Help: Lens size > Filter size

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Craig Bailey - 28 Jun 2006 01:49 GMT

Just bought a Canon AE-1 Program, the SLR I really _wanted_ to own back
when I was an 8th grader infatuated with photography in 1982. ;) (Back
then I had to settle for a Canonet 28, but that's another story.)

I'm looking to get a UV filter for the lens, and am a little puzzled
about what size filter(s) to get. The lens is a Canon 50mm. But a couple
filters that came with the set-up are 52mm -- and they fit fine.

I've noticed that I can't seem to buy 50mm filters.

Is 52mm the correct/preferred size for a 50mm lens?

To complicate matters, the set-up also came with a Canon 28mm and a
Vivitar 75-205mm zoom. (Though the Vivitar also has "55mm" printed on
it.)

What's the best scheme for buying filters/adapter rings? Should I stick
to one filter size, and buy adapters for the other two lenses? What
filter size should I get?

Also: What filter size does the Vivitar take? 55mm?

Thanks in advance for any help.

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CRAIG BAILEY <ccb@floydianslip.com>
Winooski, Vt. USA
www.floydianslip.com

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Joe Friday - 28 Jun 2006 02:30 GMT

Lens focal length (55mm, 28mm, etc.) and filter size are 2 totally separate
measurements. Focal length is just that, the focal length of the lens. The
focal length of a lens is defined as the distance in mm from the optical
center of the lens to the focal point, which is located on the sensor or
film if the subject (at infinity) is "in focus".

Filters, on the other hand are measured according to the diameter of the
front element of the lens. Wider lenses equal wider filters.

This is, of course, assuming you are using screw-in filters. Larger lenses
(300, 400, 500, 600 mm and larger) use drop-in filters toward the back of
the lens body There are also other systems (Cokin, for example) which use a
mount on the front of the lens into which different square filters (and/or
vignettes) are dropped.

Hope this info helps!!

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J. Clarke - 28 Jun 2006 14:24 GMT

> Lens focal length (55mm, 28mm, etc.) and filter size are 2 totally
> separate
[quoted text clipped - 5 lines]
> Filters, on the other hand are measured according to the diameter of the
> front element of the lens. Wider lenses equal wider filters.

Nitpicking here but they're measured according to the filter mounting
ring--while large diameter front elements will necessarily have large
diameter mounting rings the converse is not necessarily true.

> This is, of course, assuming you are using screw-in filters. Larger
> lenses (300, 400, 500, 600 mm and larger) use drop-in filters toward the
[quoted text clipped - 4 lines]
>
> Hope this info helps!!

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--John
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(was jclarke at eye bee em dot net)

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no_name - 28 Jun 2006 03:44 GMT

> Just bought a Canon AE-1 Program, the SLR I really _wanted_ to own back
> when I was an 8th grader infatuated with photography in 1982. ;) (Back
[quoted text clipped - 7 lines]
>
> Is 52mm the correct/preferred size for a 50mm lens?

You're confusing two different dimensions. The "50mm lens" refers to the
focal length.

52mm is the diameter of the front thread. I've seen 50mm lenses with
49mm front threads, 52mm front thread, and 55mm front thread.

You get the filter size that fits the front thread.

> To complicate matters, the set-up also came with a Canon 28mm and a
> Vivitar 75-205mm zoom. (Though the Vivitar also has "55mm" printed on
[quoted text clipped - 7 lines]
>
> Thanks in advance for any help.

If it says 55mm on the front bezel, it takes a 55mm filter.

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dadiOH - 28 Jun 2006 13:44 GMT

> What's the best scheme for buying filters/adapter rings? Should I
> stick to one filter size, and buy adapters for the other two lenses?

That's the cheapest way...buy filters large enough to fit your largest
diameter lens and step up rings for the smaller diameter lenses to fit the
larger filters.

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dadiOH
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Jimbo - 28 Jun 2006 16:20 GMT

> Is 52mm the correct/preferred size for a 50mm lens?

It should say the thread size on the inside of the lens where the
threads are or on the outside

> To complicate matters, the set-up also came with a Canon 28mm and a
> Vivitar 75-205mm zoom. (Though the Vivitar also has "55mm" printed on
> it.)

> What's the best scheme for buying filters/adapter rings? Should I stick
> to one filter size, and buy adapters for the other two lenses? What
> filter size should I get?

If $ is an issue buy the filter for the largest lens then get to
adapter rings - best to have dedicated filters though.

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robert_pascual - 30 Jun 2006 12:22 GMT

My old Canon FD 50mm f/1.8 and FD 28mm f/2.8 have the same filter
diameter. A friend has my old FD lenses at this moment so I'm
not so sure of the measurements. I believe the filters are indeed 52mm.

If you are not sure of the filter diameters of your lenses
just take them with you to the shop. You can find plenty of
skylight and UV filters for your FD lenses second-hand.
Try those first before buying new.

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