Re: Ikelite dome is sharp even with 20mm lens

Posted by Rick on June 13, 2002 at 04:11:37:

In Reply to: Ikelite dome is sharp even with 20mm lens posted by john on June 12, 2002 at 08:04:20:

: There has been some ongoing threads about lack of sharpness in corners with 20mm lenses in the ikelite dome due to its small (6 inch) size.

: Some folks have stated that the edges will always be out of focus due to bending of the virtual image.

: I just returned from Caymans and shot a 20mm lens and got tack sharp images corner to corner. The secret is to manually focus (focus closer than the center of the viewfinder to improve corner sharpness) and use a small aperture (f/8-11) to gain enuf DOF to keep center in focus.

: The ikelite system is a bargain.

Hi John, a couple of questions - which dome port are you using? How have you rigged the port so that you can manually focus? The clamp I have with my 5503.50 is too bulky for me to use with my 20mm lens so I'm going to make up a rubber ring to go around the focus ring of the lens and glue a couple of ribs on it to fit into the geared sleeve that goes with the port. But if you have a better idea, I'd love to know about it. By the way, Ikelite told me that the 5503.50 would give `vignetting' with the 20mm but it doesn't seem to to me. I just have to be careful how I place the shade cover.

Follow Ups:

Re: Ikelite dome is sharp even with 20mm lens john 06:27:32 06/13/02 (1)
- Re: Ikelite dome is sharp even with 20mm lens Rick 21:55:09 06/20/02 (0)

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: : There has been some ongoing threads about lack of sharpness in corners with 20mm lenses in the ikelite dome due to its small (6 inch) size. : : Some folks have stated that the edges will always be out of focus due to bending of the virtual image. : : I just returned from Caymans and shot a 20mm lens and got tack sharp images corner to corner. The secret is to manually focus (focus closer than the center of the viewfinder to improve corner sharpness) and use a small aperture (f/8-11) to gain enuf DOF to keep center in focus. : : The ikelite system is a bargain. : : Hi John, a couple of questions - which dome port are you using? How have you rigged the port so that you can manually focus? The clamp I have with my 5503.50 is too bulky for me to use with my 20mm lens so I'm going to make up a rubber ring to go around the focus ring of the lens and glue a couple of ribs on it to fit into the geared sleeve that goes with the port. But if you have a better idea, I'd love to know about it. By the way, Ikelite told me that the 5503.50 would give `vignetting' with the 20mm but it doesn't seem to to me. I just have to be careful how I place the shade cover.

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