I have fixed my front focus problem - how to

[coleviolin]

Thanks for clarifying this. I removed some front focus from my DS yesterday, and I figured that there are 3 screws to adjust some focal plane in there, not only back and forth but also side to side along x and y axes, more or less. Anyway, what you illustrate makes sense to me.

The only thing I'm concerned about is that isn't it good to have very slight front focus? DOF comes in 1/3rds doesn't it, but I guess all that matters is what you see on the final test image.

I was just testing my DA 18-55 vs. my friend's DA 16-45 directly aimed at a map on my wall, and after adjusting my slight front focus problem yesterday, I can't seem to get a really sharp focus in the center.... so, I gave it just a little more front focus, as it would appear on the test chart retaken, and I will let you know how how the map test turns out with those 2 lenses.
--
Lipo

**

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

 

[coleviolin]

I'm looking at these samples I took with DA 18-55 and DA 16-45 after setting my DS to have a slight front focus with the D-FA 50/2.8 macro. The center appears more in focus than before the front focus was removed.

It seems that a slight front focus is good to have if you shoot a with lot of wide angle.I think the reason for this may be the factor of the aspherical lens element which makes the edges of the frame appear slightly closer that the center of the image. I'm not really sure what I'm talking about, but I'm sure that others with more knowledge will correct me soon enough.
--
Lipo

**

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

 

[jeffkrol]

f I remember correctly DOF approaches 50/50 at Macro distances.

--
360 minutes from the prime meridian. (-5375min, 3.55sec) 1093' above sea level.

 

[Wagga]

Did you adjust just the screw in front or all three?

--
Wagga [Jean]

[UTC/GMT + 2 hours]

 

[coleviolin]

Hey, I adjusted all 3, but then played a bit more and gave the one by itself a slightly different angle. I tested it with my D-FA 50 macro on a closer scale (reducing DOF) and it seems to be good. Now the bottom center AF point and top center AF point are evenly balanced. The top one has a slight front focus, and the bottom has a slight back focus. The center AF point is pretty much spot on with a slight front focus. The D-FA 50/2.8 has very accurate AF.

I concluded that my Da 18-55 does not always focus accurately at 18mm. I can see it by watching the focus ring which does not always land in the same spot. Why do you ask if I only adjusted one screw?
Thanks.
--
Lipo

**

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

 

[Wagga]

I concluded that my Da 18-55 does not always focus accurately at
18mm. I can see it by watching the focus ring which does not always
land in the same spot.

Try to focus at 55 and move to 18, it should hold the focus.

Why do you ask if I only adjusted one screw?

Just out of curiosity. I would like to know if you have identified which screw does what.

I send an e-mail to Pentax France about it. I'm sure they will answer me but I don't think they will give me technical details. We'll see.
--
Wagga [Jean]

[UTC/GMT + 2 hours]

 

[Ivan Glisin]

Thanks for great mini tutorial: I did the same with my DS with success!

I have tested with FA35 and DA18-55. Before and after test shots look identical to yours (so no need to post).

-= Ivan =-

 

[coleviolin]

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

 

[kharju]

Wagga

Thank you.
With you tips, i fix my istDS ff problem in 10 minutes.

 

[Wagga]

Wagga

Thank you.
With you tips, i fix my istDS ff problem in 10 minutes.

My pleasure. If you noted the original position of the screws carefully, you can always revert to the original setting if necessary.

Happy focussing.

--
Wagga [Jean]

[UTC/GMT + 2 hours]

 

[Pasvorn]

I have just got my 77mm ltd yesterday (my first FA lens besides the kit lens.)

After a couple of test shots, it clearly shown that my DL back-focus by about 10% e.g. a subject is at 3 meter, the lens focused at 3.3m.

-Pasvorn

 

[Pasvorn]

I adjusted the picture during the weekend with my 77ltd.
When I tested this, I adjusted at 2 meters range.

It is now focus correctly. I tested at various portrait range and it seems to be working.

I am out and about and noticed that the AF now could not focus at infinity. I'll need to play withit some more.

Sigh. Since the lens is more expensive than the body, I would think that I screwed up the AF on the body.

Any words of advice?

I think I'll go back to use MF. When will Katz focusing screen be available for DL?

Thanks.

-Pasvorn

 

[Wagga]

I would think that I screwed up the AF on the body.

I don't t think it's possible, but maybe you shifted the range too much.

Any words of advice?

I would reset the screws to their original position, things should get back to normal - you'll still have the focussing problem with this particular lens (maybe it's faulty).

Thanks.

Sorry for your problem, please keep us informed.

--
Wagga [Jean]

[UTC/GMT + 2 hours]

 

[Charrua]

So i performed the test yesterday using the FA 50 1.4. I noticed it was front focused, but the blown up images seemed a bit soft (not crisp) to tell exactly where it was actually focusing.

Then I put the 43mm LED and it was definitely front focusing in the same area.

My question is.... I have a 24 2.0, 43 1.9 LED, 50 1.4 & 77 1.8 LED.

Should I try calibrating the CCD using the middle of the range lens? so either the 43mm or 50? As to not totally screw up the other lenses?

I had initially noticed the focusing issue with the 77 1.8 LED... like for instance, i would take a picture of my fiancee's ring wide open, and the picture would come out focused on her knuckle instead after I made sure to put the center AF point on the ring itself.

 

[Wagga]

My question is.... I have a 24 2.0, 43 1.9 LED, 50 1.4 & 77 1.8 LED.

Should I try calibrating the CCD using the middle of the range
lens? so either the 43mm or 50? As to not totally screw up the
other lenses?

I had initially noticed the focusing issue with the 77 1.8 LED...
like for instance, i would take a picture of my fiancee's ring wide
open, and the picture would come out focused on her knuckle instead
after I made sure to put the center AF point on the ring itself.

Hi Charrua,

I tested all my lenses and found that they were all more or less within acceptable range except for my FA 50mm f/1.4 (my fastest lens).

I deliberately decided to privilege this lens and tune the camera for it.

The impact on the other lenses is not really noticeable (this is easily explained by the fact that my next fastest lens a Limited DA 40mm f/2.8 and the DOF is therefore wider).

Before you attempt anything, make sure you read Pasvorn's posts in this thread.

I would like to make it clear that my intention was to share my experience with fellow Pentaxians. I am not in a position do advise you on how you should deal with your particular problem.

The only piece of advice I can give you is that if you decide to adjust the screws, you should note their position carefully so as to be able to revert the tuning process if it is unsatisfactory.

For information, I send an e-mail to Pentax-France to tell them of the focussing problem of my 50mm and they answered that I should use manual focus!

Im my mail to them, I also asked details on the three Allen head screws and they didn't mention them in their answer. I believe that this was deliberate...

I hope this helps.
--
Wagga [Jean]

[UTC/GMT + 2 hours]

 

[Bronto]

Well, all of you who tried the focus with 50/1.4, did you try to focus manually as well? I tried with M50/1.7 and there is some back focusing with it! Focusing manually. The same with M135/3.5 but lesser amount because of the DOF. So if you had problems with 50/1.4 in AF did you compare it to the MF?

--
Regards,
Andres

 

[Brett St Pierre]

I might be wrong, but from earlier threads on this I believe this
cannot be done on the *istD, only the DS and later.

--
Brett

Brett, time ago there was a threat on this concerning the *istD,
with this picure.



--
rgrds. Henk (*istD&DBG-1).

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 )

--
Brett
http://www.pbase.com/shreder



The Journey is the Thing

 

[Pasvorn]

Andres,

I finally adjust my FA-77 limited to my liking. It is now auto-focus more accurately than when I focus the lens manually at any distance.

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.

Regarding manual focus lens, I currently have A50/1.4, which sometime back focus. It seems to be much better now. I think it take sometime for me to adjust to how the camera works.

Good Luck,

-Pasvorn

--

 

[Pasvorn]

The auto-focus at infinity turned out to be a glitch in the system. I'm not sure how it happened, but it has not been repeated, yet.

I now have it dialed in for my 77mm limited. It seems to be accurate at any distance. I also tested and the autofocus mechanism works much better than when I manual focus at any range.

I'm happy - at least for now.

-Pasvorn

 

[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
*ist-anbul