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Something I don't understand about this lens...
Take a look at this Sony lens. It's described as a 135mm lens. But then it says that the lens can focus from arm's length to a long distance. Hmmm...isn't this what a zoom lens does? But they call it a 135mm, not 50-135mm, or something like that..

So is this a fixed focal length (prime) lens, or is it a zoom lens?.

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Comments (8)

Actually, they don't call it a zoom lens. It's called a telephoto lens...

Comment #1

BigBen08 wrote:.

Take a look at this Sony lens. It's described as a 135mm lens. Butthen it says that the lens can focus from arm's length to a longdistance. Hmmm...isn't this what a zoom lens does? But they call it a135mm, not 50-135mm, or something like that..

So is this a fixed focal length (prime) lens, or is it a zoom lens?.

Well, it's a fixed focal length lens. A zoom lens is one whose focal length can be changed..

For example, say you're taking a picture of some mountains (far away). With a zoom lens, you can change the angle of view (so you can take a picture of one mountain or several mountains). With a 135mm fixed-focal length lens, the field of view is fixed..

What Sony is saying is that the lens can focus relatively close. Zoom lenses also have adjustable focus. If you're taking a picture of something 10 feet away, you have to adjust the focus. Then you can adjust the zoom to change the field of view..

All (as far as I know) DSLR lenses have adjustable focus. Only zoom lenses have an adjustable field of view at a constant focal distance..

Leonard Migliore..

Comment #2

One specification for a lens is it's shortest focus distance, and these vary from lens to lens. This is important for some photographers, and shots, as a specific lens might not be able to focus at the desired, short, focus distance..

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Comment #3

Doug J wrote:.

One specification for a lens is it's shortest focus distance, andthese vary from lens to lens. This is important for somephotographers, and shots, as a specific lens might not be able tofocus at the desired, short, focus distance..

Yes. The special feature of this fixed focal length (non-zoom) lens, is it's wide focusing range. Mostly telephoto lenses do not focus as close as other types ... this one is an exception..

However, the mentioning of it's ability to focus at great distances was a bit stupid, I'm afraid, and is perhaps the reason for the OP's confusion. Fact is, any lens that did NOT focus all the way out to infinity would be more or less useless for general photography, and completely disastrous in a telephoto type!!.

The zoom feature is a different and separate thing to focus distance range. Zoom lenses can change their focal length from short (wide-angle) to long (telephoto).Regards,Baz..

Comment #4

Barrie Davis wrote:.

Zoom lenses can change their focal length from short(wide-angle) to long (telephoto)..

Now Baz, don't go confusing the newbie!.

:~).

Rob.

Everyone, everywhere, has to do everything for a first time. There is no shame in failure, only in failure to try...

Comment #5

No, they just need to be able to adjust their focal length. Assuming a 1.5x crop sensor, A Sigma 10-20mm goes from ultra-wide to wide, a Pentax 50-135mm goes from short telephoto to medium telephoto, the new Sigma 150-500mm goes from medium telephoto to long (really long, I want this lens!) telephoto..

Barrie Davis wrote:.

The zoom feature is a different and separate thing to focus distancerange. Zoom lenses can change their focal length from short(wide-angle) to long (telephoto).Regards,Baz..

Comment #6

Egordon99 wrote:.

No, they just need to be able to adjust their focal length. Assuminga 1.5x crop sensor, A Sigma 10-20mm goes from ultra-wide to wide, aPentax 50-135mm goes from short telephoto to medium telephoto, thenew Sigma 150-500mm goes from medium telephoto to long (really long,I want this lens!) telephoto..

You are right, of course, but I think you have taken pedantry to new lengths (infinity?). This is supposed to be a beginners forum, after all..

Barrie Davis wrote:.

The zoom feature is a different and separate thing to focus distancerange. Zoom lenses can change their focal length from short(wide-angle) to long (telephoto)..

Regards,Baz..

Comment #7

BigBen08 wrote:.

Take a look at this Sony lens. It's described as a 135mm lens. Butthen it says that the lens can focus from arm's length to a longdistance. Hmmm...isn't this what a zoom lens does?.

No. You are confusing focus adjustment with zoom adjustment..

All serious camera lenses have a focus adjustment, to allow sharp pictures of near or far subjects. Commonly this is accomplished by simply moving the entire lens towards and away from the camera body..

Zoom lenses can do this too, but that isn't why they are called zoom lenses. It's because the zoom has a complex construction, internal elements of the lens move relative to each other and alter the focal length. In non-technical terms, that changes the magnification, so the subject appears larger or smaller, without changing the distance from camera to subject.Regards,Peter..

Comment #8

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