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07-30-2013, 05:48 AM   #1
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55-300 lens issue ?

Hello,

I have been using 55-300 DA L lens from past 16 months. Initially the pictures were sharp, but from past 3-4 months i find them soft at 300mm. Right now i have a picture taken at 300mm and will post more once i go back home. I am wondering whether focus has gone wrong or my camera is not working as intended.

Exif data

Camera make : PENTAXCamera model : PENTAX K-xDate/Time :2009/01/01 00:01:30Resolution : 982 x 1689Flash used : NoFocal length : 300.0mm (35mm equivalent 450mm)Exposure time : 0.0050 s (1/200)Aperture : f/5.8ISO equiv. : 100Exposure bias : 1.30Whitebalance : AutoMetering Mode : center weightExposure : LandscapeModeExposure Mode : ManualFocus range : distant

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PENTAX K-x  Photo 
07-30-2013, 06:04 AM   #2
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Maybe it's the combination of the wide-open aperture and atmospheric haze? Although that wouldn't explain the good performance of the year before...
07-30-2013, 06:25 AM   #3
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Looks like there might be something wrong with the lens. Focus looks ok since it looks like the closer foreground and the background are both blurred.

Are you shooting RAW or jpg? If jpg what are you jpg settings (sharpening, etc.)?

RAW will come out better than jpg. Shooting RAW+jpg will give you the same jpg quality as just shooting jpg.

It really should be quite a bit sharper than that.
07-30-2013, 06:27 AM   #4
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The EXIF data says you used manual focus. It can be quite hard to focus correctly with a slow (small aperture) lens.

Try to stop down to F9.5 or F11 next time for more depth of field and better contrast/resolution, bump the ISO to 200 or 400 to compensate for the smaller aperture, and use autofocus if possible, and let us know.

07-30-2013, 06:27 AM   #5
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I had a similar issue with mine, but it also seems to have something broken inside. I sent mine to CRIS for an evaluation. There was some catching when zooming and focusing, something is broken. I seem to have lost sharpness at infinity, though with airplane pictures I could never be sure if it was just haze. Sometimes the photo was obviously in focus but hazy. Other times, not as conclusive.

Something's not quite right with your focus, though. Do closer images look right at 300mm, or just as focus approaches infinity. My closer shots were fine.
07-30-2013, 08:10 AM   #6
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@Giklab i dont think it was haze
@cyclone3d i always shoot in raw and convert the image
@Ole yes.. for this shot, i have shot it with manual focus.. as you know this lens hunts a lot and ended up with lot of bad shots before i switched to manual focus. I sold my k-x and my k30 is on the way.. will try and let you know, once its home.
@TER-OR I am not sure from what focal length I am seeing the issue. But, the closer images under 250mm are tad sharper, beyond that they look little mushy.. i tried with high iso, auto mode, etc... I am from india and here technicians are reluctant to look into my lens ( another con for being pentaxian ).. so, i am wondering whether i can do anything on my own
07-30-2013, 12:26 PM   #7
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QuoteOriginally posted by mourya Quote
Hello,

I have been using 55-300 DA L lens from past 16 months. Initially the pictures were sharp, but from past 3-4 months i find them soft at 300mm. Right now i have a picture taken at 300mm and will post more once i go back home. I am wondering whether focus has gone wrong or my camera is not working as intended.

Exif data

Camera make : PENTAXCamera model : PENTAX K-xDate/Time :2009/01/01 00:01:30Resolution : 982 x 1689Flash used : NoFocal length : 300.0mm (35mm equivalent 450mm)Exposure time : 0.0050 s (1/200)Aperture : f/5.8ISO equiv. : 100Exposure bias : 1.30Whitebalance : AutoMetering Mode : center weightExposure : LandscapeModeExposure Mode : ManualFocus range : distant
f5.8 and 1/200 exposure are pretty difficult to shot with that lens. Were your older photos shot at f5.8? I have the DA55-300 and it's very sharp at f8 and above, but not very good at f.58. You are using a very slow shutter speed (for 300mm) and the lens is wide open, there really isn't a lot of chance for success here, it can be done but the odds are low. Check the EXIF on those old shots and see what aperture and shutter speeds you were using.
07-30-2013, 01:26 PM   #8
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There are a few things you can do to help diagnose. As said above, set autofocus to center point, set metering to spot. Use f8 or above, and in bright sun, with a nice fast shutter speed, start doing some test shots. I prefer TAv mode for shooting, and try to keep my ISO above 400 for most shots in the sun, that means I'll have a high shutter speed. Maybe even turn off your shake reduction, you won't need it with the shutter speed over 1/125 or so.

At different zoom levels shoot test subjects at different distances. Use your max zoom pretty close, see how sharp the images are. Pick subjects easy to focus on - like a flagpole or a fence post, which is nicely isolated from its background. Then you can compare your infinity focus - a building or a tree a few hundred yards away - to your closer subjects at max zoom

You'll have to isolate the variables.

07-30-2013, 10:23 PM   #9
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@TER-OR sure... will try that.
@ramseybuckeye Here is a previous shot.. with higher ISO. This was from the time when i had no issues with the lens. Also, this image is cropped.. still it is usable.
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07-30-2013, 10:27 PM   #10
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aah i accidentally replaced the above image and lost exif data

here is the exif from my memory f5.8 3200 ISO 500 300mm auto focus, center weighted mode
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