ND Filters to replace Dichro's

[Tony Lakin]

Hi
I have a 2000 watt colour head on my De Vere enlarger which under certain circumstances is too bright (short printing times), I use the yellow and magenta dichroic filters for vc printing, as I no longer do any colour printing I am thinking I could replace the cyan dichro's with neutral density filters of some sort which would need to be heat resistant, the size is 25mm X 25mm, any suggestions would be greatly appreciated.
Thanks for looking.

[Greg Lockrey]

I don't have a DeVere so I might not be speaking with any real knowledge here and I don't want to give any misinformation. Couldn't you add 30 units each of Cyan , Magenta, and Yellow as a starting point for an extra 1 f/stop equivelent less exposure and then add your necessary Yellow and Magenta to get to your VC for your paper? My color head has 150 units each color (5 f/ stops) to work with.

[Tony Lakin]

I don't have a DeVere so I might not be speaking with any real knowledge here and I don't want to give any misinformation. Couldn't you add 30 units each of Cyan , Magenta, and Yellow as a starting point for an extra 1 f/stop equivelent less exposure and then add your necessary Yellow and Magenta to get to your VC for your paper? My color head has 150 units each color (5 f/ stops) to work with.

Hi Greg thanks for your reply, I should have explained thoroughly, when I use the colour head for vc printing the density of the filters is sufficient to allow longer print times without resorting to tiny apertures, however I mostly print on graded papers this is when the print times are too short I suppose I could use the dichroic filters to create neutral density I just thought the ideal would be to change the cyan filter array for nd filters.

[Phil Hudson]

The way it is done in some other enlargers (including the extra ND needed when switching from Ilford to Kodak settings on the De Vere 504 Varicontrast head) is by switching in a perforated metal disc infront of the lamp to reduce its effective brightness.

Could something like this be devised by drilling out a small piece of metal to fit the cyan Dichro holders? The spread and size of holes would allow you to gain different amounts of ND as a basic starting point as well as varying degrees of switching in and out.

I believe that this principle is also used in cine some projectors to reduce the brightness (and hence the heat) reaching the film when playing at slow fps speeds where the frames are exposed for longer.

Phil

[Tony Lakin]

The way it is done in some other enlargers (including the extra ND needed when switching from Ilford to Kodak settings on the De Vere 504 Varicontrast head) is by switching in a perforated metal disc infront of the lamp to reduce its effective brightness.

Could something like this be devised by drilling out a small piece of metal to fit the cyan Dichro holders? The spread and size of holes would allow you to gain different amounts of ND as a basic starting point as well as varying degrees of switching in and out.

I believe that this principle is also used in cine some projectors to reduce the brightness (and hence the heat) reaching the film when playing at slow fps speeds where the frames are exposed for longer.

Phil

Hi Phil
Thankyou, great idea.
Regards
Tony

[Gene McCluney]

You can get hobby sized quantities of aluminum and brass sheeting at most hobby shops, that are thin enough to make this job an easy task. Also at full-service hardware stores.

[Tony Lakin]

You can get hobby sized quantities of aluminum and brass sheeting at most hobby shops, that are thin enough to make this job an easy task. Also at full-service hardware stores.

Hi again
Thanks to all the job is now complete, I had some thin aluminium sheet around and cut it with snips followed by flattening in my vice, I decided not to perforate them as it occured to me that as the filters are of the interference type the aluminium replacements would be gradually introduced into the light path of the lamps, I have tested and it works great.
Thanks again
Tony