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08-31-2007, 07:25 AM   #16
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QuoteOriginally posted by sft Quote
Thanks for the reply mate but let me assure you that I am a technically advanced user and that I have tried everything there is to try - AFS, AFC, Tripid & Mirror Lock Up, Manual Focus Bracketing, etc etc. I can guarantee that the issue here is not a user one but the lens is simply backfocusing almost eveytime. I have plenty of other fast & faster lenses (even f/1.4 and f/1.8) so I know how to use my equipment and judge performance.

I will get in contact with Pentax to send the lens for warranty repair, otherwise I have also judged the lens optically and it is a very good performer - it just has a definete backfocus problem but thanks anyways for your long reply mate - wish I could say it was user error but unfortunately it isn't.
I'm not surprised at your response. Your messages suggested that you
had not recently fallen off the turnip truck.

I guess the other question I have: Did you attempt to duplicate the issues
that you observed in the 'cam-shaft' focusing mode as opposed to the SDM mode???

This would go a long ways to isolating whether the issue you are seeing is with the camera body or the lens. In the SDM mode I can contemplate
a possiblity that the stepper motor could screw up, but in the cam-shaft
mode, the lens is completely stupid and simply cranks to where ever the cam shaft cranks it to.....

Another possibility, I suppose is that the lens has a floating element
that is floating free, but I would expect that if this were the case the AF
mechanism in the camera body would compensate for it.

If I understand the logic of the focus mechanism, it watches the contrast
on the sensor and activates the 'adjust focus' regime until maximum contrast is detected at which time it stops and displays the hex light in the viewfinder. If I am correct in my understanding the camera should keep trying until it gets it right regardless of how the lens behaves.

One other thing that I have noticed on the K10 which seems to be more of an issue than on my ist D is that the AF will try for a while, and then apparently time out and declare success. this seems to be an issue if the lens is
clear at the other end of its focusing range when activated.----it won't cycle the full range before going back....

It's probably why some optics (some macros come to mind) have focus range locks on them, because a feed back system like this can get the jitters and go into the prepetual search and never satisfied mode


I would rather assume this issue is why thet AF.S in the default, because it prevents the potential for a 'shimmy' in the focus which can be extremely annoying if you are using some lens such as the 50mm macro.

08-31-2007, 09:22 AM   #17
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Thanks for the replies Erl and rvannata.

Rvannata - by Cam-shaft you mean using manual focus with the confirmation right? Or are you implying using the screw driven AF in another body? Since my K10D is firmware v1.30 I can't use the screw driven AF.

I have indeed tried using manual focus with the focus confirmation hexagon and when I manual focus and rely on the indicator I can get better results when I focus in from the macro side towards infinity and stop turning the focusing ring as soon as I see the hexagon, since the hexagon itself has quite a large tolerance (ie. I can keep turning a little towards inifinity and still see the hexagon (all my lenses are like this - the manual focus indicator by design has a pretty large tolerance)) I focus on the closer/macro side of the confirmation range than the infinity side and get good/better results. Thus, I do think it is a problem with the SDM function. All my lenses show quite a high tolerance focus indicator in manual focus too so they are no different but with AF they all focus correctly except the DA* so I am certain there is no problem with the body but it is the lens.

My lens a couple times also declared success in AF with SDM when it was completely OOF (ie. the whole thing was blurred - say in macro focusing when it should be focused close to inifity), just like you state, interesting indeed.

Anyways - I am trying to figure out if I can get an international warranty card from Pentax US to get it serviced by the Pentax contracted service company here in Turkeyand if they don't have the resource to fix it then send it to the Pentax Europe service center. If not - worst case scenario I will give the lens to relatives coming to the US in a few weeks and they will send it to the Pentax US Service center in Colorado.

Last edited by sft; 08-31-2007 at 09:30 AM.
08-31-2007, 01:18 PM   #18
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Similar prob

If it's any consulation I'm having the same mild out of focus with my new 50-135. Mine does mild front and back focus. AF is very inconsistant. I also have a DA 70mm that was spot on focus before I upgraded to the new firmware for the DA* (1.30). After upgrade, the 70 is now showing similar focus issues. Maybe firmware related? I'm using the lens professionally in my studio every day. I love the rendering of the lens, but the focus is driving me nuts! Guess it's back to manual focus.
I don't want to be with out the lens (MANY studio sessions and several weddings coming up). Pentax service is anything but fast (really wish they had a Pro service like OLY, C and N). Oh well.Good luck!

Paul
08-31-2007, 05:29 PM   #19
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QuoteOriginally posted by sft Quote
Thanks for the replies Erl and rvannata.

Rvannata - by Cam-shaft you mean using manual focus with the confirmation right? Or are you implying using the screw driven AF in another body? Since my K10D is firmware v1.30 I can't use the screw driven AF.

I have indeed tried using manual focus with the focus confirmation hexagon and when I manual focus and rely on the indicator I can get better results when I focus in from the macro side towards infinity and stop turning the focusing ring as soon as I see the hexagon, since the hexagon itself has quite a large tolerance (ie. I can keep turning a little towards inifinity and still see the hexagon (all my lenses are like this - the manual focus indicator by design has a pretty large tolerance)) I focus on the closer/macro side of the confirmation range than the infinity side and get good/better results. Thus, I do think it is a problem with the SDM function. All my lenses show quite a high tolerance focus indicator in manual focus too so they are no different but with AF they all focus correctly except the DA* so I am certain there is no problem with the body but it is the lens.

My lens a couple times also declared success in AF with SDM when it was completely OOF (ie. the whole thing was blurred - say in macro focusing when it should be focused close to inifity), just like you state, interesting indeed.

Anyways - I am trying to figure out if I can get an international warranty card from Pentax US to get it serviced by the Pentax contracted service company here in Turkeyand if they don't have the resource to fix it then send it to the Pentax Europe service center. If not - worst case scenario I will give the lens to relatives coming to the US in a few weeks and they will send it to the Pentax US Service center in Colorado.
by the cam shaft I am speaking of the old style AF. -- this would indeed involve using a different body or undertaking to retro-grade your K10 to
older software.

As for the declared success issue. I've seen this with my DA 50-200.
I was watching it pretty closely when it did it. --- it turned back and forth
a couple of times---but never far enough to 'find the focus'--and then declared success with the best of nothing.--- totally out.

I took some more photos today and will investigate a little more.

08-31-2007, 05:43 PM   #20
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QuoteOriginally posted by pkstudio Quote
If it's any consulation I'm having the same mild out of focus with my new 50-135. Mine does mild front and back focus. AF is very inconsistant. I also have a DA 70mm that was spot on focus before I upgraded to the new firmware for the DA* (1.30). After upgrade, the 70 is now showing similar focus issues. Maybe firmware related? I'm using the lens professionally in my studio every day. I love the rendering of the lens, but the focus is driving me nuts! Guess it's back to manual focus.
I don't want to be with out the lens (MANY studio sessions and several weddings coming up). Pentax service is anything but fast (really wish they had a Pro service like OLY, C and N). Oh well.Good luck!

Paul
I'm thinking its more likely firmware related. my vision of the lens is that it is completely stupid and incapable of making a mistake. this could be wrong however in that Pentax doesn't excactly document (to my knowledge) what information is passed from the lens to the body although focal length
and largest F/stop is included.

What would be very helpful to the firmware would be if the lens mount
were capable of passing a 'unique identifier' for each lens.

If this were possbile the firmware writers could produce an optimized
focus program customized to the characteristics of each lens, rather
than having a generic focus driver.

It is sort of like writing a printer driver with out knowing which printer is to be connected.
08-31-2007, 08:46 PM   #21
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QuoteOriginally posted by pkstudio Quote
If it's any consulation I'm having the same mild out of focus with my new 50-135. Mine does mild front and back focus. AF is very inconsistant. I also have a DA 70mm that was spot on focus before I upgraded to the new firmware for the DA* (1.30). After upgrade, the 70 is now showing similar focus issues. Maybe firmware related? I'm using the lens professionally in my studio every day. I love the rendering of the lens, but the focus is driving me nuts! Guess it's back to manual focus.
I don't want to be with out the lens (MANY studio sessions and several weddings coming up). Pentax service is anything but fast (really wish they had a Pro service like OLY, C and N). Oh well.Good luck!

Paul
I think it is worthwhile to pursue the 'theory' that the focus issues we are seeing are indeed a firmware programming error.

It will take several people working to isolate and identify the issue. I didn't buy the K10 to be a beta site, but we may be there by default.

My theory is that if it is a software error, there is probably a fixed set of
conditions under which it occurs as software bugs are usually not random,
they just seem that way but the key to getting them fixed is understanding and isolating the conditions in a repeatable way that makes the error occur.

First off, I agree that the issue of focusing errors is not limited to any particular lens. I"ve seen it with a variety of lenses on the K10 and sort
of blown it off---but have also done some things that may have mitigated the issue without fully understanding there was a 'problem'.

My theory of the moment is that there is a linkage between the ISO setting
and the focusing accuracy. Now this may not stand a test, but at least
the first pass today, I fiddled with the ISO and had no problems. I retook
photos this morning in low light conditions and had no focusing errors
even though the subject was as close to what I took the day before
as I could get for an out door scene.

My thought is that a low ISO number also makes a low sensitivity setting for the autofocus making it more prone to error.

such a relationship---if it exists--- could either be a 'feature' or a 'bug' in the software. A 'feature' is a bug that a programmer can't figure out how to remove.

Anyhow, what I did with today's test sequence is to simply set
the camera to the 'SV mode, and force the ISO to 400 or more for a variety of shots---and I can't find one with a focus issue.

One day's shooting isn't enough to prove the theory, because changing the ISO also changes a bunch of other things.

Indeed some of you observing the focus issue may already be using
higher than the default 100 ISO (there are several ways to do it)
and contemplate whether you can demonstrate whether or not changes
to the ISO impact focusing accuracy (aside from the possibility that
fiddling with the ISO may change the F stop and impact the ultimate depth of field.)
09-01-2007, 03:44 AM   #22
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Hmm, interesting replies guys. However let me add that I have tested basically all of my other lenses (DA21, FA31, FA50, DFA100, DA18-55, DA50-200, DA10-17) and only the DA* 16-50 is displaying this problem. All of my other lenses focus fine - even the FA50 at f/1.4 - I am firmware 1.30 like I mentioned.

I also messed around with the ISO as I found the posts interesting however it did not make a differenece - the DA* backfocused like it always does and the other lenses still focused fine whether at ISO100 or 1600. I don't know about you guys but my problem seems to be solely lens related and not firmware or body. As a side note - I thought that higher ISO in digital is really all just artificial - it just boosts the signal of the base ISO of the sensor (so in the case of the K10D - ISO100) the sensors don't really have an ISO range (that is solely decided by the manufactuers - ie. Pentax may use ISO100-1600 of the 10MP Sony Sensor whereas Nikon uses ISO100-3200 on the same sensor on their D80) - Pentax didn't like the IQ they were getting at ISO3200 so decided to limit it at 1600 - there is however inherintly no limit as far as I know of how much ISO can be pushed - just that as you do so the results will start getting worse and worse and so a reasonable compromise point is required to get high speeds (ISO) and good IQ. This increase in ISO should not affect the AF sensors but simply give a digital boost to the sensor itself. The AF sensor is affected by the light hitting it by bouncing from the mirror and this is most affected by the aperture size of the lens used as all AF lenses auto focus with wide-open aperture to allow the most light through I believe.

The only other time I get AF problems is when the battery on my K10D is running low with the FA50 at which point the AF accuracy really suffers - with a normal battery the FA50 focuses just fine - interestingly my other lenses seem better/fine with a low battery - maybe slight inaccuracy but that much is expected - however the FA50 really starts to miss focus for some reason.

Last edited by sft; 09-01-2007 at 03:57 AM.
09-01-2007, 08:29 AM   #23
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QuoteOriginally posted by sft Quote
Hmm, interesting replies guys. However let me add that I have tested basically all of my other lenses (DA21, FA31, FA50, DFA100, DA18-55, DA50-200, DA10-17) and only the DA* 16-50 is displaying this problem. All of my other lenses focus fine - even the FA50 at f/1.4 - I am firmware 1.30 like I mentioned.

I also messed around with the ISO as I found the posts interesting however it did not make a differenece - the DA* backfocused like it always does and the other lenses still focused fine whether at ISO100 or 1600. I don't know about you guys but my problem seems to be solely lens related and not firmware or body. As a side note - I thought that higher ISO in digital is really all just artificial - it just boosts the signal of the base ISO of the sensor (so in the case of the K10D - ISO100) the sensors don't really have an ISO range (that is solely decided by the manufactuers - ie. Pentax may use ISO100-1600 of the 10MP Sony Sensor whereas Nikon uses ISO100-3200 on the same sensor on their D80) - Pentax didn't like the IQ they were getting at ISO3200 so decided to limit it at 1600 - there is however inherintly no limit as far as I know of how much ISO can be pushed - just that as you do so the results will start getting worse and worse and so a reasonable compromise point is required to get high speeds (ISO) and good IQ. This increase in ISO should not affect the AF sensors but simply give a digital boost to the sensor itself. The AF sensor is affected by the light hitting it by bouncing from the mirror and this is most affected by the aperture size of the lens used as all AF lenses auto focus with wide-open aperture to allow the most light through I believe.

The only other time I get AF problems is when the battery on my K10D is running low with the FA50 at which point the AF accuracy really suffers - with a normal battery the FA50 focuses just fine - interestingly my other lenses seem better/fine with a low battery - maybe slight inaccuracy but that much is expected - however the FA50 really starts to miss focus for some reason.
You provide another clue that could explain your difficulty---not that you could do much about it.-----but the low voltage issue suggests the possiblity of
a bad electrical connection somewhere.

as for the ISO, I quite agree that the setting SHOULD NOT make any difference, but then the focusing issues should not exist either. Something is causing that which should not happen.

WE may indeed all be looking at different issues. All of our thoughts as to the source of the issue may be wrong. when subtle issues appear
it is important that several people 'focus' if you will on isolating the issue
in a collaborative way.

You have tried a host of lenses on your camera, but unfortunately do not have a host of cameras to try on your lenses.

I can see it all now that Pentax service will put your lense on the test bench
exercise it, find nothing wrong and send it back to you, which won't mean that something isn't dreadfully wrong, just that their test bench doesn't find the issue. Intermittant issues are the most difficult for any mechanic to fix because they never (usually) misbehave while the mechanic is watching.

Your observation about the voltage issues leads me to think of another
possibility---Since this SDM lens is the ONLY lens you have that uses the
'2' electric contacts of the KAF2 mount, a problem with that electrical circuit
could account for your difficulty. It could be a short or bad contact at the mount.

But what is interesting is I just put my 16-50 on my XZ-5 under low light conditions (light meter proposing 1/20" at f/2.8 -- and the AF would
occassionally get completely baffled, sometimes finding the focus
and then turning it completely out and declaring success.

Again I draw no conclusions from this, but some more investigation seems
called for.

09-01-2007, 09:47 AM   #24
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Interesting points again about the electrical contacts. Indeed I do not have another body to test the lens on unfortunately - that would have really helped in pinpointing what may be the problem. I am sure that my problem is not firmware or ISO based - however I cannot rule out a possibilty of a bad contact for SDM as you say - especially since this is my only SDM lens. However, my grunch is that this is simply a badly calibrated lens somehow.

I do fear what you state - that Pentax test it and return it to me saying it is within spec. That would be very dissapointing. To counter this point I plan to send a CD along with the photos showing the examples of backfocus with the lens and then my manually focused shots to show how it should have focused. I will also type all this up on a sheet of paper and label the shots accordingly so that they can exactly see that I do have a problem. I just hope that they will not ask for me to also send the body to them too - that would be a bummer since I have no backup dSLR.

In the end - I agree it is a little tough to draw conclusions but I am quite certain that the issue is either badly calibrated lens or (god forbid) something in the contacts from body to lens in the SDM mechanism causing this problem, that would force me to send my camera too which would really suck - however as unscientific as it sounds I just feel that the SDM of the lens (and not the contacts in the body) is what is the problem so they should hopefully be able to fix it without asking for my body too. At least I hope so!
09-01-2007, 12:54 PM   #25
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QuoteOriginally posted by sft Quote
Interesting points again about the electrical contacts. Indeed I do not have another body to test the lens on unfortunately - that would have really helped in pinpointing what may be the problem. I am sure that my problem is not firmware or ISO based - however I cannot rule out a possibilty of a bad contact for SDM as you say - especially since this is my only SDM lens. However, my grunch is that this is simply a badly calibrated lens somehow.

I do fear what you state - that Pentax test it and return it to me saying it is within spec. That would be very dissapointing. To counter this point I plan to send a CD along with the photos showing the examples of backfocus with the lens and then my manually focused shots to show how it should have focused. I will also type all this up on a sheet of paper and label the shots accordingly so that they can exactly see that I do have a problem. I just hope that they will not ask for me to also send the body to them too - that would be a bummer since I have no backup dSLR.

In the end - I agree it is a little tough to draw conclusions but I am quite certain that the issue is either badly calibrated lens or (god forbid) something in the contacts from body to lens in the SDM mechanism causing this problem, that would force me to send my camera too which would really suck - however as unscientific as it sounds I just feel that the SDM of the lens (and not the contacts in the body) is what is the problem so they should hopefully be able to fix it without asking for my body too. At least I hope so!
One 'thing to do' is to visually inspect the contacts and see if you see anything interesting. Both contacts should look identical.

Also if you gently push on the contacts on the camera body you will
learn that they are spring loaded. I would suggest pushing each one gently with a blunt instrument to verify that the spring is working and that they retract and extend smoothly. A missing or broken spring behind one of the contacts in the camera body could explain your problems----and a possibility that is easy to rule out.
09-01-2007, 01:28 PM   #26
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opps, I see another thread "photozone cancelled' has picked up on the issue we
are discussing --- and his a more technical finger on the issue.


looks like a qualitliy control issue over these SDM lenses is about to hit the fan.
09-02-2007, 03:46 AM   #27
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Yeah I visually inspected - no problems. Check this thread out: DA*16-50 focusing test: Pentax SLR Talk Forum: Digital Photography Review - exact same problem I am reporting on here: Zenfolio | Sinan Tarlan | Focusing Accuracy, Vignetting, Distortion Test of DA* 16-50 (New)

It indeed does look like quality control/implementation of SDM in this lens to me, since that user reports that with his *Ist camera using the screw driven AF there are no problems with AF. Some suggest it could be firmware but then all of these DA*16-50's would have this problem and I have seen people stating their AF is fine.
09-02-2007, 07:25 AM   #28
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QuoteOriginally posted by sft Quote
Yeah I visually inspected - no problems. Check this thread out: DA*16-50 focusing test: Pentax SLR Talk Forum: Digital Photography Review - exact same problem I am reporting on here: Zenfolio | Sinan Tarlan | Focusing Accuracy, Vignetting, Distortion Test of DA* 16-50 (New)

It indeed does look like quality control/implementation of SDM in this lens to me, since that user reports that with his *Ist camera using the screw driven AF there are no problems with AF. Some suggest it could be firmware but then all of these DA*16-50's would have this problem and I have seen people stating their AF is fine.
hopefully Pentax will do the right thing here. I still have no firm opinion
as to whether my lens is misbehaving or not. I'm still watching and hoping that the issues I have seen can be attributed to 'operator error' on my part and that I can find work arounds that will minimize the issues.
09-02-2007, 04:15 PM   #29
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QuoteOriginally posted by sft Quote
Interesting points again about the electrical contacts. Indeed I do not have another body to test the lens on unfortunately - that would have really helped in pinpointing what may be the problem. I am sure that my problem is not firmware or ISO based - however I cannot rule out a possibilty of a bad contact for SDM as you say - especially since this is my only SDM lens. However, my grunch is that this is simply a badly calibrated lens somehow.

I do fear what you state - that Pentax test it and return it to me saying it is within spec. That would be very dissapointing. To counter this point I plan to send a CD along with the photos showing the examples of backfocus with the lens and then my manually focused shots to show how it should have focused. I will also type all this up on a sheet of paper and label the shots accordingly so that they can exactly see that I do have a problem. I just hope that they will not ask for me to also send the body to them too - that would be a bummer since I have no backup dSLR.

In the end - I agree it is a little tough to draw conclusions but I am quite certain that the issue is either badly calibrated lens or (god forbid) something in the contacts from body to lens in the SDM mechanism causing this problem, that would force me to send my camera too which would really suck - however as unscientific as it sounds I just feel that the SDM of the lens (and not the contacts in the body) is what is the problem so they should hopefully be able to fix it without asking for my body too. At least I hope so!

I have another observation to try on you for size. I just went
out at shot up a bunch of photos (a whole card full of raws to be exact)
and I spent some of the time looking at the lens instead of the viewfinder.

What I saw was a bit alarming.

Take a look at the little window on the lens where the "oo" marks the spot of focus at infinity.

Now every other Pentax lens I own is mechanically stopped so when
it reaches infinity the 'hash mark' is directly centered between
the two 'oo's --- except however, guess which lens I own. It will mechanically turn past the center of the infinity marker to approximately the center of the 2nd o.

Next I pointed the camera accross the field where I would expect it
to focus at infinity and watched. --- some times I hand cranked
the focus to other areas--- some times I didn't.--- and I watched, and watched

What I saw by watching was that the focus was inconsistent as to where it stopped. --- sometimes it turn clear to the mechanical stop, some times it turned to the 'center' of the infinity symbol.

Sometimes if you hand turned it out of focus and then pushed the button,
it would go to the over center position for the first photo, and then back up to the middle of the marker for a second photo.

Now, I would expect that the mechanical stop should be set precisely
at 'infinitity' from an optical standpoint ---which might or might not
correspond to where the infinity marker is painted on the Barrel, however given that every other pentax lense I own, mechanically stops at a particular place --- i.e. the center of the infinity marker--- except this one, I wonder
if
a) the barrel markings are sloppily applied.
b) the lens is actually mechanicallly capable of focusing 'beyond infinity'
c) the inconsistency in the stop point makes no difference.

I tried the lens out on my istD --- to get a mechanical focus as an alternate to the SDM--- and observed the same thing.

If the lens due to a defective mechanical stop has the mechanical abilityi to turn past the 'optical' infinity, it could explain the inconsistent results that you
have seen.

It also ought to be possible to check this issue out in the manual focus mode.
09-02-2007, 05:11 PM   #30
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QuoteOriginally posted by rvannatta Quote

Now, I would expect that the mechanical stop should be set precisely
at 'infinitity' from an optical standpoint ---which might or might not
correspond to where the infinity marker is painted on the Barrel, however given that every other pentax lense I own, mechanically stops at a particular place --- i.e. the center of the infinity marker--- except this one, I wonder
if

b) the lens is actually mechanicallly capable of focusing 'beyond infinity'

Many lenses, especially longer telephotos, are made with the capability of focusing beyond infinity. One reason is that changes in temperature will shift the infinity focus point as glass, metal and plastic expand and contract.

My old Pentax M* 300mm f/4 provided considerable movement past the marked infinity focus. This was by design. I recall that older versions of the Pentax lens instruction booklets mentioned this feature with the M* lens and certain A* lenses. Sometimes the infinity mark is marked on the barrel as a range. For example, my Sigma APO 100-300mm f/4 EX DG has a marked infinity range of about 5 mm (indicated with a square bracket). My DA* 50-135mm allows focus well past the marked infinity (and past the true infinity focus as far as I can tell). I think this is how the lens is designed. I seem to recall that my DA 16-45mm f/4 would also turn past infinity.
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