[Kerri-Ann]

Hi folks
I'm new to this. I have a K30 with an 18-135 zoom (SMC Pentax-DA etc WR).
While I'm mainly happy with it, as I have progressed in my photography, I realise it does not seem very sharp in various circumstances - in particular, it's very 'soft' on the outside edges when zoomed in on something, and in darker conditions.
I love the flexibility of a zoom, and having it dirt and water resistant is helpful as I use it out bush a fair bit.
Any suggestions?
Thanks
Kerri-Ann

[WhiteFeather]

Hi Kerri-Ann, and welcome to the forum!


If you like the comfort of a zoom and you can live without the extra reach, the DA 16-85 is tack sharp from edge to edge, it is also weather resistant, and for cityscape and landscape, the ability of going down to 16mm is a big, big plus.

[Culture]

I have this combination. Can you post some pictures to explain what you are talking about.

[Paul the Sunman]

The DA 18-135 is very nice lens, sharp at centre and a useful focal length range. However, as you note, it is less sharp at the edges, and chromatic aberration is an issue there too. Hardly surprising for a 7.5x zoom. For most purposes though, it is very usable.

But if you want to step up in optical quality, the obvious choice is the DA 16-85, as suggested by WhiteFeather. It's a really excellent lens, not dissimilar to the 18-135 in size and look. You give up 50mm at the long end but gain 2mm at the short end. That bargain may not look attractive at first sight, but there is a big difference between 16mm and 18mm in practice. For urban shooting it is definitely worth taking.

If I were taking one lens on a hike, I would choose the 18-135, but around town or for most other purposes, the DA 16-85 is a great choice.

[VoiceOfReason]

Next step in sharpness is the DA*16-50 paired with the DA* 50-135 or DA* 60-250.

[Na Horuk]

While I'm mainly happy with it, as I have progressed in my photography, I realise it does not seem very sharp in various circumstances - in particular, it's very 'soft' on the outside edges when zoomed in on something, and in darker condition

Lots of users love that lens, just like you do. If you want sharper, you will have to step up a tier, which will cost a bit more. I shoot primes, but I think the following zooms would be logical upgrades, unless you are also considering FA and F and other older series of lenses. Generally speaking, the longer the zoom range, the lower the IQ. So the next level of better optics has a little less zoom range. This is why people end up with a number of zooms, even with some overlap

HD Pentax-DA 16-85mm F3.5-5.6 ED DC WR Reviews - DA Zoom Lenses - Pentax Lens Reviews & Lens Database
SMC Pentax-DA* 50-135mm F2.8 ED [IF] SDM Reviews - DA Zoom Lenses - Pentax Lens Reviews & Lens Database
HD Pentax-D FA 28-105mm F3.5-5.6 ED DC WR Reviews - D FA Zoom Lenses - Pentax Lens Reviews & Lens Database
HD Pentax-D FA 24-70mm F2.8 ED SDM WR Reviews - D FA Zoom Lenses - Pentax Lens Reviews & Lens Database

There are also DA 17-70mm and DA 16-50mm. These are optically good, but are not as super popular on these forums on account of some problems, so a lot of people don't think they are worth the full price.
I think Sigma and Tamron make some lenses in the range of 24mm to 75mm. The Tamron is popular, if I remember right. Check out the Third party Lens reviews

[pres589]

The 18-135's softness comes in around 75mm, maybe with a bit of sample variance. What I think makes sense is keeping the 18-135 and getting some other lens to deal with working beyond the range where the 18-135 excels. The DA60-250 seems like an excellent performer, as an example. Na Horuk also listed some good options.

What focal length are you wishing was better with the 18-135 that you have?

[videoman]

I was wondering if a fixed lens would be better. An old manual K mount 135mm with f2.8/2.5 would give you a fast lens & better optics for a very reasonable price. It would also encourage you to be more creative in your photography as you would have to move back & forth to compose your images, something that professionals often do.

[cpk]

DxO Optics Pro does a good job of fixing the 18-135's lack of sharpness in the corners and other issues, but that is more software at potentially more cost and an extra step in the workflow. Earlier versions of Optics Pro may be available free, and there is a free trial for the current version. It may be worth a test run before getting another lens; the software would be cheaper. I've been using the Lightroom/Optics Pro combination for a long time now with the 18-135 as well as other lenses with good results.

Check my post #8 in the following thread for the results of my DxO tests with this lens.

https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/175026-da-...treatment.html

[timb64]

Just buy a 16-85 and be done with it!

[Des]

Welcome to PF Kerri-Ann.

I use the 18-135 out in the bush a bit too. Like you, I love the versatility and the weather resistance. And it produces good contrasty images with strong colours.

Have a look at this thread for what people can do with the DA 18-135: DA 18-135 WR, Show us what it can do - PentaxForums.com

The corner softness doesn't matter much for a lot of shots. Here are some examples:
2017-01-02_S0402E_LeesCk_DxO_sRGB_1
2017-01-24_S0810E_Heyfield_DxO_sRGB_1
2017-01-25_S0942E_GuysHut_DxO_sRGB_2

The extra reach is also very handy.


Again, for a shot like this, corner softness is less important than centre sharpness. In fact, the corner softness tends to enhance the impression of centre sharpness.

At the telephoto end, the 18-135 isn't as good as say the DA 55-300 (any version), but it's often good enough.

With most zoom lenses - and the 18-135 is no exception - sharpness (particularly in the edges and corners) improves a lot if you stop down one or two stops (that is, use a narrower aperture). If the light is good enough (without too much compromise on shutter speed or ISO), and you are not trying to get short depth of field for effect, aim to use f8 if possible.

And @cpk makes a good point about post-processing. I also use DxO Optics Pro, which is good for automatically correcting for distortion, chromatic aberration, etc, for the particular lens.

But for the sort of shot where you want more edge-to-edge sharpness the DA 16-85 might be more suitable. For more speed (you mention dark conditions), either one of the f2.8 zooms (e.g. DA*16-50,Tamron 17-50, Tamron 28-75) or a prime lens (e.g. the plastic fantastic DA 35 f2.4 or DA 50 f1.8, or the DFA 100 f2.8 macro which is WR).

It's all a trade-off. But don't jump ship until you have exhausted what you can get from the 18-135.

[videoman]

timb64
Great pics. I'm still finding my feet with the K50 but already finding out what a fantastic camera it is. I think I've got this right if so it's a picture taken with the Takumar 135mm
https://www.pentaxforums.com/forums/attachments/10-pentax-slr-lens-discussion/353896d1493369084-sharper-18-135mm-lens-my-k30-imgp0046.jpg

[videoman]

After some night time rain took these pics. The first is from the kit 18-55 lens & the second is again from the 135mm.https://www.pentaxforums.com/forums/attachments/10-pentax-slr-lens-discussion/353899d1493371339-sharper-18-135mm-lens-my-k30-imgp0076.jpg
Hope you like.https://www.pentaxforums.com/forums/attachments/10-pentax-slr-lens-discussion/353900d1493371339-sharper-18-135mm-lens-my-k30-imgp0079.jpg

[normhead]

Hi folks
I'm new to this. I have a K30 with an 18-135 zoom (SMC Pentax-DA etc WR).
While I'm mainly happy with it, as I have progressed in my photography, I realise it does not seem very sharp in various circumstances - in particular, it's very 'soft' on the outside edges when zoomed in on something, and in darker conditions.
I love the flexibility of a zoom, and having it dirt and water resistant is helpful as I use it out bush a fair bit.
Any suggestions?
Thanks
Kerri-Ann

Buy a DA*60-250 to go with it. In conditions where the 18-135 is weak on the edges, the DA*60-250 will be excellent.

Or second possibility, get a DA* 50-135 to go with it.

The 18-135 is a "step above kit", but not as good as a DA* type lens a sort of intermediate type of lens. It is very typical for this type of lens to be good everywhere in it's range. The 16-85 is, but it has reduced range, that also is very typical. The 18-135 is a 7:1 zoom, it's tough to make an APS_c lens that's good enough to use. So that's your issue. To get the wide range, you sacrifice edge sharpness in some of it's range. There is no premium quality 18-135 type zoom. But the 18-135 gives you excellent centre sharpness throughout it's range and very good (close to excellent edges) from about 20mm to 50mm.

So, you don't really have another choice. IF you want the range, you have to make use of the IQ as it is. If you don't want the range and will carry more lenses then there are lots of options.

[Kerri-Ann]

Thanks all!
I can't believe the speed and helpfulness of responses. The discussion and example photos made me think carefully about my issues. I've pulled out some of my pics to illustrate, as suggested. Hope my posting has worked ?
As Des points out, there are many photos where edge/corner softness does not matter (eg monitor (135mm, 1/60,ISO 800, 5.6), grasshopper (135mm, 1/160, ISO 400, f13). These are usually when picking out a subject against a relatively incidental background.
My main concerns arise at 135mm or close to that zoom in two circumstances - when the subject is all on one plane in the distance such as the pelicans (135mm, 1/180, ISO 400, f5.6) or all on one plane closer in such as the Christmas beetles (135mm, 1/15, ISO 400, f5.6).
I also find a softness at full 135 zoom when shooting just a landscape eg the surf and cliffline (100mm, 1/750, ISO 400, f9.5). But maybe that is lack of accurate focus? If i think critically, I have not always optimised my selectionof f stop and speed. I'm never really on a photo shoot -
usually just cycletouring or bushwalking or at home. So I should take more time...

There are some great suggestions here, and I'll look more positively on my 18-135mm as a pretty good all-rounder, but consider some of the DA type lens options for future investment. Perhaps as suggested by a few, the DA*16-85 but sadly beyond my budget unless I rob a bank the DA*60-250, as suggested by WhiteFeather and normhead. I might just also look at an old manual fixed telephoto. I've recently worked out (thanks to this forum!) how to use my old ME Super manual M lenses - a 50 mm f1.7 and 28 mm f2.8.

Thanks again

Cheers
Kerri-Ann