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08-30-2014, 08:43 PM   #1
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FA* 80-200 f2.8 focus issue... ADVICE NEEDED for lens adjustment!

I purchased an FA*80-200 a few months back and the lens is beautiful. When I happen to catch something in focus, it's beautifully sharp but mostly my images are slightly fuzzy. From what I can tell, it appears as though it has a slight focusing issue. I've adjusted the AF fine tune adjustment to +10 (as high as it will go) and have seen some improvement however the lens still appears to be focusing in front of the object in view. I can see this because often times there are items slightly closer to the camera that appear sharper and in better focus than the object I told the camera to focus on. I'm not sure what to do at this moment because CRIS camera is no longer the Pentax contracted servicing & repair shop. The problem with this is that the new servicing shop in New England (who now has all of Pentax's special equipment) charges an arm and a leg ($300+) just to look at the lens and/or camera. I had my K-5 repaired at CRIS for about $220 so the price of this new place is outlandish. In talking with CRIS, the problem with the lens may be optical as opposed to electrical. If optical, they can adjust/calibrate. If electrical, then I would have to send it to the Pentax contracted place in New England because only the equipment they have from Pentax can fix the problem.
In addition, I am having a slight infinity focus issue as I shared in this thread found here: https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/213027-infinity-focus.html Could this indicate an optical problem and the need for calibration? Has anyone ever had a lens adjusted? Has it been an FA* 80-200 f2.8? Thoughts?

08-30-2014, 09:00 PM   #2
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The AF fine adjustment works the other way in Pentax land. If you are experiencing front focus, you move the AF plane of focus backward to meet the sensor plane of focus. So you would need to dial in a negative amount. Adding a +ve correction would just make it worse. Try going the other way with the adjustment and see what it looks like.
08-30-2014, 10:35 PM   #3
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QuoteOriginally posted by jbinpg Quote
The AF fine adjustment works the other way in Pentax land. If you are experiencing front focus, you move the AF plane of focus backward to meet the sensor plane of focus. So you would need to dial in a negative amount. Adding a +ve correction would just make it worse. Try going the other way with the adjustment and see what it looks like.
Thanks a ton! I'll give it a try and see how it works. My biggest problem is that when the lens is on focus it is stellar sharp! I hate knowing that and missing the focus. I'll dial the AF fine adjust back a few notches and see how it works.
08-31-2014, 12:10 AM   #4
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Hope fine tuning sorts out your problem!
I use this lens quite a lot. Liike the OP mentioned, image quality is excellent when it is in focus. However, for one reason or the other AF with this lens is not quite as accurate and consistent as with some other lenses. This has been reported by other users as well.
I do not consider this a major problem but would be curious to know whether someone knows the reason for this.

08-31-2014, 04:21 AM   #5
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What did you use to determine the lens was front or back focusing? For what I know of this lens it is inherent for it to not nail the auto focus all of the time due to it's construction and not having the aid of an internal motor to focus, so often times some manual adjustment may be needed or re-focusing. The other factor that comes into play is this is a fast super zoom so it has a very narrow depth of field especially at the lower apertures so care needs to be taken regarding that also.
08-31-2014, 06:44 AM   #6
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QuoteOriginally posted by Oldbayrunner Quote
What did you use to determine the lens was front or back focusing? For what I know of this lens it is inherent for it to not nail the auto focus all of the time due to it's construction and not having the aid of an internal motor to focus, so often times some manual adjustment may be needed or re-focusing. The other factor that comes into play is this is a fast super zoom so it has a very narrow depth of field especially at the lower apertures so care needs to be taken regarding that also.
Good points. I did think of the depth of field issue due to the fast lens. Originally I used a test chart for focus accuracy. This got me to place my AF fine adjust at +10. But as I investigated my images more recently, it revealed that items closer to the camera were in slightly better focus. That was my clue to the continued problem. And I thought this meant I needed to got to +12 in the adjustment menu (which is impossible in Pentax). As the first reply above mentioned, I needed to dial back to maybe +8, thus moving the plane of focus backwards.
At this point, I'll experiment and pay close attention to my images hoping that this helps. I still wonder if a labs' lens calibration is valuable. Hopefully +8 will get me better focus. Thanks.
08-31-2014, 07:09 AM   #7
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QuoteOriginally posted by mattieyp3 Quote
Good points. I did think of the depth of field issue due to the fast lens. Originally I used a test chart for focus accuracy. This got me to place my AF fine adjust at +10. But as I investigated my images more recently, it revealed that items closer to the camera were in slightly better focus. That was my clue to the continued problem. And I thought this meant I needed to got to +12 in the adjustment menu (which is impossible in Pentax). As the first reply above mentioned, I needed to dial back to maybe +8, thus moving the plane of focus backwards.
At this point, I'll experiment and pay close attention to my images hoping that this helps. I still wonder if a labs' lens calibration is valuable. Hopefully +8 will get me better focus. Thanks.
What camera are you using? My guess is, before you answer, that you are using a K5, K20 or K10.

I have the same lens and know the same problem. I tried adjustment etc but never really got that consistent sharp shot that I 'know' you can get (just as you say).

Then, by chance, I had to use my K30 body one day. BANG, focus every time. Sharp and consistent.

My bet is the AA filter is playing a role, as are the AF inaccuracies reported for the K5. The K30 has a weaker AA filter (so I hear) as does the K01 and, if true, I can say it makes a difference. Both the K30 and K01 deliver sharper shots than my K5 - although the K5 does give me more in other areas .....

Anyway keen to know what camera you are using.

Mark
08-31-2014, 05:45 PM   #8
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QuoteOriginally posted by Wild Mark Quote
What camera are you using? My guess is, before you answer, that you are using a K5, K20 or K10.

Mark
Spot on! I use a K-5. I guess the only solution is to get a new camera? Should I worry about trying to calibrate the lens or is the K-5 most if not all of the problem?

08-31-2014, 05:52 PM   #9
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QuoteOriginally posted by mattieyp3 Quote
Spot on! I use a K-5. I guess the only solution is to get a new camera? Should I worry about trying to calibrate the lens or is the K-5 most if not all of the problem?
It could also be the lens but I would check out the body issue first. By the way that does not make the K5 a dud of a camera - just limited when using the bazooka lens

Do you know anyone with a K3, K5iis, K30/50 or even a K01???? Try it out with those bodies and see what results you get. They should give you a better AF outcome (although please note the K01 is not fast at AFing a large lens like this).

Also, make sure you are shooting at f2.8 in such tests - the narrow depth of field will help in diagnosis - it certainly did for me as the 'control' conditions I used were a dimly lit concert hall with no flash.

In testing I suggest you have both candidate bodies at hand. Take a series of shots at varying distances then replicate with the next camera body. Compare and contrast and see what you think. I for one would be keen to know what results you get.

Mark
08-31-2014, 08:28 PM   #10
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QuoteOriginally posted by Wild Mark Quote
It could also be the lens but I would check out the body issue first. By the way that does not make the K5 a dud of a camera - just limited when using the bazooka lens

Do you know anyone with a K3, K5iis, K30/50 or even a K01???? Try it out with those bodies and see what results you get. They should give you a better AF outcome (although please note the K01 is not fast at AFing a large lens like this).

Also, make sure you are shooting at f2.8 in such tests - the narrow depth of field will help in diagnosis - it certainly did for me as the 'control' conditions I used were a dimly lit concert hall with no flash.

In testing I suggest you have both candidate bodies at hand. Take a series of shots at varying distances then replicate with the next camera body. Compare and contrast and see what you think. I for one would be keen to know what results you get.

Mark
Thanks WildMark! I greatly appreciate this. The trouble is I don't know anyone who shoots Pentax. I used to live on the east coast and NEVER saw a Pentax. Now that I live in Washington I see them from time to time. I'll try and find something.

In addition, I seem to have a slight infinity focus problem between 80 and about 150mm. The camera/lens will have trouble focusing beyond 100ft. Could this be a similar issue or a lens issue!
08-31-2014, 09:06 PM   #11
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QuoteOriginally posted by mattieyp3 Quote
Thanks WildMark! I greatly appreciate this. The trouble is I don't know anyone who shoots Pentax. I used to live on the east coast and NEVER saw a Pentax. Now that I live in Washington I see them from time to time. I'll try and find something.

In addition, I seem to have a slight infinity focus problem between 80 and about 150mm. The camera/lens will have trouble focusing beyond 100ft. Could this be a similar issue or a lens issue!
That is a small problem I guess. Perhaps a local PF member can link up with you and help out - put the call out and see what happens

I would help save for being based in Australia .... minor geographical challenge!

As for the infinity focusing issue - can't say I have encountered this issue. I do not think I have used the lens for infinity at these FLs. If I were I would probably be selling my prime collection - which I am not doing.

I suggest one step at a time. Isolate the camera issues first and then re-examine the infinity focus matter. It might be that both issues are the one ????

As for me the solution is to use the K30 with that lens while I wait for the Pentax FF body that has the improved AF performance ....... sigh

Mark
09-05-2014, 08:29 PM   #12
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The variable focus lenses as yours, may have different focal plane at the different focus length.
Just my 2c.
09-06-2014, 09:13 AM   #13
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QuoteOriginally posted by pavpen Quote
The variable focus lenses as yours, may have different focal plane at the different focus length.
Just my 2c.
Would you mind elaborating? Im not sure I thoroughly understand what you are saying.
09-06-2014, 07:56 PM   #14
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QuoteOriginally posted by mattieyp3 Quote
Would you mind elaborating? Im not sure I thoroughly understand what you are saying.
Sorry for too brief response. I was trying to say that for instance at focal length of 100 mm it's right on target but at 200 mm it is back focusing. I hope this is make sence.
Cheers.
09-06-2014, 08:40 PM   #15
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QuoteOriginally posted by pavpen Quote
Sorry for too brief response. I was trying to say that for instance at focal length of 100 mm it's right on target but at 200 mm it is back focusing. I hope this is make sence.
Cheers.
For the FA* lens, I expect the lens characteristic to be parafocal (focus plane would not change regardless of focal length). If the lens exhibits FF behaviour, the AF adjustment should be -n instead of +n. I think both lens and camera can be adjusted to ensure focus accuracy as long as both are calibrated within certain tolerance. If the camera is still under warranty, I suggest sending both camera and lens to Pentax repair to align for focus accuracy.
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