I don't see why it needs to be so complicated (?) why not just use a fresnel lens to spread and even out the light -if done properly (?)
This was the basic plan - a quick sketch I just did for the purpos of communcation...
the top is a section and the lower a quick sketch to show the zone of cutaway- that occurs in the negative carrier, upper and lower stages - just using an angle grinder - I used a jigsaw for the 6x9 carrier plates I modified... seems like it just might work...
bump?
Maybe that would work ... I don't know enough about the way fresnel lenses work (and the idea didn't cross my mind back when I was playing with this stuff).
seems to me that a view camera is a good analog for this- insofar as the projected light by a lens has a similar fall off to what we're looking at here - and a decent fresnel lens seems to correct it well enough ... enough maybe to give it a whirl (?) -well anyway I guess I'll do just that - I don't see why this rig wouldn't work (diffuser or fresnel aside) - it's just a matter of what falloff corrector I use I guess (?). At any rate - I'll let y'all know how it works out...
okay- well it seems to have been a somewhat successful project so far - NICE to know you can 'chop' an enlarger like you can a car... so now my 4x5 DeVere is fully 6x17 capable... pics to follow. Please note: I ended up NOT using the fresnel after all. It didn't have an obvious effect - in one test it appeared to do the OPPOSITE of spread the light field but rather focus it. I suspect it would have to be used AFTER the diffuser - at which point the risk of seeing the fresnel ridges defocused in the print is too great I think...
These pictures show the cutting on the lamphouse bottom and the top of the bellows platform I did. I DID need to cut the bellows away a little bit to accommodate the full 17cm frame... but it shouldn't be an issue in terms of light spill etc at all from what I can tell.
and the bottom frame shows the projected image at the negative stage by the zone VI cold light
Looking forward to seeing the mod.Originally Posted by JW Dewdney
Cheers Shane
mod is above. see pictures. I posted the pics with the text.
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