Dichroic Filters - Can I clean them...should I?

[BobNewYork]

I'm looking to kind of refurbish a couple of colour heads - D5500 and Chromega D. Is it OK to clean the dichroic filters? If so, what should I use and how should I go about it? My concern is that I don't want to make things worse than they are.

Bob H

 

[keithwms]

I'd blow them first, at very high pressure to get rid of as many particles as possible. And if that doesn't work for some spots, then lens tissue and isopropanol.

I have a bath sonicator in my lab and sometimes dunk various filter in spectral grade methanol or isopropanol in that, it works very well. I clean my glasses that way too

 

[BobNewYork]

Cool. I'm on my way to Virginia Keith - packing my dichroics and specs now

These will need more than a blowing unfortunately. I just wasn't sure if these filters were surface coated like the mirrors on grain focussers.

Appreciate the response.

Bob H

 

[Bob-D659]

All dichroic filters are surface coatings. Most are just much harder than the silver or aluminum used on first surface mirrors.

 

[Neal]

Dear Bob H.,

I cleaned the ones on my Omega by treating them like lenses.

Neal Wydra

 

[keithwms]

Cool. I'm on my way to Virginia Keith - packing my dichroics and specs now

Well, there is the postal service

 

[ic-racer]

I think you saw some of my threads last spring where I refurbished 3 of my D5500 heads. I used lens paper and lens cleaner to get the haze off. I also cleaned the UV filter in a similar manner.

Also note, if your Magenta does not go to at least 190 then it is not because the dichroic filter, it is likely the color probe green filter that has faded. The Red and Blue color probe filters are the special long-lasting Wratten filters, but the green is a 'regular' Wratten and it fades with time.

Make note of the contacts on the lamp socket. If they are oxidized they can be cleaned, but also that style lamp holder is still available as a replacement from some of the bulb stores.

If your numbers jump around when in 'white-light-calibration-mode' (or if your motors are always 'hunting' in focus/expose mode) you might try DeOxit on the color probe plug. Mine are rock steady after the DeOxit treatment.

Feel free to PM me.

 

[Peter De Smidt]

Dichroic filters, especially Magenta ones, do fade. I was getting low contrast with my enlarger using VC BW paper. After checking out everything else, I ordered new filters. The old magenta one was lighter and less magenta than the new one. Swapping them out got rid of my low contrast problems.

 

[ic-racer]

Dichroic filters, especially Magenta ones, do fade. I was getting low contrast with my enlarger using VC BW paper. After checking out everything else, I ordered new filters. The old magenta one was lighter and less magenta than the new one. Swapping them out got rid of my low contrast problems.

Notice I said nothing about printing contrast, just the value 190 on the digital readout. With respect to the special case of the D5500 closed loop system, the weakest link is the one 'non-special' Wratten filter sensing magenta (the green one). This will fade long before the dichroic filter fades. And it will fade before the other two 'special' Wrattens fade.

 

[Peter De Smidt]

Hi Ic-racer,

I wasn't disagreeing with you. I'm sure you're right.

 

[ic-racer]

A little off topic but I'm curious about your filter, was the fade just on the part in the light path, or the whole filter?

 

[BobNewYork]

Thanks for the responses guys. ic-racer - I did have in mind to pm you when I embark on the project. I'm in the middle of running my calibration tests having just got back into the darkroom. I've used the EIs and development times that I had been using and it's looking like all the films are over-developed. (The tests are TMX and Tri-X in three formats and two developers. My suspicion is that the fading green filter in the D5500 mixing chamber probe gradually caused my "white light" (which I used as grade 2 and for calibration tests) to become increasingly yellow and, over time resulted in my increasing film development times. While I'd thought I was generating negs that printed a full range on Grade 2, I was actually producing normal negs that fit a much lower paper grade.

I really appreciate the input and advice and I'll be in touch.

thanks again

Bob H