"Petzval" Photoshop Filter or Action?

[Jay Decker]

Has anyone encountered a Photoshop filter or action that creates a Petzval lens effect?

[Dave Aharonian]

Only once hell freezes over!!

[Mark Sawyer]

Has anyone encountered a Photoshop filter or action that creates a Petzval lens effect?

God, I hope not...

Then again, we may somerday find that all the old-lens-gurus here were really 14-year-old kids who'd been fuzzing up their cell-phone pictures in Photoshop...

[Jay Decker]

... Then again, we may somerday find that all the old-lens-gurus here were really 14-year-old kids who'd been fuzzing up their cell-phone pictures in Photoshop...

I've had the same thought... I've never met Jim Galli, but it would be funny if "he" turned out to an adolescent girl with a pierced tongue who likes the SciFi channel and getting middle aged men all lathered up about Petzval's and Heliar's...

[Gordon Moat]

You could fake it in a few steps, though it would likely look very obvious. The issue with 2D defocus post production is that it cannot replicate a 3D defocus effect. The distance of objects from foreground to background is rendered differently by a lens at a location, with some further objects more defocused, and closer objects less so. When you try that in PhotoShop, the software treats all objects as being at the same distance relative to the plane of focus and each other. The only work-around is to ensure that all objects in an image that will undergo defocus style post processing, is to make sure the original capture contains all elements at the same plane and orientation. It might work okay for portraits, but even then the closer the portrait (like head shots), then the more unnatural a manipulated result will become. There is absolutely no software solution to this, beyond making your images in 3D software and not using a camera at all, but then that's not photography.

The reason for using these lenses is exactly the uniqueness of the defocus effects. While they may not be user friendly, and they might only be adaptable to a few cameras, I am certainly glad that the uniqueness cannot be matched with post processing. I have nearly 15 years of PhotoShop experience (professionally), yet I have no desire to use software when a lens and camera set-up will allow better results in-camera.

Ciao!

Gordon Moat Photography

[Ben Syverson]

I'm an image processing engineer by trade... I did a test recently to simulate a "bad" lens digitally. It involved firing a virtual "laser" through a 3D model of a meniscus lens, and raytracing the caustics it produced. The "laser" traveled back and forth in scanlines like an old CRT, saving a frame for every pixel (over 16,000 of them). Then I wrote software to go through every pixel of a reference image, pull up the associated raytrace for that pixel, multiply it by the input pixel, and add it to the buffer.

It's a slow process, but it can produce images that "accurately" model coma and other lens aberrations as opposed to merely faking them. Attached are three images. The first is a side view of a simple lens in 3D. The second is a test render from the software. The third is the input image before cropping. This particular virtual lens is particularly rough -- I'd like to do one that's "cleaner."

However, the entire process is like a copy camera. In other words, the virtual lens is locked at one point of focus -- there's no way for something to be "out of focus" or beyond the DOF. You could do it by dynamically rendering the caustics for every pixel, but it would take many many hours for one 256x256 pixel image. You could do it by having a library of caustics for different depths, which would render faster, but for 256x256 it would occupy many gigabytes. Either way, you would need an accurate depth map in addition to the color reference image.

In other words, the answer to your question is "no." If you want an image that looks like it was shot with a petzval, by FAR the least painful option is to... shoot with a petzval.

[Jay Decker]

I'm an image processing engineer by trade... I did a test recently to simulate a "bad" lens digitally. It involved firing a virtual "laser" through a 3D model of a meniscus lens, and raytracing the caustics it produced. The "laser" traveled back and forth in scanlines like an old CRT, saving a frame for every pixel (over 16,000 of them). Then I wrote software to go through every pixel of a reference image, pull up the associated raytrace for that pixel, multiply it by the input pixel, and add it to the buffer.

It's a slow process, but it can produce images that "accurately" model coma and other lens aberrations as opposed to merely faking them. Attached are three images. The first is a side view of a simple lens in 3D. The second is a test render from the software. The third is the input image before cropping. This particular virtual lens is particularly rough -- I'd like to do one that's "cleaner."

However, the entire process is like a copy camera. In other words, the virtual lens is locked at one point of focus -- there's no way for something to be "out of focus" or beyond the DOF. You could do it by dynamically rendering the caustics for every pixel, but it would take many many hours for one 256x256 pixel image. You could do it by having a library of caustics for different depths, which would render faster, but for 256x256 it would occupy many gigabytes. Either way, you would need an accurate depth map in addition to the color reference image.

In other words, the answer to your question is "no." If you want an image that looks like it was shot with a petzval, by FAR the least painful option is to... shoot with a petzval.

Fascinating! Thank you for taking the time respond. I suspected that was the answer, but did not know what it would take to digitally create such a rendering.

[Jim Galli]

Damn! My cover blown again. Now I'll have to call off the *LGM's. OOPS they just brought me one of those little Gundlachs to sell. No more boys no more! $95 for the Gundlach if you're still a believer.

*little green men

[Ben Syverson]

If I ever eventually commercialized my software as a plugin, there's no way I'd be able to sell it for less than $250. So buy a $95 petzval from Jim instead!

[Brian Ellis]

You could fake it in a few steps, though it would likely look very obvious. The issue with 2D defocus post production is that it cannot replicate a 3D defocus effect. The distance of objects from foreground to background is rendered differently by a lens at a location, with some further objects more defocused, and closer objects less so. When you try that in PhotoShop, the software treats all objects as being at the same distance relative to the plane of focus and each other. . . .

Actually by use of the gradient tool to create a transition mask and then Filter > Blur > Lens Blur you can replicate the way a camera renders blur in Photoshop. I haven't done it myself but I've seen it demonstrated in a Photoshop tutorial and it appeared to work well in the sense that near objects were relatively sharp and then other objects got progressively less sharp as they got farther away. You perhaps already know of this method and know that it often doesn't work for some reason but in the demonstration I saw it appeared to work pretty well. I have no idea whether it duplicates a Petzval effect since I don't know what that effect is. But it did appear to generally produce an effect similar to the effect produced by a lens with respect to nearer and farther out of focus objects.