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08-17-2008, 07:39 AM   #1
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Just received the K20 and 18-250 Lens

Hi all,

Well I decided after having my *istDS for 3 years to upgrade to the K20D and the Pentax 18-250 lens. I just received the goods on Friday and have taken a number of pictures around the back yard.

However, I'm wondering if I picked the right lens. I've taken about 100 pictures and noticed that many images are not in focus. I also noticed that those images that are in focus are somewhat soft. I have tried Raw and JPG with minor adjustments on the in camera sharpness setting. Is the Pentax 18-250 contributing to out of focus or soft images? Should I have bought a faster zoom lens? I will do some testing with my old 18-55 lens that came with my *istDS and see if I get more focused images.

Anyway . . . just sharing my first impressions and I do understand that there is a lot to learn about the K20. Just hope it doesn't take me too long to get the best image possible . . .

Peter

08-17-2008, 07:46 AM   #2
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The 18-250mm is probably a terrible lens, im sure you can look it up online.

www.photozioe.de might have a test posted on it.

Any lens with such a huge zoom range will have obvious optical compromises.

The 18-55 kit lens isnt all that great, but probably trounces this.

edit: yep photozone got a test up -

http://www.photozone.de/pentax/367-pentax-smc-da-18-250mm-f35-63?start=1

interesting to note, is that its a rebadged tamron 18-250

look at the 135mm results - absolutely dismal - only gets worse from there.

The fact that the K20D has a 14mp sensor will only compound this problem due to the (lack of) resolution of this lens and the small photosites.

Last edited by Athiril; 08-17-2008 at 07:52 AM.
08-17-2008, 09:25 AM   #3
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QuoteOriginally posted by Petermgr Quote
However, I'm wondering if I picked the right lens. I've taken about 100 pictures and noticed that many images are not in focus. I also noticed that those images that are in focus are somewhat soft.
Most people report the 18-250 is at least as good as the original 18-55. Side-by-side comparison would be useful. With SR, you *should* be getting sharper images. Of course, if you are viewing your images at 100%, the K20D has so much more resolution than the DS that it would be great;y magnifying any small focus discrepancy or lens softness. That is, your camera is out-resolving your lenses. Viewed at only the same size as your DS images, they should look about the same, but of course it's going to get softer the bigger you view.
08-17-2008, 09:29 AM   #4
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QuoteOriginally posted by Athiril Quote
The 18-250mm is probably a terrible lens, im sure you can look it up online..
I did look it up online (i.e. Amazon, etc) and from what I gathered, it was a good lens. However, I read the review in the link you gave me and it tells another story. Very interesting.

I appreciate your response and link. It looks like I would have been better off going with my original thoughts, a 16-45 lens and simple hold off on a zoom . .

Peter

08-17-2008, 09:42 AM   #5
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Don't forget that the sweet spot for most lenses us mere mortals can afford is around f5.6-8-11, I'd expect that holds especially true for zooms.

I usually stop down at least 2 stops from whatever the minimum aperture is for a given focal length, e.g. with the kit DA 50-200mm, I try to use f8 and higher when zoomed as the minimum aperture there starts at f5.6.

Then there's the sweet spot for the focal length as well.. Not sure, but maybe a K20D user can comment on the camera's ability to store information about particular lenses and optimal settings for various focal lengths?
08-17-2008, 10:14 AM   #6
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I was pretty disappointed when I got my K20D and the 16-45, but figured out it was truly a focusing issue. It needed an adjustment of +5/6 to be dead on. I would recommend doing a little informal testing and see if you discover consistent front/back focus. The 18-250 while not stellar seems to be a relatively solid performer so it sounds like you have some sort of issue there...
08-17-2008, 10:37 AM   #7
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QuoteOriginally posted by Athiril Quote
The 18-250mm is probably a terrible lens, im sure you can look it up online.

www.photozioe.de might have a test posted on it.

Any lens with such a huge zoom range will have obvious optical compromises.

The 18-55 kit lens isnt all that great, but probably trounces this.

edit: yep photozone got a test up -

Pentax SMC DA 18-250mm f/3.5-6.3 ED AL [IF] - Lab Test Report / Review

interesting to note, is that its a rebadged tamron 18-250

look at the 135mm results - absolutely dismal - only gets worse from there.

The fact that the K20D has a 14mp sensor will only compound this problem due to the (lack of) resolution of this lens and the small photosites.
Actually, the 18-250 is one of the best superzooms out there, per numerous tests and user reports. I can vouch for it personally on the K100D, K10D and K20D.

Perhaps the OP got a bad copy of it? I'd suggest returning it and getting another copy. The only compromises you'll notice from this lens is vignetting at the wide end, and a little edge softness at full zoom, which is to be expected. Some people have reported purple fringing, but out of thousands of shots with mine, I've only seen it a couple of times. Both the vignetting and purple fringing are easily correctible in post processing.

The 18-250 is a great walk around lens (easily equal to the 18-55 and 50-200 kit combo - I can't comment on the new 55-300 as I don't have it). You should get sharp shots with it (unless you're doing large upsizing, extreme crops, or viewing at 100% [not full screen, 100%]).

You can check the "Peru" set on my Flickr stream, or search the Pentax Photogallery for 18-250 shots to see what this lens is capable of. Here's one quick example with the Tamron 18-250 on the K20D:

Last edited by rfortson; 08-17-2008 at 10:42 AM.
08-17-2008, 11:10 AM   #8
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Beat me to it, Russ.

Got mine about a month before I got the K20 and was extremely happy with the results on my K10. Then I got the K20 and noticed that a lot of my pics were coming out 'soft'. I tweaked the AF adjust, tried different lenses, etc. before I had the epiphany that actually the K20 was just showing me in glaring detail how I, the photographer, was missing the shots and that the camera equipment was working just fine and dandy.

Another 18-250 sample...


Last edited by Venturi; 05-07-2011 at 11:07 PM.
08-17-2008, 12:14 PM   #9
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What ^^ those^^ guys said; the newb that i'm, is in a similar siuation where i'm learning the Pentax system's little nuances.

When i moved from film to digital, Canon was at the forefront but i had to learn the "digital" way of setting up camera, lenses etc now i'm moving to a new system i am quickly learning each manufacturer has their own little "quirks" <don't know if that's the right adjective> to work with. Digital lab now is a whole story by itself too vs the chemical way.
08-17-2008, 05:20 PM   #10
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QuoteOriginally posted by pingflood Quote
I was pretty disappointed when I got my K20D and the 16-45, but figured out it was truly a focusing issue. It needed an adjustment of +5/6 to be dead on. I would recommend doing a little informal testing and see if you discover consistent front/back focus. The 18-250 while not stellar seems to be a relatively solid performer so it sounds like you have some sort of issue there...
Thanks, I will play around with the settings and see what I get. I'm hoping I'm the one at fault, and not the lens or camera . . . .

Peter
08-17-2008, 08:04 PM   #11
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The 18-250 is an excellent lens. Not too long ago I posted a test here that compared the 18-250 to the DA*50-135. You couldn't tell the difference unless you went to 100% crops and "squinted."
08-17-2008, 08:06 PM   #12
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I love my Pentax 18-250 zoom on K20D.
08-17-2008, 09:05 PM   #13
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Hi guys,

Just letting you know that I've been reading all your comments and taking some advice given, and keeping an open mind.

I have done some testing and starting to realize I really need to understand that a zoom lens needs to handled differently from the standard kit lens. Perhaps the softer image I see in the K20D (compared to the *istDS) may not be a fault, but rather the way the image should look, more natural and allowing room for post sharpening by software.

I tested the 18-250 this afternoon in between breaks from my work. Couldn't fire off many shots but the following example is telling me that I likely need more testing and learning before making conclusions about the equipment.

First, from the EXIF:

Exposure time - 1/125 s
F-number - f/8
Exposure program - Aperture priority
ISO speed rating - ISO 400
Component config - YCbCr
Exposure bias value - 0.50 eV
Metering mode - Pattern
Focal length - 250 mm
Subsec time - 371
Colorspace - sRGB
Contrast - Hard
Saturation - Normal
Sharpness - Hard

Hand held at 250


100% Crop(large file)

Thanks for all the feedback!

Peter
08-17-2008, 09:18 PM   #14
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QuoteOriginally posted by Petermgr Quote
Hi guys,

Just letting you know that I've been reading all your comments and taking some advice given, and keeping an open mind.

I have done some testing and starting to realize I really need to understand that a zoom lens needs to handled differently from the standard kit lens. Perhaps the softer image I see in the K20D (compared to the *istDS) may not be a fault, but rather the way the image should look, more natural and allowing room for post sharpening by software.

I tested the 18-250 this afternoon in between breaks from my work. Couldn't fire off many shots but the following example is telling me that I likely need more testing and learning before making conclusions about the equipment.

First, from the EXIF:

Exposure time - 1/125 s
F-number - f/8
Exposure program - Aperture priority
ISO speed rating - ISO 400
Component config - YCbCr
Exposure bias value - 0.50 eV
Metering mode - Pattern
Focal length - 250 mm
Subsec time - 371
Colorspace - sRGB
Contrast - Hard
Saturation - Normal
Sharpness - Hard

Hand held at 250


100% Crop(large file)

Thanks for all the feedback!

Peter

Hi Peter,

Your shot looks fine to me. When I looked at the 100% crop, it's pretty much what I see from my lens. If this isn't meeting your standards, then you should look at the DA* lenses or the limited lenses. However, be sure of how you use your shots. I contend that if you printed that shot at 8x10 or even 11x14 it will look just as good as a shot with an expensive prime. Of course, only you can decide what your standards are.

I do know of a pro photographer (Don Gale) that shot his friend's daughter's wedding using this lens (along with an assistant holding an off camera flash) and the results were up to his professional standards. You can see the shots here (click on the link called "Wedding - Kevin and Crystal"). He shot this as a favor to a friend, and he considered the lens suitable for that purpose. It all depends on how you want to use the shots.
08-17-2008, 09:35 PM   #15
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QuoteOriginally posted by rfortson Quote
Hi Peter, Your shot looks fine to me. When I looked at the 100% crop, it's pretty much what I see from my lens. If this isn't meeting your standards, then you should look at the DA* lenses or the limited lenses. However, be sure of how you use your shots. I contend that if you printed that shot at 8x10 or even 11x14 it will look just as good as a shot with an expensive prime. Of course, only you can decide what your standards are. . .
Thanks Russ, appreciate your comments. This picture certainly is acceptable to me. My initial pictures were not . During my tests this afternoon I changed settings such as the ISO (to 400) and I also closed down to F8. I also increased the in-camera sharpening. Not sure if I'm using the best settings for the lens. I want to get comfortable with the camera and lens asap. I would like it to shot a friend's wedding at the end of the month . . .

Peter
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