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02-14-2010, 08:36 AM   #16
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QuoteOriginally posted by mamba909 Quote
I'm posting another sample. To me it seems like it's in focus, but it has a more extreme case of glowing.



Another person I asked thinks that it might be the result of SR being enabled. I've always assumed that SR only kicks in when the shutter speed demands it. Does it always kick in when it's enabled?

Ok, I'm seeing some veiling flare on that one. It could be the filter, most likely is. Make sure your glass is clean though, and don't carry your camera around with your hand over the front element of the lens. It's too easy to get a big palm print on the lens that way, and if nothing else, there is tremendous potential for fogging the lens that way.
Let your lenses go naked in the world. It's what they are designed for, and they aren't the delicate little damsels that people often think they are.

02-14-2010, 09:53 AM   #17
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I get the same thing with both 18-55 I, 18-55 WR when using it at 55 mm and f/5.6 in CLOSEUP situations.

I believe that's how the kit lens behaves. WR version being somewhat better.
At f/7.1 it is already gone. It is also much less visible with subjects at normal distances.

It looks like spherical aberration to me:
https://www.pentaxforums.com/forums/377907-post25.html
02-14-2010, 01:38 PM   #18
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Looks pretty much as I'd expect from the kit lens wide open at minimum focus distance and maximum zoom with a UV (aka image-degrading) filter in place. That's probbably the most sure-fire way to get soft images. Also guessing you might not have used the hood?
02-14-2010, 01:42 PM   #19
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QuoteOriginally posted by Marc Sabatella Quote
Looks pretty much as I'd expect from the kit lens wide open at minimum focus distance and maximum zoom with a UV (aka image-degrading) filter in place. That's probbably the most sure-fire way to get soft images. Also guessing you might not have used the hood?
If anyone has the kit lens (I assume most of you do, from the way you talk about it) I challenge you to take a wide open 55mm f/5.6 at min focusing distance and post it here.

There is no way it will look that foggy. I've posted mine; the spider one is pretty close to min focusing distance and there is no glowing.

If my equipment were putting out these results, I would return it immediately for an exchange or repair.

02-14-2010, 03:13 PM   #20
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You asked for it. 18-55 WR, hand-held. The circumstances are not the best for testing, but you are free to define more constraints if you want:

(click for very larger)

I Don' t have my 18-55 mk1 any more to test it too.

You can see in the LARGE image, that the areas in focus has a "cloudy overlay" to them. Pay attention to the further 2.8 and 5.6 f-stop numbers. If those areas would be brighter - as highlights or white features on darker background, it would be even more visible. I could compare this with M50/1.4 and 50-200 mk1 if your'e interested.

Still, i think it is perfectly acceptable for the specific lens. Keeping in mind its range, price, good performance at other more usual focal ranges/settings and that it's driven to its extreme in such closeup situation.

With such attitude i would not be able to use Pentax where i live, since we only have Canon service. Here one must learn to work around obstacles. Nobody will replace anything that isn't falling apart. We have the same prices for brand new and demo/display products.

Last edited by ytterbium; 02-14-2010 at 03:21 PM.
02-14-2010, 10:28 PM   #21
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Well, those who said that it's a property of the kit lens, you guys are right. I took some more shots today and here are the results.

Comparison between shots taken with and without the filter:


Shot with SR OFF:


Each 1600x900 pixel crop in the full size versions is at 100%.

The filter wasn't creating a significant difference, even though I discovered a slight smudge on it. (I'm thinking it could've been from a fried chicken dinner I had a couple weeks ago... Now you know why I keep the filter on. ) It also looks like SR doesn't affect the image at all.

Well, all in all, I'm just glad we figured out what was going on. I know not to expect much from a kit lens, so I'm not disappointed or angry or anything. I just gotta become familiar with its limits and be creative and find ways around the limits or even use it to my advantage.

I just want to thank all of you for your help, and I hope that this thread helps any other "newbie" who might be having the same "problem" that I'm having.
02-14-2010, 11:28 PM   #22
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QuoteOriginally posted by mamba909 Quote
Well, all in all, I'm just glad we figured out what was going on. I know not to expect much from a kit lens, so I'm not disappointed or angry or anything. I just gotta become familiar with its limits and be creative and find ways around the limits or even use it to my advantage.
Your test was a great exercise in finding the limits of your lens, virtually all lenses exhibit some kind of aberration/s when pushed to their limits (though some people seem to have a tough time accepting that their beloved $1k+ lens isn't perfect).

Finding out what these limits are is the key and may prevent you from finding out when it's too late.

Cheers,
02-15-2010, 12:16 PM   #23
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QuoteOriginally posted by enoeske Quote
If anyone has the kit lens (I assume most of you do, from the way you talk about it) I challenge you to take a wide open 55mm f/5.6 at min focusing distance and post it here.

There is no way it will look that foggy. I've posted mine; the spider one is pretty close to min focusing distance and there is no glowing.
Pretty close to min focus distance isn't the same as *at* minimum focus distance. And unless that spider was practically microscopic, you don't appear to be all that close to minimum at all. Also, your shot is entirely different from his - different lighting, but more importantly, we don't get to the see the transition area between in and out of focus, which is where the "problem" is. Plus you presumably shot without filter; he shot with, as his later pictures show, makes a noticeable difference.

I stand by my comments. Unfortunately, I don't have any comparable pictures to post - the only pictures I took at 55mm at minimum distance and maximum aperture all had this soft glow to them, so I deleted them. Plus I got rid of my filters long ago, so I can't repeat the experiment.

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