Birefringence basics

In one of my previous posts I mentioned birefringence. Here are some more details.

Polarizers set up the direction of light polarization. If you apply two filters at the same time you can get  complete light blocking, complete transparency or something in between. This is how some adjustable Neural Density filters work. 

Some materials change the polarization of the light. If such object is place between two polarizing filters set to maximum blocking, the only thing one can get in the picture is the light disturbed by such material.

In order to try birefringence photography following are needed:
source of polarized light  - LCD screen/tv/monitor/tablet works perfectly. 
object made of material that disturbs polarization - cheap plastic is perfect, hi-quality glass is useless.
polarizing filter attached to your camera.

Place object in front of the polarized light source, rotate the filter so the source looks black and shoot.

Depending on orientation of the object polarization changes, so try moving object around.

As example I used plastic bag/pocket. First two pictures are without setting the polarizing filter to full black to show how the orientation affects color.





And now with polarizing set up to black



The thicker material the more interesting patterns you can see. 

The color of the light (or image displayed on the screen) affects the result. First I used blue droplets background (filter not set to full black).



Now with filter set to black:



The same setup, but with green/yellow background displayed on the screen:



The more complex shapes add more patterns to the polarization and in effect more interesting result





Hope you will enjoy your birefringence project. Please add comments or questions. I'm feeling quite alone in this blog ;).

Bookeh shapes

Not to anyone's surprise there are two characteristics of the hole - shape and size.

Common advice is that cutout size has to be smaller then the real apperture - so for 50mm lens and f/2 it has to be smaller than 25mm

Cutting tiny shapes is not my thing (I'm not great at DIY) and the results were far from pleasing. In most cases edges were jagged and you could spot it in the final pictures.






And another example with skull and bones.



Even that I put a lot of effort to do it correctly you can see that it is not something I can be proud of.

I decided to go digital. I have used laser printer to print on transparent media (transparent foil used for presentations). I'm not sure if it is related to the toner or set-up of the printer, but the results were quite bleak.



I used permanent marker to blacken surrounding area.



The advantage of this method is that I can use extremely complex shapes.




The disadvantage is that foil is not crystal-clear and it adds soft focus effect (like pantyhose over lens). This is even worse when shape is complex and have some dark elements in the middle.



If the shape has a lot of empty space in the middle it gets slightly better.




Another test I did was based on the fact that cutout adds shape to the lights, but it can also add some color. I used the same foil, cut the shape of the heart (ok... shape of something vaguely similar to heart) and marked edges using red marker.



The effect:



It can be improved, but it suffice as proof of concept.

I have already planned some more tests:

• using laser cut shapes - it will take time as it require some preparation.
• using combination of color foils to get multi-color bokeh.

Have fun.

Bokeh Setup

As promised before I would like to describe my setup for custom shaped bokeh. 

At first I checked what others had to say about it and try their ideas. I tried a lot of them 

1) fancy paper shape held by rubber band 

• Advantages: 
• Lightweight 
• Cheap 
• Disadvantages 
• Tends to get folded in backpack. 
• Rubber band and bits of paper tend to obstruct my manual focus ring. 

2) Paper tube shape put over the lens. 

• Advantages: 
• Lightweight 
• Cheap 
• Disadvantages 
• Even more prone for backpack crushing. 
• Still obstructing manual focus ring 
• More complex to create 
• Need some way of changing cutout shapes. 

3) Plastic tube shape over the lens 

• Advantages: Looks slightly better than paper version 
• Still cheap 
• Disadvantages: 
• Plastic tube has to match outer diameter of the lens perfectly - if it does it scratches outer parts of the lens. If it does not then it rattle a bit and can easily fall off. - I did try slightly bigger tube with some EVA foam as cushioning, but results were far from great due to lack of DIY skills on my part. 
• Complex to create, 
• Needs some way of changing cutout shapes. 

4) using old socks as described in this tutorial. 

• Advantages: 
• Cheap 
• Easy to mount
• Disadvantages: 
• Not something I would like to be seen with. 
• Blocks manual focus ring. 
• Did I mentioned the looks? 

I'm far from saying that all of those are bad ideas. I just was looking for better setup. My goal was to create something that: 

• Is easy to attach to lens 
• Doesn't cover manual focus ring 
• Is sturdy 
• Allows changing bokeh shapes 
• Does not pass light on the sides 
• Is easy to store and carry 
• Does not attract disgusted looks 

Some of my designs would make me instant internet meme, so I won't describe them. The best one - the one I'm using now - consists of three elements: holder, paper insert and foam filler. 

The holder is the step-up adapter 55-77 - my lens has a 55mm diameter filter screw. Additional space helps holding the card with custom shape hole and prevents light leaks Holder 



The paper inset is circle cut from black technical paper with custom shaped hole in the middle. As I'm using 55-77mm adapter as the holder the circle diameter have to be slightly smaller than 77mm to avoid brushing against thread. If it is too big the paper bends outward and it is harder to remove from holder. Talking about removing it - I attached a piece of tape to each circle to make it easier. Insert 



The foam filler is the circle cut of black craft EVA foam (purloined from my daughter school project). The outer diameter is 77mm - this circle has to fit the thread and hold the card in place. There is a hole in the middle (approx 25mm) - has to by slightly bigger than the size of the shaped hole in the card. Small piece cut at the top allows easier removal.



Insert card is put in holder  and held by filler. Holder can be attached to lens as long as needed. For regular photo (without custom bokeh) I simply remove foam and card. At end of the session I unscrew the adapter. 



All together (holder, filler and few inserts) fit without problem in filter box. 



Next time I will describe different attempts at cutting complex shapes and the outcome, so please come back. 

 Any comments or suggestions are more than welcome.

Blur Bokeh

While working with custom shaped bokeh I initially tried the standard heart and star shaped ones and then moved to some complex shapes. In some cases it worked perfectly in some effects where not visible or not worth the effort.

I will write another blog entry related to custom shaped bokeh and tests I made (hopefully quite soon). 

One of the shapes that I tried lead to interesting effect. It is the bokeh in the shape of the slit.

At first I tried to do it using my typical bokeh models (very patient, lot of personality and great at standing still) and my normal setup with some lights in the back.

Lights were not that interesting, but I noticed that the other elements of background looked blurred horizontally as well. 

In most tutorials you will find tips suggesting to have distinct lights far in the back. However bokeh works also in full light outdoor conditions - custom shapes are just not as easy to notice. Even better! So my next attempts were concentrated on shooting slit bokeh during the day. 

Both camera position and photographed object did not move during shooting following pictures:

Conclusion is that slit shaped cutout makes bokeh effect similar to motion blur (direction depends on angle of the slit). It is not exactly the same blur effect you get when panning picture aiming at fast moving object, but close. 

I'm not great at panning - high percentage of my panned pictures have main object blurred as well - this method had additional benefit for me. The object/model does not have to move at all. Having said that there are differences that many can dislike. For example picture of the car that is done with this motion blur bokeh will have wheels not blurred, while the one done with panning will have them blurred due to spinning. I will update this entry once I have photo good examples.

Update (18-02-2016): I tried to use it with landing plane. As the plane was far enough, the effect was almost not visible. So the motion blur bokeh method is better for objects that are really close. I will try with macro photography.

Tools needed:

• Lens with big aperture (mine is 50mm 1.4)
• Piece of cardboard/this paper.
• Scissors
• Way of attaching the shape in front of lens

Process:

• Cut the shape of the slit (few mm wide) in cardboard.
• Attach in front of the lens so the slit is positioned centrally.
• Set to aperture priority and open as wide as possible.
• Shoot object that is quite close with background far back.

Things to try next:

• Different widths of the slit.
• Slits in not linear shapes (waves, long ovals, zig-zags).

As previously, I would appreciate any comments/questions/suggestions. 

Hair birefringence and LCD backlight

One of the tricks I tried is birefringence of plastic objects. I set up LCD screen (tv), polarizing lens and some objects that would generate required effect (like the bottle below).



At some point my daughter walked into frame. She usually moves way to fast and considers posing to be extremely boring. This time she was preoccupied with some snack and I managed to shoot few pictures. However it was done with the setup I had for testing birefringence (in front of LCD TV, and my lens had polarizing filter on). I immediately discovered that her hair affected light in similar way as some plastic objects.



From this came idea of using LCD screen to highlight the hair of the person. Few days later I shoot few more pictures with slightly better light setup,



I tried it with myself as subject, but since my hairstyle is far from lush/luxuriant the effect was not that great. It doesn't mean it was complete disaster. Hair were highlighted from the back with the colors displayed on the screen.



This led to more attempts and LCD displaying color patterns can create interesting lighting for portraits. I didn't use much of the additional lighting (just whatever was available in the room), however to add some dramatic lighting I held a tablet with a one-color image displayed. Below is the test with some pattern displayed on screen (I have intentionally rotated polarizing filter to show the pattern behind).



Tools needed:

• Lens with polarizing filter.
• LCD TV (the bigger the better).
• Ability to display patterns on that screen.

Process:

• Put subject in front of the screen (back toward screen).
• Display color or pattern on the screen.
• Rotate filter so the screen looks black.
• Shoot.

Tips and Tricks:

• Distinct patterns (like horizontal b/w stripes) do not have much effect. I was hoping that skin would reflect part of the pattern, but was unable to do so. I will try to make skin more reflective by using baby oil in the future.
• Color wheels, or two color gradients work nicely.
• If subject is close to the screen the effect of back-lighting is more visible.
• Clean your screen - the dirt on the screen (yes - I'm ashamed) is adding bright spots to the background - I had to remove it in post-processing. As example see last picture.

Hope you enjoyed it and will have some fun testing this technique. I would appreciate any comments/questions/suggestions. I will answer them as fast as I can.

Yay! First post!

I'm an amateur photographer. Amateur as in photography is not my profession. I do try different techniques both during the shooting pictures as well as during post processing. Some of them are well known, but some were invented (mostly by accident) by yours truly.

So I decided to create a blog to document some of attempts and share my observations, tips, tricks and quite possibly what went wrong.

Welcome and please share your opinions and suggestions.