Finding the right Lens

Recently I have been working on a few projects that has caused me to learn some stuff about lensing.  It is one of those things that the more I learn, the more I realize how little I know.  But, even though I’m a rookie, there are a few fundamentals that are important to know.

When we are dealing with IMAG, for the most part we need lenses that have a long zoom range so we can get in tight from a distance.  When it comes to hand held cameras or POV shots, most of the time standard lenses work great, but rarely do we get to place cameras where we want and we either deal with bad shots or we need a different lens to better the shot.

When you look at a lens you will see numbers such as 17x or 20x.  These numbers refer to how many times over it can zoom (Zoom ratio).  When I talk with most people looking at lenses they stop with the first number (I was guilty as well), but the number after the x is really more important than the first number because that is the backstop, or the starting point of the lens. So what you really have is a math equation.

All lenses are measured in millimeters so a 20×8.5 has a range of 8.5 to 170 millimeters. A 40×10 has a range of 10 to 400 millimeters. You get the idea. Different lenses get us to different ranges.  And in IMAG, I’m not usually as concerned with the backstop or the zoom ratio as much as I’m concerned with the overall maximum range to get those nice tight shots.

So when you are finding lenses or figuring out camera placement, how can you use this millimeter number to your advantage?  Well, you need a lens calculator.  There are a few that I have found online but I decided to make my own.  I don’t know if it is 100% accurate but it seams to be close and has worked well for me so far.

But I have kind of a rule of thumb. For every 50 feet, I like to see at least 150mm.  This will get a decent shot, not extremely tight but not too wide either.  So if my cameras are at 100ft, I need 300mm;  75ft, 225mm and so on.  That is my rule, I have used smaller lenses a bit farther away, but most of the time I would prefer an even bigger lens at that distance.  The lens dictates the type of shot you get, so if you don’t mind a wider shot than you can go with a smaller lens, it all goes with what you need your end product to look like.

Now lenses are expensive, especially getting over 170mm.  You may be tempted to use a doubler, but I would steer you away from that.  Doublers cut down your light levels and shows the imperfections in the glass.  I have used them before but they are never ideal and I recommend to only use them in a pinch, or as a last resort.

There are so many things to consider when finding a lens, but getting a lens with the right amount of power is in my opinion the most important.  Like I said before, there is so much more I have to learn about specking lenses, just because it comes with the camera or is cheap doesn’t mean it is right for the job.  Take time in finding the right lens or work hard to find a good location for camera with a stock lens.

If you want to try my lens calculator here it is: Brandon’s Lens Calculator

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About brhoda

I freelance doing a few different thing in the video and live production market. I worked for a church for 5 years directing services and designing control rooms.
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2 Responses to Finding the right Lens

  1. Nick says:

    Is this calc 35mm?

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