10x8 condenser lenses

[scratched&grainy]

Hi,
Does anyone know where to get hold of condenser lenses that would cover 7x7 inches?
i have a devere 5x7 enlarger with a neg holder rebored to 7x7 inches but the condenser lenses don't cover my 7x7 glass negs.
I guess i need 10x8 condenser lenses (280mm?)
I have come across some durst laticos but they cost an absolute fortune, so not an option.
Thanks,
Mark

 

[ic-racer]

The few 5x7 enlargers I am familiar with are not "7x7" where as many 8x10 enlargers are actually 10x10. Too bad for you, however. I think you need an 8x10 enlarger or 8x10 head to cover your 7x7 negatives. The other 'too bad' is that if you go down to 5x5 negatives, many 4x5 enlargers will cover that.

The other current popular route is a LED illuminated panel.

 

[Luis-F-S]

Sounds like you need a 10 x 8 Devere.

 

[scratched&grainy]

How about buying some big condenser lenses, putting them in somekind of metal box and mounting it on the existing 5x7 enlarger? The only problem would be thinking a way around the fact that the lenses would extend too far back onto the steel post that the top bellows moves along. Hmmm...

 

[ic-racer]

The other current popular route is a LED illuminated panel.

 

[RobC]

I would phone these people on Monday and ask if what you are doing is feasible and if so they may be able to supply condensors. They are/were "Devere".

http://www.odyssey-sales.co.uk/products/enlargers/

 

[scratched&grainy]

I talked to the people at odyssey a while back and they had very limited products at incredibly high prices.
I have found no 10x8 condenser lenses anywhere, only a durst enlarger on ebay for 10,000 dolLars.
So, is there any way to cover 8x8 inches or 7x7 without 10x8 condensers? Adjusting Distance between neg and light source and enlarger lens? Inverting condenser lenses? Different enlarging lens?

 

[RobC]

does it need to be condensor? You could buy some opal flexi to cover it and build a mixing box with the opal plexi at the bottom very cheaply.

 

[scratched&grainy]

Yes, that sounds interesing, can you elaborate?
1.) From my limited layman's understanding of condensers, the top condenser gathers uneven light, condenses it to a point and then the bottom condenser ( if there are only 2 lenses) receives the point source light and distributes it evenly on the negative.
2.) From my limited research into aristo cold light heads, it seems that (especially the old ones) they seem to produce incredibly uneven light.
3.) Apart from increased contrast, there seems to be no advantage to condensers, they definitely do not produce sharper images when contrast difference is adjusted, and the dust and hairs etc are a real pain ( for me, anyway).
So, I was thinking, since Im in the process of building a darkroom, why not make a hole in the ceiling or wall and Insert a flexible pipe with, say, a 10 x 10 inch square frosted glass ending and use natural daylight as a light source for the enlarger?

 

[ic-racer]

1) This image shows how condensers work
2) Probably more misused or out-of-adjustment condensers out there than out of whack cold cathode enlargers
3) The major advantage of condensers is simplicity and efficiency. Smaller power requirements and simper construction can yield greater value compared to some dichroic diffusion heads
4) Daylight enlarger is an old solution. Frequently overlooked today.

 

[RobC]

This is a durst 4x5 mixing box.

The larger piece has opal plexi in the bottom and the top has opal plexi too.

If you can fabricate something like this and have the bottom of it a few millimeters above the negative/holder.

Its important that the correct opal plexi is used. It should be milky looking with no grain in it.

Like this stuff I think

http://www.theplasticshop.co.uk/opal-perspex-sheet.html

i.e. opal and not frosted. You can line the box with silver foil to increase light level and diffusion if necessary but the correct opal plexi will give very diffuse light. 3mm or possibly 5mm should do it. I expect you can buy smaller pieces than they are selling.

My durst mixing box has changeable plexi system for different light levels. It will take a bit of experimentation for you but negates the need for condensors if you don't really need them which I doubt you do with that size negative, unless you are printing very very large.

 

[scratched&grainy]

Hmmm. Thanks.

 

[RobC]

yeah, wood and cardboard catch fire much more easily than metal. Maybe an LED lightsource would be the thing for you. I hear that some people are making their own for next to nothing and they don't generate heat. i.e. and LED lightsource with opal plexi bottom. I think you may find this is precisely the way the commercial ones are built.

 

[RobC]

Here's one and infact you can have it made to your own size and specification.

http://heilandelectronic.de/led_kaltlicht

 

[scratched&grainy]

Do you have any more plans/pictures/ideas on a natural light source for an enlarger? Like:sky light or wall light, angle of light entering enlarger, NSE or W facing?
thanks

 

[scratched&grainy]

Thanks. Im looking into this.

 

[Rick A]

Frosted glass diffuser used between light source and negatives. This is in my Elwood 5x7 and it works very well. I get slower exposure times, but any dust is virtually invisible.

 

[Maris]

I have used giant condenser lenses to build a solar furnace; but the lenses were fresnels. These lenses have the advantage over glass in that they are huge, relatively cheap, can be cut to size, light weight, and can be combined for a variety of focal lengths. The downside is that the optical quality isn't good enough for imaging but if you are just condensing light this doesn't matter.

 

[ic-racer]

The rings will show.

 

[Jim Jones]

Fresnel rings and other problems in condenser lenses might not show if the rings are fine enough and there is enough separation between the condensers and the film. Sheet magnifiers typically have about 50 lines per inch. It doesn't take much separation to throw this out of focus. As for diffusion, my 5x7 Elwood had quite uneven illumination. Graphite on drafting paper worked for a mask to cure this.

 

[Luis-F-S]

De Vere 5108

 

[scratched&grainy]

Yeah, I can't get hold of one of those, even if I did, I wouldn't be able to afford the shipping. So I need to make one myself. Can't be that hard.