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10-26-2013, 01:49 PM   #1
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k-5 focus problems

After using K-5 for a while, I've decided that I cannot trust auto-focus sensor at all.
I've turned off the focus beep and trust nothing but my eyes anymore.
When I don't want to manual focus, I use live-view for perfect focus. I think something is wrong with my camera.

Any way I could fix this?

10-26-2013, 01:55 PM   #2
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Sounds like you may have front focus or back focus. You will need to test your camera and lens and mamę adjustments as needed - we have an article in the homepage with the steps you need to take.

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10-26-2013, 02:12 PM   #3
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Ricky, I am with you on this too. This year I took a bunch of really crappy photographs at Yellowstone by trusting the focus confirmation. When I got home I spent a day sitting in my backyard checking things out. I have a 40 year collection of various Pentax mount lenses for my camera, but only one auto focus lens. So I am trusting my eyes again too. It's what I have done for the last 45 years or so anyways.

I am having a bit of a dilemma though. I want the new K3 and the Sigma 50-500mm lens. Unless someone here gives me $1,500 I think that I can only get one or the other for now.
10-26-2013, 04:23 PM   #4
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Sorry to hear.
I love my K-5 (compared to my K-x it was a bit step up).

I had hit and miss focussing until I changed to fixed center point and fine tuned AF outdoors using focus charts.
Presume you have done this? If not it makes a big difference (did for me anyway).

10-26-2013, 10:33 PM   #5
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QuoteOriginally posted by RickyFromVegas Quote
After using K-5 for a while, I've decided that I cannot trust auto-focus sensor at all.
I've turned off the focus beep and trust nothing but my eyes anymore.
Are you experiencing issues in normal daylight?

If so, you may want to read my AF adjustment hints. You need to set aside a lot of time to get this right, though. Improper fiddling, can make things worse.

If your AF troubles occur in low-light and/or with odd colour temperatures then you may be suffering from the K-5's AF issues. The K-5 II did away with these issues.

A common source of AF woes is that the AF areas the camera uses to obtain focus is larger than most people think. It is a lot larger than the small red focus indicator you see in the viewfinder. You need to aim at a target until you get visual confirmation that the AF system focused on the detail you intended to capture (as opposed to something nearby in the 2D image space, but that is quite a bit away in the 3D space).
10-29-2013, 08:14 PM   #6
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Cross posted in large part from another thread:

When using the center AF spot, keep in mind that:
- The ends of the center horizontal and vertical AF sensors '+' extend almost to the center circle ( ) markings of the original equipment focusing screen.
- Any line of greatest contrast with in the ( ) is going to grab the attention of the sensors, regardless of whether it is the intended subject or not.

As a good exercise:
Tape a penny or other dark coin to a blank bright contrasting wall. Set the camera on AF center spot- then stand back a distance, zoom in and pan the camera from the side, top and bottom moving towards placing the penny in center position. Watch for when and where the camera can confirm focus. Then play with this to find the edges of actual sensor + cross hatch lie relative to the ( ) markings.

Also, I’d recommend updating your firmware to at least V1.14. I’ve been using it without any issues since it came out. There is a possibility that it improves performance slightly- however I don’t think any of us have proven it (although is perhaps suspected). Naturally updating firmware isn’t going to solve the issue entirely, but it may help.

Personally, I believe that somehow the establishment of a solid and accurate focus foundation plays a key role in the final outcome of AF performance with the K-5. This is referring to AF performance in general usage and not the reported incandescent lighting issue.

The fundamental problem of course is how to establish that foundation (e.g. via AF fine adjustment or other means).

I’ll come back with some comments based on my personal experience with AF fine adjustment shortly. A purchased system is surely a good route to go, but it is also possible to do it using crude yet equally effective techniques.
10-29-2013, 08:31 PM - 1 Like   #7
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I’d like to echo that my experience has been similar to that of kiwi_juno.

I believe your experience might change if you can establish a more accurate AF fine adjustment. And I also believe that the K-5 AF may hunt much less once an accurate fine adjustment is established. Now I very seldom lose shots due to poor focus.

Look over the details found at the previously mentioned link provided by Class A. Based on my personal experience or research I would only make a slight adjustment to that info:
- For zoom lenses, I understood that manufacturers often recommend doing AF fine adjustment at of the zoom range (e.g. physical lens rotation or focal length). However, by doing it yourself you could elect to modify this according to other strategies (e.g. most important focal length or best fit compromise based on the variation across the zoom range as measured at each focal length marking).

Based on my personal experience I recommend the following:

With exception of purchased systems, skip trying to use a (albeit theoretically correct) 45 degree angle style lens chart or test target. Create yourself a simple large flat panel target set-up for which you shoot with the camera pointed perpendicular to the target:
- Use a center AF targeting concept similar to the 45 degree angle style (e.g. a thick single high contrast black line or shape passing through center of the target surround by a large white field with no contrast). This is the most critical component of the test target. It must extend past the edges of the central AF sensor marked by ( ) on the OEM focusing screen. And the camera must be set to center point only AF mode.
- Near the edges that surround the no contrast center field- place high contrast black details in a symmetrical arrangement above, below and to each side.
- Symmetry of the edge details should occur between the each diagonally opposing corner. This will enable your image analysis to automatically account for minor misalignments in which the camera may not be perfectly perpendicular to the test target.
- The edge details could be various sized enlargements from the USAF test target patterns or varying sizes of text fonts or numbers. I used a combination, but in the end I felt like a stream of varying text fonts and sizes proved more useful.

To create the target, I simply stapled printouts from my home computer onto a 4x4 foot sheet of plywood. Use daylight sun or open shade lighting and a lens setting for minimum depth of field. Depending on the lens, I used a camera to target distance of about 5 to 17 feet.

For analysis:
- Display two images side by side and look for the AF fine adjust setting that shows greatest sharpness.
- Zoom in to evaluate the finer edge details.
- If focus seems poor in one quadrant be sure to check its opposing quadrant. It doesn’t matter in which quadrant an image is sharpest- only how sharp its sharpest quadrant is.

In between each test shot for a new AF fine adjust setting:
- Always turn the camera away (e.g. rotate or tilt the tripod head) and refocus on a fixed point that is either significantly closer or further than the actual calibration target.
- Focus at least once on this alternate point before returning to and focusing on the calibration target.
- This practice greatly improves the reliability and repeatability of the test shots until AF fine adjustment has been completed.
10-30-2013, 01:36 AM   #8
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+1 focus fine tuning needed

Check ur focus everyday and adjust if needed. When light change then focus maybe change also...maybe not, but can not trust that really.

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