Photography lessons

DOF

2009-08-18T13:45:00.000-07:00

DOF = Depth of Field
What does this mean?

Depth of Field determines the sharpness in front and behind the photographed subject. This is influenced by the aperture or diaphragm. The higher the F-value of the diaphragm, the higher the Depth of Field will be.

If you would like to photograph scenery where everything ( or almost everything) should be sharp, you should use a high F-value. If you would like to have only one object sharp and the rest blurry, you will use a lower F-value.

F-value: 6.7 - almost everything in the picture is clear and sharp
F-value: 4.5-only the object in the front is clear and sharp, the rest is blurry.
This effect is usually used when you want to draw attention on your subject ( e.g. portrait photography).

Focal length and FOV

2009-08-18T07:50:00.001-07:00

What is focal length you may ask...well, the focal length of a lens is defined as the distance in mm from the optical center of the lens to the focal point. The focal point is located on the sensor or film ( the subject is in focus).
FOV stands for field of view, and is determined by the angle of view from a lens out to the scene.
It can be measures horizontally or vertically. The FOV depends on the film or sensor size, so it is not fix for all lenses.

But, to get an idea of what focal length and FOV is let's see some examples:

Focal length: 55mm and FOV of 28 degrees.

Focal length: 105 mm and FOV of 15 degrees

Focal length: 205 mm and FOV of 8 degrees.

So, the greater the focal length, the more closer the objects appear BUT less object in the scene. This means that the FOV is getting smaller.

That is it...

White balance..

2009-08-18T07:21:00.000-07:00

When you take a picture with your digital camera, the camera will look for a white spot to calibrate itself ( to ensure that the colors are correct, so, white parts are truly white). This is not failure free.
For example, in an enviroment where there is less white , the colors tend to have a yellow tint ( e.g. grass is green and the white will be either yellow or green tint..).
You can avoid this by using manual white balance. Take a white sheet of paper as a reference for the camera, then selece manual white balance.Put the paper in front of the lens and now the camera should adjust the settings correctly . You can take the picture with the correct colors.

See example below:
Here we have the white balance set to sunny. The colors are warm, but white at the window is actually kind of yellow.

Here we have the correct balance.

!!! Notice the difference of the 2 pictures. White balance can change your pics a lot.

ISO, shutter speed and aperture...

2009-08-18T02:00:00.000-07:00

Sometimes people keep asking me what is ISO or shutter speed and how do they influence the photo...

Well, I will be short on this... not to short...but I will try to keep it simple..

ISO indicates the sensitivity of the film used in the camera. Most cameras detect the coding on the film and as suchthey automaticly know what ISO value the inserted film has. This values can vary from 50, 100, 200, 400, 2000 etc. If there is a lot of light available it is desired to use a film with a lower ISO value (for example ISO 100 or 200). When darker,it is recommended to use a film with a higher ISO value, because higher value means more sensitive to light a

In a digital camera instead of a film we have the CCD's or CMOS sensor in the camera. This will influence which shutter speed to select and which diaphragm to use. For some sensors that do not support very high ISO values, when we select a high value, the image will get extremely saturated and this will result in white pixels or white areas on the picture.

Diaphragm

In every camera there is a diaphragm.A diaphragm is a mechanical part out of overlapping blades. You can adjust the diameter of the opening. If the diameter value is greater, more light will enter . This opening is indicated with the letter F.The HIGHER the number of the selected diaphragm setting the SMALLER the diameter.

So when we select an F-value f16, less light will be received then when an f8 value is set. This setting will affect the photography in combination with ISO and the shutter speed setting we choose.

Shutter speed

The shutter speed indicates how fast the diaphragm is opened and closed. We need to know this because if the image is not static and we choose a long time, the result will be a blurred image.

Now, you might ask what is the relation between those 3?

ok, let me make it clear.

Here is an example on how shutter speed can change the look of a photo

ISO 200, F4, Shutter speed 1/500

ISO 200, F4, Shutter speed 1/250

As you can observ, if the shutter speed is longer ( 1/250 >1/500) the image will be lighter ( see the sky and the persons).

Now, we have another example:

ISO 800, F5.6, Shutter speed 1/45
ISO 800, F 4.5, Shutter speed 1/20
ISO 200, F4.5, Shutter speed 1/8

So, now we can see the relationship between those 3.
Picture 1 we have a relativ normal ISO for those low light condition( value 800)and an aperture of5.6and shutter speed 1/45 sec. As you can see, the picture is not very bright. due to the great ISO number. The diaphragm is not open enough and the time that the diaphragm is open is to short.
Picture 2 we have the same ISO value of 800 but we opened the diaphragm more ( from 5.6 to 4.5) and also the time in which the diaphragm is open and lets light to get onto the sensor is greater ( from 1/45 to 1/20).
Picture 3 we have lower ISO value ( 200 ) same aperture at 4.5 but now the time is longer ( it is now 1/8 of a second ).

So that would be it for now... if you have questions, ask me.

About photography...

2009-08-18T01:46:00.000-07:00

Although the first photograph was taken in 1839, the principle of camera was first discovered in the 11th century ( camera obscura or pinhole camera).

Since then, many have tried different designs and different cameras. Now we have all sort of cameras from analog to digital, from compact to SLR ,D-SLR and SLR-like.

Compact cameras are small and portable. They are calledpoint and shoot, cause they are usuallz easy to use. With their live preview feature, a user can see on the display the photo that he will take, thus helping people who have no idea of shutter speed, aperture or ISO to take acceptable photos. Most of the compact cameras have a built in flash, but that has very low power.

Then we have the SLR-like cameras, also called bridge cameras. These are cameras that resemble DSLR-s ans have some advanced features. The main thing is that, like compact cameras, the lens can not be changed and the sensor is usually low quality.

SLR cameras have a unique viewing system. A mirror reflects light from the lens through a separate optical viewfinder so in order to capture an image, the mirror is flipped out and it allows the light to fall on the sensor. SLR stands for single lens reflex.

In the next article we will learn some of the basic terms in photography, that every photographer should know....