Meaning of a 2 strength close-up diopter for macro

[paul]

I asked this in another thread but didn't get an answer. Specifically,
I'm wondering what effect this would have on a 400mm zoom lense which is
only capable of getting as close as 7.5 ft. I don't understand what they
mean when they say "changes the closest focusing distance from infinity
to 9.9" My current 200mm zoom will get up to 1.3 ft away so I assume
this would end up having me a couple inches away. I don't know what
exact impact to expect.

paul wrote:

> OK I found the item I was looking for.
> $140 Canon 500D +2 77mm 2-element close-up diopter
> [url]http://www.adorama.com/CA77CU500D.html[/url]
> More info:
> [url]http://www.earthboundlight.com/phototips/closeup-diopters.html[/url]
> [url]http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=0005yN[/url]
>
> The descriptions says "changes the closest focusing distance from
> infinity to 9.9"
>
> What exactly does that mean? Sounds like it will not focus on anything
> beyond 9.9 inches away. It is supposed to have a very narrow depth of
> field but I guess that's a given. Sounds not much quality difference
> from a 'real' macro lense except the incovenience of having to unscrew
> it for anything over 10 inches away.

[Bob]

On Tue, 04 Jan 2005 13:49:16 -0800, paul <paul@not.net> wrote:

>I asked this in another thread but didn't get an answer. Specifically,
>I'm wondering what effect this would have on a 400mm zoom lense which is
>only capable of getting as close as 7.5 ft. I don't understand what they
>mean when they say "changes the closest focusing distance from infinity
>to 9.9" My current 200mm zoom will get up to 1.3 ft away so I assume
>this would end up having me a couple inches away. I don't know what
>exact impact to expect.
>

I just got a Hoya close up filter set, and it has +1, +2, and +4 element, and
they can be added up... for anything up to +7.

I use them on my Sigma zoom, since it can only focus from about 3 feet.

I just did a test using the +2+4 combination, and if I zoom to 300mm on a
subject 3 feet away with out the filters, I can then take the same picture from
about 7" away zoomed back to 28mm, with the +6 filters. This gives some
advantages...

I posted the example on alt.binaries.photos.original under "Glasses for my
camera".

The focus range with the +6 is very small, just a few inches back and forth. You
use the zoom to adjust the frame... but the camera MUST be about 7" from the
subject.

These filters are ONLY for macro work - you must take them off to take any other
type picture. But they work very well indeed! ($80 is a good price!)