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01-03-2024, 10:36 AM - 1 Like   #1
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14 point AF Tune spread in a zoom lens.

I pulled out my old LensAlign slanted ruler and the FocusTune software to check on my 5 month new Pentax 70-200mm f/8 lens. Discovered the software is no longer being updated and does not work with anything new than a Pentax KII and I was using the K3 Monochrome. The LensAlign ruler is no longer being sold either as company may be gone.

However, the slanted ruler was telling me at the 200mm end the AF needed to be set to a -9 in the K3 Monochrome body. Worse was at the 50mm wide end it went the opposite way and needed a +5 - or a 14 point spread for the Auto Focus!??!!

Since I had the slanted ruler out, I also have the Reikan FoCal 4 that is used to set the AF on Canon and Nikon cameras. It will read manually loaded JPEGs to evaluate too, so I loaded the Monochrome's shots taken with the 70-200mm into it. Pretty much the same scenario: A -9 at Tele end, and +5 at the Wide end. Only the 135mm was at zero. I also tried the Reikan FoCal test target and same results. The lens is non-linear over the zoom range tor sharpenss.

Filed a service request to Precision Camera in CT since it is only 5 months old. Listed a as warranty. Out of warranty it is $489 to fix! Still it cost me $75 for UPS Ground to ship it to them (They got another raise according to the UPS girl.). Might know more in a couple of weeks as one week ti takes to get there, and another to evaluate. Hopefully it doesn't go on vacation to Japan.

Hopefully they fix it. Too bad Pentax doesn't offer the lens tuning puck like Sigma does to fix this sort of thing, or have in the camera's menu a Tele and Wide AF Tune section for the zooms.

01-03-2024, 02:20 PM - 2 Likes   #2
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Will they not need your camera too ? AF/FA is not simply a lens thing.
01-03-2024, 10:21 PM   #3
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QuoteOriginally posted by pschlute Quote
Will they not need your camera too ? AF/FA is not simply a lens thing.
Thatís also my question. I donít own this lens, so I canít comment on how other copies behave, but zooms are notorious for having this type of focus shift and difficulty fine tuning on dslr systems.
01-03-2024, 11:03 PM   #4
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QuoteOriginally posted by Mack53 Quote
Filed a service request to Precision Camera in CT since it is only 5 months old. Listed a as warranty. Out of warranty it is $489 to fix! Still it cost me $75 for UPS Ground to ship it to them
Did you send them the camera, or the lens? That seems like a camera repair price, though I don't know the repair cost of a rather-new lens.

01-03-2024, 11:46 PM   #5
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The 70-200 has a quite visible adjustment spread between 70 and 200, but 14 values is really huge. For a proper job they should ask for camera AND lens, but that might mean that all other lenses are affected, in case they fix something on the camera. The price is probably for a full setup plus a single lens, you may want to ask what additional lenses would cost for alignment. I had all my lenses aligned once and paid alignment only for a couple older ones that were out of warranty.
I hope you do not use a quick release plate on the camera, these can mess up the af adjustment readings if screwed in too tight.
01-04-2024, 08:53 AM - 1 Like   #6
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QuoteOriginally posted by pschlute Quote
Will they not need your camera too ? AF/FA is not simply a lens thing.
I just sent the lens in as my Pentax 16-50mm f/2.8 is pretty consistent in the zoom range, but it too still needs a -7 overall but I can live with that as long as it doesn't have the 14 point spread like the 70-200mm has. The 70-200mm I have is pretty darn sharp though when it nails focus and the AF sensors on the sensor itself (Live View C-AF? or whatever its called to avoid the bottom AF sensor array thing.). Too bad Pentax didn't learn the lesson form Canon when Canon put a Tele and Wide adjustment into their cameras that use that auto-focus array sensor. Nikon finally got around to using it too.

There are some posts - I think on here? - where people have tuned the AF sensor position in the bottom of the camera that supposedly has 3 adjustment screws to fix that -7 general part. I have done the cam screw on my old Nikon D800E where it was up against the wall for most all lenses needing a -19 on it. Wasn't too hard with a long handle 1.5mm hex wrench.

---------- Post added 01-04-24 at 08:02 AM ----------

QuoteOriginally posted by UncleVanya Quote
That’s also my question. I don’t own this lens, so I can’t comment on how other copies behave, but zooms are notorious for having this type of focus shift and difficulty fine tuning on dslr systems.
I have a Sigma 35mm ART lens. I thought the AF was off on it new so I bought their Sigma USB AF Tuning dock which uses their software to adjust the AF. Even though it was a prime lens, Sigma has several focus distances one needs to use to align the AF in their software that then burns the fix into the firmware in the lens. If it is a zoom lens, then their could be four zoom ranges and maybe 4 distances for each one for a total of 16 different AF tuning points that need to be done. It's use is explained in the YT video below.


Sigma made a dock for the Pentax K mount for use with their lenses too. One could tune their lens up better to their camera. Cost of the dock was around $60, but it only worked with the Sigma lenses that accepted it. Unfortunately, Sigma seems to have abandoned Pentax so pretty much a moot point now.

---------- Post added 01-04-24 at 08:14 AM ----------

QuoteOriginally posted by leekil Quote
Did you send them the camera, or the lens? That seems like a camera repair price, though I don't know the repair cost of a rather-new lens.
Just the lens went in.

When you begin a repair with Precision Camera online, you enter the item and it will show the cost of repair outside of warranty. I agree the price does seem a bit high though at $489.

Aside, I bought a used Olympus lens from KEH once and found it needed a firmware update for some diaphragm stutter that occurred while shooting video on a drone's m43 camera. Since the drone camera did not do updates to lenses, I had to send it in. When I called it was only $40 to do the firmware update. After several weeks of no lens, I called to find out the delay and found they had raised the rate to $180 for the firmware update since that was their flat-rate base price for repairs to that lens. Argument ensued and they came down to $140 for what amounts to a 2 minute update job if one owns a body that would do it (Fwiw, I do own several Olympus bodies that will do that now. What a way to get into the m43 system!).. Bad part was the cost of a new lens verses this new repaired one with the needed update was the same. Should have bought a new lens had I known the used one had a costly issue.

---------- Post added 01-04-24 at 08:36 AM ----------

QuoteOriginally posted by zapp Quote
The 70-200 has a quite visible adjustment spread between 70 and 200, but 14 values is really huge. For a proper job they should ask for camera AND lens, but that might mean that all other lenses are affected, in case they fix something on the camera. The price is probably for a full setup plus a single lens, you may want to ask what additional lenses would cost for alignment. I had all my lenses aligned once and paid alignment only for a couple older ones that were out of warranty.
I hope you do not use a quick release plate on the camera, these can mess up the af adjustment readings if screwed in too tight.
You can find the prices on the Precision Camera Repair's website. Enter the item and it will show their flat rate price if out of warranty.

The 70-200mm has a rotating foot on it. I attached an Arca-Swiss plate to it for tripod use, but it should not affect the focusing as the zoom lens does not extend like some zooms do to shift the weight. It just was poorly setup from the factory, imho, if they align the lenses much like Sigma does above (And I doubt Sigma spends that much time aligning either given the time it takes to use their AF dock and software to do one lens, and keep retesting it over the sixteen point in the guy's video above.). Seems Pentax calibrated it for the 135mm spot, and let the others hopefully close enough to whatever standards they settled for.

Aside, Olympus is far worse for AF tuning in that they have 25 spots on the sensor they align too. Make it 50 to align with a zoom lens as you align for both the Wide and Tele both. Seems overkill, but maybe the smaller m43 sensor is more sensitive to irregularities in the alignment or lens coma. Below is their 45mm f/1.2 lens on their E-M1X body. Some of the left-right differences were caused by the bayonet not parallel to the sensor.



Last edited by Mack53; 01-04-2024 at 09:38 AM.
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