Friday, June 5, 2009

What Lens Should I Buy?

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Summer time in Montreal is a great time to be taking pictures. There are many festivals, sports, events, concerts and places to see and find in our wonderful salad-bowl of a city. And when we are out, we want to make sure we have the right lens for the right type of shot. A common question I get is "what lens I should buy?" You already have your 18-55mm kit lens and now want to expand. The typical choice would be to get a zoom lens. Although it may be the natural second lens, it may not always be the right choice. Below I will cover two very important aspects of lens selection, conversion and range.

Is my 18-55mm lens the same as film? Do I see the same thing?

When you have a digital SLR, the lens range (focal length) on the digital body is not the same number. Let me explain. 35mm film had a very large surface area. With modern DSLRs, this area now being used by either a CCD or CMOS sensor is much smaller. As a result, the light entering the lens covers a smaller area. This means basically that you will get more zoom than what is marked on the lens but less wide-angle. So for Pentax, Sony and Nikon DSLRs, you must multiply the focal length by a factor of 1.5 (x1.5 crop factor). So if you put a 50mm lens on these DSLRs, it will give an equivalent-to-film lens of 75mm. This means that when you take a picture, it look like what a 75mm lens did on a film camera. So your 18-55 lens gives you the look of a 27-83mm or the old 28-80 mm lenses from a film camera. For Canons the crop factor is 1.6 and for Olympus it is 2.

So Who Cares What It Looks Like In Film!?!

Well this actually has an affect on what lenses we choose to use. Let's have a look at the ranges and their uses:

Lens Focal Length* Terminology Typical Photography
Less than 21 mmExtreme Wide AngleArchitecture
21-35 mmWide AngleLandscape
35-70 mmNormalStreet & Documentary
70-135 mmMedium TelephotoPortraiture
135-300+ mmTelephotoSports, Bird & Wildlife

The above are focal lengths for film cameras.

These are the ranges used for the different types of shots. Once you consider the crop factor, theri usefulness changes dramatically.
For instance, the 50mm prime lens is becoming a newly found favorite amongst digital photgraphers. It was popular in the days of film because it saw the same thing as what our eyes saw. Now on digital, it doesn't serve the same purpose because it gives a look that is more zoomed than what our eyes see.
The same can be said for wide-angle lenses; traditionally wide-anlge (despite above) cut-off was 28mm. Now with say a Pentax, having a 28mm lens is really like shooting with at 42mm film lens.
Even the most popular telephoto lens today, the 70-200 has changed. With a 105-300mm, it can be a little strong for traditional protraiture.

The factors that may be affected include the depth-of-field look and the perspective.
If you are like me and want that traditional look, the way in how the picture was meant to be seen, think of the focal length after the conversion. For instance, I shoot portraits and I use PENTAX DA* 50-135mm f/2.8 because after the conversion, it's like using a 70-200. The way the DOF (bokeh) looks and the perspective it gives for my portraits is how it has always loked. I have used the SIGMA 70-200 f/2.8 and it was too strong for portraits, expecially in studio having to stand farther back.

Although many have only been shooting in digital and don't know what film would give as a result, it really depends on the end users preference to the final look of the picture. In retrospect, the landscape of digital photography will forever change. The purpose of one film lens will now change to suit a new look for a new generation. It has been partially the manufacturer's faults for not considering this. Pentax is one of the few that has taken this to heart early on. There is also Olympus that has factored this in and even Nikon with their new 35mm DX lens that gives the traditonally loved 50mm look.

Anyway you look at it, as long as you get your shot and "be interesting", the only question you need to ask yourself, "am I suffering from LBA - Lens Buying Addiction?"

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