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12-04-2011, 09:19 PM   #1
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Fixing Front and Back Focus on the K-x

Nice article but it mentions the K-x as having the AF Fine Adjustment option. If I'm not mistaken I do not believe this option is available on the Pentax K-x; unless I'm missing it somewhere...

I've got FW 1.00

12-04-2011, 09:35 PM - 2 Likes   #2
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For the K-x you either have to enter debug mode or get someone to do it for you (i.e. a service center).

https://www.pentaxforums.com/forums/pentax-dslr-discussion/103446-selective-a...stment-kx.html

What you need to do is create a file called MODSET.492 in the root of the SD card with the following contents:

[OPEN_DEBUG_MENU]

Make sure there is a carriage return at the end of the line (i.e. hit enter after the last ] ). Then, turn on your camera while holding the AV button. You will see the text "debug mode . Press the right arrow button and it will become enabled.

Next, press ok, go into the menu, and scroll past the 4th tab of the setting menu. Instead of going to custom function tab #1, a debug menu will open.

Then, select "AF Test" and you will see the same screen that is now publicly accessible on newer SLRs.

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12-04-2011, 09:39 PM   #3
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Ugh... I just spent like 10 minutes looking for a firmware update that would add this, since I figured the article wouldn't have said it if there wasn't such a menu feature.. Maybe change the wording a bit?
12-04-2011, 09:46 PM   #4
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There is a firmware update in our camera database, but if you want to be sure you can access the debug menu, stick with 1.0.


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12-04-2011, 09:53 PM   #5
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Went to Spyder's website and looked at the instructions for their Lenscal. It says to use 5 to 10 times the FL of the lens as the distance between the lens and the Lenscal. This makes very little sense as the 15mm would give a spacing of 150mm, 15 CM, between the lens and the test gig. The lens has a minimum focus of 180mm so this is not possible. This holds true for many of my primes. They do not focus close enough to do the test as described. What gives? Did I read it wrong? Dave
12-04-2011, 09:57 PM   #6
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Well, there needs to be some breathing room- if the lens is at MFD, then you're not going to get anywhere because the AF might not lock on or be able to make a mistake.

I would recommend starting by shooting close to the minimum focusing distance, but far enough away that the whole lenscal unit is visible in the VF. This is so that you minimize the DOF and make any potential ff/bf problems as easy to discern as possible. You can also try the test and larger distances and see if any misalignments have an adverse effect in practice. With a lens as wide/slow as the 15mm, the DOF is very wide, so FF or BF is typically not going to be as much of a problem as it would with longer lenses like the 77mm or a 50mm.

Also, the reason their rule is off is that you can't generalize stuff like this in a linear fashion, so it's more like a rule of thumb. There are some lenses that focus closer than 10x their FL, while there are some that can't focus until you're 20-30x out

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12-04-2011, 11:11 PM   #7
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Here's a more detailed explanation of tuning the AF in the K-x's debug mode: RiceHigh's Pentax Blog: K-x Debug Mode Tutorial - AF Adjustment

I do wish you could adjust the AF for each lens, but any adjustment you make applies to all lenses.
12-05-2011, 04:06 AM - 1 Like   #8
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There are more hints and pointers to DIY solutions in my AF adjustment hints.

12-05-2011, 04:54 AM   #9
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QuoteOriginally posted by Adam Quote
For the K-x you either have to enter debug mode or get someone to do it for you (i.e. a service center).

https://www.pentaxforums.com/forums/pentax-dslr-discussion/103446-selective-a...stment-kx.html

What you need to do is create a file called MODSET.492 in the root of the SD card with the following contents:

[OPEN_DEBUG_MENU]

Make sure there is a carriage return at the end of the line (i.e. hit enter after the last ] ). Then, turn on your camera while holding the AV button. You will see the text "debug mode <DIS>. Press the right arrow button and it will become enabled.

Next, press ok, go into the menu, and scroll past the 4th tab of the setting menu. Instead of going to custom function tab #1, a debug menu will open.

Then, select "AF Test" and you will see the same screen that is now publicly accessible on newer SLRs.
Thanks Adam, I am fully aware of the debug mode and the K-x as well as other Pentax DSLRs not mentioned in the article. I see this morning the article has been amended by mentioning the K-x needs to be in debug mode...

The point of my OP was to simply bring this to your attention as there are probably way way more Pentax owners that are not aware of the debug mode (or should not even attempt the debug mode), thus purchasing the AF Test Kit would be useless.

Last edited by theunartist; 12-05-2011 at 05:15 AM.
12-05-2011, 05:38 AM   #10
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Adam, Yes my own experience from doing my line up of lenses was that the formulas on the forums went from 10x to 50x the FL. This kind of left the whole distance thing in the air. Some times you were too close and other times the target was so far away it was hard to analyses. I eventually just found a comfortable distance for each lens to do the test and used it. The idea that the Lenscal instructions kind of emphasized was to make the target fill the frame as much as possible. That seems to be a good starting point. For the Lenscal tool, I think it is most important to have the image large enough that the center focus point is just looking at the small set of boxes and nothing else or do I have this wrong. It was never really clear whether the small boxes or the center of the large boxes were the aiming point. Any clarification would be appreciated. Thanks again for your article. Dave
12-05-2011, 08:55 AM   #11
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Hum I tried to open the debug mode with my Pentax Kr. But I don't able to open this mode ??????? Why I have updated to 1.11 version Firmwave. I tried the instructions on the second message on this page but ?????????

Jean Mario
12-05-2011, 09:12 AM   #12
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QuoteOriginally posted by Jean Mario Quote
Hum I tried to open the debug mode with my Pentax Kr. But I don't able to open this mode ??????? Why I have updated to 1.11 version Firmwave. I tried the instructions on the second message on this page but ?????????

Jean Mario
Your K-r does not need to go into debug mode... I believe you will find the AF adjustment somewhere in your custom settings...
12-05-2011, 10:26 AM   #13
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Firmware...
12-05-2011, 10:27 AM   #14
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Yes I found this on my manual. Fonction 21 on personal option...
12-05-2011, 03:38 PM   #15
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QuoteOriginally posted by tentacles Quote
Ugh... I just spent like 10 minutes looking for a firmware update that would add this, since I figured the article wouldn't have said it if there wasn't such a menu feature.. Maybe change the wording a bit?
The option to Fine Tune AF is not available with any Firmware update for the Kx... However using the Debug Mode as described above will allow you to Fine Tune AF on a Kx.

I have used the debug mode and it does work nicely for the Kx, allowing general AF to be slightly adjusted. I found mine to be factory set at +20 and found it needed to be set to +60 for the best AF possible.

if you follow the link to RiceHigh's Blog.. (above post) it will give you further details, quite helpful
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