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11-24-2009, 10:51 AM   #1
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FA 77mm/1.8 Ltd & Purple Fringing

Hi guys,

I have a question for those who knows and already tried this. (Pls don't make assumption )

Do you see purple fringing on your photos in an extreme contrast condition taken with Pentax FA 77mm/1.8 Ltd on your 35mm FILM CAMERA ?

The reason I asked this because I can see a little bit purple fringing on extreme contrast photo taken with my K20D and FA 77Ltd.
Not that it's a big deal to me because I can always remove it in PP.
What makes me curious is after reading the review at photozone.de. Here is the quote about purple fringing:

QuoteQuote:
"Please don't let you put off by this problem though. This happens only in extreme contrast situations when the bright portion is at or beyond the contrast latitude capabilities of the sensor. "
Photozone tested the lens using K10D and it seems from the quote, the problem is with the digital sensor capability on K10D.
So, does anyone know about this and probably made a test with their film camera?

Thanks in advance.

11-24-2009, 10:57 AM   #2
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The interesting thing about that review is that the state the AF is fast on the FA 77mm. When the reviewed the DA 70mm, that said it was very fast. When people here compare the focusing speed of the 2, they sometimes refer to the 77mm as focusing slower than the 70mm. However, I that may be a bit deceiving in that because one is faster than the other doesn't automatically mean the latter is slow.

Also, they "forced" the purple fringing in the FA 77mm but didn't really try to do the same with the DA 70mm. I realize the 70mm does better in this area, but they should have tried to force it to purple fringe under the same circumstances. If the DA 70mm had the aperture ring, I'd be sold on it with out reservations.
11-24-2009, 11:04 AM   #3
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No, no problems with film that I recall. I use the 77 limited on my film cameras, but lacking exif, I can't say for certain which photos were taken with which lenses.

As for the photozone review. Klaus has methods of bringing PF out and has demonstrated great success with most lenses! It is enough to say that the 77 limited will exhibit PF on the K10D. Mine does. It also enough to say that several of my lenses are far, far worse and that I have no particular issues with the 77 limited in regards to PF.

Steve

(Don't really have any PF issues on film...classic CA, yes...PF, no...)
11-24-2009, 06:59 PM   #4
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for me, i definitely didn't see as much fringing (CA or Purple) from using film with the FA77
although the problem becomes more of finding a scanner that can resolve that much detail out of your film

11-24-2009, 09:24 PM   #5
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i suspect you are reading something into this which is not intended.
I strongly doubt that photozone does any testing on film.
I never saw any problems with the 77 on film, other than I found it to be too sharp for a portrait lens, and I don't recall seeing any fringing on digital either, but I honestly don't see fringing with very many lenses.
I suppose I don't like the pictures that go along with PF, so I don't shoot that type of picture.
11-25-2009, 12:25 AM   #6
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QuoteOriginally posted by Wheatfield Quote
i suspect you are reading something into this which is not intended.
I strongly doubt that photozone does any testing on film.
They don't

QuoteQuote:
I never saw any problems with the 77 on film, other than I found it to be too sharp for a portrait lens, and I don't recall seeing any fringing on digital either, but I honestly don't see fringing with very many lenses.
I suppose I don't like the pictures that go along with PF, so I don't shoot that type of picture.
There is some discussion as to whether PF is ever present on film or whether it is actually just garden variety yellow/blue CA. That being said, the FA 77 has measurably low CA, but does have some PF on the K10D. I have never seen the flagrant, blooming PF that is typical of the DA 18-55 and certain other lenses that I own. I can't speak for the CMOS sensors on the newer cameras.

As I mentioned above, I use my FA 77 with film and don't recall ever seeing PF or CA with that medium and that lens.

Steve
11-25-2009, 11:26 AM   #7
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QuoteOriginally posted by k100d Quote
for me, i definitely didn't see as much fringing (CA or Purple) from using film with the FA77
although the problem becomes more of finding a scanner that can resolve that much detail out of your film
How do you scan your film?
Do you print it first and then scan the developed film? If yes, how big do you print it to get the max result?
Or do you scan the negative film and then develop it digitally?

Thanks,
11-25-2009, 11:27 AM   #8
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QuoteOriginally posted by Wheatfield Quote
i suspect you are reading something into this which is not intended.
I strongly doubt that photozone does any testing on film.
I never saw any problems with the 77 on film, other than I found it to be too sharp for a portrait lens, and I don't recall seeing any fringing on digital either, but I honestly don't see fringing with very many lenses.
I suppose I don't like the pictures that go along with PF, so I don't shoot that type of picture.
No, like Steve said, photozone only tested it on K10D.

I don't have K10D but I can see sometimes the PF on my K20d's CMOS sensor.

11-25-2009, 11:29 AM   #9
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QuoteOriginally posted by stevebrot Quote
There is some discussion as to whether PF is ever present on film or whether it is actually just garden variety yellow/blue CA.
Steve
Steve, this is interesting. How can you tell if it's just a garden variety yellow/blue CA and not PF?
I'm trying to learn here.

Thanks,
11-25-2009, 11:41 AM   #10
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QuoteOriginally posted by HermanLee Quote
How do you scan your film?
Do you print it first and then scan the developed film? If yes, how big do you print it to get the max result?
Or do you scan the negative film and then develop it digitally?

Thanks,
usually i'm lazy and use the lab scans to put up online. and if i felt like, i would scan with a Coolscan V.

but to elaborate on your point a little bit, the purple fringe on the FA77 is a problem on digital. on film, it definitely is hard to spot if it's even there for all the FA limiteds. i did see it once taking a picture of a street lamp with my FA31 at dusk wide open, but that was about it. but if the resolution of your output with film isn't very high (be it scans or prints), then it's probably less likely that you would notice it anyways.
11-25-2009, 12:04 PM   #11
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QuoteOriginally posted by k100d Quote
usually i'm lazy and use the lab scans to put up online. and if i felt like, i would scan with a Coolscan V.

but to elaborate on your point a little bit, the purple fringe on the FA77 is a problem on digital. on film, it definitely is hard to spot if it's even there for all the FA limiteds. i did see it once taking a picture of a street lamp with my FA31 at dusk wide open, but that was about it. but if the resolution of your output with film isn't very high (be it scans or prints), then it's probably less likely that you would notice it anyways.
Thanks for the info.
Your comment is very interesting and raise another question to me

since you mention about the print size with film,
how big is the print from a film usually made by the user of FA 77Ltd?
Is it big enough in order to be able to notice the PF?

With digital, it's so easy for us to pixel peep and enlarge the photo even bigger than 1:1 ratio which will make it easier for digital shooter to notice the tiniest PF on their photos.
11-25-2009, 03:25 PM   #12
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QuoteOriginally posted by HermanLee Quote
Steve, this is interesting. How can you tell if it's just a garden variety yellow/blue CA and not PF?
I'm trying to learn here.

Thanks,
This is going to sound sort of hokey, but given a back-lit tree branch, yellow/blue CA will generally show yellow (often vague) on one side of the branch and blue on the other. PF, on the other hand, will be blue or purple on both sides. CA is also visible as a color band extending a set distance (x number of pixels) from a light/dark boundary. PF is of inconsistent width and will span gaps. And finally...CA is generally correctable in Lightroom or ACR using the CA correction feature. PF does not correct except by de-saturating the blue and/or purple channels. (At this point it is important to note that CA is actually present throughout the frame, not just where you can see it. The result is a generalized decrease in sharpness both with color and b&w photos that improves when the CA is corrected in PP.)

The reason I made the earlier statement regarding PF as a myth is that I was involved in a fairly active thread several weeks ago where this assertion was emphatically and repeatedly made. At that time, I offered to do comparison film and digital images with my 77 limited on both film and the K10D. Unfortunately, I went out to try it and came back empty handed. I could not coax any PF from the FA 77.

I did go back through my film image scans looking for the illusive blue/purple artifact. Mind you, I have been shooting film since the late 1960s and have never seen anything like the PF thrown by my two digicams. CA, yes. Bluish halo around white shirts from flare, yes. But no PF. On the other hand, I have never looked for it either. After a short search, I came up with a couple of frames taken with my Olympus XA of high contrast subjects in bright overhead light. There it was...a wide bright blue swath of color where none should be.

"That sure looks like PF", I thought to myself and it really did. I did a higher resolution scan and started looking a little more closely. At that point I saw less intense, matching yellow bands on opposing borders. When I applied aggressive CA correction in Lightroom, the blue disappeared with a general improvement to the image as a whole. So, was it PF on film? I would say no. Others would likely disagree.

Steve

Last edited by stevebrot; 11-25-2009 at 03:33 PM.
11-25-2009, 04:37 PM   #13
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PF on the 77mm is a moot point.

Any fast, longish lens will have PF.

If you need any consolation look for examples of the canon 50mm f1.2 L. It's a $1500 lens with absolutely hideous PF wide open. Yet people seem to find uses for it...
11-25-2009, 05:15 PM   #14
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QuoteOriginally posted by kristoffon Quote
PF on the 77mm is a moot point.

Any fast, longish lens will have PF.

If you need any consolation look for examples of the canon 50mm f1.2 L. It's a $1500 lens with absolutely hideous PF wide open. Yet people seem to find uses for it...
the really funny thing is that the Pentax K 50mm f/1.2 doesn't have quite as much of it as the canon lens.
11-25-2009, 05:25 PM   #15
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This shot was taken 4 years ago on colour negative and scanned with the Minolta Scan Elite at 2800dpi using Vuescan. FA77 f4. The cropped section is untouched. Called it CA or PF won't matter imho, the purple aberration is there.





But the FA*24/2 beats it by a wide margin.

FA*24/2 chromatic aberration photo - Alan Chan photos at pbase.com
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