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02-17-2007, 11:00 PM   #1
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I could use some help understanding these results

This 18-55mm kit lens doesn't seem to focus properly at infinity. Either that, or it's really really soft. Close objects are fine but distant ones are not. My Canon S410 P&S is sharper than these first two shots. All shots were taken with a tripod, although the wind was blowing a little.

Thinking I have a focus problem, I switched to MF and set the focus ring on infinity.

Here's a shot taken earlier this afternoon stopped down a little bit.

Lens: 18-55mm kit lens
Camera: PENTAX K100D
Timestamp: Sat Feb 17 17:53:11 2007
Shutter: 1/250 s
Aperture: F5.6
ISO speed: 200
Focal length: 50.0 mm
Focal length in 35mm equivalent: 75.0 mm

EXIF data read by Exiv2 0.10





Lens: 18-55mm kit lens
Camera: PENTAX K100D
Timestamp: Sat Feb 17 17:53:31 2007
Shutter: 1/400 s
Aperture: F4.5
ISO speed: 200
Focal length: 45.0 mm
Focal length in 35mm equivalent: 67.0 mm

EXIF data read by Exiv2 0






I also took a bunch of shots with a 55mm, f2 smc Takumar lens. It's an old m42 screw mount from the early 70s.

This lens has always been sharp but it's never produced vibrant colors. This shot looks as bland as everything I've ever shot with this lens since about 1973. This is one of the more colorful pictures with this lens this afternoon too. It was an overcast day and it's a subdued winter scene but it wasn't this depressing.

Lens: sms Takumar 55mm f2.0 m42 mount
Camera: PENTAX K100D
Timestamp: Sat Feb 17 17:58:50 2007
Shutter: 1/125 s
Aperture: F0
ISO speed: 200
Focal length: 0.0 mm
Focal length in 35mm equivalent: Unknown

EXIF data read by Exiv2 0.10




What's going on here? Is the kit lens that bad? Is this what people mean by "soft"?

This last shot looks razor sharp when viewed full screen on my 26" monitor. The first two look out of focus, a little. I couldn't be more pleased with how sharp every picture taken with the old 55mm lens is.

Should the kit lens be capable of better results than this? Am I doing something wrong? I'll try getting it closed down to F11 or even higher on my next bright day shots.

02-17-2007, 11:31 PM   #2
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I've never seen the kit lens perform that badly! I'm at a loss to explain. I'm looking around my laptop (home and work) to see if I can find a similar picture for comparison.
02-17-2007, 11:36 PM   #3
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All three of those shots are full resolution crops, by the way.
02-18-2007, 05:51 AM   #4
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Tom,
Was SR on? I've had similar results to these with my K10D on a tripod, when I forget to turn off SR.


Last edited by roscot; 02-18-2007 at 05:56 AM.
02-18-2007, 06:07 AM   #5
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Tom I have never seen any 18-55mm preform this way. The darkness and out of focus just doesn't fit the results I have ever seen on a kit lens. in looking over your EXIF I can see nothing that would cause this problem in the way your menu is set up. I would say it's the lens. (How long have you had the camera and lens?) If you can take the lens back and exchange it. And before you leave the store try it out right there. If you get the same results you should see them in the rear screen right away.
02-18-2007, 07:27 AM   #6
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Either the lens is a dog or you have turned the focus ring past infinity. Still pretty blurry for that though. Did you check the focus in the viewfinder or did you just turn the ring and took the picture?
Where does this heavy underexposure come from?
02-18-2007, 08:00 AM   #7
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My 50-200 has trouble locking AF in that kind of scene - there is not enough contrast withing the scene for it to get a good lock because of the small aperture.

However dont set the lens to infinity, the barrel markers are not that accurate - try manually focusing instead. Mine works OK if I do that. It may not be quite as sharp as the takumar but it should be a lot better.

Also try it with AF on a bright sunny day with a high contrast scene.

Steve
02-18-2007, 09:30 AM   #8
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Hey Tom,

Here is a shot from my kit lens and some 100% crops. JPEG straight from camera, in P mode. Handheld through a somewhat dirty window.

EXIF
55mm
F/11
1/500 sec
ISO-200
Center Weighted

Does seem a touch soft, but not as bad as yours. Just realized my aperture setting. I'm going to try again with your aperture setting.

Oh, as the crow flies, about 5 km to the mall in the second crop. (My buddy just corrected me and we checked a map - lol).

Attached Images
View Picture EXIF
PENTAX K100D  Photo     

Last edited by Alvin; 02-18-2007 at 09:44 AM. Reason: Wrong distance
02-18-2007, 09:53 AM   #9
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Handheld shot through my dirty window again.

EXIF
50mm
F/5.6
1/3200 sec
ISO-200
Center Weighted
Aperture Priority
Attached Images
View Picture EXIF
PENTAX K100D  Photo     
02-18-2007, 11:33 AM   #10
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QuoteOriginally posted by roscot Quote
Tom,
Was SR on? I've had similar results to these with my K10D on a tripod, when I forget to turn off SR.
The camera was on a tripod with SR turned on.


QuoteOriginally posted by Photo Tramp Quote
The darkness and out of focus just doesn't fit the results I have ever seen on a kit lens.
The darkness doesn't bother me particularly because 70% of the scene is blanketed with snow. If I go to Ev+1.7 or Ev+2, it will be bright. How much Ev compensation depends on how bright a day it is... the brighter, the more compensation required.

My film cameras always worked the same way. You had to put the meter into overexposure to get a bright snow scene.


QuoteOriginally posted by Jonas B Quote
Either the lens is a dog or you have turned the focus ring past infinity.......Did you check the focus in the viewfinder or did you just turn the ring and took the picture?
I just turned the ring to the limit and took the picture. I was unaware it could be turned past infinity.



I will return this afternoon and try experimenting with a few things.

- No SR when on the tripod
- very careful focus (not easy to do but I will do my best and perhaps heavily bracket what looks like the best in the VF)
- much higher aperture (it's a very bright day today)
02-18-2007, 12:01 PM   #11
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QuoteOriginally posted by Tom Brown Quote
I will return this afternoon and try experimenting with a few things.

- No SR when on the tripod
- very careful focus (not easy to do but I will do my best and perhaps heavily bracket what looks like the best in the VF)
- much higher aperture (it's a very bright day today)
No SR is a given
Careful focus, or as good as you can

Both those ideas sound okay.

For the aperture opening... don't go beyond f/11. The kit lens is what it is. So is the sensor. You'll get less sharp pictures at f/16 and smaller openings due to diffraction and lens construction.

I also suggest you bring your other lenses for the sake of comparision.
02-18-2007, 12:59 PM   #12
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the lens should be adjusted so the stop is true infinity.. u are best doing a better light shot to test this.. if vaguely in focus no lens is as bad as your first shot.. "dog" would not be the word..

if the stop is out it should be easy to verify..

trog
02-18-2007, 01:07 PM   #13
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Tom...

I too have never seen this lens act so poorly. Check all optiions and if images look the same by all means return it. I have even used this lens for some of my web page stuff and other business images when I was not in the mood to put on a high performer and the images were fine.


wll
02-18-2007, 01:40 PM   #14
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QuoteOriginally posted by trog100 Quote
-snip-
if vaguely in focus no lens is as bad as your first shot.. "dog" would not be the word..
if the stop is out it should be easy to verify..
trog
You mean pure scheizze but I didn't want to write that. To my eyes it looks like a hint of axial CA on the bushes in the "front". If so I can think of a lens where infinity is way beyond infinity. Let's see what the next round of pictures shows.
02-18-2007, 02:50 PM   #15
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If Truth Were Know

QuoteOriginally posted by Tom Brown Quote
The camera was on a tripod with SR turned on.




The darkness doesn't bother me particularly because 70% of the scene is blanketed with snow. If I go to Ev+1.7 or Ev+2, it will be bright. How much Ev compensation depends on how bright a day it is... the brighter, the more compensation required.

My film cameras always worked the same way. You had to put the meter into overexposure to get a bright snow scene.




I just turned the ring to the limit and took the picture. I was unaware it could be turned past infinity.



I will return this afternoon and try experimenting with a few things.

- No SR when on the tripod
- very careful focus (not easy to do but I will do my best and perhaps heavily bracket what looks like the best in the VF)
- much higher aperture (it's a very bright day today)
You may have the first Pentax zoom that duplicates a Holga lens :-) It may go for a lot on e-bay. Or, if you take enough photos and enter them in fine art shows you may make a fortune :-)


wll
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