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-   -   [Recovered Thread: 66542] (https://forums.steves-digicams.com/add-lenses-49/%5Brecovered-thread-66542%5D-64774/)

ken212 Aug 23, 2005 11:06 PM

I want to buy a wide angle lens for my Olympus c 770. I have seen fisheye ytpe and true/corrected view type. Which is the better type to use? I am lost on these.

DGehman Aug 25, 2005 6:58 AM

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You're kind of mixing apples and oranges here.... sort of.

Three things to look for in a w/a:

1. ratio

2. sharpness/focus

3. distortion

The ratiotells youbasically how wide it goes. A 0.6x w/a on a lens that has a 50mm equivalent focal length will become 30mm equivalent focal length; 0.5x would be 25mm, and so on.

The quality of glass and design will determine sharpness -- that, and the fit of the add-on lens with your camera's built-in lens. On my Kodak camera, a Raynox w/a resulted in very soft corners, even though the Raynox adapter works well on many other cameras. It turned out that a Kodak adapter at a little less cost is sharp almost to the edges.

Generally, the wider the angle, the more likely you will see barrel distortion, so-called because straight lines begin to bow out, like the shape of a barrel. The wider the angle, the more expensive the adapter that avoids this distortion. A fisheye lens, which takes in a very wide angle, generally has distortion in the extreme -- in fact, many fisheye adapters, rather than fighting this, play it up as part of the effect.

The Kodak adapter for my camera causes quite a bit of barrel distortion, but I can remove it easily with editing software.You can see it in the photo below.

A real "true/corrected" w/a (and it's a term I haven't run across, since my pocketbook is limited) sounds as though it corrects the barrel distortion in the glass. If such lenses are sharp to the edges, I'd guess these would be expensive adapters.

Barrel distortion (0.6x adapter on 39mm lens = 24mm equivalent w/a, pretty wide):



DGehman Aug 25, 2005 7:02 AM

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Here's the same shot with the barrel distortion handled by software. (I've also done perspective correction, because the camera was pointed downward a bit). The gray line at the bottom is a bridge railing only a few inches from the camera, illustrating another w/a phenomenon: you get extra depth of field.

nonilady Sep 10, 2005 11:47 PM

hi dgehman



mind telling me what software u used to get rid of the barrel distortion?



thanks

nonilady

DGehman Sep 12, 2005 7:38 AM

nonilady wrote:
Quote:

mind telling me what software u used to get rid of the barrel distortion?
Photo-Brush from Mediachance (http://www.mediachance.com/pbrush/index.html)

It has a number of digital photo built-ins, plus it takes Photoshop plug-ins. But it doesn't have layers or much by the way of drawing tools.

I haven't done a Web search for this for quite a while, so there might be some standalone filters/plugins that are low cost or free. The Imaging Factory used to have a free Debarrelizer Photoshop plug-in, but it looks as though they're charging $30 for it now.

nonilady Sep 12, 2005 8:50 AM

thanks for the info !

cheers


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