[hjortron]

Hi,
I've been trying to find a versatile zoom lens for my K-S1. A 24-120mm eq. would be an optimum for my purposes but I know that Pentax doesn't offer this exact range.

I first tried SMC Pentax-DA 17-70mm F4 AL [IF] SDM Reviews - DA Zoom Lenses - Pentax Lens Reviews & Lens Database but had to returned it as 9 out of 10 were (from slightly to terribly) out of focus. Only like 1/10 was perfectly focused. (Architecture, landscape shots.)

My next try is SMC Pentax-DA L 18-50mm F4-5.6 DC WR RE Reviews - DA L Zoom Lenses - Pentax Lens Reviews & Lens Database. I like its small size (especially while retracted) but even this one doesn't focus very well. It's better than the 17-70 above but still too many out-of-focus shots.
The camera runs latest firmware 1.20, optimised for this SMC Pentax-DA L 18-50mm F4-5.6 DC WR RE.

Strangely, my old Pentax 50-200mm f/4-5.6 ED SMC DA WR Review (cheap and noisy) focuses 100% reliably on this body.

My setting is AF-S and 1 point (tried 5 or 11 points - no difference).
It doesn't look like a front/back focus issue.

Could someone point me to a setting I could have missed or suggest me a lens for a desired range, that would auto focus reliably with this body?
Thanks in advance!

[ChristianRock]

You might want to read up on focus adjustments. There are a lot of helpful resources on this site.

Also , the Pentax DA 16-85mm has exactly the range you are after, ocuses fast and is sharp on all settings. The tradeoff for that good optical performance is that it is a bit larger and heavier than other wide to telephoto lenses like the DA 18-135mm.

[Adam]

A 24-120mm eq. would be an optimum for my purposes but I know that Pentax doesn't offer this exact range.

Yup, another recommendation for the 16-85mm:

HD Pentax-DA 16-85mm F3.5-5.6 Review - Introduction | PentaxForums.com Reviews

Regarding the focusing issues:

-Have you compared live view / manual focusing accuracy to what you get in viewfinder AF mode?
-Are you using aperture settings optimal for each lens? Wide-open may be soft, too small will cause diffraction.

[richfam]

A 24-120mm eq. would be an optimum for my purposes but I know that Pentax doesn't offer this exact range.

I've been using the SMC Pentax DA 18mm-135mm f/3.5-f/5.6 Zoom on my K-S1 with excellent results. It would give you the range you're looking for, and it's affordable (especially if you buy a used one).

I use aperture settings from f/8 to f/11 for the reasons that Adam mentioned, favoring f/8 at the wide end and f/11 at the long end.

[hjortron]

@ChristianRock: I'll try to go through these focus adjustment tips. Thanks.

The DA 16-85mm indeed looks like the range I need. Don't know why I missed it. The larger size and its price would be perfectly acceptable provided it focuses very reliably with my K-S1 body.


@Adam: The MC Pentax-DA L 18-50mm F4-5.6 DC WR RE isn't a lens designed for manual focusing. In the manual focus mode, the electronics is still employed and very fine manual adjustments don't seem to work/are skipped. I have some old manual prime lenses and these are tack sharp with manual focusing. But I was never 100% successful to focus manually with this lens.


Aperture settings like f/6.3 or f/8 can provide really sharp 20MPix pictures provided the auto focus snaps at the right moment. Unfortunately it seems to find something glittering or contrasty (?) nearby good enough and makes no effort to focus better. The noisy 50-200mm lens focusing takes much longer but it's almost 100% accurate.


@richfam: The SMC Pentax DA 18mm-135mm f/3.5-f/5.6 Zoom also looks good if it works on K-S1 well.


Thanks for the tips, guys.

[pschlute]

The MC Pentax-DA L 18-50mm F4-5.6 DC WR RE isn't a lens designed for manual focusing. In the manual focus mode, the electronics is still employed

Are you using the Autofocus/Manual Focus switch on the body ? The AF should not work when this is selected to manual.

[peggers]

I'd suggest my favourite travel lens, a Sigma 18-200 for APSC. It is really sharp and very versatile. It focuses pretty quickly and accurately too.

[hjortron]

I only use Autofocus/Manual Focus with manual lenses to turn on/off the Catch-in focus feature. The camera/lens tries to focus but it's very often imprecise or completely out.
Here are four sample crops from 100% size images with a red ring painted on the place where the focus indicator (Superimpose focus area) was shown while pushing the shutter button halfway.
Sometimes the focus is perfect but too often it is like this.

[MarkJerling]

Remember that the red square / ring is indicating where the camera is trying to focus, not where it has obtained focus. For focus confirmation, you need to see a green hexagon in the bottom of your viewfinder.
Can you confirm that you saw that green hexagon for these four images?

[hjortron]

@MarkJerling
The camera is in the "Focus-priority" mode so it wouldn't allow to take a picture if successful focus hasn't been reported.

I don't look at the green hexagon but listen to the beep.
If the red ring appears somewhere else, I try to re-focus but still many (not all) pictures with two different lenses are like this (actually even worse with SMC Pentax-DA 17-70mm F4 AL [IF] SDM).

@ChristianRock
Could you possibly point me to such an article? I'm new to this site and I've mostly found reviews only. Thanks.

[ChristianRock]

@ChristianRock
Could you possibly point me to such an article? I'm new to this site and I've mostly found reviews only. Thanks.

This article is a good place to start, it's very detailed.

Fixing Front and Back Focus - Introduction - In-Depth Articles

[MarkJerling]

@MarkJerling
The camera is in the "Focus-priority" mode so it wouldn't allow to take a picture if successful focus hasn't been reported.

I don't look at the green hexagon but listen to the beep.
If the red ring appears somewhere else, I try to re-focus but still many (not all) pictures with two different lenses are like this (actually even worse with SMC Pentax-DA 17-70mm F4 AL [IF] SDM).

Thank you for that feedback.

Can you please post the photos listed above, individually, unmodified and with their EXIF data intact?

[hjortron]

@ChristianRock: Thank you. I've already tried that focusing on a ruler and I don't think there's a front/back focus problem (see my original post). But I'll go through it.

@MarkJerling: Here are those four out-of-camera JPEGs with no modifications. They're f/5.6 and f/6.3 but it's not a wrong aperture choice problem. I've added a f/5.6 (the tree) and f/6.3 (the bridge) pictures as a proof that the same lens/camera can take sharp photographs if the auto-focus selects the right spot. (I could probably find some f/8 or even f/10 shots that are clearly out of focus).

Microsoft OneDrive - Access files anywhere. Create docs with free Office Online.

(click on the picture and find a Download button on top)
Some of the pictures are just focusing samples, the other are private ones, please don't republish them anywhere. Thank you.

[photogem]

@Adam: The MC Pentax-DA L 18-50mm F4-5.6 DC WR RE isn't a lens designed for manual focusing. In the manual focus mode, the electronics is still employed and very fine manual adjustments don't seem to work/are skipped. I have some old manual prime lenses and these are tack sharp with manual focusing. But I was never 100% successful to focus manually with this lens.

The DA L 18 50 is not great for manual focus, it has very little focus throw. I never liked it at all, prefered the DA 18-55 II or WR for it.
The only advantage is the DC motor.
The DA (without L!) is better. But still not a lens I would use.

But what sounds strange is that you had problems with 9 out of 10 samples of the DA 17-70 SDM:

I'd say it is either your K-S1 which is at fault.
Almost impossible to have such bad results with so many samples of the DA17-70.

[MarkJerling]

@ChristianRock: Thank you. I've already tried that focusing on a ruler and I don't think there's a front/back focus problem (see my original post). But I'll go through it.

@MarkJerling: Here are those four out-of-camera JPEGs with no modifications. They're f/5.6 and f/6.3 but it's not a wrong aperture choice problem. I've added a f/5.6 (the tree) and f/6.3 (the bridge) pictures as a proof that the same lens/camera can take sharp photographs if the auto-focus selects the right spot. (I could probably find some f/8 or even f/10 shots that are clearly out of focus).

Microsoft OneDrive - Access files anywhere. Create docs with free Office Online.

(click on the picture and find a Download button on top)
Some of the pictures are just focusing samples, the other are private ones, please don't republish them anywhere. Thank you.

Thank you for the link.

For image IMGP6274.JPG: I can't figure where the camera actually focussed, but it's not on the clocktower. If anything, it's probably focused somewhere closer to your viewpoint.

For image IMGP6258.JPG: As for the above.

For image IMGP6820.JPG: This one is interesting in that it seems to have focused on the building.

For image IMGP6822.JPG: What this focused on is anyone's guess.

A few suggestions / questions before we decide the camera is somehow faulty:

Have you shot any RAW shots with the same issues? Some of the images display some JPG processing artifacts, so I do wonder if that's part of the problem.

Do you, per chance, have a filter fitted to the front of the lens? If so, I'd suggest removing that and doing the tests again.