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View Full Version : How to create chromatic aberration in PS?


cecofuli
11-15-2007, 08:36 PM
Hello guy, for my rendering i need to replicate (not correc ;) ) the Chromatic aberration

See here
from this....

http://www.treddi.com/upload/cecofuli/Upload/09%20-%20TEMP/20%20-%20Living_P2_pre.jpg

to this...

http://www.treddi.com/upload/cecofuli/Upload/09%20-%20TEMP/21%20-%20Living_P2.jpg


and see the LCD Zoom


http://www.treddi.com/upload/cecofuli/Upload/09%20-%20TEMP/22%20-%20Comparation.jpg


Thera is some RGB correction or cromatic modification in RGB, but i don't found the correct way for this... :(


Can ypu help me?

Thank's

Laserschwert
11-15-2007, 09:07 PM
You might try to apply the "lens correction"-filter to all three color-channels separately (using different values, of course). Your sample image uses a lot more filters though, like sharpening, but I'm sure you already know that ;)

EDIT: Oh, I just saw that the "lens correction"-filter can't be applied to individual channels, BUT it does have sliders for "chromatic aberration"... so, enjoy!

cecofuli
11-15-2007, 09:57 PM
Thank's for the Tips.... :thumbsup:

But for the green filter, what do you think's that i can do?

Thank's

_cecofuli

Laserschwert
11-15-2007, 11:55 PM
Well, use color-balance and/or curves to decrease red and blue in the darker areas (and adjust the contrast as well of course)... all kinds of color-correction tools available. The image above also contains blueish glows at bright areas, so those have to be added too in separate layers.

cecofuli
11-16-2007, 10:48 AM
Thank's! Very usefull the CUrve TIPS :thumbsup:

Ciao

_cecofuli

berniebernie
11-16-2007, 10:50 AM
...or you could go to your r,g,b channels and shift each by 1 pixel in opposite directions =)


It's a fake chromatic abberation as I guess the 'true' one entails 3 render passes for the 3 channels (maybe mental ray has some nifty lens node to do it I have no clue), but it does the job well enough.

berniebernie
11-16-2007, 11:07 AM
And because a picture is worth a thousand words and I don't type really good, here's a Potatochop example (it kinds of screws up your image but isn't it the whole point...)

http://mlkdesign.online.fr/dump/no_chr_ab.jpg

http://mlkdesign.online.fr/dump/yes_chr_ab.jpg

Laserschwert
11-16-2007, 11:43 AM
Well, it shows that shifting the channels a whole pixel is too much ;-) The aberration-setting of the lens-correction filter supports sub-pixel sizes.

berniebernie
11-16-2007, 11:56 AM
Yar, but the cheap and dirty way works as well; most of the time I use it on way larger images and it looks fine when resampled.

BlueFlare
11-20-2007, 12:57 AM
I don't understand why someone would like to add chromatic aberration, it's what every professional photographer likes to avoid like the plague. For realism? If that's the case, then I think you go too far. What's next, barrel/pincushion distortion, dark corners, out of focus corners and dead pixels?

Anyway, just my 2 cents ;)

Per-Anders
11-20-2007, 01:19 AM
I don't understand why someone would like to add chromatic aberration, it's what every professional photographer likes to avoid like the plague. For realism? If that's the case, then I think you go too far. What's next, barrel/pincushion distortion, dark corners, out of focus corners and dead pixels?

Anyway, just my 2 cents ;)

Barrel/pincushion has been simulated for a long time by lenses on 3d programs, vignetting is also often used and simulated in 3d apps and by people looking for photorealism. Those are all old effects, chromatic aberration is currently in vogue. I don't get why you think it's going too far, that's like saying that adding all these nasty textures to these nice smooth perfect clean surfaces is going too far...

BlueFlare
11-20-2007, 02:19 AM
Someone posts an image with a few single red and blue pixels you expect to hear everybody saying: “What a nice idea to make it look more realistic with those dead pixels!”?

Maybe now you understand what I’m trying to say here.

Oh, and btw, there are cameras that do this, like my 5 year Olympus 3040 ;)

TheBladeRoden
11-20-2007, 02:31 AM
Barrel/pincushion has been simulated for a long time by lenses on 3d programs, vignetting is also often used and simulated in 3d apps and by people looking for photorealism. Those are all old effects, chromatic aberration is currently in vogue. I don't get why you think it's going too far, that's like saying that adding all these nasty textures to these nice smooth perfect clean surfaces is going too far...

Depth of field and motion blur are both are both flaws of photography yet CGers are always trying to stick them into their works.

KV99
11-21-2007, 10:24 AM
I don't understand why someone would like to add chromatic aberration, it's what every professional photographer likes to avoid like the plague. For realism? If that's the case, then I think you go too far. What's next, barrel/pincushion distortion, dark corners, out of focus corners and dead pixels?

Anyway, just my 2 cents ;)

That's the difference in rendering and taking photographs. Renderers try to render images that have subtle flaws of photographs. Photographers try to take a picture with as little of those flaws as possible. That's why many of those 'fake or not' tests can create some confusion, since one literally tries to emulate another - subconciously or not.

The real trick here is that real life photographs have chromatic aberration, lens distortion and vignetting no matter what you do. It's just in a very very small amounts and barely noticable. That's what you should do in rendering, you should not -see- chromatic aberration in your photoreal renders, but you should sense that it is there (aka seeing bits of it when zooming up close).

Depth of field and motion blur are both are both flaws of photography yet CGers are always trying to stick them into their works.

No, they are not flaws of photography. These two expand the options of photography and are both used alot. Photography would not be what it is without these two.

Cheers

pgraham
11-21-2007, 09:17 PM
I did a glint on a piece of (CG) metal once with chromatic aberration. It's also really nice to add to glass or water for realistic looking refraction. These are not camera specific effects either, you can see them with the naked eye. Like the stripes at the bottom of a swimming pool... one edge is blue and the other yellow. But it does also happen in cameras and it can add artistic quality like a *good* lens flare or bloom.

For a photographic aberration, I copy the image on a new layer, scale the red channel up by a very small amount, scale the blue channel down, and leave the green alone. Then I take a color range or an edge filter of the bright parts of the original image and apply it to the aberration layer. The scale makes the aberration stronger towards the outer parts of the image, and the mask makes it only visible around bright areas, which is realistic. Aberration is more pronounced where the image is overexposed, just like a lens flare.

You can blur and fade the aberration layer to get a softer effect, or sharpen it to get a harsh digital camera look.

KV99
11-21-2007, 11:26 PM
Tried out two different render tests (models from artist-3d.com) adding subtle or more pushed (in the second one) photographic flaws to the images. Neither really add to how photoreal the images are, or are not, however if an image is photoreal or close to photoreal then these flaws can enhance the effect a bit.

http://www.waher.net/prtest.jpg

http://www.waher.net/buddhatest.jpg

Photoshop has been used in post for both, mainly Distort Lens adjustments, Noise and Curve adjustments. Depth of Field in the original image was rendered and not added in post.

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