DA 17-70 - any tips?

Hello All

I have used the DA 17-70 as a better reaching lens and one which has a F4 aperture at all focal lengths. Outdoors it seems to lock onto the subject and focus well. Indoors it is often a challenge to get it to focus and allow the shot to be taken.

I'm sure I've read that other members have had slow focus issues with this lens in poor lighting conditions. Has anyone found any camera settings that improve the experience with the combo of this lens and the K5? I usually have the centre point focus setting in use.

My impression is that the normal kit lens locks on better and this means the 17-70 isn't the first choice for indoor shots despite it having a constant F4. I'm ending up with the 17-70 in the bag and the kit lens on the camera.

One thing for sure is that its very annoying to miss shots because the lens isn't happy! (manual focusing is nostandard t good for me due to glasses and also poor light also doesn't help)

As a secondary question would I have been better to have bought a different standard zoom (Pentax or TP)?

Thanks all

Indoors or out the focussing on this lens can be a pig, usually at the long end. Which is a great shame, as when it does lock on the results are very good indeed. Because of this I generally end up using a Sigma 17-70 if I want this range even though the IQ is not as good. The only suggestion I can make is to clean the contacts frequently - it does seem to help.

I have had the same problem and found nothing much seemed to help. I would try re-locking the lens and sometimes it would help, which I suppose would be similar to Philip cleaning the contacts.

I'm trying some alternatives at the moment and so far it's the Pentax 16-45 with a Sigma 24-70 that's leading. Two others that I have not tried, but are talked of a lot, are the Pentax 16-50 and the Tamron 17-50.

Just thinking about cleaning contacts and lens factory setup, has anyone had the 17-70 serviced and then found any improvement?

Just tried mine on the K5 and K5II. I've never really had any problems with my 17-70, in fact I bought it after trying someone elses briefly and was impressed with the speed of focus, far quicker than the other SDM lens (16-50, 50-135, 300) I have.

On both cameras in a back room with no lights and it is dull, it pretty much locked on to whatever I pointed it at, albeit more positively on the K5II as would be expected.

On the odd occassion it didn't lock on with the K5 I just fractionally lifted my finger and gently pressed the half shutter again and it locked on. This can be done very quickly and I have used this technique for sports events with longer lenses as I find the AFC to be slower to react than this method for me. If you've not tried it then it may be worth trying this method to see it makes a difference.

Regards

George

Thanks for the comments and suggestions. I will give George's method a go. Just seems so frustrating that the kit lens is much snappier.

Happy New Year one and all.

Stand to be corrected here, but I seem to remember reading that AF is quicker if you 'pre-set' the lens to infinity before using AF, as it seems Pentax cameras always rack out to infinity then back to the focus point.

None of my lenses behave in this way, the 55-300mm sometimes hunts if focus fails to lock on, but the others don't. The cameras apply tiny adjustments only if the focus is already close to accurate.

Never had a problem with mine, locks quickly.

I've never had the kit lens to compare, but my 17-70 rarely has a problem focusing, even in low light

Thanks for the further comments. I'm now wondering why the same lens can be more problematic to some of us and perfectly fine for others.

For me its always in situations where there is lowish contrast. I usually have the camera in its P setting and set either shutter or aperture according to need. The iso is set to allow hand held exposures. The frustration is that you see the shot yet the camera won't fire. I use centre point focus and AF-S with centre weighted exposure.

The lens will have been used for maybe 5000 shots (tops) on K10, KX and now K5. I don't remember it being better on the older bodies when used on low contrast indoor shots.

I'd use manual focusing but the adjustment ring is too sensitive for me (as in small adjustments make big differences)

Could I ask CMW and Obione if they use any different settings on their camera bodies to those of mine above?

Thanks all

I've had a look at the reviews of the 17-70 on the USA forum and it's the same. Some praising the AF and some saying it won't lock. This is an extract from a comparison test the forum did with two Sigma 17-70 models.


"The Pentax lens is a different matter. Sadly, we must report that hunting occurred frequently with our test sample. Good lighting conditions were not a problem, but as soon as light levels started to fall, hunting problems began occurring. Problematic conditions included contrasty subjects in well-lit rooms, focus charts, and low-contrast subjects under sunlight. Hunting occurred more often when the center focus point was selected. When using the focus test chart, closing the selected aperture surprisingly increased the occurrence of hunting. This last observation leads us to believe that the issue is electronic and not optical."

I generally use M or Av, generally centre-point focus, AF-S, and a mix of metering biases. I am intrigued by this discussion and will try to encourage mine to misbehave tonight -- while hoping it won't. It certainly hasn't in normal use. I don't recall ever failing to get a shot because the focus hadn't locked.

If my experiment shows I've been giving this lens too easy a ride, I'll post again!

Mine is variable. Sometimes it locks just fine, but at other times it will hunt and hunt. I usually switch to MF then and rely on the green hexagon to indicate focus.
It is very frustrating, but I love the lens so much I put up with it's quirks.

A point worth noting... the inertia on the focus ring is very light and it seems (to me at least) that this played a big part in the focus hunting.

Gently resting a finger on the focus ring while autofocusing pretty much resolved the hunting

(Added to that that I generally use centre focus point, with the AF button - and not the half press shutter)

Matt

Hi All

It is challange indeed. I checked again and agree with comments that the issue is most pronounced at 60-70mm zoom. The same shot (always centre focus) works fine at wider zoom settings.

Not sure that I fancy focussing wide and zooming in as I feel the danger of going off focus it too great. As the problem only happens in low light (ie indoors) the chances are that I'd be using a wide aperture with shallow DOF.

The use of the green button (thanks Matt) is a thought which I'll use next time I use the lens for real.

Thanks for all your thoughts