Animated: How locks works! (by Stian Berg Larsen)
by Brent Pearson
The good news is that you don’t need a lot of expensive equipment to do night photography. Here’s what you need.
• Your camera needs to have a bulb setting (which allows you to lock the shutter open) and manual control over your lens’s aperture.
• You need a reasonably sturdy tripod
• You need a cable release that allows you to lock the shutter open
• A bright torch to help you compose and focus.
Step 1: Compose and focus
Find a good composition and set up your camera securely on the tripod. To help you see, you want to use a bright torch that is illuminating your subject. ideally get an assistant to help you out with the torch, otherwise I grip the torch between my knees (which frees up my hands to work the camera controls).
Zoom in all the way on the point of focus and either manually focus or use your autofocus. Once your lens is focused, you will need to put your lens into “manual mode” so that it does not try to autofocus again.
Step 2: Estimating exposure
In my eBook I explain a more accurate way of calculating exposure, but for this quick guide let me just give you a simple exposure table to get you started. Make sure that you set your camera’s ISO to 200. To estimate exposure, you start off by looking down the column to the moon setting that matches your current conditions. So if you were shooting under a half moon, then you would go down to the third row. Then you can read across that row to explore different exposure settings.
So you could expose your image for 2min @ f4 or equally 4min @ f5.6 or 8min @ f8.
I would recommend you use the widest aperture you have for your initial test shot to ensure that your exposure is correct.
When evaluating your exposure, I strongly recommend you use your camera’s histogram rather than just viewing the image on the LCD. At night the LCD looks bright, and it is easy to think an image is correctly exposed only to find when you get back to your computer that it is 2 stops under exposed. If you need more information on reading histograms, check out this article.
I would recommend you do your first night photography experiments under a full moon, as this will require the shortest exposures and allow you to correct any mistakes relatively quickly.
Getting the exposure right in camera is critical. If you find that you need to boost your exposure later on the computer, you will probably find that you magnify a lot of noise that is produced in your images. Long exposure photography does introduce more noise to your images, but providing your exposure is correct, this noise is manageable. Any amplification of your exposure or signal during post production will amplify the noise to the point where it becomes a major problems.
Once you start becoming comfortable with the world of night photography, then you are ready to start experimenting with light painting. I’ll write a separate article on light painting in a future post. If you are hungry to learn more about the world of night photography and light painting, then check out my web site for lots of tips and tutorials as well as my eBook on Night Photography and Light Painting.
Great Photographer Elena Kalis
by The Cellular Scale
Deep Brain Stimulation (DBS) is one of the miracle cures of our lifetime. Used to treat Parkinson’s Disease, and now being applied to depression, it is a drastic but amazingly effective measure.
Deep Brain Stimulation (DBS)
To apply DBS, an electrode is implanted deep in the brain (the SubThalamic Nucleus for Parkinson’s Disease). An implanted wire under the skin connects the stimulation electrode in the brain to a stimulator implanted on the chest. The stimulation can be turned on and off here.
Here is a short video showing the effect of DBS on and DBS off. (The actual demonstration starts at 1 minute in, the rest is some arguing in French)
Once the stimulation is turned off, the man has twitches an tremors that prevent him from functioning normally. As soon as the stimulation is turned back on, he can walk and talk smoothly.
This is pretty astounding, right? I mean honestly, if I just saw this video and didn’t know anything about it, I might not even believe that it was real. How can electrical stimulation in the brain completely alter this person’s ability to move?
Well, scientists around the world are wondering the exact same thing. One recent study made use of optogenetics to dissect the pathways involved in deep brain stimulation.
They first elicited Parkinson’s Disease in mice by destroying the dopaminergic cells (in the substantia nigra which feeds into the striatum) on only one side of the brain. Then they give the mice a stimulant drug which makes them hyper. While normal mice would run all over the place on this stimulant, these hemi-parkinson’s mice run in a circle because of the imbalance between the two sides of the brain.
To test whether the treatment you are giving the mouse ‘cures’ their Parkinson’s Disease, you literally count how many times the mouse runs in a circle. If it runs in a lot of circles, your ‘cure’ didn’t work.
Implanting an electrode into the STN of the mice and applying the stimulation did reduce their circle running, just like the DBS reduces Parkinson’s symptoms in humans. But here’s the thing, the STN has a lot of neurons in it, and a lot of axons passing through it. Stimulating this brain region could be inhibiting firing, orexciting neurons, or something else entirely.
So Gradinaru et al. (2009) decided to stimulate specific (genetically identified) classes of neurons to determine which aspect of the electrical stimulation was actually ‘curing’ the Parkinson’s symptoms.
First they tested the most common hypothesis, that the stimulation inhibited the STN. However, when they directly inhibited the neurons of the STN, their mice still ran in circles, indicating that the brain was still unbalanced.
Second they stimulated the glial cells around the STN, but still no luck.
Thirdthey excited the neurons of the STN…. but… still the mouse ran in circles.
I imagine this was very puzzling to the scientists conducting this research. If stimulating the STN with a big metal electrode is not exciting, and not inhibiting the STN, what on earth could it be doing?
Finally they tried targeting the axons of the motor cortex which run through the STN. And! low and behold, the mouse did not run in circles any more. Below, rotations per minute is basically a measure of circle running, and the HFS is the stimulation. You can see that as soon as the stimulation is activated the mice generally stopped running in circles, but when the stimulation was turned off, they ran in circles again.
Gradinaru et al., 2009
So a new theory has emerged, that the stimulation of the STN might actually be acting on other neurons which are not even located in that brain structure. It clearly works in mice, but whether this is the way that Deep Brain Stimulation works in humans is still not clear.