voigtlander 25/4 on Nex: purple corners

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Joop Mees
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p.1 #1 · voigtlander 25/4 on Nex: purple corners

Hello,
I like using my voigtlander 25/4 on my Nex5 (14Mpix).
Unfortunately, this lens gives purple corners on this camera. see below

image by swedenholland, on Flickr

Are there any tricks to avoid this?

Thanks,
Joop

Edited on Dec 26, 2012 at 10:20 AM · View previous versions

Dec 26, 2012 at 10:14 AM

Makten
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p.1 #2 · voigtlander 25/4 on Nex: purple corners

https://sites.google.com/site/cornerfix/

Dec 26, 2012 at 10:18 AM

Joop Mees
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p.1 #3 · voigtlander 25/4 on Nex: purple corners

Thanks!

Dec 26, 2012 at 10:26 AM

Jim Schemel
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p.1 #4 · voigtlander 25/4 on Nex: purple corners

If you have lightroom on the Color adjustments sliders ( HSL / COLOR / B & W Tab) Turn down the purple and magenta on HUE / Saturation/ Luminance until you get the result you want.I find this works pretty good in most shots and is much easier to navigate than Cornerfix.
-Jim

Dec 26, 2012 at 12:39 PM

legaltrouble
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p.1 #5 · voigtlander 25/4 on Nex: purple corners

Lightroom's flat field plug in from Adobe Labs.

Dec 26, 2012 at 01:28 PM

Olaf G
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p.1 #6 · voigtlander 25/4 on Nex: purple corners

legaltrouble wrote:
Lightroom's flat field plug in from Adobe Labs.

+1

Dec 26, 2012 at 02:14 PM

Lee Saxon
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p.1 #7 · voigtlander 25/4 on Nex: purple corners

I don't understand it. The sensors Sony sells to Nikon are so good...

Dec 26, 2012 at 04:20 PM

douglasf13
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p.1 #8 · voigtlander 25/4 on Nex: purple corners

Lee Saxon wrote:
I don't understand it. The sensors Sony sells to Nikon are so good...

Nikon doesn't have an aps-c or FF camera that can use M mount lenses and their short registration distances, and, if they did, they'd be battling the same issues. The Sony 16mp sensor in the NEX-5R and NEX-6 does a better job with color shift.

Dec 26, 2012 at 04:40 PM

LightShow
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p.1 #9 · voigtlander 25/4 on Nex: purple corners

...& C3, & F3.

Dec 26, 2012 at 06:44 PM

RustyBug
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p.1 #10 · voigtlander 25/4 on Nex: purple corners

Douglas (et al) ... could you expand on that a bit. I get some shift with my SLR/C to varying degrees with my alt, wide and tilt glass. It would help if I better understood the optics of what is creating this issue, so I could better determine how to approach preventing it.

Dec 26, 2012 at 07:15 PM

Jacob D
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p.1 #11 · voigtlander 25/4 on Nex: purple corners

It's been talked about quite a bit in the NEX thread(s), cornerfix thread, and maybe even in a Zeiss thread somewhere where a recent article from Zeiss on the subject was brought up.

I don't have links to the pertinent threads available.

Long story short, it comes down to registration distance, configuration of the lens optics, and the sensor size, sensor optics, and/or incident angle of the light rays. Trial and error is the best way to know when a given combination of the above will work or not.

In terms of NEX, all 16mp sensors AFTER the 5 handle the issue much better, the 24mp sensor only makes it worse. The problem mostly arises with focal lengths under 35mm.

Dec 26, 2012 at 08:24 PM

Mescalamba
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p.1 #12 · voigtlander 25/4 on Nex: purple corners

For this reason is better to get NEX-5N.

Otherwise its caused by sensor being bit more 3D then flat and light goes under wrong angles on corners, causing colors to shift.

Only happens when you use lens designed for rangefinders and only some (mostly wide-angles). Regular adapted dSLR lens shouldnt do that. It happens on wide-angle zoom from Sony too.

Dec 26, 2012 at 10:50 PM

contas
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p.1 #13 · voigtlander 25/4 on Nex: purple corners

Corner (angle) color shift, is caused by microlens (reside right over pixel on most of digital sensor -but not all ), those are far from the center may make negative effects on the lightbeam.Bayer or Foveon sensors are suffered but in the last one this is more critical, where the fotons need to go deeper as it has 3 layers.Usually this phenomenon is met with wide angle ,where the angle of view over 60 degrees, but I myself suffered from this also with supertele 400mm, when did a conversion Canon 400mm f/5.6 L to Sigma SA mount.
CornerFix is convenient for batch file processing.It helps but not for all occasions, fortunately for landscapes, when I reduce the iris this phenomenon becomes subtle and the pics are acceptable.

Dec 27, 2012 at 02:29 AM

RustyBug
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p.1 #14 · voigtlander 25/4 on Nex: purple corners

So, if I understand correctly, the broader incident angles are not completely redirected (AI=AR @ refraction / reflection) by the microlens, allowing scattering of energy to occur to nearby subpixels. Such that for that energy that isn't fully captured by green subpixels, there will be residual/reflected/scattered energy being captured by neighboring red & blue (thus purple) subpixels, or conversely if the red/blue subpixels aren't fully capturing, the nearby green (thus green) subpixels will capture some scattered energy.

So, the wider the angle of incidence, the greater the difference between refracted vs. reflected ... and the wider the aperture, the more varied the AI Similarly with tilt functions, the varied AI's aren't fully refracted, allowing for more reflection to neighboring subpixels. Thus, the more stopped down the aperture, some reduction in the angles of incidence occurs ... mitigating some of the scattering.

I think I got it ... thanks.

http://www.lumerical.com/tcad-products/fdtd/applications/cmos_image_sensor_pixel_microlens.html

Dec 27, 2012 at 11:17 AM

Makten
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p.1 #15 · voigtlander 25/4 on Nex: purple corners

Doesn't necessarily have to do with the microlenses alone, but also the filter infront of the sensor. Anyone with a Leica M8 will know what the UV/IR filter you put on the lens does with the corner color.

Dec 27, 2012 at 11:36 AM

Mescalamba
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p.1 #16 · voigtlander 25/4 on Nex: purple corners

Agreed, too thick IR/UV is blamed for this too. And considering what happens on DP2M and SD1M I think its right deduction too.

Dec 27, 2012 at 05:15 PM

contas
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p.1 #17 · voigtlander 25/4 on Nex: purple corners

I mentioned about IR cut filter already, but it's correctable easily- microlens design is the same as sensor design and we'll do nothing to it, that only suffer from it.How about tilted microlens or angle-correctable sensor?
@RustyBug: thanks for the link, I read alot : how does it work?, but not this before, now I know more about MICROLENS SHIFT to correct green/magenta edges.

Dec 28, 2012 at 01:23 AM

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