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12-23-2007, 10:17 AM   #1
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Front Focus - K10D

Been lurking for awhile now, and finally took the plunge.

Recently bought the K10D that came with the Kit lens and bought the FA 50 1.4 and the new Pentax 18-250. I have noticed, what I consider, some serious front focuses issues with all three lenses.

The test below are all shot 50mm at 5.6.
Kit Lense 18-50


FA 50


Pentax 18-250


It becomes much more obvious when I used the 50mm at 1.4



In a real world application, I have taken a lot of pictures of my dog (she's an unpaid model) with all three lenses. I generally AF on her eyes and looks clear in the view finder. However her eyes are blurry in the resulting picture but the tip of her nose will be very clear especially with the 50mm 1.4 (See my Avatar).

Now the question I have, is this enough of an issue to send the K10D to Pentax for calibration? In your opinion will Pentax actually view this front focusing as an issue or is my camera within Spec?

Is there anything I can do here at home to "fix" this problem? I remember reading about the focusing screws on the bottom of the camera. Is this advisable or can I really mess up my camera by doing this?

Any help and advice you can give me will be greatly appreciated.

~Matthew

Edit fixed inline pictures


Last edited by BeerCur; 12-23-2007 at 10:31 AM.
12-23-2007, 12:45 PM   #2
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This has been discussed multiple times and I myself do not favour test like this. Other than the camera was really having FF/BF, there are 2 other reasons which might contribute to the problem. 1) The AF sensor might not be aligned 100% dead centre. That means the AF sensor might be pointing at something else. 2) Each AF sensor (11 total) covers quite a wide area and the camera might pickup anything to AF within this area, usually favours higher contrast, but you really have no say to this charasteristic. This also leds to the what seems to be BF problem when the camera locks onto the high contrast background instead of the subject in front in real world sitations.
12-23-2007, 01:26 PM   #3
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First, welcome to the forum Mathew. I don't necessarily agree with these tests also. Tungsten lighting and close focus don't always generate accurate results. However, in this case since you are seeing this effect in everyday shots, it probably is worth sending it in. As a dog shooter myself, this would drive me nuts.

Usually calibration issues show differently for different lenses. Are you using the center AF sensor, and recomposing? If you are, and since you are getting the same FF issue on all your lenses, I strongly suspect the center AF sensor is not in alignment.

Depending on how old your camera is, you might be able to talk your dealer into swapping it with a new body, but you would not have any guaranty that you would not experience the same issue. I'd give Pentax CS a call and get their advice. Whether it is lens calibration or AF sensor realignment, I'm sure they will take care of you.
12-23-2007, 03:12 PM   #4
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I use CF for AF. I do not think it's the lenses, as they all have the same issue.

I guess there is no really good test out there to test BF / FF. I have to use what is available.

I did a few more test
The following is the test chart perpendicular to the camera... aka hung on a wall and a picture taken. Incandescent light (No Flash)

50 at 1.4


50 at 2.8


50 at 5.6


50 at 13.0


50 at 1.4 My Dog, I believe around 40% reduction, Part 1... used 360 flash, center focus, with diffuser


50 at 1.4 My Dog, I believe around 30% reduction, Part 2... used 360 flash, center focus, with diffuser


I have Dog "Part 1" and "Part 2" the original images Here


Am I just being whinny? I just recently bought the Camera direct from Amazon. How is Amazon about returns of possible defective product?

~Matthew

Edit corrected ratio on last two pictures. (2)Additional information about pictures


Last edited by BeerCur; 12-23-2007 at 03:25 PM.
12-23-2007, 04:57 PM   #5
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The FA50 f1.4 is a bit soft at f1.4. Starts getting sharp at f2.0 and is very sharp at f2.8. Your crops show this. On your focus chart crops, at f1.4 it looks to be totally mis-focusing, the lens is not THAT soft. Is that result repeatable?

CF= Continuous focus or Center focus?

Your first dog pic, looks about right. It's a bit soft as I would expect from the FA50 wide open, the focus appears to be on his/her left eye, and everything in that plane is also in focus.

The second shot is a bit strange. The focus appears to be on his/her left eye, the eyebrow is sharp, although the eye itself is soft. The right eye is totally out of focus, and is in a plane slightly behind the left eye. At f1.4 you don't have much DOF. Looking at the full image, it almost looks like the lens is de-centered, although I've never heard of a FA50 having that problem.

Sorry, I can't help on Amazon. I've never had to return anything to them.
12-23-2007, 05:56 PM   #6
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Sorry, it's Center focus, and I took the following CF.S, no delay.

The test on the wall is repeatable.. this time with flash... 50mm 1.4

The PEF here

My dog again, With Flash... The focus is smack dab in the center,.. between the eyes...
Full Picture

Cropped

The PEF Here

~Matthew

edit Added the bold face comment regarding focus

Last edited by BeerCur; 12-23-2007 at 08:55 PM.
12-24-2007, 02:00 AM   #7
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Your FF pics look yellowish. If you took your pics under yellow light sources, this would be the main cause of your problem:-

RiceHigh's Pentax Blog: AF Accuracy's Dependency on Lenses and Yellow Light

Re-try the same test under daylight, you'll find the difference (even though the lighting levels are close).

So, before you get your camera "re-calibrated", just make sure it is working as it is supposed to be!

QuoteOriginally posted by BeerCur Quote
Been lurking for awhile now, and finally took the plunge.

Recently bought the K10D that came with the Kit lens and bought the FA 50 1.4 and the new Pentax 18-250. I have noticed, what I consider, some serious front focuses issues with all three lenses.

The test below are all shot 50mm at 5.6.
Kit Lense 18-50


FA 50


Pentax 18-250


It becomes much more obvious when I used the 50mm at 1.4



In a real world application, I have taken a lot of pictures of my dog (she's an unpaid model) with all three lenses. I generally AF on her eyes and looks clear in the view finder. However her eyes are blurry in the resulting picture but the tip of her nose will be very clear especially with the 50mm 1.4 (See my Avatar).

Now the question I have, is this enough of an issue to send the K10D to Pentax for calibration? In your opinion will Pentax actually view this front focusing as an issue or is my camera within Spec?

Is there anything I can do here at home to "fix" this problem? I remember reading about the focusing screws on the bottom of the camera. Is this advisable or can I really mess up my camera by doing this?

Any help and advice you can give me will be greatly appreciated.

~Matthew

Edit fixed inline pictures
12-24-2007, 03:18 AM   #8
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Wall chart: Kind of looks like camera shake. Assuming you had the camera mounted on a tripod, was SR turned off?

On the dog photo, either you've got front focus issues, or the center AF sensor is set lower in the frame than it indicates in the view finder. As Rice suggests, try the same test and photos in daylight. If you get the same results, it probably a misaligned AF sensor. You could also try setting AF to manual select, use a different AF sensor, recompose and see if you get the same results. If it focuses properly, that would confirm the problem is the center SAF sensor.

12-24-2007, 04:17 AM   #9
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I also have the FA50/1.4. At wide open, the depth of field is so shallow that I do get a fair bit of FF/BF problems and initially this drove me mad. Then I read in a magazine that 50/f1.4 lenses (be it Canon, Nikon, Pentax) should always be set to f2.0 or f2.8 to get an accurate shot so as to avoid misfocusing problems. A point that you might want to consider.

My K100D did exhibit some degree of FF before and I did send my K100D back to Pentax service centre and they did calibrate the body with all my lenses. I must say, they did really fix the FF problems I have before. According to Pentax service technical manager, our K100D and K10D can be calibrated with any nos. and any model of pentax lenses and the process is all done via computer plug into the USB port of the k100D/K10D.

Oh...another thing the service manager told me is that if by using flash, we get an accurate shot, then the camera do not have FF/BF problems. Hope this helps
12-24-2007, 08:39 AM   #10
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Thanks everyone for the information and advice. I'll follow-through with some more test and then figure out what to do when I get back from the Christmas in-law trip.

~Matthew
I'm, I'm not sick but I'm not well
And I'm so swell
To live this well
12-24-2007, 11:24 AM   #11
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With my Tammy 18-250mm and DA*16-50mm I've tried the same tests.
There are complaints on this forum of back focus problems with the 16-50, with my camera it seems to work fine for both lenses.

I guess the best thing to do is to have your camera callibrated.

- Bert
12-25-2007, 01:43 AM   #12
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I have the FA50mm 1.4, I do get photo like yours however I did test like yours with tripod and set camera with 2sec timer, my 50mm at 1.4 focus is right on... so I think it is me who rocking my body front and back and shaky hand. ( Don't have any problem with other lens tho, so I can't say if it is really your K10D has the problem or not, just that you should hold the camera really still when you are using f1.4 to 2.8)
01-27-2008, 01:50 AM   #13
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Hey guys,
I have a 50 1.4 as well. I do a lot of shooting at high ISO in less than idea light (clubs, restaurants,
etc) mostly just for fun. It is absolutely infuriating when I sit there and take 20 frames of my friends with the most brilliant bokeh backdrop of strung up christmas lights to find out later that even though I double checked every shot after shooting (I took the softness to be the dark lighting and high ISO) that every. single. shot. was out of focus. This is, of course, a result of the tungsten lighting thing. I'm not about to go scrounging around for 1.1 firmware so I can adjust my focus back and forth for lighting... are there any other solutions? Why hasn't this been adressed?
01-27-2008, 03:09 AM   #14
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Try taking advantage of your barrel markings. Measure the distance from your focal plane to your subject, and then try to maintain that distance. Keeping subjects within decent focus shouldnt be to difficult as long as you have adequate depth of field.
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