am not sure about the focus indicator.. I wont say it doesnt work for sure because I am also new to the K10D and I actually only played with the focus indicator against my manual lens for a bit. But I had the impression I'd better do it 100% manually than relying on the focus indicator.


With that in mind, whenever I am using one of my manuals, I place the focus selector at MANUAL and I shoot whenever I feel comfortable.


I do have the SMC-A f/2.0 so that'd give me some narrow DoF and I am willing to test the focus indicator a bit more.


Actually, I am interested in knowing if my FA is sharp when using FA lenses as well... I was planning on doing the AF soon...



Later

BB

04-29-2008, 02:18 PM   #9
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If its only MF lenses you're having a problem with most likely you just need to adjust your eyepiece. put the cap on and adjust it so the led readout is as sharp as possible. If you're using AF to confirm the MF focus, it sound more like a lens problem than a camera problem.
04-29-2008, 05:14 PM   #10
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If you are using the auto select exposure point, the camera has operated correctly in accordance with its programming. The camera selects the focus point with the nearest subject with hard contrast. Set the camera to the center point only.

Next, to set the eyepiece, I use the lines in the focusing screen rather than the LEDs. Point the camera at the sky, or a white wall, and move the eyepiece diopter adjuster so that the engraved lines on the focusing screen are as sharp as possible. It is often easier to do this with the eyecup removed.

Now try focusing on the boxes and watch carefully the area at the square red focus point indicator, while listening for the beep, or watching for the indicator in the viewfinder, or both.

If the indicator disagrees with the screen, your camera needs adjusting. If it does not, then your technique needs adjusting.

Enjoy your camera - it's a keeper!
04-30-2008, 06:03 PM   #11
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I must admit I don't have a MF lens. However my experience with manual focusing suggests that the focus indicator or beep is not accurate enough to nail precise focus. Neither is the matte focusing screen good enough particularly when using a wide angle lens. Manual lens usually has a much longer focus throw than AF lens so should make focusing somewhat easier. My opinion is that the K10D or most DSLRs is simply not very MF friendly.
05-01-2008, 10:32 PM   #12
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Following up:


I posted this in another thread.. but just in case it helps some future Pentax user...



Jeffkrol,
you were right.

For the longest time I was thinking that where the red box lit up that was EXACTLY the point where the camera was focused on. With new mindset I took the same photos again, using center focus, this time taking into account that the focus would be the "point" of HIGHEST CONTRAST between the "( + )" rather than where the red box popped up. I haven't tested long distances. BUT for the 1-12' range it was DEAD ON 100% of the time, with BOTH my DSC-A series and DA-series lenses. Also Manually focusing or using AF-S mode worked equally well.

Some subjects were harder than others, of course. But I know that it's because some subject's point of highest contrast are harder to find than another's. Also... MIND THE SHADOWS!!!

It now also stands to reason why it's HARDER "hit focus" using wider lenses.. simply ... there is more STUFF between the "( + )" area thus more possibility to confuse the camera... but really not that much of a problem in MF.

THANK YOU ALL for all your help in helping me understand my camera and making it seem a bit more predictable.
05-02-2008, 12:13 AM   #13
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QuoteOriginally posted by dresden_phoenix Quote
Geekybiker...

Thanks for the link. The test was very helpful and it seems I may have somewhat of a front focus issue.

It only seems to occur on my SMC-A 50/f2.0 prime lens tho, but this may be because my other lenses don't me to get such shallow DOF. Or Could it be because the k10d doest work that well with old manual lenses. A friend of mine said something about digital SLR not liking lenses NOT made specifically for digital cameras ( she uses a



After running the test ... I did a modified test of my own... these are my results:




Exactly the problem I was having. While sitting on the floor, shooting up at the model and double focussing on her face, her feet would be tac sharp and her face would be out...HHHHHEEELLLPPPP...Thank goodness the K20D rectified this problem. My K10D's are in being revised.

Ben

Ben
05-02-2008, 01:06 AM   #14
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QuoteOriginally posted by Wheatfield Quote
These cameras are not built accurately enough to withstand the scrutiny that people put the images to, if they were, they would cost a whole bunch more money.
Alas, if that's true! K10D costs a lot of money to have such a severe focus problem because of mechanical toleramces (it doesn't take to much scrutiny to see it).
I couldn't believe that's the case here!
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