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Olav Naess
Guest
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 Posted:
Sat Nov 27, 2004 6:02 pm Post subject:
Common with cheating about wide and tele conversion? |
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I just bought a set of Merkury wide angle and telephoto converters through eBay.
They were advertised and marked x.45 and x2.
I immediately checked them out on my new Minolta Dimage Z3.
With the zoom lens set at wide (35 mm equiv.), I got 16 fence posts horizontally
in a picture, and 22 1/2 when the WA converter was on. Its ratio was not .45,
but .71.
With the zoom lens set to tele (420 mm equiv.), I got 7 roof tiles horizontally
in a picture, and about 5.3 when the WA converter was on. Its ratio was not 2,
but only 1.32!
I also checked out the Kenko .42x converter (KCW-042) I have for my old camera
(a conventional little 3x zoom Medion MD 6126), but my balcony hadn't fence
posts enough for it. The angle of this one (as well as a .5x converter I have
tried) was so much stronger that the Merkury models were simply turkeys.
Well, a 25 mm wide angle without vignetting and with decent linearity has some
usefulness - the next one I order can now be a real fisheye. A Phoenix .25x
advertised on eBay looks interesting. Anybody who knows this?
The stated Merkury magnification factors become reasonable if areas are compared
(i.e. the actual values are squared), but do any honest people define
magnification factors by dividing areas?
-- -- Olav Nęss (Naess) olav.n@c2i.DROPTHISnet
-- -- Bergen, Norway
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Dave Martindale
Guest
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| Posted:
Sat Nov 27, 2004 6:02 pm Post subject:
Re: Common with cheating about wide and tele conversion? |
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olav.n@c2i.DROPTHISnet (Olav Naess) writes:
| Quote: | The stated Merkury magnification factors become reasonable if areas are compared
(i.e. the actual values are squared), but do any honest people define
magnification factors by dividing areas?
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No. Magnification is always a ratio of linear dimensions, not area.
The ratings on the Merkury adapters were simply lies.
Dave |
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dj_nme
Guest
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| Posted:
Sat Nov 27, 2004 6:03 pm Post subject:
Re: Common with cheating about wide and tele conversion? |
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Olav Naess wrote:
| Quote: | I just bought a set of Merkury wide angle and telephoto converters through eBay.
They were advertised and marked x.45 and x2.
I immediately checked them out on my new Minolta Dimage Z3.
With the zoom lens set at wide (35 mm equiv.), I got 16 fence posts horizontally
in a picture, and 22 1/2 when the WA converter was on. Its ratio was not .45,
but .71.
With the zoom lens set to tele (420 mm equiv.), I got 7 roof tiles horizontally
in a picture, and about 5.3 when the WA converter was on. Its ratio was not 2,
but only 1.32!
I also checked out the Kenko .42x converter (KCW-042) I have for my old camera
(a conventional little 3x zoom Medion MD 6126), but my balcony hadn't fence
posts enough for it. The angle of this one (as well as a .5x converter I have
tried) was so much stronger that the Merkury models were simply turkeys.
Well, a 25 mm wide angle without vignetting and with decent linearity has some
usefulness - the next one I order can now be a real fisheye. A Phoenix .25x
advertised on eBay looks interesting. Anybody who knows this?
The stated Merkury magnification factors become reasonable if areas are compared
(i.e. the actual values are squared), but do any honest people define
magnification factors by dividing areas?
-- -- Olav Nęss (Naess) olav.n@c2i.DROPTHISnet
-- -- Bergen, Norway
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I use a Dimage 7i and bought a Phoenix 0.25x converter a few month ago
(it was cheap on eBay) and found that it vignettes badly at the wide end
of the zoom range.
The vignette did not disappear until zoomed (for a "full frame" image)
to about 75mm (35mm equiv), so I suppose that the equivalent shortest
focal length would be about 18 or 19mm (35mm equiv).
So if you desperately want a slightly wider focal length, it might be
considered okay. |
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Matt Ion
Guest
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| Posted:
Sun Nov 28, 2004 12:13 pm Post subject:
Re: Common with cheating about wide and tele conversion? |
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Olav Naess wrote:
| Quote: | I just bought a set of Merkury wide angle and telephoto converters through eBay.
They were advertised and marked x.45 and x2.
I immediately checked them out on my new Minolta Dimage Z3.
With the zoom lens set at wide (35 mm equiv.), I got 16 fence posts horizontally
in a picture, and 22 1/2 when the WA converter was on. Its ratio was not .45,
but .71.
With the zoom lens set to tele (420 mm equiv.), I got 7 roof tiles horizontally
in a picture, and about 5.3 when the WA converter was on. Its ratio was not 2,
but only 1.32!
|
Teleconverter ratings are expressed as a factor of the focal length, not
width of view. Your equations don't apply; trigonometry comes into
play, and unfortunately, my trig is far too rusty to work out the exact
numbers right now. All you can derive from simple multiplication is
effective focal length: a 35mm-equivalent length with a .45X converter
will give you the approximate equivalent to a 16mm lens; likewise,
420mm-equiv. with a 2X converter will give you the same field of view as
an 840mm lens. |
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