[lele8491]

Ho una pentax k20 del 2008. Dopo averla lasciata ferma per circa 5 anni mi sono accorto che quando la utilizzo con l'obbiettivo originale SMC PENTAX DA 1:4 17-70mmAL (IF) SDM l'esagono che segnala nel mirino l'autofocus lampeggia in continuazione e non mi lascia fare la foto, mentre insistendo a volte riesco a farla. Quando invece monto un altro obbiettivo TAMRON AF 70-300 la macchina funziona perfettamente e scatta senza esitazione alcuna. Come mai questa differenza di comportamento? Qualcuno mi sa dare qualche suggerimento? Grazie.

I have a pentax k20 from 2008. After leaving it stationary for about 5 years I realized that when I use it with the original SMC PENTAX DA 1: 4 17-70mmAL (IF) SDM lens the hexagon that signals autofocus in the viewfinder it blinks continuously and does not let me take the picture, while insisting at times I manage to take it. But when I mount another TAMRON AF 70-300 lens, the camera works perfectly and shoots without any hesitation. Why this difference in behavior? Can anyone give me some suggestions? Thanks.

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Last edited by Parallax; 09-03-2021 at 02:23 PM.

[ramseybuckeye]

The K20D is fully compatible with your lens, so that is not the problem. I would try with the basic cleaning the contacts on the lens and camera. The Tamron probably is a screw drive lens but the SDM lens uses the electronic contacts. If you have not used the lens for a long time either, it may have a bad SDM motor, or even one that needs "woken up". I have never done this, only read about it on PF.

[photogem]

Of course the K20D supports SDM lenses! The K10D does as well.
From older entry-level bodies SDM support started with the K100D Super and the K200D.

Most likely it is a stuck SDM Motor. The DA 17-70 is SDM only, it can't be converted to screwdrive.


So you need to see if you can get the stuck SDM Motor moving again.
Here in a German Pentax-forum you can see how it is done:
[Tutorial] SDM Reparatur DA* ? Pentaxians

You can use google translator, but the pictures show everything very well.
At the end a very thin oil (red arrows) is supplied with a very thin needle, the same to the gears.
Recommended oil is gearoil

[scc]

Hello,
Does it happen irrespective of the selected focal length ? Do you hear the SDM operating?
Try manually focusing the lens back an forth and then focusing with the AF. Do that several times, it could wake up the lens SDM.
Regarding the failure to take the picture with the focus hexagon blinking it is probably due to a AFS setting with focus priority selected.

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Last edited by scc; 09-04-2021 at 07:33 AM. Reason: Info added

[rgknief60]

I have a pentax k20 from 2008. After leaving it stationary for about 5 years I realized that when I use it with the original SMC PENTAX DA 1: 4 17-70mmAL (IF) SDM lens the hexagon that signals autofocus in the viewfinder it blinks continuously and does not let me take the picture, while insisting at times I manage to take it.

More than likely it is a problem with the SDM. The SDM went out on my DA* 300mm f4, and I changed it to screw drive focus following the directions given by Uncle Vanya.


There is a small chance that you have a different problem, but I doubt it.


I had a similar problem when my K20D was new, and did not know anything about digital cameras. I tried to take pictures of monuments in Egypt, but the K20D would not let me if I could not achieve proper exposure. It was very frustrating. When I got home, I found out that there is a setting that I had to set to allow the camera to take a picture, when proper exposure is not achieved.

After five years, all of your setting were probably back to default. Check your settings to make sure that taking a picture is allowed when exposure is not perfect.

Edit: I just noticed that @scc just gave you the same advice!