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01-14-2016, 03:40 AM   #31
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I wonder how sensible it would be to build a teleconverter with a apodisation filter built in...

A 1.7x converter would turn a 50mm f1.4 into about an 85mm f2.5, with better bokeh...

Maybe it will be the first Lensbaby teleconverter...

- Eric

01-14-2016, 03:47 AM   #32
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QuoteOriginally posted by Digitalis Quote
That effect on highlights is called coma, it is a complex effect caused by optical/mechanical occlusion of the COC.
Did you intend to write "cat's eye effect"?

Coma has nothing to do with mechanical occlusion.
01-14-2016, 04:21 AM   #33
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QuoteOriginally posted by TwoUptons Quote
I wonder how sensible it would be to build a teleconverter with a apodisation filter built in...
I think the APD filter or element has to sit very close to the aperture diaphragm. If not I suspect it will only cause heavy vignetting.

If people accept reducing light by one stop, the aperture may be replaced by a b/w LCD screen that makes an artificial aperture. Since LCD screens can have high contrast, many gradations between transparent and non transparent, and lots of pixels it can simulate both a apodizing filter, ordinary round apertures, not so round apertures, and have a collection of special shaped apertures to make figure bokeh. It would be a very artistic lens that fits well in Lensbabys lens lineup. I'm not sure LAOWA would go into that niche.
01-14-2016, 04:32 AM   #34
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QuoteOriginally posted by Class A Quote
Coma has nothing to do with mechanical occlusion
In some instances, It can. Especially with long telephoto lenses where the optical center of the lens is distant.

01-14-2016, 05:05 AM   #35
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QuoteOriginally posted by Digitalis Quote
In some instances, It can. Especially with long telephoto lenses where the optical center of the lens is distant.
Coma is defined by varying magnification for rays that enter the lens at an angle, causing distortion.

Again, it has nothing to do with occlusion.

Care to share your source?
01-14-2016, 06:03 AM   #36
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Ok guys so for information coma aberration is due to the difference between real lens and Abbe sin condition. Abbe condition is respected only for light rays close to optical axis. So basically it is a peripheric light rays problem, that has nothing to do with any kind of mechanical occlusion.

There is a quick source (scan from my own master course around optical design), if you want to read more you can go to read the Handbook from Malacara (http://optdesign.narod.ru/book/Handbook_of_Optical_Design.pdf) or if you can find it the bible from the Zeiss optical designer H. Gross (Vol3 Aberration theory and Vol4 Survey of optical instruments)




Hope this helps !
01-14-2016, 11:00 AM   #37
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QuoteOriginally posted by Digitalis Quote
All lenses suffer from it to some extent, it is most visible at close focusing distances even the Minolta (R.I.P) 135mm STF would suffer from it, probably even with the apodization filter in full effect
For the six weeks I had the Sony STF, I was unable to get a picture, even close-focus images, that showed noticeable signs of coma.
01-14-2016, 05:42 PM   #38
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Great pics. But I'd still use standard Pentax mount AF lenses.

01-14-2016, 10:17 PM   #39
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I would consider this lens for my Sony A7II. I might buy it in K-mount and use it on both the K-1 and the A7II. I really enjoy using manual glass on the A7II.
01-15-2016, 05:31 AM   #40
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I wonder how this compares with a Samyang 135mm F2.
01-15-2016, 10:55 PM   #41
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QuoteOriginally posted by Class A Quote
Coma is defined by varying magnification for rays that enter the lens at an angle, causing distortion.
Coma and Vignetting can also be influenced by the presence of baffles within the lens, it is also problematic with lenses large diameter front elements and small exit pupils.

QuoteOriginally posted by Class A Quote
Care to share your source?
Most of the books i'm recalling were very old and well and truly out of print and still packed in boxes from my last move. But as I recall they refer to extreme telephoto lenses which were little more than four elements and a long tube - coma and vignetting with these lenses was frequently caused by flare reducing baffles inadvertently occluding the exit pupil, making the problem worse.
01-16-2016, 07:52 AM   #42
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QuoteOriginally posted by D1N0 Quote
I wonder how this compares with a Samyang 135mm F2.
I think this one focused on the bokeh. It sacrifices 1 stop due to the additional APD filter.

---------- Post added 01-16-16 at 07:53 AM ----------

QuoteOriginally posted by TwoUptons Quote
I wonder how sensible it would be to build a teleconverter with a apodisation filter built in...

A 1.7x converter would turn a 50mm f1.4 into about an 85mm f2.5, with better bokeh...

Maybe it will be the first Lensbaby teleconverter...

- Eric
Gosh, what a good idea!
01-16-2016, 05:57 PM   #43
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QuoteOriginally posted by Digitalis Quote
That effect on highlights is called coma, it is a complex effect caused by optical/mechanical occlusion of the COC. All lenses suffer from it to some extent, it is most visible at close focusing distances even the Minolta (R.I.P) 135mm STF would suffer from it, probably even with the apodization filter in full effect.
Well, I'm mostly talking about the shape of the rendered highlight bokeh shapes, not cometic aberration, yes the 135 STF has that, and I agree pretty much all lenses suffer from it. However what I mean is, from my user experience of the 135 STF in turns of rendering and the shape of the bokeh highlights compare to the sample image of the the LAOWA lens, the Sony/Minolta 135 STF is superior.
01-16-2016, 07:36 PM   #44
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QuoteOriginally posted by ColiNiloK Quote
the Sony/Minolta 135 STF is superior.
It is too early to say that, no one here has enough data to confirm this.
01-16-2016, 08:28 PM   #45
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QuoteOriginally posted by Digitalis Quote
It is too early to say that, no one here has enough data to confirm this.
Like I said above it's purely based on comparing the sample images of the LAOWA lens and my past experience of the Sony/Minolta STF Lens, there are many "sample" pictures online also about the Sony/Minolta STF lens, we can all make our own judgement based on those, yes thus it's purply subjective at this stage.
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