Cross Polarized Light

[smoke665]

Have had the equipment to do this, but never got around to trying, until today. The flower is just under an inch in diameter. 135mm, f/8, 1/125, with extension tubes. Multiple images focus stacked to improve on the DOF. The only real purpose of the practice was to use a CPL on the camera, and a Linear Polarizing Film on the off camera flash, to cancel out the reflections. Flower petals up close have a tendency to reflect Specular highlights, this is first attempt to kill the reflections. Still have a ways to go, but I can see the results. Anyone tried/used Cross Polarizing, and have any suggestions?

 

[Overread]

I keep meaning to try it having heard of it years ago - and just never got around to it.

I'd really like to hear your results and see what difference things make. Though I'd say if you want to compare results I'd put stacking to one side and instead take a series of shots. First without any cross polarizing or polarizing filters on anywhere. Then add the one to the flash and lens and turn the lens one it to vary the polarizing effect. Seeing the results would be very interesting - esp close up and zoomed in.

If you can keep the diffusion on the light otherwise the same it would prove very neat to see the results.


edit - also top middle petal - is that what looks like a fly that was in a few frames and then left?

 

[tirediron]

Nice! This is another one of the classic techniques that's all but been lost.

 

[petrochemist]

I've used crossed polarizers to photograph stress in clear plastics (using transmission). When doing this I use a LCD screen as the light source (as this is already polarized). I've not yet tried it for reflected subjects, from the looks of it I should give it a go.
I'll add it to the list for when I'm no longer going into work.

I may have shared this example previously, but as it was taken using crossed polarizers I'll add it anyway:
stressed stencil by Mike Kanssen, on Flickr

 

[smoke665]

I'd really like to hear your results and see what difference things make. Though I'd say if you want to compare results I'd put stacking to one side and instead take a series of shots.

I did several to get to this point, probably should have kept some of the first ones as examples. Flower petals (Corolla) are not flat or smooth, they have a texture that will reflect light (especially flash) as specular highlights, that gets worse the closer you are. The other solution is to increase the size of your light, but then you loose the detailed structure of the Corolla. So to really see the effect I had to get up close. Plus on those petals slightly translucent, you can see the black background coming through with CP lighting.

Unlike a typically CPL where you can vary the effect, I found the Cross Polarization to be more of a Go-No Go proposition. A CPL works best when the light is at 90 degrees to camera axis, but with the cross polarization it worked better when the lines of the linear film on the flash were at 90 degrees to the those on CPL irregardless of light placement.

is that what looks like a fly that was in a few frames and then left?

Actually I think it's probably in the midge family, and was in all the frames. I'm guessing about 1-2 mm in overall length. My eyesight and hands aren't that steady to measure for sure. LOL

@tirediron Thanks man!

I've used crossed polarizers to photograph stress in clear plastics (using transmission). When doing this I use a LCD screen as the light source (as this is already polarized). I've not yet tried it for reflected subjects, from the looks of it I should give it a go.
I'll add it to the list for when I'm no longer going into work.

I haven't tried the plastic yet, but it looks interesting.

Finally while I had the lights setup and exposure calibrated, I tried another of one of the *&^%&*% Carpenter Bees that are hovering around our deck. My focus stacking still needs some work, but I liked how it seemed to penetrate the glossy eye. Still have a lot of practice to do, but it's not like I'm going anywhere.

 

[Derrel]

Good early efforts.

 

[Overread]

The 90degrees rotation to the circular polarizer orientation lines up to what I read on the subject years back when I first heard about it. I don't recall much mention of light angles, but I suspect that outside of some of the more detailed product photography; a lot of macro lighting is fairly simplistic in terms of multiple angles and the like. Though I've seen and had good luck with curving the light source (basically an inverted dome shaped diffuser) for macro. The theory being that by curving the light you're basically making the distances relative to a 3D object more evenly spread. I've seen some great work done with it in regard to insects (basically a 3D object in the frame) and always wanted to combine polarizing with curving.

 

[smoke665]

The 90degrees rotation to the circular polarizer orientation lines up to what I read on the subject years back when I first heard about it. I don't recall much mention of light angles, but I suspect that outside of some of the more detailed product photography; a lot of macro lighting is fairly simplistic in terms of multiple angles and the like. Though I've seen and had good luck with curving the light source (basically an inverted dome shaped diffuser) for macro. The theory being that by curving the light you're basically making the distances relative to a 3D object more evenly spread. I've seen some great work done with it in regard to insects (basically a 3D object in the frame) and always wanted to combine polarizing with curving.

Everything I've read on it seems to point toward light angle being immaterial. In fact one of the sources I found was shooting macro with a ring light that had a linear film applied to it, so in essence the light source was straight on. Having the lines at 90 degrees between the filters made the most difference in my experimenting. As long as the dome diffusion doesn't change that, then I supposed it would work.