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Pentax K7 and Lenses

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mera84

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I have just purchased the Pentax K7 and I have tested the Sigma 18 - 250 F3.5 - 6.3 on two occassions now and have had poor results with the sharpness of the images. The first occassion I can excuse as it was a dull day/ light was poor and I was utisling the fully automatic settings. Today was clear and sunny and I tested the lens utilising different ISO/shutter/apeture settings at a variety of focul lengths.

Still mixed result, some close ups were sharper than long focul lenths shots. I am reluctant to commit to a purchase of this lens with the results I have got so far. I am located in Australia and Pentax and Tamron have both advised they are no longer putting out this focul length with a Pentax mount. The plan was one lens for travel at this focul range. Any suggestions.
 
As Marc suggested, you need to live with a compromise when opting for such a zoom. Have you considered another zoom? In Australia, 16-45mm f4 is pretty affordable, and is quite a good choice too.

However, if you're from Melbourne, please feel free to come to PMA show this Sunday; the fair is at the Exhibition Centre, in the city, and I'll be there as well, so you may try some of my lenses too ..
Cheers.
 
Thanks gents for your responses. I will give the lens calibration a try. Its a real mixed bag of results with some macro flower shots nice and sharp and then general autumn shots of trees out of focus for the entire shot. It may well be that I have to accept the compromise of the focul length fighting against the ability to get a larger appeture settings so the depth of field is much shallower. For example one shot in open sunshine ISO 200, shutter at 1/100, apeture f10, focal length 100, automatic auto focus is out of focus from front to back.
 
That does not sound right. With my Pentax 18-250mm, at f/10 I can usually get good DOF. You can see a few samples in my gallery.

Are you giving the lens time to focus (use focus lock)? Forgive me if you have answered this already.
mera84 said:
Thanks gents for your responses. I will give the lens calibration a try. Its a real mixed bag of results with some macro flower shots nice and sharp and then general autumn shots of trees out of focus for the entire shot. It may well be that I have to accept the compromise of the focul length fighting against the ability to get a larger appeture settings so the depth of field is much shallower. For example one shot in open sunshine ISO 200, shutter at 1/100, apeture f10, focal length 100, automatic auto focus is out of focus from front to back.
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Hi Adam..

I read about this in the book. Can you pls explain this in detail. As I also bought K7 couple of weeks ago.

Thanks.
 
mera84 said:
Thanks gents for your responses. I will give the lens calibration a try.
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based on your description, this is definitely not the problem. Lens calibration helps if your focus is off by a millimeter or two in a controlled test. If you're seeing an entire landscape shot out of focus, that's something else entirely. Most likely, you simply failed to tell the camera where to focus, so it focused somewhere entirely unexpected and you just failed to notice where the shot was actually in focus. As I said before, it would help to post examples.

--
Marc Sabatella
http://www.marcsabatella.com/
Blog: http://marcsabatella.blogspot.com/
Flickr: http://www.flickr.com/photos/marcsabatella/
 
using the two types of Image Stabilization???
You have to pick one. Or in lens, with the Sigma... or in camera, with the K-7.

My guess is that one...
--
Alan Schamber

Progress is not possible without deviation from the norm - Frank Zappa
 
Adam,

I am a little confused...when you write "any lens" , are third party lenses from the likes of Sigma also included, or does the focus adjustment apply only to "any Pentax lens" ?

This is one of the issues that concerns me about stepping up to a K-7.
 
Catalana said:
Adam,

I am a little confused...when you write "any lens" , are third party lenses from the likes of Sigma also included, or does the focus adjustment apply only to "any Pentax lens" ?

This is one of the issues that concerns me about stepping up to a K-7.
Click to expand...
BUMP

I am also interested to know if AF adjustment works with individual 3rd party lenses (I read in the manual you can apply it to all lenses). About to pull the trigger on a K7 but would like to know if this might be useful on some of sigma lenses if required...
 
Yes, in-body IS and AF-micro adjustment work with any lens.
 
Pterois said:
I am also interested to know if AF adjustment works with individual 3rd party lenses (I read in the manual you can apply it to all lenses). About to pull the trigger on a K7 but would like to know if this might be useful on some of sigma lenses if required...
Click to expand...
It does work, with the caveat that some 3rd-party lens "share" the same ID code, and are therefore considered the same lense by the camera. (For example, the Sigma 17-70/2.8-4.5 and the Tamron 35-90/4 apparently have the same ID).

That being said, I believe the chances of one person having two lenses with the same ID are pretty remote.
 
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