Thursday, March 27, 2014

Mar 26 (Day 85) - More St. Mark's NWR, photography stuff, and NERD TIME!

OK, I told you yesterday that I REALLY enjoyed my time at St. Marks NWR. In fact, I liked it so much that I went back for several hours this morning. This might not have been the wisest decision since it meant I did a lot of riding today, but it was hard to leave such a beautiful place behind. This refuge is very large and contains many different habitats. However, the best thing about the refuge is the balance between the auto tour and the hiking/biking trails. Many refuges have a main auto tour and just a few short, token trails. St. Mark's has a series of dikes that run through the refuge, and visitors are allowed to walk or bike basically all of these! This really opens up a whole host of birding possibilities. This is very unique as dikes at many refuges are off limits to the general public. It is really easy to get off the road and find your own little slice of the refuge since so much of it is public access. I have visited many refuges, and I would venture to say that this is one of, if not the most, impressive facility that I have visited. It is definitely worth a visit if you are in the area.

On the bird front, today I was able to add 3 more species to the 5 I added yesterday. I heard a Chuck-will's-widow (#258) this morning when I walked out of my lodging from last night. This was a nice surprise and it got the day going right away. I was also able to find a single Cliff swallow (#259) among lots of Barn and Tree swallows, and I picked out a lone Semipalmated sandpiper (#260) in with the several Western sandpipers I saw today. There were loads of shorebirds both yesterday and today. I probably had a dozen different species, many of which were new for the year. I also saw several Bald eagles and a nice assortment of land birds.

Bike at the refuge

Blue goose given to me at Sanibel NWR finds
a friend at St. Mark's NWR! He normally rides on 
the front of my bike.

St. Mark's lighthouse

I am currently working on doing more shooting in manual mode on my camera. I have done most of my shooting in AV (aperture priority) mode up until now. I just feel that I am at a point where I want maximum control over what the camera is doing. I know I will miss some shots as I continue to practice exposure theory, but I think my photography will benefit greatly in the long term. Here are some of the results from yesterday and today! 

***again, click for bigger images***

American coot - check out his feet!

Tricolored heron

 Boat-tailed grackle

Sora  - LOTS more on this photo below

 Quick record Stilt sandpiper shot


In addition to my 400mm bird lens, I have been carrying a landscape lens with me. This lens has seen minimal action so far,  but I expect it to get more use as I move west. The location snaps taken with my iPhone are serviceable, but I am really looking forward to doing more real landscape shooting as I move west. Here are 2 shots from St. Marks and one from the road today. Bascially, anything with my "dorianandersonphotography2014" watermark is a real photo taken with my SLR (compared to what I call iPhone 'snaps'). I am realizing I am going to have to start using a tripod for serious landscape work. I generally like to photograph when the sun is really low (early and late). This means that with the sun at my back, my body casts a long shadow that can work its way into the shot and ruin it. I will start using a remote trigger with the camera on a tripod to prevent shadows in my shots. I was able to avoid the shadow issue in the shots below!

**click for bigger images**

St. Mark's NWR

St. Mark's NWR

"Tin Shanty" along the road

The 25-mile "backtrack" to the refuge 
made today very long - 90 miles. I stayed next to
the Chevron station.

Tomorrow I will head to Panama City for the night. I will have some time to bird along the way so we'll see what I can turn up.

OK, time for a bit of nerdy stuff. Look at the following two images.

Do you see how you can see under the water in the first shot but not in the second? This is because I took the first shot at a high angle (I had to do this since I was shooting over grass) and the second shot at a low angle. Why does this matter? It all has to do with refractive index. Refractive index is a experimentally determined number that describes how fast light travels in a particular substance. This straw example should look familiar to some people, and it is caused by the different refractive indexes of water (1.33) and air (~1). In order tho avoid the math, I'll give you the basic idea. As light moves between different mediums, such as air and water, it gets bent according to the relative refractive indexes of those mediums.

 A light ray is bent as it enters and leaves a plastic block

As I said, light rays that originate under water are bent as they leave the water and enter the air. This is why the straw looks broken above and the light ray "kinks" in the plastic. However, not every light ray that originates under water escapes into the air. As you can see below, only light waves that are steep enough make it out of the water and into the air. These are the light rays represented by the yellow lines below. Shallow rays, depicted in red, are reflected back into the water and never make it to the air.

So what does this have to do with the two photos above? Since I took the first photo standing up, the steep light rays from under the water (like the yellow lines) escape to the air and register on the camera's sensor. Since I crouched down to take the second shot, the light rays from things under the water are now at a shallower angle (like the red lines) and do not escape the water. There is just as much junk under the water in shot 2, but you don't see it because the light from it never leaves the water to reach the camera. You will also notice how the bird's reflection is stronger in the second shot. Generally, the lower you get to take the photo, the better the reflection will be since it is not "diluted" by light coming from under the water. In this shot, I am lying on my stomach in the pond to get as low as possible!

Interestingly, birds that eat fish for a living have a built in refractive index correction factor. I assume this is learned over time as the bird learns to fish. The bird must learn to aim a bit below where its eyes tell it the fish is. This might also explain why Osprey like to hover above where they dive so as to minimize the correction that must be made.

Lastly, diamonds have one of the highest know refractive indexes. Light enters into a diamond and becomes trapped as it bounces around inside the carbon lattice. The light is bounced around so many times before it escapes back into the air that the individual colors of different wavelengths separate. This is why a diamond sparkles. 

I know it is a bit more than people might have expected, but I hope folks have learned a bit about refractive index and how it can affect their photography. On that note, I am going to unplug to get some sleep. I do have to ride 60 miles tomorrow!


  1. I assume blogspot is stripping EXIF data from your photos. That's too bad because it's really helpful for those of us trying to figure out bird photography basics to know about exposure settings used in photos we admire.

    1. I have been thinking about posting the camera setting so this tells me this would be well received. I will try to do this moving forward (assuming I have the time and energy!)

  2. I applaud your all around nerdiness, sir. Also: nice Sora.


    1. This comment has been removed by the author.

    2. Thanks Jonah. I am very proud of my neediness!

    3. DAMN YOU AUTOCORRECT! Not neediness, but nerdiness!

  3. Great post, Dorian. I had never really thought about refraction and water reflections before.

  4. Thanks Rob! Glad to hear you enjoyed it!

  5. We're excited to see the blue goose is still riding strong! Also I loved the refractive index lesson! Your photography tips are great and please continue throwing them out there. I always heard that getting down to the bird's level makes for a much better photo, but I never thought about its effect on the water! Awesome!