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12-21-2010, 08:56 PM   #31
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I'm missing something here.......granted I am not a high tech shooter or PF expert, but from all my years on various Forums, it has come to be my understanding that PF had more to do with the particular lens used, much more. My personal experience has always been that I can, for example, always get PF with my old Tamron 70-300 on a backlit scene.....but using the Sigma 50-500 shooting the same scene, never once get it. How could that be the sensor? Just asking? I use the K20D currently, but soon will own the K5, this PF sounds like pure nonsense to me.

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12-22-2010, 05:27 AM   #32
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QuoteOriginally posted by falconeye Quote
JohnBee, the first crop clearly is Bokeh CA from the lens. You can see this by going to the full image in the top of the article and look at the cropped region. it is in the foreground and purple. But there is a second almost identical region in the background (second lamp) which is green.
Yes, I didn't find that worrying at all, the region with PF is slightly in front of focus, I get very similar results with my DA70

QuoteQuote:
The son is less clear. It shouldn't be this purple and not if his face is in focus. Maybe, this was indeed from the defect lens with Long.CA.
Yes, that shot really puzzles me.
12-22-2010, 09:18 AM   #33
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QuoteOriginally posted by Rupert Quote
I'm missing something here.......granted I am not a high tech shooter or PF expert, but from all my years on various Forums, it has come to be my understanding that PF had more to do with the particular lens used, much more. ...
Yes, of course PF has more to do with the lens. Some lenses do not exhibit PF, regardless of the camera. Some lenses, on the other hand, are very prone to PF. No one is disputing this. So what are you missing? If you take a lens that is prone to PF, it will exhibit the trait more strongly with some cameras than with others. Such cameras do not "create" PF, but they exaggerate the effect. The issue is whether the K-5 is such a camera. It's just that simple.

Dan
12-22-2010, 09:39 AM   #34
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What are some of the lenses that don't show pf in k mount?

12-22-2010, 09:52 AM   #35
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QuoteOriginally posted by chuck luck Quote
What are some of the lenses that don't show pf in k mount?
Here's a couple of lenses that I own in K mount that seem completely free of PF:

Voigtlander 125mm APO-Lanthar
Voigtlander 180mm APO-Lanthar

When Klaus at Photozone tested the 180mm lens using a Nikon (with a Sony sensor) he concluded that "Purple fringing is absolutely absent with the Voigtlander". I have found the same thing, even with my K10D.

Dan
12-22-2010, 09:55 AM   #36
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Actually the K-5 could be somewhat more prone to CA showing up with its dense pixel pitch; it would seem to me that the photozone guys are implying something like this by using pixel as a measurement of CA and considering >= 1 pixel a problem (as I seem to recall)?
12-22-2010, 10:03 AM   #37
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QuoteOriginally posted by Dan Quote
If you take a lens that is prone to PF, it will exhibit the trait more strongly with some cameras than with others. Such cameras do not "create" PF, but they exaggerate the effect. The issue is whether the K-5 is such a camera.
I've heard this repeated many times about the K10D and now the K-5. I'd love to see a formal test, K10 vs K20 or K7 vs K5. If there is a difference, would it be in the sensor? I would have thought the AA filter would be the more likely source.
12-22-2010, 10:51 AM   #38
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Can't remember the name of the guy, but a couple of years ago I read an article interviewing a top Japanese lens designer (Olympus I think). The one thing I remember clearly from the article was that he reckoned that you only get the best bokeh smoothness if you allow some CA/PF to remain uncorrected.

12-23-2010, 06:07 PM   #39
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Its not a professional review, but it sounds like this USER on amazon compared the Purple fringing to his K7.

"The next thing I noticed when shooting in bright high contrast situations was how much purple fringing it shows. Doing side by side comparisons between it and my K-7, I noticed the K-7 was relatively purple fringe free, where this camera fringed quite noticeably. Think the difference between the K10d and K20d (K20d had almost no purple fringing where K10d had a lot). This shouldn't be a deal breaker for most, but be aware of it. Proper RAW developing can take care of much of it."
Amazon.com: Pentax K-5 16.3 MP Digital SLR with 3-Inch LCD (Black Body Only): Camera & Photo
12-23-2010, 06:44 PM   #40
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QuoteOriginally posted by SteveB Quote
Can't remember the name of the guy, but a couple of years ago I read an article interviewing a top Japanese lens designer (Olympus I think). The one thing I remember clearly from the article was that he reckoned that you only get the best bokeh smoothness if you allow some CA/PF to remain uncorrected.

QuoteOriginally posted by PixleFish Quote
Think the difference between the K10d and K20d (K20d had almost no purple fringing where K10d had a lot). This shouldn't be a deal breaker for most, but be aware of it. Proper RAW developing can take care of much of it.
I think that in most conditions it could remain manageable. Though in other cases(such as OOF foliage etc). it can be a deal breaker. Of course that's not to say we couldn't invest in better glass too, then again... the legacy shooter may find himself skipping the K-5 for manual shooting too.

So I can see it going both ways.
FTR. I've found the D700 to have less CA(with same lenses) than my K20D also.
12-24-2010, 07:22 AM   #41
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Could there be a simpler test?

QuoteOriginally posted by Dan Quote
Here's a couple of lenses that I own in K mount that seem completely free of PF:
Voigtlander 125mm APO-Lanthar
Voigtlander 180mm APO-Lanthar
Dan
Perhaps there is a simpler method for testing whether, or not, the K-5's sensor might be generating some purple fringing:
If someone, who owns both a K-5 and one of the above lenses, would mount this lens on his/her K-5 and do his/her best to photograph, say, the sun behind tree branches/leaves, would the resulting photographs enable a determination of whether, or not, the K-5's sensor might be generating some purple fringing?
For example:
Result 1: There is NO purple fringing in the photographs. Would this absolve the k-5's sensor of complicity in generating purple fringing?
Result 2: There IS purple fringing in the photographs. Would this indicate the K-5's sensor does, in fact, generate purple fringing?
Just a thought.
RayGunn
12-24-2010, 07:54 AM   #42
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QuoteOriginally posted by RayGunn Quote
If someone, who owns both a K-5 and one of the above lenses, would mount this lens on his/her K-5 and do his/her best to photograph, say, the sun behind tree branches/leaves, would the resulting photographs enable a determination of whether, or not, the K-5's sensor might be generating some purple fringing?
While that would be interesting, I don't think it would be conclusive. I'd rather see a comparison using K-7 or K20 vs K-5 and a lens that's known to fringe. Some people have said for example that the new 18-135 is better used on a K-7 or K20 because of PF.

Surely someone here has a Samsung sensored camera and a K-5 with a fringe-prone lens?
12-24-2010, 09:43 AM   #43
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QuoteOriginally posted by RayGunn Quote
Perhaps there is a simpler method for testing whether, or not, the K-5's sensor might be generating some purple fringing:
If someone, who owns both a K-5 and one of the above lenses, would mount this lens on his/her K-5 and do his/her best to photograph, say, the sun behind tree branches/leaves, would the resulting photographs enable a determination of whether, or not, the K-5's sensor might be generating some purple fringing?...
This test would do nothing to alleviate my concerns, because I am not the least bit concerned that the K-5 creates purple fringing. There is no evidence that any camera can create purple fringing. Purple fringing is created by the lens. The concern that I have is that the K-5 exaggerates the effect. This is the case with the K10D. With PF-free lenses, the K10D doesn't somehow magically create PF. But with lenses that are prone to PF, the effect is more severe with the K10D than with the K20D. To see if this is also the case with the K-5 the test needs to be conducted with a lens that exhibits PF.

QuoteOriginally posted by audiobomber Quote
... I'd rather see a comparison using K-7 or K20 vs K-5 and a lens that's known to fringe. Some people have said for example that the new 18-135 is better used on a K-7 or K20 because of PF.

Surely someone here has a Samsung sensored camera and a K-5 with a fringe-prone lens?
This is exactly the sort of comparison I would like to see. If no one runs such a test, then perhaps I will rent a K-5 and test it against the K20D.

Dan
12-24-2010, 10:44 AM   #44
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My personal take on this is that PF is just a characteristic of CA with certain lenses when a high contrast subject is posed against backlighting. As a free-lance writer in the firearms field, I've taken some shots which show this tendency. It's probably not strictly a K-5 problem, but related to the lens used and the circumstances. For example, this is a shot of an M4 carbine which is backlit. It was taken with a K200D using a Pentax 50mm f/1.4 prime at f/5. I wanted a near-silhouette picture for dramatic effect. Note the purple fringing around the Aimpoint scope mounted on the rifle. I think it's just a function of the strong backlighting and the particular lens in use. It would probably happen on any camera mounting that particular lens in similar circumstances (VERY strong backlighting).



Now, here is another shot taken with the K-5. Unfortunately, the time of day was not the same, and because of that I could not use the same background. However we do have a more mildly backlit picture of the same subject. The same 50mm 1.4 prime was used at the same f-stop, f/5. It is apparent to me that there is a difference - in favor of the K-5. Perhaps because of the better DR on this camera, or perhaps the backlighting was not so strong. So, for what it's worth, here is a comparison - I wish it were more exact. FWIW, I see NO traces of PF with this lens using the K-5.



It's also worth noting that automatic focus with backlighting is virtually impossible with either camera - the AF hunts and hunts. Had to go to manual focus with both the K200D and the K-5.

Last edited by PALADIN85020; 12-24-2010 at 12:03 PM.
12-24-2010, 11:02 AM   #45
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Should we not expect a higher resolution sensor to be more revealing of lens defects, such as CA and PF?

Rob
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