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11-25-2009, 05:39 PM   #16
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QuoteOriginally posted by wlachan Quote
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
Reflection of your friend's sweater.

Edit: I checked out the FA*24/2 shot. Ouch, that is a nasty bunch of unwanted color. I imported it into LR and quite a bit cleaned up with CA correction. Even with that gone, there is still quite a bit of blooming purple...PF. Film image?

Steve


Last edited by stevebrot; 11-25-2009 at 06:33 PM. Reason: Added comment regarding FA* 24/2 shot
11-25-2009, 06:11 PM   #17
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For anyone interested in seeing PF from the FA 77/1.8 Limited, jsherman999 has a recent post where PF is present in several shots:
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/81080-77ltd-en...ay-season.html
This is not a reflection on Jay's skills. Rather, it indicates one of the limitations of current technology.

Steve
11-25-2009, 06:38 PM   #18
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QuoteOriginally posted by wlachan Quote
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.
BTW...Nice scan. Pity the Minolta scanners are no longer available. Is that the suspension bridge over Capilano Canyon?

Steve
11-26-2009, 05:16 AM   #19
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QuoteOriginally posted by wlachan Quote
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
In my humble opinion, this is longitudinal chromatic aberration, not purple fringing. Longitudinal CA typically shows green fringing behind the plane of focus and purple fringing in front of the plane of focus, like in this picture, linked from Photozone.de (this is from the review of the DA*200/2.8, another Pentax lens which has a real problem with purple fringing and longitudinal CA):



In many situations, purple fringing is nonetheless the FA 77 Ltd's weak point. I have had so many shots ruined by ugly purple fringing, that now I only use this lens in studio or in subdued lighting. The FA 77 Ltd can deliver stunning results, but not when brightly lit items or specular highlights are presents in the frame. Of course, it is always possible to hide the dust under the rug in post processing but then, I prefer to get clean pictures in the first place.

Cheers!

Abbazz

11-26-2009, 06:18 AM   #20
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QuoteOriginally posted by Abbazz Quote
In many situations, purple fringing is nonetheless the FA 77 Ltd's weak point. I have had so many shots ruined by ugly purple fringing, that now I only use this lens in studio or in subdued lighting. The FA 77 Ltd can deliver stunning results, but not when brightly lit items or specular highlights are presents in the frame. Of course, it is always possible to hide the dust under the rug in post processing but then, I prefer to get clean pictures in the first place.

Cheers!

Abbazz
If an artifact can be removed as part of the raw conversion, I'm not really seeing why it is a problem. Of course, I've also never seen PF off my 77 either.
11-26-2009, 07:37 AM   #21
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QuoteOriginally posted by Wheatfield Quote
If an artifact can be removed as part of the raw conversion, I'm not really seeing why it is a problem. Of course, I've also never seen PF off my 77 either.
As stated in my previous post, it is always possible to hide chromatic aberrations and purple fringing in post processing. It is also possible to enhance the contrast of a soft lens, to correct distortion of a bad wide angle and to remove vignetting from a lens with a front element of insufficient diameter. That's how cheap digicams and camphones manage to get good enough pictures from crappy lenses. I am sorry but if I pay quite a lot of money for a Pentax Limited, then I expect it to be a superior lens, meaning that I don't have to spend time correcting its defects!

The 77 is a certainly not a bad lens. It's fast, has beautiful construction, good sharpness, superb contrast and bokeh, but its behavior regarding longitudinal chromatic aberration and purple fringing is sub par for a high end lens.

Here are a few random samples taken from my pictures. First, some purple fringing:







Then some ugly "green fringing" in the contrasted areas of out of focus background:



Cheers!

Abbazz
11-26-2009, 08:04 AM   #22
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HEATHEN!! Burn him, burn the devil!

For the record i have said the same thing many times, it is capable of supreme results, colour, contrast and sharpness are all wonderful but it's something akin to treason to suggest that, imho, concerous bokeh cyan fringing is far too common for a $900 lens.

In particular, the final image youy posted with the trade mark cyan clinging to any border it can find.

In saying that, i took it for a spin the other night and look what she does




QuoteOriginally posted by Abbazz Quote
As stated in my previous post, it is always possible to hide chromatic aberrations and purple fringing in post processing. It is also possible to enhance the contrast of a soft lens, to correct distortion of a bad wide angle and to remove vignetting from a lens with a front element of insufficient diameter. That's how cheap digicams and camphones manage to get good enough pictures from crappy lenses. I am sorry but if I pay quite a lot of money for a Pentax Limited, then I expect it to be a superior lens, meaning that I don't have to spend time correcting its defects!

The 77 is a certainly not a bad lens. It's fast, has beautiful construction, good sharpness, superb contrast and bokeh, but its behavior regarding longitudinal chromatic aberration and purple fringing is sub par for a high end lens.

Here are a few random samples taken from my pictures. First, some purple fringing:







Then some ugly "green fringing" in the contrasted areas of out of focus background:



Cheers!

Abbazz
11-26-2009, 09:35 AM   #23
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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.
Just for clarification, I was just pointing out that photozone used them on the same k10d body and tried to force the 77mm to PF but didn't the DA 70mm.

I have no doubt the 77 is more prone to PF than the 70. I still wonder why since they in theory have the same coating. The other differences wold be in the different element materials and number of elements. I don't see how the 7mm in focal length difference would be the answer here.

11-26-2009, 12:57 PM   #24
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QuoteOriginally posted by Blue Quote
Just for clarification, I was just pointing out that photozone used them on the same k10d body and tried to force the 77mm to PF but didn't the DA 70mm.

I have no doubt the 77 is more prone to PF than the 70. I still wonder why since they in theory have the same coating. The other differences wold be in the different element materials and number of elements. I don't see how the 7mm in focal length difference would be the answer here.
Different optical formulation. The 77 is a holdover from the film era and there is no way Pentax had a digital sensor in mind when they developed it.
11-26-2009, 03:31 PM   #25
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QuoteOriginally posted by Wheatfield Quote
Different optical formulation. The 77 is a holdover from the film era and there is no way Pentax had a digital sensor in mind when they developed it.
I was referring to the SMC coating and didn't say anything about the optical formula. Besides, the optical formula in and of itself doesn't have much to do with whether its digital or film where as the coatings do and perhaps the location of the rear element.

However, it isn't completely true do say Pentax didn't have a digital sensor in mind when the developed it. The release of the 77mm dates from 1999. I also want to point out that the MZ-D full frame proto-type was rolled out in 2000. While a different area, don't forget that Pentax as been involved in medical optics and security optics and ccd devises for several decades for things with C-mount.

Anyway, again, my point was that they didn't do forced P.F. test with the 70mm and I think that is creating a bit of a misconception with the 77mm vs. the 70mm.

Edit: From dimitrov:




I think the real goal here was to get a short-tele pancake lens and not any perceived problems with the 77mm. Also, those 7 elements of the FA are arranged very close to 5 groups because those last 2 elements are barely separated.

Last edited by Blue; 11-26-2009 at 03:37 PM.
11-27-2009, 07:03 AM   #26
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QuoteOriginally posted by Blue Quote
I was referring to the SMC coating and didn't say anything about the optical formula. Besides, the optical formula in and of itself doesn't have much to do with whether its digital or film where as the coatings do and perhaps the location of the rear element.

However, it isn't completely true do say Pentax didn't have a digital sensor in mind when the developed it. The release of the 77mm dates from 1999. I also want to point out that the MZ-D full frame proto-type was rolled out in 2000. While a different area, don't forget that Pentax as been involved in medical optics and security optics and ccd devises for several decades for things with C-mount.

Anyway, again, my point was that they didn't do forced P.F. test with the 70mm and I think that is creating a bit of a misconception with the 77mm vs. the 70mm.
You appeared to be writing off the coatings as a potential difference when you said " I still wonder why since they in theory have the same coating". I didn't realize that also meant that any other potential cause was off limits for discussion. perhaps in future you would clarify this for people.
Lens coatings don't really do anything for CA or fringing, and about all digital coatings do is prevent sensor reflections from causing flare (rear element coatings with better anti reflection properties), but lens design does.
My understanding of the design history of the 77 is that the designer of the lens was designing a lens with film cameras in mind and had fairly specific parameters in mind (bokeh, 3-dimensionality).
11-27-2009, 08:31 AM   #27
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QuoteOriginally posted by Blue Quote
I think the real goal here was to get a short-tele pancake lens and not any perceived problems with the 77mm. Also, those 7 elements of the FA are arranged very close to 5 groups because those last 2 elements are barely separated.
Is it? Please bear also in mind that the FA77 Limited has the FREE focusing system, i.e. "Fixed Rear Element Extension". So the rear element stays in place while focusing; don't know what happens to the second last element while focusing.
11-27-2009, 12:31 PM   #28
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QuoteOriginally posted by Asahiflex Quote
Is it? Please bear also in mind that the FA77 Limited has the FREE focusing system, i.e. "Fixed Rear Element Extension". So the rear element stays in place while focusing; don't know what happens to the second last element while focusing.
I don't know about the movement of that 2nd to last element either. My main point was that they were going for the pancake design with very good resolution. Its like they snatched out the last element and diaphragm.

DA 70mm



FA 77mm



These are from lenstip who also reviewed both lenses. I wish the diagrams were on the same scale showing film/sensor plane.

Lenstips reviewed the FA 77mm using the K20d and the DA 70mm using the K10D.

Pentax smc P-DA 70 mm f/2.4 limited review - Build quality - Lenstip.com

Pentax smc P-FA 77 mm f/1.8 limited review - Build quality - Lenstip.com

Last edited by Blue; 11-27-2009 at 12:38 PM.
11-27-2009, 12:56 PM   #29
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QuoteOriginally posted by Wheatfield Quote
You appeared to be writing off the coatings as a potential difference when you said " I still wonder why since they in theory have the same coating". I didn't realize that also meant that any other potential cause was off limits for discussion. perhaps in future you would clarify this for people.
Lens coatings don't really do anything for CA or fringing, and about all digital coatings do is prevent sensor reflections from causing flare (rear element coatings with better anti reflection properties), but lens design does.
My understanding of the design history of the 77 is that the designer of the lens was designing a lens with film cameras in mind and had fairly specific parameters in mind (bokeh, 3-dimensionality).
QuoteQuote:
Full Quote for context: I have no doubt the 77 is more prone to PF than the 70. I still wonder why since they in theory have the same coating. The other differences would be in the different element materials and number of elements. I don't see how the 7mm in focal length difference would be the answer here.
Actually, I mentioned the design including # of elements. I don't think the coatings are a factor because they are theoretically the same.

No where did I say that discussion was off limits but in fact was hoping to see a discussion about it. The later post I was merely commenting that I think the major goals in the DA 70mm was the pancake design AND resolution performance. I'm not convinced that Pentax recognized problem in regards to CA or PF on the 77mm during the design.

As far as SMC coating goes, here is what Pentax had to say about in a 1985 brochure:

QuoteQuote:
All Pentax lenses have the exclusive Super-Multi-Coating (SMC), a remarkable seven-layer lens coating process that cuts the reflection ration down to just 0.2% per lens surface. The result is a dramatic improvement in both color fidelity and brightness and the elimination of flare and ghost images.
11-27-2009, 01:15 PM   #30
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Neither the DA 70mm nor the FA 77mm has low dispersion elements, but both are stated to have high performance optics.

However, the DA 70mm has the SP (super protect) coating in addition to the SMC.

Both lenses have the "ghostless" coating on the rear lens as per Dimitrov.,

The FA 77mm has PENTAX's exclusive FREE (Fixed Rear Element Extension) focusing system that supposedly ensures sharp, crisp image reproduction over the entire focusing range.

The DA 70mm was developed specifically for Pentax digital SLR cameras while the FA 77mm was developed for film but with compatibility with dSLR.



Last edited by Blue; 12-01-2009 at 10:07 AM. Reason: ghostless coating
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