a few months back I purchased the DA* 300mm F4. and I cant say enough about this lens. It's sharp, renders great colour and contrast, and usually very nice smooth bokeh. with occasionally some odd graininess in the bokeh which I have read is not uncommon.
Last week after weeks of hardly picking up the camera due to house renovations, i decided to clean the mirror box because I had been having trouble with focus lock. The expected fibers, dust and unexpected numerous spots on the af mirror.
all were cleaned off gently, and after doing some test shots in the back yard i was happy with the increased focus lock.
But one thing that has puzzled me since the beginning with this lens.
Now I have read a few articles here and there about the SDM motor failures and most noted that sometimes the lens would lock at infinity. Mine however locks at the other end, and no amount of pressing of the shutter button will make it retry. I have to manually move the focus then press the shutter button, then it will cycle through. I find this to be the case almost all the time I am doing in flight shots against heavy cloud or overcast. I am assuming the clouds are the reason for the lack of lock and definition/contrast for the camera to resolve properly. But why at the other end and not infinity ? occasionally it will ratchet back and fourth on a lizard in heavy brush and then just stop trying. I have read that after periods of non use manually cycling the lens will help free it up and leaving it powered on for 2 minutes recharges the caps in the lens. This in itself doesn't make sense since these lenses sit in warehouses for months, so even though that article was written by a UK Pentax tech, I have reason toe question that information since the lenses are stored for sale.
Anyway, question is, has anyone else had the focus lock at the short end rather than infinity ? seems contrary to what I have read. It still tracks well for in flight, and in clear skies works every time.
this weeks shots at
https://www.pentaxforums.com/forums/12-post-your-photos/330932-nature-finaly-...ing-again.html

DeWolf

[jbinpg]

I have had the DA*300 since it was first released, I have had occasional bouts of it refusing to focus at all which were all traced to poor contact between the lens and body contacts. I have never had it lock at its minimum focusing distance,

[wibbly]

are you using the center point when this is happening? i found my 60-250 behave this way in low contrast when using a focus point nearer the edge

are you using the center point when this is happening? i found my 60-250 behave this way in low contrast when using a focus point nearer the edge

i always use center point and set it with the lever on the k5iis. when shooting things that are small and move its a must

---------- Post added 10-01-16 at 10:48 PM ----------

I have had the DA*300 since it was first released, I have had occasional bouts of it refusing to focus at all which were all traced to poor contact between the lens and body contacts. I have never had it lock at its minimum focusing distance,

Yup, did a LOT of cleaning, overlooked the contacts, but this has been happening since i got it. good call but I don't think that's going to be it, however I'm cleaning the contacts momentarily

[dlai]

Yes my lens does exactly the same when in less than bright light. I know now to manually return it to infinity to get it started again.

Yes my lens does exactly the same when in less than bright light. I know now to manually return it to infinity to get it started again.

well good to know im not the only one lol, our forecast of heavy all day rain is turning out to be sunny with no clouds, heading out in a few to grab more shots