I have fixed my front focus problem - how to

[Wagga]

Good on you.

As long as you carefully note the original position of the allen screws (to revert if necessary), it's a safe operation.

As a matter of fact, the shape of the allen screw makes it easy to note their position.

--
Wagga [Jean]

[UTC/GMT + 2 hours]

 

[Harri R'is'nen]

Andres,

......

It may take some experiments. (I have to take the plate off and
adjust the focus more than 10 times. However, eventually it
should be working out at the end.....

-Pasvorn

Isnt it possible to leave bottom plate open while taking test pictures?

--
Harri

 

[coleviolin]

I've done some more adjustments to my DS focus plane since this old post, and I've found that the one allen screw closest to the lens controls the upper AF plane, and the two further allen screws control the lower 1/3rd AF focal plane (focus points).

So, if you loosen the upper two screws you increase backfocus on the lower 1/3rd. of your AF points in the viewfinder. If you loosen the bottom allen screw you increase backfocus on the upper AF points in the viewfinder. Loosening either screw will increase backfocus in the center. It's like leveling a small desk, anything you do affects the center, but you must try to get the edges of the desk level first of all. If you change the upper two screws unevenly, then you start to go side to side, which you shouldn't need to do.

This link shows that actually a slight backfocus is better, though as long as the line in focus is within the focus area. http://www.focustestchart.com/chart.html

So, I'm happy finally with my focus adjustments on my DS! The lower and upper planes are sharp towards the bottom, though just barely, of the DOF area and are equal to eachother. The center AF point is now approximately 1/3 of the way into the depth of field, meaning that most of the focus is behind (back focus). If you notice the sample on that D70 you'll see that the backfocus there is considered acceptable. It could be that my testing wasn't super accurate, but neither does it seem to matter. I'm not looking at it through a macro lens anymore. As the D70 tester says, just try to fill the screen with the focus chart, and don't get too close. Try to see where your AF points fall within the visible DOF on the 100% image on your computer instead of limiting the DOF to one AF point.

I know it would make sense to reduce the DOF to a minimum and try this test at F/1.4, but I don't think autofocus was ever meant to be THAT accurate, and it just creates more headache if you can't average things out according to some visible DOF.

Sorry, don't have more time for more specifics. Hope this helps.

Thanks Wagga, I'll see how that works with the kit lens.

I think the screw closest to the lens adjusts the front to back
tilt of the AF sensor, and the two which are in line away from the
lens adjust the side to side tilt.

I assumed this because the two away from the lens appeared to be
set similarly to eachother, by looking at the position of the allen
sockets, but the one screw by itself was set to a different
position. Now I've got them roughly all the same, and my ff test
seems to be pretty accurate.

I get these sort of problems with all my tools.
--
Lipo

**
'If life were fair, Elvis would be alive and all the impersonators
would be dead.' --Johnny Carson

--
Lipo

 

[RPRII]

Any thoughts on how this might impact your warranty? Mnay are voided by an end user opening up the body.

 

[Wagga]

Any thoughts on how this might impact your warranty? Mnay are
voided by an end user opening up the body.

You shouldn't fiddle with it while it is still under warranty, of course.
--
Wagga [Jean]

[UTC/GMT + 2 hours]

 

[Wagga]

I've done some more adjustments to my DS focus plane since this old
post, and I've found that the one allen screw closest to the lens
controls the upper AF plane, and the two further allen screws
control the lower 1/3rd AF focal plane (focus points).

So, if you loosen the upper two screws you increase backfocus on
the lower 1/3rd. of your AF points in the viewfinder. If you loosen
the bottom allen screw you increase backfocus on the upper AF
points in the viewfinder. Loosening either screw will increase
backfocus in the center. It's like leveling a small desk, anything
you do affects the center, but you must try to get the edges of the
desk level first of all. If you change the upper two screws
unevenly, then you start to go side to side, which you shouldn't
need to do.

This link shows that actually a slight backfocus is better, though
as long as the line in focus is within the focus area.
http://www.focustestchart.com/chart.html

So, I'm happy finally with my focus adjustments on my DS! The lower
and upper planes are sharp towards the bottom, though just barely,
of the DOF area and are equal to eachother. The center AF point is
now approximately 1/3 of the way into the depth of field, meaning
that most of the focus is behind (back focus). If you notice the
sample on that D70 you'll see that the backfocus there is
considered acceptable. It could be that my testing wasn't super
accurate, but neither does it seem to matter. I'm not looking at it
through a macro lens anymore. As the D70 tester says, just try to
fill the screen with the focus chart, and don't get too close. Try
to see where your AF points fall within the visible DOF on the 100%
image on your computer instead of limiting the DOF to one AF point.

I know it would make sense to reduce the DOF to a minimum and try
this test at F/1.4, but I don't think autofocus was ever meant to
be THAT accurate, and it just creates more headache if you can't
average things out according to some visible DOF.

Sorry, don't have more time for more specifics. Hope this helps.

Thanks Lipo, my K10D has taken over and the Ds is resting on a shelf at the moment, but I'll certainly do further testing.

--
Wagga [Jean]

[UTC/GMT + 2 hours]

 

[Timbert]

How cool is that! Another reason I'm glad I made the switch!

--
Timbert
http://timshouse.zenfolio.com

 

[DS_Dave]

--
GMT +9:30
http://www.colourpixels.net
Click on Dave on the menu

 

[ahilgaz]

Last night I had the courage to fix my DS' FF problem. Everything
went fine and yes I did it. Thanks a lot for this thread.
But newbies beware: dont try to do it unless you have some
experience and you fully understand what you are going to do.
--
Ahmet

Hello again,

After fixing my FF problem 3 months ago, I found out that my focus was dead sharp on the focus chart where it should be, so I thought I had fixed it; BUT when I started taking pictures in dim light I found that my sigma 17-70zoom and my Fa50 1.4 lens began back focusing. SO my conclusion is that even though the test chart might say the focus is right it might not be the case in real life shooting situations esp in dim light. SO I think what I will do now is readjust the screws to their original positions or maybe somewhere in between (I had adjusted the screws counter clockwise to the 8 o'clock position - exactly as the original poster did - not because he said so but because my tests had given the same result; so I am thinking that it is no coincidence and the pentax guys knew what they were doing while adjusting those screws.)
I wonder if any of you had a similar experience.
--
Ahmet
*ist-anbul
http://www.pbase.com/13johnson

 

[PG Thomas]

Has anyone considered that - due to the slaoc in the mechanical linkage between lens and body - and due to the step size of the focusing motor - Pentax may purposly set the focus to be between 0+1 steps rather than
-1+0, I.e always just focusing at or beyond the true focus point.

Given that the critical focus on a face is the eyes, and not the nose, this make sense to me.

Pete T

 

[wlachan]

After fixing my FF problem 3 months ago, I found out that my focus
was dead sharp on the focus chart where it should be, so I thought
I had fixed it; BUT when I started taking pictures in dim light I
found that my sigma 17-70zoom and my Fa50 1.4 lens began back
focusing. SO my conclusion is that even though the test chart might
say the focus is right it might not be the case in real life
shooting situations esp in dim light. SO I think what I will do now
is readjust the screws to their original positions or maybe
somewhere in between (I had adjusted the screws counter clockwise
to the 8 o'clock position - exactly as the original poster did -
not because he said so but because my tests had given the same
result; so I am thinking that it is no coincidence and the pentax
guys knew what they were doing while adjusting those screws.)
I wonder if any of you had a similar experience.

I have never touched these 3 screws so I cannot help you much. But I think it's a mistake to test AF accuracy with 45 degree target as the AF sensor might not dead centre as most assumed (so to the spot meter).
--
Alan Chan
http://www.pbase.com/wlachan

 

[John Upgood]

Problem for later. Well, other than I am sure you just voided your warranty, nothing major.

John

--
Pictures are like potato chips. You can't stop at just one.

 

[35mmfilm_user]

--
35mmfilm_user
http://www.marclangille.com

 

[Cideway]

Brett St Pierre wrote:

That is not an *istD - just open your battery compartment and see
the different layout of the batteries compared to the photo. I am
pretty sure that image is of the *istDS (but always happy to be
wrong )

Hmm, just thinking bret, the battery layout may not be the tell all, the thing that jumped to my attention immediately was if that is a D, where does the battery grip plug in...
--
Fanboy, and proud of it...

GMT +9.5

 

[CThomas]

I managed to adjust the AF of my K100D using the prescribed method. Before the adjustment my FA77 had a significant BF, my FA50/1.4 a slight BF and my FA50/1.7 was spot-on. After the adjustment the FA77 has only a very slight BF, the FA50/1.4 is spot-on and the FA50/1.7 very slightly FF. I will leave it like that.

Be careful with this operation. I lost one of the screws that fix the camera botten. I replaced it with a screw from my wrecked DS which I fortunately kept as a toy for my son.

 

[Wagga]

I managed to adjust the AF of my K100D using the prescribed method.
Before the adjustment my FA77 had a significant BF, my FA50/1.4 a
slight BF and my FA50/1.7 was spot-on. After the adjustment the
FA77 has only a very slight BF, the FA50/1.4 is spot-on and the
FA50/1.7 very slightly FF. I will leave it like that.
Be careful with this operation. I lost one of the screws that fix
the camera botten. I replaced it with a screw from my wrecked DS
which I fortunately kept as a toy for my son.

I am glad it worked for you. I'm still happy with my settings. Coleviolin investigated further and his contribution is worth reading.

Regards,

--
Wagga [Jean]
http://www.flickr.com/gp/47418676@N00/068b39

 

[Cybur]

Just tagged for future reference

 

[Rodelion]

Tag this for reference.

 

[aklance]

Very Interesting!

 

[Bich]

Did you test with the camera upside down? You may have a correct focusing, but slightly below the center of the viewer.
--
Jacques Bijtebier