Focusing with Sigma 170-500mm lens

Hello,

Last year I bought a used Sigma 170-500mm APO DG lens for use with my Pentax K7 and K5 DSLR.

I can obtain reasonably decent sharp shots when used at close distance (if the subject is within 10 meters) however when I try and shoot wildlife which is further away my shots appear to be out of focus or the focus point is not on the subject itself.

Can anyone advise me on how to improve my technique.

Whilst talking about using this lens I have used it on a Velbon Tripod with a Calumet Ball head is that the best tripod head for using this lens or should I get one of those heavy duty tripod heads or a Gimbal?

Best Regards,

Paul

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Quote:
Pentax K5D, Pentax 16-45mm f4 DA ED AL, Pentax 55-300mm ED, Pentax 100mm Macro f2.8 D-FA, Tamron 28-200mm, Sigma 170-500mm.

Simple first question. Are you switching the SR off when on the tripod??????
CHEERS Vic.

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Born again biker with lots of Pentax bits. Every day I wake up is a good day. I'm so old I don't even buy green bananas.

Also, just checking: are you clamping the lens collar rather than the camera to the tripod? are you using a cable release (or equivalent) or alternatively the camera's timer? As you obviously know judging from your questions about the tripod, the lens at its further reach will be intolerant of the slightest vibration. Another no-no of course is (if the Velbon has one) to extend the central column.

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Regards, Christopher

ChristopherWheelerPhotography

Hello, thanks for responding to my enquiry.

Good questions! Firstly I have NOT gone into the settings to de-active the shake reduction. I used to have a switch on the back of my K10 so forgot all about that!

I did secure the Lens to the Tripod and not the camera. I used the lens both hand held and on the tripod but had hold of the camera when pressing the shutter button! So that could be the cause of the issue I suppose?

I will try taking more images using the lens and tripod combination this weekend and will de-activate the vibration and see if that resolves the issue.

Best Regards,

Paul

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Quote:
Pentax K5D, Pentax 16-45mm f4 DA ED AL, Pentax 55-300mm ED, Pentax 100mm Macro f2.8 D-FA, Tamron 28-200mm, Sigma 170-500mm.

As the Sigma has shake reduction (3 modes, off, static and panning) I always turn off the in-camera SR to avoid conflict when hand-held, and both for a static tripod shot. I have found that over a long distance the Sigma loses sharpness at 500mm and it is reported that it does better at say 450mm; also I use back-button focusing in case there is manual fine tuning needed. Depending on what you are photographing, if you have the time try live view to eliminate mirror flap, with a remote switch or timer. On the last point I tried two photos at full stretch, one exposed when pressing the button and the second with the 2 second timer - it's surprising how much difference that made!

Thanks RobL my Sigma lens does NOT have Optical stability built in its just a 170-500mm 1:5.6-6.3 APO DG lens, I had thought of buying a lens with image stability built in then sell mine. But I have just bought a 100mm Macro lens at the recent photo Show so don't have the cash to do that. I will however try taking shots as you say below 450mm and with Live View and a trigger cable.

Whilst in the Bird Hide, I usually use a Manfrotto G-Clamp then insert the top section of my Tripod center column with Ball head.

If the weather is Ok I plan on going out into the Hills this weekend and will give everything a try.

Best Regards,

Paul

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Quote:
Pentax K5D, Pentax 16-45mm f4 DA ED AL, Pentax 55-300mm ED, Pentax 100mm Macro f2.8 D-FA, Tamron 28-200mm, Sigma 170-500mm.

the big Sigma lenses, 170-500, 150-500 have a reputation for needing good light to get the best from them as well

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odd lens or 2

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