When I bought the Nikon I have no clue what those photography terms mean, like the lens mm, max aperture, focal length, ISO etc. The reasons I choose D40x was probably because of its cheap price tag, and also want to be different from most of the people around me that carry canon:) To extricate myself from being a DSLR noob, i went to Santa Clara Library, borrowed a very basic photography book from which surprisingly i learned a lot. This post is more like my digital photography 101 summary.

I am always fascinated by those object-focused-background-out-of-focused (or bokeh) photos taken by DSLR. I tried to compose such a picture using my camera but the results weren't as great. Reading this book helps me to understand more about the whole concept of depth of field, the theory behind bokeh. Four things influence DOF: f/stop, distance to the subject, focal length and the size of the print.

F/Stop: small aperture (higher numbers such as f/11) increase depth of field (less bokeh-ish), and large apertures (such as f/4) decrease depth of field (more bokeh-ish). Say a camera offers a range of f/stops from f/4 to f/22. The number 22 is the largest number, yet the f/stop it represents is the smallest. On the other hand, f/4 is the largest f/stop, though the number is small. Confusing? haha

Distance: The farther you are from the subject, the greater the depth of field. The closer you get, the shallower depth of field becomes.

Focal Length: Wide-angle focal lengths give greater apparent depth of field while telephoto focal lengths reduce the depth of field.

Print size: Small prints appear to have more depth of field. Totally make senses. As the picture gets bigger, the difference in sharpness of the background/foreground becomes more noticeable, therefore DOF decreases.

I never bother about the lens number of my previous point and shot digital camera. I bet the average joe won't know what those number means either. But the exciting part of DSLR is that you can swap different lens under different shooting condition, provided that you understand what lens you are using.

But before we talk about lens number, let's see what focal length and aperture first. Basically, longer focal length equals to zoom in, which means smaller angle of view. On the contrary, short focal length equals to zoom out, which means wider angle of view. This diagram below will probably help you recall some of your form 4/5 physics:) Of course a lens' focal length is meaningless without a reference to the image area, or frame size within the camera but let's ignore that. Aperture on the other hand measures the opening of the lens which determines the maximum amount of light that a lens lets into the camera.

Back to lens number. For example the lens on my SD1000 digital camera is labelled as 5.8-17.4mm 1:2.8-4.9. Does anyone actually pays attention to this number? Basically it means the camera's zoom lens has focal length range of 5.8-17.4 mm and aperture range of 2.8 - 4.9. At 5.8mm, it is f/2.8, at 17.4, it is f/4.9. The kit lens that came with the my D40x is 18-55mm 1:3.5-5.6 which should be good enough to take normal picture. You can also read this number as the speed of the lens. The wider the aperture, the faster the lens. An f/2.8 lens is twice as fast as an f/4 lens because it lets in twice as much light. So why the f/stop is no doubled? Dang the theory behind f/stop is more complicated than i thought!

Some of my nooby attempts with different focus:





As a photography dummy indeed i learnt quite a bit from this little book. Apart from my daily technical work, frankly speaking, it has been a while since i really learn something new. Man I have been missing the joy of learning. What should I read next? perhaps an introductory to motorcycle engine? haha