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10-05-2009, 08:30 PM   #31
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I was expecting to lose one stop with my CPL, but it's actually losing two.

10-05-2009, 08:57 PM   #32
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Good Evening,

I have a couple of questions. What type of focus were you using (AF or Manual) and what were you focusing on, or did you set the focus to infinity? If you were using manual focus was it possible you had exceeded infinity on the focus ring?

The reason why I ask is it the views you are photographing have very large depth of view. I would think that you would want to probably focus on something mid-way, or switch to manual and set it to something around say 20 feet so that everything from say 10 feet to infinity would be in focus.

Online Depth of Field Calculator

On at least the first couple of images, the center of the image was above the area that you have been doing the 100% view of. So it appears that the area you are focusing on is substantially in back of the area that you are looking at in detail.

Bottom line - I think that you are focusing on infinity, and then doing your image analysis on an area substantially closer, thus out of focus. By taking depth of field into consideration, you can essentially have the entire frame in focus from 6 feet or so out to infinity. Then camera shake and wind motion would come into play - however with the brightness shown, I would have to think that the shutter speed would be fast enough even at ISO 200.

Just some thoughts....

Last edited by interested_observer; 10-05-2009 at 09:03 PM.
10-05-2009, 10:25 PM   #33
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QuoteOriginally posted by Crepusculum Quote
So I took my K7 and DA* 16-50 out for the first time today since receiving them a few weeks back. When I got home to further look at my shots I noticed very bad image quality on all my shots. Here is an example. When viewed at 100% the image seems to be double. I have heard stories about bad copies of the 16-50 and I have heard about the shake reduction messing up shots. I had shake reduction on at all times. Any opinions would be welcome. Thanks!



I realize that this one's been answered, but I'd like to add that when I've switched between camera systems I tend to take quite a while to remember how to hold whatever I'm using. Like any other tool, it takes time to (re)learn the vibe of the thing.

P.S. Nice work, here! I really like the use of the skies with those sweeping clouds, and your use of a polarizer really compliments the colours nicely. More so than I would have expected from what appears to be mid-day.
10-06-2009, 01:21 AM   #34
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QuoteOriginally posted by audiobomber Quote
I was expecting to lose one stop with my CPL, but it's actually losing two.
Most polarizers "swallow" more than 1 f-stop even in the least-blocking position, except for the latest, modern modells - a handy replcement, if one needs a ND. If rotated to their densest position, some can reach 2.5 f-stops. It all depends on the foil inside.

Ben

10-06-2009, 03:33 AM   #35
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1) Remove all filters.
2) Set 2sec shoot delay mode (SR will be off automatically).
3) Place SLR on some heavy and flat rock.
4) Make focus target quite large and distant.
5) Shoot and show us results.

From that I see this lens in on par with faulty one I have.
Kit lens at F/8 is quite sharp, and Vivitar Superzoom I have is so sharp at 1:1 that it is same as or better then your reduced pictures.
My faulty Tamron looks quite similar, fuzzy even at F8. And it is not repairable as lenses are pressed in plastic :-)

I have simple opinion here. If it is hard to obtain good image in normal life and lens always requires small apertures just send it for repairs or sell it.
10-06-2009, 05:31 AM   #36
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I am not convinced at all, the first two images are trocious. I still suspect the lens as even the tripod image is a little fuzzy.
10-06-2009, 06:01 PM   #37
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For those who were wondering what type of filter I was using. On that day I was using the Hoya HD Circular Polarizer. Other then that all my filters are B&W. I do have to do some more testing to see why my shutter speeds weren't higher, I just have not gotten around to it yet. Those who mentioned that the crops were not at the focus point are correct, but they still should have been better. I am still convinced that it was more of the wind/shutter speed issue then anything else. I am most likely going to go out this Sunday and look for shots in the washes around Tucson, these will all be hand held, but it will give me more of an idea on what is going on.
10-06-2009, 06:04 PM   #38
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QuoteOriginally posted by Alfisti Quote
I am not convinced at all, the first two images are trocious. I still suspect the lens as even the tripod image is a little fuzzy.
The wind was quite bad in the tripod shot as well. But the shutter speed was still low for a 1pm Arizona sun. That is the part which I am working on figuring out.

10-06-2009, 07:20 PM   #39
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To rule out wind etc take a shot indoors .... on a tripod. Remember to turn the SR off when on a tripod.

Still. i am highly suspect it's a lens with misaligned glass ... seen it before on a lens i used to own.
10-06-2009, 09:58 PM   #40
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I'd be interested in your followup findings with your camera / lens combination. I own this duo myself and have noticed some odd behavior with the lens as well. I am a long time DSLR shooter but newer Pentax shooter. Have you gotten any more results that you're willing to share?
10-07-2009, 09:09 AM   #41
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I don't belive in "misaligned glass" as in mass-produced lenses it is almost impossible to misalign something. Most probably it is either bad glueing or faulty glass.
10-07-2009, 09:29 AM   #42
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QuoteOriginally posted by tr13 Quote
I don't belive in "misaligned glass" as in mass-produced lenses it is almost impossible to misalign something. Most probably it is either bad glueing or faulty glass.
All you need is the box that sat on the edge of the pallet or for one of the handlers to have dropped the box. As soon as i see that sort of ghjosting ... i think the Op called it "doubling" of edges .... i dunno .. i get edgy.
10-07-2009, 11:20 AM   #43
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Ok so I set up my tripod in my backyard today to get some controlled sample shots. I took three shots in the same conditions. I used a wireless remote with a 3 sec delay for each shot. I set the aperture to F/5.6 for each shot. This is a comparison of quality between the DA*16-50 and the DA 18-55 kit lens, then a shot again with the DA* 16-50 /w the circular polarizer (Hoya HD) on. Shake reduction was turned off for all these shots.

DA* 16-50, AV mode, F/5.6, ISO-200, @ 1/800



Now a 100% crop



DA 18-55, AV mode, F/5.6, ISO-200, @ 1/1600



Now a 100% crop



DA* 16-50, AV mode. F/5.6, ISO-200, @ 1/400 /w Hoya Circular Polarizer



Now a 100% crop




If you look at the quality of the DA* vs. DA, it is very hard for me to notice much a difference in quality of the picture, but the DA* does take a slight edge, but it's not as much as I thought it would. One thing I found odd was how in AV mode the DA* would only allow 1/800 shutter speed, while the DA was twice that @ 1/1600. The darker image left by the DA would have to be because of the shutter speed. If you also notice when used with the polarizer the DA* went from 1/800 to 1/400 and the quality of the image dropped very noticeably.

I wonder if there is something wrong with my DA* 16-50. I don't know any reason why the shutter speed would be reduced in half. Any ideas?
10-07-2009, 11:32 AM   #44
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The 16-50 shot is brighter exposed. Maybe one stop?
10-07-2009, 11:36 AM   #45
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QuoteOriginally posted by Supernaut Quote
The 16-50 shot is brighter exposed. Maybe one stop?
All the shots were taken with the same settings.
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