[neokind]

Hey all,

It took me a while, but after more than a year of using my K3ii, or a little more than a year ago, I realized that a lot of my shallow DOF pics were back focused. So, I did some googling, bought a lens calibrating scale, and tried to dial in each lens. The problem was, that even at +10, they were still focusing at -3cm on the scale I used. And this wasn't one particular lens, it was all of them. Frustrated, I started to just manually focus more. Now, I've been shooting a lot more and the backfocusing has been more of a nuisance. I pulled out the scale again, did some more reading, saw that someone suggested a global +10. I did it. Still back focusing. Somehow, though, I'd missed a step that suggested shutting off shake reduction. Suddenly, my lenses were dead on at a global +10. That's sort of good, I guess. But what's the deal? It's really frustrating, and I'm well out of warranty so it's not like there's an inexpensive solution. Are there other things I should consider doing? I'd like to use BOTH AF and SR simultaneously. Sheesh. I'd love suggestions.

Thanks!

[W.j.christy]

Shallow depth of field and back focusing you say?

A little more information about your shooting style and the test method used to determine the front/back focusing might help direct folks to a solution for you. Maybe address the use of the a tripod and typical aperature in general shooting style and your methodology for focusing testing such as if you used a tripod during your focus testing. Also, perhaps, include if you were able to compare pictures using the contrast detect v.s. phase detect focus methods as contrast detect is very accurate but slow and phase detect is faster but not always accurate.

However, most of my experience with shallow depth of field relies on the use of a tripod to keep the whole rig steady and that also means that the SR is off. With the shake reduction on while on a tripod it can cause some undesirable effects, though others may be best to state whether your particular issue is related.

[Adam]

Hey all,

It took me a while, but after more than a year of using my K3ii, or a little more than a year ago, I realized that a lot of my shallow DOF pics were back focused. So, I did some googling, bought a lens calibrating scale, and tried to dial in each lens. The problem was, that even at +10, they were still focusing at -3cm on the scale I used. And this wasn't one particular lens, it was all of them. Frustrated, I started to just manually focus more. Now, I've been shooting a lot more and the backfocusing has been more of a nuisance. I pulled out the scale again, did some more reading, saw that someone suggested a global +10. I did it. Still back focusing. Somehow, though, I'd missed a step that suggested shutting off shake reduction. Suddenly, my lenses were dead on at a global +10. That's sort of good, I guess. But what's the deal? It's really frustrating, and I'm well out of warranty so it's not like there's an inexpensive solution. Are there other things I should consider doing? I'd like to use BOTH AF and SR simultaneously. Sheesh. I'd love suggestions.

Thanks!

I'd send the camera in for AF calibration, which is what you should probably have done while still under warranty. I don't think it would be too costly, and it's likely worth it if you plan to hang on to the camera for a while.

I'm not sure how/why SR would affect the AF accuracy, though. Could it be technique-related? Or perhaps there's actually a problem with the SR system in your camera? That might be another story, repair-wise. In any case, re-testing the camera carefully, then contacting Precision would be a good first step IMO. Good luck!

[neokind]

To clarify, my testing is done on a tripod, using LV, and an IR remote shutter trigger. I'm using aperture priority, set wide open (1.8, 1.9, 2.8, or whatever the lens I'm testing allows) I'm using a 5x5" target in line with 0 on the DSLRKit calibration scale. I've also used the DSLRKit scale and target on its own with the same results. I've found that with this setup, and SR off, it focuses correctly (multiple attempts, starting with the lens out of focus both directions) when I am NOT using LV. However, using LV, it back focuses consistently. If I AF a second time before releasing the shutter, it is correct.

[W.j.christy]

To clarify, my testing is done on a tripod, using LV, and an IR remote shutter trigger. I'm using aperture priority, set wide open (1.8, 1.9, 2.8, or whatever the lens I'm testing allows) I'm using a 5x5" target in line with 0 on the DSLRKit calibration scale. I've also used the DSLRKit scale and target on its own with the same results. I've found that with this setup, and SR off, it focuses correctly (multiple attempts, starting with the lens out of focus both directions) when I am NOT using LV. However, using LV, it back focuses consistently. If I AF a second time before releasing the shutter, it is correct.

Interesting. So its good when you are using phase detect (view finder) and back focusing when using contrast detect (live view) on a tripod. Does it back focus when you have the shake reduction on when using the veiw finder on the tripod (i know you shouldn't do this but just for reference....)

I have heard of live view requiring a press or two of the AF butting to get the image in correct focus so this may be something inherent in the camera. If I may make a recommendation, when focusing for shallow depth of field using live view, turn on focus peaking (if you haven't already) which will outline the object that is in focus in white lines. Also, pressing "ok" during focusing will magnify the image when using live view and again outline the portion of the image in white that is in focus. I have found this to be a life saver when doing stuff with shallow DOF.

[stevebrot]

To clarify, my testing is done on a tripod, using LV, and an IR remote shutter trigger. I'm using aperture priority, set wide open (1.8, 1.9, 2.8, or whatever the lens I'm testing allows) I'm using a 5x5" target in line with 0 on the DSLRKit calibration scale.

AF fine adjustment does not apply to Live View (CDAF). It is limited to the viewfinder (PDAF) focus system.


Steve

[neokind]

Interesting. So its good when you are using phase detect (view finder) and back focusing when using contrast detect (live view) on a tripod. Does it back focus when you have the shake reduction on when using the veiw finder on the tripod (i know you shouldn't do this but just for reference....)

I have heard of live view requiring a press or two of the AF butting to get the image in correct focus so this may be something inherent in the camera. If I may make a recommendation, when focusing for shallow depth of field using live view, turn on focus peaking (if you haven't already) which will outline the object that is in focus in white lines. Also, pressing "ok" during focusing will magnify the image when using live view and again outline the portion of the image in white that is in focus. I have found this to be a life saver when doing stuff with shallow DOF.

I always use 'OK' to zoom when doing shallow DOF work on the tripod, since I've been less than impressed with the AF. I wasn't aware that focus peaking outlined the focal area when in LV. I'll give that a shot to see where it's focusing. Thanks.

[maw]

It took me a while, but after more than a year of using my K3ii, or a little more than a year ago, I realized that a lot of my shallow DOF pics were back focused. So, I did some googling, bought a lens calibrating scale, and tried to dial in each lens. The problem was, that even at +10, they were still focusing at -3cm on the scale I used. And this wasn't one particular lens, it was all of them. Frustrated, I started to just manually focus more. Now, I've been shooting a lot more and the backfocusing has been more of a nuisance. I pulled out the scale again, did some more reading, saw that someone suggested a global +10. I did it. Still back focusing. Somehow, though, I'd missed a step that suggested shutting off shake reduction. Suddenly, my lenses were dead on at a global +10. That's sort of good, I guess. But what's the deal? It's really frustrating, and I'm well out of warranty so it's not like there's an inexpensive solution. Are there other things I should consider doing? I'd like to use BOTH AF and SR simultaneously. Sheesh. I'd love suggestions.

Hi all,

Follow these guidelines, last summer I calibrated some lenses and the correct procedure is this one. (regardless of the calibrator brand in this case I used SpyderLens Cal)

1. Set up
Position the SpyderLENSCAL as shown below, with the main target vertical and ruler “0” mark aligned with the center cross-section of the target.
Make sure the SpyderLENSCAL is level by placing it on a flat surface, mounting it on a tripod or on a light stand with a bubble indicator.

2. Next,
Set up your camera and lenses by enabling autofocus, turn off the stabilizing function (for Pentax, Shake Reduction), set the aperture to the largest f-stop (lowest number) on the lens with the lowest native ISO setting. If you are calibrating a zoom lens, set it to its longest focal length.

3. Make sure your camera and SpyderLENSCAL are 25-50 times the focal length apart. They should always be at the same height, with your lens and the SpyderLENSCAL target parallel to your camera's sensor plane.

4. Take Photo
Aim your lens at the center of the board on the SpyderLENSCAL target. Use the center autofocus point and capture an image. Use the self-timer or a cable release so you do not introduce any vibration.
(Do not use live view to focus and capture the image of the target)

5 – Evaluate and Adjust
View the image of your SpyderLENSCAL target on the camera screen or even on your computer’s monitor. Zoom in on the ruler to evaluate the point of sharpest focus.
If the sharp focused mark is not “0”, enter the autofocus correction menu on your camera (this can be found in your camera's manual) and select “adjust by lens”. When the mark of sharpest focus is above “0” your camera and lens are back focusing. You should adjust forward to make a correction. When the mark of sharpest focus is below “0” your camera and lens are front focusing. You should adjust backward to make a correction.

Note: The numbers on the SpyderLENSCAL ruler do not correlate to the numbers in the adjustment menu.

Final Step – Check and Repeat

De-focus your lens manually then repeat step 2 and 3 to check that you made the optimal adjustment(s). Repeat this process for each camera and lens combination until “0” is the sharpest point on the scale.

Note: It is recommended to recheck the settings annually, when the lenses have been used frequently, when they have been exposed to extreme temperatures, or anytime you believe your focus performance has changed.


Happy work ! ''Buon lavoro''

[neokind]

Hi all,

Follow these guidelines, last summer I calibrated some lenses and the correct procedure is this one. (regardless of the calibrator brand in this case I used SpyderLens Cal)

1. Set up
Position the SpyderLENSCAL as shown below, with the main target vertical and ruler “0” mark aligned with the center cross-section of the target.
Make sure the SpyderLENSCAL is level by placing it on a flat surface, mounting it on a tripod or on a light stand with a bubble indicator.

2. Next,
Set up your camera and lenses by enabling autofocus, turn off the stabilizing function (for Pentax, Shake Reduction), set the aperture to the largest f-stop (lowest number) on the lens with the lowest native ISO setting. If you are calibrating a zoom lens, set it to its longest focal length.

3. Make sure your camera and SpyderLENSCAL are 25-50 times the focal length apart. They should always be at the same height, with your lens and the SpyderLENSCAL target parallel to your camera's sensor plane.

4. Take Photo
Aim your lens at the center of the board on the SpyderLENSCAL target. Use the center autofocus point and capture an image. Use the self-timer or a cable release so you do not introduce any vibration.
(Do not use live view to focus and capture the image of the target)

5 – Evaluate and Adjust
View the image of your SpyderLENSCAL target on the camera screen or even on your computer’s monitor. Zoom in on the ruler to evaluate the point of sharpest focus.
If the sharp focused mark is not “0”, enter the autofocus correction menu on your camera (this can be found in your camera's manual) and select “adjust by lens”. When the mark of sharpest focus is above “0” your camera and lens are back focusing. You should adjust forward to make a correction. When the mark of sharpest focus is below “0” your camera and lens are front focusing. You should adjust backward to make a correction.

Note: The numbers on the SpyderLENSCAL ruler do not correlate to the numbers in the adjustment menu.

Final Step – Check and Repeat

De-focus your lens manually then repeat step 2 and 3 to check that you made the optimal adjustment(s). Repeat this process for each camera and lens combination until “0” is the sharpest point on the scale.

Note: It is recommended to recheck the settings annually, when the lenses have been used frequently, when they have been exposed to extreme temperatures, or anytime you believe your focus performance has changed.


Happy work ! ''Buon lavoro''

Thank you! I'll retest the lenses with the 25-50x distance. I was not aware of that.

[Adam]

I always use 'OK' to zoom when doing shallow DOF work on the tripod, since I've been less than impressed with the AF. I wasn't aware that focus peaking outlined the focal area when in LV. I'll give that a shot to see where it's focusing. Thanks.

Indeed, AF adjustments only apply when shooting through the viewfinder, so you should use the viewfinder only for all your tests.

You can use live view with manual focus to obtain a baseline image showing optimal sharpness. If you expect live view AF to be accurate, make sure the area you're focusing on has sufficient contrast, and that the AF area is sufficiently small if you want to guarantee focus there (otherwise the camera will pick where it wants to focus).

Finally, if you're on a tripod, SR should always be off. If you turn it on, it may introduce a blur.

[neokind]

Indeed, AF adjustments only apply when shooting through the viewfinder, so you should use the viewfinder only for all your tests.

You can use live view with manual focus to obtain a baseline image showing optimal sharpness. If you expect live view AF to be accurate, make sure the area you're focusing on has sufficient contrast, and that the AF area is sufficiently small if you want to guarantee focus there (otherwise the camera will pick where it wants to focus).

Finally, if you're on a tripod, SR should always be off. If you turn it on, it may introduce a blur.

Great advice. Thank you on all points. I’ll test everything tomorrow.