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11-23-2018, 04:19 PM   #1
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DA*300mm F4 stuck at minimum focus

Hi all, this morning i was taking pics of the moon with the K1 & 300, which i put in the computer, then thought i will take a few more BUT the lens just goes to minimum focus and wont budge, i took the lens off and wiggled some things on the back of the lens and it focuses again, tried again and same thing blocked at min focus, any ideas or help, thanks ian. Hmm just been out in the daylight and it seems to be okay now, ian


Last edited by k1man; 11-23-2018 at 04:58 PM.
11-23-2018, 08:34 PM   #2
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sorry i put another question in the wrong thing, still about the 300 it seems to work fine except that looking at a clear blue sky it still just goes to min focus and stays there, what is wrong, ian
11-23-2018, 08:45 PM - 1 Like   #3
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a lens can't focus on nothing
11-23-2018, 09:43 PM   #4
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QuoteOriginally posted by k1man Quote
sorry i put another question in the wrong thing, still about the 300 it seems to work fine except that looking at a clear blue sky it still just goes to min focus and stays there, what is wrong, ian
A few questions. Does the lens squeek when focusing? Is it unsure - focus shifty a bit more than normal before settling down? What body or bodies can you try this on? When it fails focus you should be able to turn the focus ring and change it from minimum are you saying it locks and you can't manually adjust focus either?

11-24-2018, 12:36 AM   #5
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hi, thanks for the reply, no it doesnt squeek, no it looks at the sky from infinity and seems to go straight to min focus, no no i can manually go to infinity, i tried it after some moon shots this morning and just stopped working, as to knowing i have only had the lens for 2 weeks, it focuses ok but just not on infinity, sorry i am pretty useless even trying to explain, ian
11-24-2018, 01:08 AM   #6
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QuoteOriginally posted by k1man Quote
sorry i put another question in the wrong thing, still about the 300 it seems to work fine except that looking at a clear blue sky it still just goes to min focus and stays there, what is wrong, ian

The AF system cannot focus on a featureless subject. Try again on something terrestrial with texture, say a tree a few hundred meters away.


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11-24-2018, 01:38 AM   #7
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yes i understand that, but the sky was not featureless as i had taken 20 odd shots and tried again and it went straight to min focus, tried later daytime and it works fine on subjects but sky clear blue does the same, i put a pic on moon shots this morning so you can see, ian

11-24-2018, 07:25 AM   #8
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Does live view change this behavior?
11-24-2018, 11:56 AM   #9
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2am here just got up, I have not tried it on live view but will have a look a bit later, also try it on the old k7, thanks for the reply, ian
11-24-2018, 03:21 PM   #10
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QuoteOriginally posted by k1man Quote
yes i understand that, but the sky was not featureless as i had taken 20 odd shots and tried again and it went straight to min focus, tried later daytime and it works fine on subjects but sky clear blue does the same, i put a pic on moon shots this morning so you can see, ian
In the clear sky, there's nothing to focus on. It's like trying to focus on air - it IS trying focus on air. Try focusing on a cloud if you must focus on the sky. Try focusing on a neighbor's house or chimney. But trying to focus on the clear blue sky is an exercise in futility.

And you said that it focuses on objects so it's functioning perfectly fine. There nothing for the lens to focus on in the sky.
11-24-2018, 04:25 PM   #11
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i was doing the moon, this morning i got out the 70-200 & the 300 handheld pointed the center dot in the k1 at the moon and both worked fine, if you look at MOON pics i uploaded yesterday most came out ok there was cloud around the moon but maybe not dense enough for the sensor to grasp onto, so for off center shots i will focus manually, thanks for replying everyone, at least now i know everything works and not faulty, regards ian
11-24-2018, 04:43 PM   #12
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QuoteOriginally posted by k1man Quote
if you look at MOON pics i uploaded yesterday
It is often a good idea to provide a link to the page being referenced rather than expect the reader to go looking for it. Is this the post?
Show me your ......MOON ! - Page 35 - PentaxForums.com

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11-24-2018, 04:50 PM   #13
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sorry about that , i am not very good at this stuff, when a subject pops up and i have a pic i just stick it up, glad you found it as i know i have pics on here but where ??? sorry again, regards ian
11-25-2018, 12:36 PM   #14
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Do you use the half-press of the shutter button to get focus confirmation by the camera, or a rear AF button? In either case, it is always good idea to "catch an edge" of something at the same distance of your subject, such as part of your subject, so the AF has something to grab onto. Then hold your half-press without letting up on it, reposition your camera and complete the press to fire your shot. I'm talking about using the center-only spot focus sensor setting of the camera. There isn't much having an edge in your picture, which is probably at the heart of the problem here, but the edge of the moon itself should be good enough for your AF center-only bullseye in your VF to be trained on.

Last edited by mikesbike; 11-25-2018 at 12:47 PM.
11-25-2018, 03:32 PM   #15
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My DA*300 has done something similar numerous times except focus gets "stuck" at infinity and can't be focused either automatically or manually (focus barrel rotates but doesn't move the lens internals or change the lens focus - as if the clutch is slipping). Nothing feels amiss when rotating the focus barrel (but of course focus doesn't actually change and the indicator remains at infinity). Unmounting, remounting, wiping contacts etc. seem to make no difference, but then for seemingly no reason it'll start to work again and it'll be fine for months. After it happens I try to remember to leave the lens at some intermediate focus position when I remove it from the camera, but I'm not really diligent about it, especially as time goes on... I hope yours frees up.
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