Questions for Photographers

[ibr_remote]

I want to add a lensflare effect to my 3D render. I am using an HDRI background and am not adding lights to my scene. It is a daytime outdoor scene. I am not a very experienced photographer, so I need to ask : from which direction does lenseflare typically come from ? Should it be from the sun's direction, or some angle to it ?

 

[Rae134]

I think you get the shooting into the sun (or slight angle). If a photographer doesn't respond, maybe look at photos with real lensflare to try and work it out?

 

[Hornet3d]

I think you get the shooting into the sun (or slight angle). If a photographer doesn't respond, maybe look at photos with real lensflare to try and work it out?

Your right, the flare happens when you are shooting into the sun either directly or from a slight angle. The phenomenon is caused by imperfections in lens itself which flares or scatters the light and therefore the effect varies from lens to lens. Telephoto lenses tend to be more prone because they have more glass in them with multiple lens elements. Most image manipulation programs allow you to add lens flare, that and the cross filter which turns highlight into star shapes is probably one of the most often used effects. I guess flare could be simulated in Poser or DS but I suspect there would be less control over the result.

 

[robert952]

To add to Hornet's response, a large part of effect comes from reflections inside the lenses. Telephoto lenses are more prone to the effect because of more distance between each lens elements. Think about it this way. A lens with 3 elements (let's call them 1, 2, and 3). Each has a front (f) and back (b) surface. Light enters 1f. Some light gets reflected off of 2f to 1b. That reflection then reenters 2f to 3f. Some of 3f light gets reflected back to 2b (and even 1f when the light source is strong) and back through element 3 to the focal plane (film plane) of the camera. With greater distance between the lens elements, the light spreads with the spread amplified by the curvature of each element. Hence the lens flare has many artifacts more noticeable with brighter light. (The math gets more complicated if you consider the internal surfaces of lenses. This is what causes light loss in the lens from one end to the other. And here the imperfections of the glass comes into play.)

The shape of the flares tends to be hexagonal since the plates that control the f-stop aperture create a 6-sided hole. The light refracts (bends) around those edges.

The star effect comes from small aperture settings (openings) and the light waves refracting around the 'corners' of the hexagon vertices.

Reflections can be reduced with the use of lens hoods and such as long as they don't get into the field of view.

The physics of light waves as they refract and reflect creates all types of artifacts and effects. I teach a training session on radio control for lifting cranes in industrial environments. One big aspect covers what happens to radio waves as they bounce around and move in the environment. Similar thing happens with light (and water) waves. I use the following as my visual aid.

You probably see the obvious movement of the waves originating from the bottom of the image. You can see the waves reflect off the ship and the waves bend (refract) around the ship. Note the reflections curve following the rules about angle of incidence = angle of reflection. Refraction can be thought of (on a simplistic level) as friction of the surface which slows the waves down. For radio waves the calm areas are dead zones (little to no signal). For light waves, those dead zones represent shadows.

Likely I am providing more than you really want (or need) to know. But that's the professional trainer in me coming out.

 

[Dan30]

@robert952
Robert , I think the phenomenon you are trying to illustrate with your image is called diffraction. Refraction is happening when a wave is passing from one medium to another, usually having different densities. In the image, the waves seem to go around the ship. This is diffraction. The explanation of the lens flares formation is actually very accurate.

 

[Bonnie2001]

Lens flare is basically caused by shooting onto the sun. Lens hoods eliminate flare to a certain degree. Also, good qualtiy lenses are less prone to flare than cheap ones.

 

[Hornet3d]

Lens flare is basically caused by shooting onto the sun. Lens hoods eliminate flare to a certain degree. Also, good qualtiy lenses are less prone to flare than cheap ones.

Good point, one of the differences between a cheap and quality lens is not only the quality of the optics but the coatings that are applied to them in an attempt to limit such things as lens flare.

 

[robert952]

@robert952
Robert , I think the phenomenon you are trying to illustrate with your image is called diffraction. Refraction is happening when a wave is passing from one medium to another, usually having different densities. In the image, the waves seem to go around the ship. This is diffraction. The explanation of the lens flares formation is actually very accurate.

Whoops by bad.... wrong term. You are correct. Thanks for the correction. (Hey, I didn't say I was a good instructor... )

 

[ibr_remote]

Thank you everyone, I did learn what I needed from your responses ! I shall attempt to add a credible lense flare effect to my render, using an image editor.

 

[Hornet3d]

Thank you everyone, I did learn what I needed from your responses ! I shall attempt to add a credible lense flare effect to my render, using an image editor.

Way to go.

 

[carmen indorato]

you can also get reflections off shiny/wet surfaces in front of the lens if in the right place for sun/light bounces off and back to the lens. You can also simulate some flare effects in photoshop with a bit of work it can be made to work quite nicely.

 

[Riccardo]

Good point, one of the differences between a cheap and quality lens is not only the quality of the optics but the coatings that are applied to them in an attempt to limit such things as lens flare.

Gawrsh! One would think that J.J. Abrams has huge budgets when he shoots a film, and instead... ;-)

 

[Hornet3d]

I did say 'in an attempt" and I never said they work .