Use of diffusion disk

[Farace]

Among the items I have for my Retina IIC is something I've not paid attention to up to now, a Diffusion Disk. I understand it will soften details, and I'll test it out, but I have a couple of quick questions for anyone that's used one: 1) Does the center remain sharp and the details progressively soften toward the edges? 2) If the center stays sharp, can the effect of the disk be combined with a short depth of field to get almost a vignette effect?

Thanks!

[payasam]

If it is the kind with concentric circles, it will probably diffuse the entire image.

[Farace]

Originally Posted by payasam

If it is the kind with concentric circles, it will probably diffuse the entire image.

It has three concentric circles, with twenty straight lines radiating out from the center circle, like spokes on a wheel. The middle of the central circle is clear of lines. The box says it's "Type 217" if that means anything.

[payasam]

All I can suggest is that you do some test exposures: one at, say, f/8 without the diffuser, and the rest with the diffuser, at apertures from wide open to say f/16. Same subject, and will be good if you use a tripod or other support.

[ZorkiKat]

Originally Posted by payasam

All I can suggest is that you do some test exposures: one at, say, f/8 without the diffuser, and the rest with the diffuser, at apertures from wide open to say f/16. Same subject, and will be good if you use a tripod or other support.

From what I remember using diffusion discs (DUTO types, with cocentric engraved lines), LARGE apertures are best to use. Smaller apertures would not bring the best effect out of these diffusion attachments.

[payasam]

"...at apertures from wide open to say f/16."

This is the only way you can see the effect of different apertures. At small apertures the lens will be looking through the un-scored part of the disc.

[ped]

I just got one of these as part of a filter set for my Braun Paxette - I'll be taking some test exposures this afternoon to give it a try.

[JPD]

It's a modified DUTO-filter and should diffuse the intire emage. The rings and lines are lenses, so with the filter on two images will appear on the film, one focused (the light through the flat glass area) and one unfocused (the bent light through the ring and line shaped lenses).

[ped]

Thanks. There's a circle in the centre which is clear. Will be interesting to try.