Pentax 18-135 WR doesn't look very sharp at infinity

AnthonyGuil · 10-04-2017, 12:42 PM

Hello,
I have recently bought a Ks2 with a 18-135mm WR lens. This is a significant upgrade from my Kx+18-55mm. I took my new gears out last weekend and I took some pictures on a reasonably sunny day. I have the feeling that my pictures where not really sharp enough. Upgrading from 12Mp to 20Mp, I was hopping to see quite a lot more details. I have attached a couple of full size pictures and cropped versions around the centre. Any feedback would be very appreciated!

Anthony

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Adam · 10-04-2017, 01:17 PM

There might be some camera shake in the first two, and the last isn't focused right. More MP should mean more detail, but it also makes the camera more sensitive to technique.

AnthonyGuil · 10-04-2017, 01:55 PM

Thank you Adam for confirming my suspicions on the sharpness here.
I agree that shutter speed is relatively slow (1/100s) on the landscape shot but at 18mm focal I was not expecting that camera shake will be that noticeable.
Also here is another example with a faster shutter speed 1/250s at 40mm focal lens and it is still not very sharp either. Could that still be camera shake?

Kozlok · 10-04-2017, 07:42 PM

Did you calibrate for back focus? Your lens may be focusing past infinity. Try again focusing using live view.

Are you smooth and steady? Do you smoothly press the shutter button? Try 5s delay on a support.

AnthonyGuil · 10-06-2017, 01:34 PM

Thank you for the suggestion Kozlok. I have done some initial investigation last night at wide aperture and short focus distance. I didn't get any conclusive results. I need to try again during daylight but it seemed that the fine tune was not moving the focus point even when set at maximum correction. I'll try again this weekend. I suspect it could be the problem is there. One of my sharpest photos so far is a selfie taken with one hand. This could be because this was taken with live view so didn't have any back focusing issue.

Lake · 10-06-2017, 03:53 PM

I had my best results adjusting the front/back focus on my 18-135 lens by focusing on a distant object with good contrast in good light. I was not able achieve good results using a close object. Hope that helps.

10-04-2017, 01:17 PM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,593	There might be some camera shake in the first two, and the last isn't focused right. More MP should mean more detail, but it also makes the camera more sensitive to technique. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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10-04-2017, 07:42 PM	#4
Kozlok Pentaxian Join Date: Jun 2012 Location: Albuquerque Photos: Gallery Posts: 3,148	Did you calibrate for back focus? Your lens may be focusing past infinity. Try again focusing using live view. Are you smooth and steady? Do you smoothly press the shutter button? Try 5s delay on a support.

10-06-2017, 01:34 PM	#5
AnthonyGuil New Member Join Date: Sep 2017 Posts: 3 Original Poster	Thank you for the suggestion Kozlok. I have done some initial investigation last night at wide aperture and short focus distance. I didn't get any conclusive results. I need to try again during daylight but it seemed that the fine tune was not moving the focus point even when set at maximum correction. I'll try again this weekend. I suspect it could be the problem is there. One of my sharpest photos so far is a selfie taken with one hand. This could be because this was taken with live view so didn't have any back focusing issue.

10-06-2017, 03:53 PM	#6
Lake Senior Member Join Date: Jun 2015 Location: Minnesota Posts: 104	I had my best results adjusting the front/back focus on my 18-135 lens by focusing on a distant object with good contrast in good light. I was not able achieve good results using a close object. Hope that helps.

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