Depth of Field & Photography

"Point and shoot" digital cameras have become an important part of
lives of anyone and everyone who wants to take pictures and have made
taking pictures as easy as point and shoot. For most people they are
good enough and at most times they are good enough. Besides others,
one down side has been that people don't need to know some very basic
stuff about photography. One of them is about the way we can control
"depth of field" in a photograph.

We need to have a short/small depth of field while taking pictures
like portraits, as we are focusing on one subject and we want
everything else to be blurred so that the viewers attention only goes
on the object of interest. We need a long or deep depth of field while
taking pictures like landscapes as we want all objects, near and far,
to be in focus.

Depth of field/focus is controlled by the aperture size of the
shutter. It is represented by a number written after the letter "f" eg
f/5.6 , f/29. The smaller the "f" value, the bigger the apertures size
and vice versa. A large aperture number (eg f/29) means a very small
aperture and that acts like a "pin hole" and that makes focusing not
that important and all objects, near or far, are in focus. A small
number (eg f /5.6) means a large aperture and precise focusing becomes
very important.

While taking pictures two very important factors which control the
light exposure are the shutter speed and the aperture size. If the
aperture is large, we need to shutter to close quickly to let a
certain amount of light to pass through. If we make the aperture
small, we need to have the shutter open for a longer time for the same
amount of light to pass through.

In the two photos attached, I have focused on the red cap of the
bottle as I took the pictures. The two pictures have however, been
taken with different aperture settings and corresponding shutter speed
changes. You can read the settings in the bottom left corners of the
photos. You can make out that in the first picture the depth of field
is pretty good and almost all seems to be in focus unlike in the
second photo.


Sarbjit Singh

Make your own 3D Photos

Sarbjit Singh



You can create your own red/blue (green) 3D images to print, or look at on a computer screen, using a normal digital camera and some image processing software. Here I'll explain how to use Adobe Photoshop, but you should be able to get the same results using similar programs by playing around with the tools and settings.

To recreate this 3D effect in print or on a computer screen, we need to simulate binocular vision. In short, we need to take two photos of our subject, separated by a short distance (the distance between your eyes: about 3 inches), then make it so your left eye only sees the left image and your right eye only sees the right. To do this we will use red/blue (green) 3D glasses and when viewed through the glasses, our photo will appear three-dimensional!

Materials
• 1 Digital camera
• Photo editing software (Such as Adobe Photoshop)
• Red/blue (green) 3D glasses (You can use the red and green glass from the trial set)

Activity procedures

Step 1
Start out by picking a subject. It is easier to take photos of objects or landscapes because we need to take two photos that are as identical as possible. Shots of people can work provided they stay very still and do not move in the time it takes you to snap two photos. Take your first photo, then try to slide the camera over less than 3 inches and take the same photo again. Please don't rotate the camera. Slide it. A common mistake is to take the pictures too far apart.

Step 2
Download the photos to your computer and open them up in a photo-editing software such as Adobe Photoshop. Any program will work as long as it allows for red, blue, and green color channels to be manipulated independently.TIP: Use copies of the photos, in case something goes wrong!

Step 3
Once both pictures are open, convert them both to grayscale by clicking on IMAGE in the menu bar and selecting MODE then GRAYSCALE.
[Image>Mode>Grayscale]

Step 4
Convert the right photo back to red, green, and blue (RGB) by clicking IMAGE on the menu bar and selecting MODE then RGB (the image will still appear gray).
[Image>Mode>RGB]
In the Channels tab (in the layers palette between the LAYERS and PATHS tabs), select the red channel by clicking on the word RED - NOT the little eye next to it (eyes indicate which channels are displayed, not selected). Only that channel should appear highlighted.

Step 5
Go back to the left photo and select the entire photo [Ctrl-A] for PC or [Command-A] for MAC then copy the image [Ctrl-C] for PC or [Command-C] for MAC, and finally return to the right photo and paste the image [Ctrl-V] for PC or [Command-V] for MAC.

Step 6
Now you are ready to complete the merging of the left and right images. Go back to the channels palette. Click on the little box next to RBG. An eye should appear in all four channels but still only the red channel is highlighted. You should now have a mostly black and white image with red and blue halos.

Step 7
You are nearly done. The left and right eye images need to be better aligned to remove as many of the halos as possible. This is achieved by centering the two images on the subject of your photo (typically what is in front and center - this will be the easiest part of the 3D photo for people to focus on). Select the move tool [press V] then use the arrow keys to move the red image until you see the best alignment. We are trying to remove the halos from around our subject, though objects towards the edges will still be quite haloed.

Step 8
The final step is to crop the image down to the size you want using the crop tool located in the tool bar (left hand column, third tool down). Try to remove areas of excess red or blue around the edges. Once you have selected the area of the image you want to keep hit ENTER to crop the image. Now that you are done, don't forget to save!

Now when you look at your image using red/blue(green) 3D glasses you should see the scene appear in 3D, depending on which way your shifted the images you might need to switch which way you are looking through the glasses. You should try experimenting for a while with taking photos and creating the images to get the best results.

EyePhone, a brilliant iPhone application for Ophthalmologists

I accidently found this brilliant iPhone application called Eyephone. It gives distance vision testing Es, Near vision checking charts,Color vision charts (34 plates with interpretation just a flick away), an Amsler Grid and a Pupil size Gauge. At least in my setting, refractionists do the refractions and I just occasionally do it myself and most of the time it is for near vision a day or two after cataract surgery. Many times, just can't find the right charts when we need them. This is going to be very useful aid for me.

Sarbjit

Welcome to "Mostly Mac & iPhone" world

I have been using apple macs for a number of years now. Windows computers have been out of bounds ever since. In fact, I dread using them. Anyways, that's my opinion.

Most of us are really very weary and resistant to change fearing the unknown world. Never know what is on the other side. The mac world has changed so much for the better that I feel kind of pain when I see so many people missing on such "objects of pleasure". There are a number of die hard mac users around. I would like to bring them together to hold the "fingers" of our windows user brethren and bring them to the "mac world".

Don't miss on something so "beautiful" . Join us on the pleasure ride

Sarbjit Singh