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range-extenders/extension-tubes/diopters


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#1 Robert Glenn

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Posted 27 October 2005 - 09:40 AM

I'm pretty sure I know the answer, but maybe there's a better explanation out there.. Here's my understanding of the 3, so correct me if I'm wrong.

Range extenders - extends the focal length of the lens by 1.4x or 2x etc. while raising the minimum f stop ---don't know if it has any other capabilities however

extension tubes - makes the camera 'closer' without moving the camera too close for the lens to be able to focus. Doesn't degrade image but does cut down light and not recommended for zoom lenses

diopters - same principal as tubes but can be used on zooms and little or no light cutting. Can degrade or distort image quality

Finally does anybody use diopters regularly? If the diopter is not perfectly lined up with the lens, would the image distort?
Thanks!
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#2 Stephen Williams

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Posted 27 October 2005 - 10:49 AM

I'm pretty sure I know the answer, but maybe there's a better explanation out there.. Here's my understanding of the 3, so correct me if I'm wrong.

Range extenders - extends the focal length of the lens by 1.4x or 2x etc. while raising the minimum f stop ---don't know if it has any other capabilities however

extension tubes - makes the camera 'closer' without moving the camera too close for the lens to be able to focus. Doesn't degrade image but does cut down light and not recommended for zoom lenses

diopters - same principal as tubes but can be used on zooms and little or no light cutting. Can degrade or distort image quality

Finally does anybody use diopters regularly? If the diopter is not perfectly lined up with the lens, would the image distort?
Thanks!


Hi,

A range extender magnifies the image. That means there is a quality and a stop loss. One potential advantage is a lightweight Zoom for 16mm may cover 35mm with an extender!

Extension tubes and bellows are good for macro work. There will be a stop loss of 2 stops at 1:1 on film, the quality is very good.

Diopters are useful but there is always a quality loss, and more distortion.

Stephen
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#3 Charles MacDonald

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Posted 27 October 2005 - 08:07 PM

extension tubes - makes the camera 'closer' without moving the camera too close for the lens to be able to focus. Doesn't degrade image but does cut down light and not recommended for zoom lenses

diopters - same principal as tubes but can be used on zooms and little or no light cutting. Can degrade or distort image quality

Thanks!


What the extension tube does is move the lens farther way from the film, so you effectivly make the focus ring longer. A bellows allows one to pick a continuous range.

They don't often work with zooms, as the focus in a zoom frequently involves moving elements inside the lens relative to each other.

One trick that is sumtimes used with still cameras is to turn the lens arround for a close up. The thorey being is that if you are very close, the lens itself ends up being closer to the subject than to the film, so you use the end of the lens intended to be closer at the subject end.

The diopter is exactly like the reading glasses us folks over 50 find we have to use.
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#4 Robert Glenn

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Posted 12 November 2005 - 12:16 PM

What the extension tube does is move the lens farther way from the film, so you effectivly make the focus ring longer. A bellows allows one to pick a continuous range.

They don't often work with zooms, as the focus in a zoom frequently involves moving elements inside the lens relative to each other.

One trick that is sumtimes used with still cameras is to turn the lens arround for a close up. The thorey being is that if you are very close, the lens itself ends up being closer to the subject than to the film, so you use the end of the lens intended to be closer at the subject end.

The diopter is exactly like the reading glasses us folks over 50 find we have to use.

So regarding diopters.. How detrimental to the image quality are they? From browsing photo.net's forum, it sounds like they are not bad as long as the lens that I use is high quality.
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#5 David Mullen ASC

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Posted 12 November 2005 - 01:02 PM

People use diopters all the time for shooting objects closer than the minimal focus on the lens; to some degree, the quality loss is determined by the strength of the diopter -- generally with a +1 or +2, the quality is fine. Of course, I'm talking about good-quality professional diopters.

Besides, you're shooting macro shots, not wide shots, so a little loss of sharpness or more edge distortion is not so noticeable. It helps if you are not shooting wide-open where you already have the lens' normal distortions at maximum.

Biggest problem with diopters is that the focus marks on the lens become irrelevent and everything has to be focused by eye. So I still prefer to use lenses that focus closer and a macro lens for macro shots, but I always carry a set of diopters too.
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#6 Stephen Williams

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Posted 12 November 2005 - 01:23 PM

Biggest problem with diopters is that the focus marks on the lens become irrelevent and everything has to be focused by eye. So I still prefer to use lenses that focus closer and a macro lens for macro shots, but I always carry a set of diopters too.


Hi,

Focus conversion charts are available for diopters, so it is still possible to pull focus.

Stephen
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#7 Robert Glenn

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Posted 28 May 2007 - 02:40 PM

bumping this since there isn't much on the web that i could find other than this thread hehe..
So do range extenders work with zoom lenses? I was under the assumption that they would double the focal length (50-100 zoom becomes 100-200).
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