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O.Pen lenses in FF = AGFA ISO?
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PostPosted: Sat Oct 24, 2020 11:51 am    Post subject: O.Pen lenses in FF = AGFA ISO? Reply with quote
In 1965 AGFA put on the market the system called Agfa ISO-Rapid.

It had a frame of 24 x 24 mm.

In the theory, the lenses for O. Pen 24 x 18 system, should produce a 24 x 24 mm square image in FF cams, more bigger than the APS-C size, so useful

Anyone tried this?


PostPosted: Sat Oct 24, 2020 12:44 pm    Post subject: Re: O.Pen lenses in FF = AGFA ISO? Reply with quote
papasito wrote:
In the theory, the lenses for O. Pen 24 x 18 system, should produce a 24 x 24 mm square image in FF cams, more bigger than the APS-C size, so useful


In fact, the lens should be able to produce an image circle with a diameter equal to the diagonal of an 18 x 24 mm rectangle, ie 30 mm. Therefore, we can say that a 30mm diameter image circle is guaranteed to cover a 21.2 x 21.2 mm square, but not a 24 x 24 mm square.

In practice, lenses are usually designed for an image circle larger than what is strictly necessary, so it is possible that a lens for Olympus Pen can produce an image of 24 x 24 mm with good resolution and little vignetting in the corners.


PostPosted: Sat Oct 24, 2020 1:05 pm    Post subject: Reply with quote
Thank you Gerald.

I can't understand the following

If the 30mm diameter image circle is guaranteed to cover a 21.2 x 21.2 mm square, but not a 24 x 24 mm square, so the 18 x 24 mm is not total covered.

When I used my Pen Fv didn't see any vignetting.

When my copy of the 38/1 8 cames, will try.


PostPosted: Sat Oct 24, 2020 1:27 pm    Post subject: Reply with quote
Sorry if I wasn't very clear. What I tried to say was that a lens with an image circle that strictly covers an 18 x 24 mm rectangle does not necessarily cover a 24 x 24 mm square. To find out if the coverage of a lens is sufficient, you need to compare the actual diameter of the image circle with the diagonal of the rectangle (or frame) of the image format. The length of the rectangle (or square) side does not matter. What matters is the diagonal of the rectangle (or square) compared to the diameter of the image circle.


PostPosted: Sat Oct 24, 2020 1:49 pm    Post subject: Reply with quote
Gerald wrote:
Sorry if I wasn't very clear. What I tried to say was that a lens with an image circle that strictly covers an 18 x 24 mm rectangle does not necessarily cover a 24 x 24 mm square. To find out if the coverage of a lens is sufficient, you need to compare the actual diameter of the image circle with the diagonal of the rectangle (or frame) of the image format. The length of the rectangle (or square) side does not matter. What matters is the diagonal of the rectangle (or square) compared to the diameter of the image circle.


Many thanks, Gerald.

I apologice I don't understand properly-

It's very clear to me now.
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