Polarized Electronic Flash...Part 2

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twebster
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Polarized Electronic Flash...Part 2

Post by twebster »

Hi y'all :D

In Part 1 I used polarizing sheet material over the flash head to polarize the light. Once taped to the flash head the material cannot be turned. This somewhat fixes the position of the polarizing filter on the camera lens. The filter on the camera lens has to be oriented such that the polarizing angle of the camera filter is parallel to the polarizing angle of the filter over the flash head. Changing the angle of the polarizing filter on the camera results in a loss of light just as if a neutral density filter was added to the camera lens. We do not want this to happen. :D

In general photography we would add a polarizing filter to our lens to cut glare from the sun and saturate colors. We would attach the filter to our lens and, while looking at the scene through our viewfinder (or on the LCD), rotate the polarizing filter until the glare is diminished or eliminated from the scene. Polarized electronic flash removes glare from the flash but may not be able to reduce or eliminate glare from ambient lighting.

A shiny subject may not have glare from the flash but it may have glare from the sun, for instance. To remove this glare we need to turn the polarizing filter on the camera to eliminate the glare and then we would need to be able to turn the polarizing filter on the flash to make the polarizing angles between the camera and flash filters parallel. Kind of hard to do when the polarizing filter material is taped on the flash head. Here's my solution...

Image

I purchsed an inexpensive 49mm linear polarizing filter with a rotating mount. I cut a piece of cardboard to fit over the flash head and cut a hole in the cardboard to match the diameter of the linear polarizing filter. I glued the filter in the hole careful not to get glue in the rotating mount. The smaller tabs that stick out from the side are bent back along the flash head and a couple of rubber bands slide over the tabs to hold the adapter to the flash head...

Image

When we use flash for macro photos we are only illuminating our subjects with the light from the center portion of the flash. The 49mm filter covers the center 2/3rds of my flash head and provides an adequate amount of polarized flash. I now have a polarizing filter over the flash that can be turned parallel to the polarizing angle of the polarizing filter on the camera. Cool :!: Here's an image of the setup...

Image

This is the setup I now use the most. I view my subject through the viewfinder. If I find the glare on the subject is objectionable I turn the polarizing filter on the camera to eliminate or reduce the glare. Sometimes I turn the filter only enough to reduce the glare to a small sparkle rather than eliminate it entirely. Once I have the filter on the camera lens positioned I turn the polarizing filter on the flash head to match the polarizing angle of the filter on the flash. After I expose the image I will find that I have no glare from the flash and reduced or no glare from the ambient light. Works like a charm :!: :D

Someone asked which side of the diffuser you place the polarizing filter. You can't use a diffuser with polarizing filters. Diffusers cause light rays to scatter and vibrate in all directions. If you place a diffuser on the flash and then place a polarizing filter over the diffuser, the diffuser acts like a neutral density filter and reduces the light output of the flash. The polarizing filter is not going to let diffus light pass through the polarizing filter.

If you place polarizing material over the flash head first and then add a diffuser you, once again, defeat the purpose of the polarizing filter. The diffuser scatters the polarized light making the light, once again, vibrate in all directions. To control shadow edges and make them more diffuse you simply move the flash as close as possible to the subject. The closer the flash head is to your subject, the less the flash acts like a point light source and the more diffuse the shadows will become.

I used this flash setup to make this image...

Image

I baited the ant with a piece of sardine. The sardine had some very shiny scales and very white skin that created a lot of glare plus the ant had a lot of glare, too, from the sun. I turned the polarizing filter on the camera lens to almost, but not completely, eliminate the glare on the ant and the sardine. I then turned the polarizing filter on the flash head to match the polarizing angle of the camera filter. No glare from the flash but just enough glare from the ambient light to give the image a little sparkle. Cool beans :!: :D

Someone asked me how much light is lost using 2 polarizing filters. I have not measured the light loss but it is less than if I were using the Sto-fen Omni-bounce diffuser on the flash head. In fact, I can stop the lens down a couple more f. stops at high image magnifications than I can when I use the Omni-bounce diffuser. This doubly polarized electronic flash lighting appears to be a great way to fine tune the lighting of macro subjects. :D

Best regards to all as always :!: :D
Tom Webster
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Phoenix "The Valley of the Sun", Arizona, USA

Think about this...maybe Murphy is an optimist!!!

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teva
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Post by teva »

Great stuff...tnx for sharing.

i got my answer about using diffuser, which is not good for me. I have to use diffuser, else macro lense drop shadow on the object. And my fz5 doesn't have hot shoe. I have made a slave trigger and bought cheap flash, but flash bracket is impossible to get here...as many other stuff, so i'm stuck.
No matter, i will try follow part one. Just one question. You say that you glued the polarized paper on the flash, and then rotate the flash for 90 degres. Maybe stupid but, would it be the same effect if you cut the polarized paper in 90 degres way and use the flash in normal stand? Does this makes sense? The thing is, that the only flash bracket that will be available here is straight one, so i can't rotate flash the way you did.
Also, i am about to finish my macro flash, made from two old camera flashes on a "hand like" bracket, and again, i can't rotate them.

tnx

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twebster
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Post by twebster »

Hi ya' Teva :D

First off, I don't glue the polarizing filter material to the flash head. I simply use tape to attach the filter material to the flash head to keep it in place. This way, the polarizing material can be taken off if I want to use the flash without the polarizing material.

Second, the flash head does not need to be rotated. The way my flash bracket is made makes the flash head rotate. I don't have any control over the rotation. You can use the flash head in any position. Straight on is fine. What you do rotate is the filter that is screwed on the lens. The filter mount is made to be rotated. By rotating the filter on the lens you can make the polarizing angles of the filter material on the flash and the filter on the lens parallel.

I, personally like to use only one flash. You can put polarizing material over both flash heads on your homemade bracket. Just make sure the polarizing material is oriented the same way on each flash head. Here is a link to an article by a photographer that uses 2 flashes for close-up photography, http://www.naturescapes.net/042004/wh0404.htm. His setup will be similar to what you are wanting to do.

Best regards, :D
Tom Webster
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Phoenix "The Valley of the Sun", Arizona, USA

Think about this...maybe Murphy is an optimist!!!

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teva
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Joined: Mon Sep 19, 2005 5:29 pm
Location: Slovenia

Post by teva »

Thanks..now i get it.

The flash i'm making won't look like that, i'm using very small flash lights, Her's one i will be using. I will most certainly try your technique, once i finish this.

Will notify you about polarizing sheet, if you still care to send me.

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twebster
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Post by twebster »

Hi ya' Teva :D

Of course the offer of the polarizing material is still good. I have far more than I need. Just let me know about the shipping. OK? You shouldn't have any problems setting these flash heads up with polarizing filters. Post your results when you get the flashes done. :D

Best regards, :D
Tom Webster
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Phoenix "The Valley of the Sun", Arizona, USA

Think about this...maybe Murphy is an optimist!!!

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