Zoom Lens

Zoom Lens
Would someone please explain to me how the Zoom on a camera lens compares to the X power of a rifle scope?

For example I have 4X power rifle scope which means that what I’m looking at through the scope is magnified four times it’s actual size.
How does this work with a zoom lens? Is a 200mm setting three times closer than a 50mm setting?
Is there a formula for figuring this out?

Zoom on a camera only describes the RANGE of focal lengths of the lens.
So a 4X zoom may be from 25-100mm focal length.
A 35mm film camera was the standard for comparing magnification for most photographers (and often it still is). A 50mm lens approximated the diagonal dimension of the film frame so a 50mm lens is refered to as a “normal” lens. It came the closest to what your eye saw at 1X magnification.
That means a 25-100mm zoom lens has a magnification of 1/2X at its widest setting to 2X at its highest magnification.

Power or “x” factor on a scope is MAGNIFICATION. A 4X scope sees and object as if it were 1/4 the true distance to you.

For your question, a 200mm setting is 4X more magnification than a 50mm setting.

When reading specs on a camera, you have to dig down to get the “35mm” equivalent of the particular camera focal length. An 7-28mm zoom may actually translate to 28-112mm in “35mm equivalent” because the CCD sensor on the camera may be only 12mm diagonal.

Here is your formula:

1. Make sure you find the “35mm equivalent” focal lengths of the lenses
2. Divide by 50mm to get your magnification range.
3. If the camera is 35mm film or is an expensive “full frame” sensor, simply divide by 50mm to get your magnification.

Many DSLR’s tell you the “conversion factor” of lenses. Typical factors are 1.5, 1.7 and 2. That means when you stick a 100mm lens on a camera with a 1.7 conversion factor, the lens is equivalent to a 170mm lens on a 35mm camera and your magnification is 170mm/50mm = 3.4X

Here are some examples of 35mm equivalent focal lengths:
28mm = 0.56X good wide angle. You can capture nearly an entire bedroom view without “fish-eye” distortion
35mm = 0.7X mild wide angle. Easier to get group shots without backing up too much
50mm = 1X Pretty much what your eye sees in terms of magnification
85mm = 1.7X good portrait lens for face shots
200mm = 4X used to be the consumer limits for inexpensive telephoto shots
500mm = 10X used to be top of the line telephoto. These are the lenses used by those pro photographers that often get tackled on the sidelines of football games .

Hope that helps

Zoom Lens

Zoom Len Pictures

One of the camera features that is easy to understand is zoom lens pictures. Objects that are far away look much closer when the photographer uses zoom features. Zooms are one of the first ‘extras’ many buyers look for in a camera. But people sometimes misjudge zoom use. Here is some useful zoom information.

In the days of film cameras a zoom lens was a separate extra. Those old time zooms were sometimes very large. A person walking down the street with a camera sporting a big, fat zoom lens looks like a serious photographer, even if he or she doesn’t really know what they are doing. Today’s digital cameras have dispensed with the need for a separate zoom lens (with a few exceptions for really serious or professional cameras). Today’s digital cameras usually offer two kinds of built-in zoom features, often offering both on the same camera.

They are called the ‘optical zoom’ feature and the ‘digital zoom’ feature.

The optical zoom is, in principle, a smaller version of those big, fat zoom lenses you used to see. On a digital camera with optical zoom the lens can be made to stick out or withdraw by the touch of a button.

The principle is different with a digital zoom. The camera takes a picture, the picture is cut down to a smaller size, and the smaller picture is made to look larger. Film cameras could not takes each of these steps. Until a few years ago a film camera could do something similar to this process only if the negative was put in an enlarger in a photographers darkroom.

Shots taken by the two different are different in quality. Optical zoom pictures typically are sharper. Digital zoom lens pictures cannot match this sharpness. You can’t always tell the difference in sharpness if the picture is taken at a moderate setting. But a picture taken at the extreme settings looks different comparing these two methods. Whichever feature is used, here is a tip for zoom lens users: turn off the digital zoom if your picture is taken at the extreme end of your camera’s capacity.

Here’s another trick for zoom lens pictures takers. Many times zoom shots are blurry. A tiny movement by the photographer when taking a zoom shot results in a blurry picture. Right before you press the shutter button for your next zoom shot take a deep breath. Then exhale slowly. Press the shutter a fraction of a second after you start to exhale. Your camera hand is steadiest just when you start breathing again.

This writer once used zoom lenses but no longer does so. For a few reasons. All most published photographers use for most published pictures is an average size lens, not a big, fat zoom lens. The need to capture far-away objects in pictures is greatly exaggerated. All those blurry pictures detract from the allure of zoom lenses. But the reason that I follow most: a zoom lens subtly draws your attention away from the interesting pictures you can take of nearby objects. You don’t really need the faraway shots for the most part. So even with all my zoom lens pictures savvy I use just an average lens and am satisfied with photo subjects near me, thank you.

Get more great photography knowledge and advice at Cam K. The author has many photos published in many places, including Rolling Stone magazine.

About the Author

Noo Yawka has many photos published in dead tree magazines — like Rolling Stone magazine — as well as on the net and other places. For photo advice and tips go to Cam K, photography for the new age It’s just a click away!

what is the optical zoom on Canon EF 75-300mm lens and how to determent the optical zoom on Telephoto Lenses?

I cant figure out how to see how much optical zoom lens have.
Can you please explain me how to determine the optical zoom on lens because i have never seen any of optical zoom numbers on the box or lens itself. So please help me. Thank you.

You don’t really need a website to do this conversion, as it is 3rd grade math. Just divide the little number into the big number and you get your “X” factor.

An 18-55 zoom is a 3X zoom. A 70-210 zoom is also a 3X zoom. How can this be? You know that a 200 mm lens wold give you a much larger image than a 55 mm lens, right? The thing is, with a non-SLR camera, we tend to almost never pay attention to the focal length of the lens. It would be incredibly confusing if we tried to anyway! Image magnification is a direct function of the sensor size. There are many different sensors out there and without having some standard reference, comparing focal lengths would also become meaningless. This is why everyone still refers to the “35 mm equivalent.”

Back to your question…

Your 75-300 mm lens is technically a “4X” zoom, but who cares? On a Canon digital camera, it behaves like a 480 mm lens and that beats out pretty much ANY of the so-called Super Zoom point and shoot cameras for telephoto power. Well, it’s certainly in the same range as the best, but the image quality is immensely better on an SLR sensor.

In other words… The “power” expressed in terms of [some number]X doesn’t really mean that much. This is especially true in digital SLR’s. What matters is the actual focal length of the lens. Fortunately – at least for sake of comparison – the majority of DSLR’s have pretty much the same magnification factor and that is around 1.5 to 1.6. It makes direct comparisons a lot easier, but you have to develop a sense of what constitutes a “long” vs. a “moderate” telephoto.

Unless and until we have a major paradigm shift, it will still be helpful to think in terms of 35 mm equivalents when you are buying a lens. This is the “language” that we speak, using 35 mm as the de facto standard. Focal length comparisons make more sense that expressing the magnification by “zoom power.”

Here’s a chart that I’m making up just to get you started. It is in 35 mm equivalents. If you are putting a lens of this focal length on most DSLR’s, you would have to do some math. Multiply the numbers I gave by .67 if the camera has a 1.5 “lens factor” or by .625 if it has a 1.6 factor. For example, in my list, I say that 50 mm is the “normal” lens for 35 mm cameras. If the DSLR has a factor of 1.5, this would mean that a 33.5 mm lens would be “normal” for that DSLR.

Ultra Wide – 10-20
Wide Angle – 24-35
Normal – 45-55 (50 mm is the accepted “normal”)
Medium Tele – 85-135
Telephoto – 150-300
Super Tele – 400-600

If you are not familiar with the power of these lenses, you might want to check out my tutorial on the subject:

Canon EF 75-300mm f4-5.6 Zoom Lens Review on my Canon Eos 350d / Digital Rebel XT

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