Dichroic head + under lens filters versus Dichroic color head?

[Cymen]

What is the difference between using a dichroic head with under the lens filters versus a dichroic color head with the built-in filters? I assumed dichroic head meant color dichroic head and thus brought an enlarger that is so named yet came with an empty box where the color filters are in the color head version.

Am I missing only a slight convenience by not having built-in color filters? Or is there more to it? I have seen this discussed in terms of condenser or cold head with under lens filters versus diffusion with built-in filters but not the case where both heads have diffusion light sources.

[Bob-D659]

Ummmm.. A dichroic head has built in filters by definition. Could be someone gutted the unit you have. Now are you talking about a colour dichroic head or one for multigrade black and white. They are different, as under the lens filters don't work with C41 type colour negative printing, only black and white.

[Cymen]

No, I'm talking about the Omega/Saunders/LPL 4500-II. It comes with the option of a "B&W module" which is an empty box, a color module or a VCCE module. These modules slide in between the light source and the diffusion chamber. The B&W module really is an empty box. The front of the head (not the module) says "Super Dichroic". It doesn't help that the B&W module is the color module without the guts but with the moldings where the 3 color adjustment displays are in the color head. This is it on B&H:

http://www.bhphotovideo.com/bnh/cont...G&A=details&Q=

The description is wrong though (it discusses the two other modules).

But to return to the question: Is there much of a difference between using the same diffused light source with dichroic filtration versus under the lens filters?

[Nick Zentena]

If you mean the end results it shouldn't be. Obviously if you're printing colour it'll be more of a hassle shuffling filters then turning the dial. For B&W less so of an issue.

[RH Designs]

But to return to the question: Is there much of a difference between using the same diffused light source with dichroic filtration versus under the lens filters?

If the actual filtration is equivalent in both cases, then no, there isn't.

[bdial]

With the Saunders LPL color head you can't get to 0 or 5 contrast levels, at least with Ilford paper. At least when I tested this, max yellow was about the same as a 1/2 Multigrade filter, and at max magenta it was about the same as a print made with a 4 MG filter.
So, I've hung on to my MG filters for just this reason, but I've never had a reason to actually use them for doing anything other than the original test/comparison prints.

The convenience and the ability to tweak even in-between half grades, makes the color head really nice however.

If you are contemplating buying a dichroic module, I'd recommend the VCCE module, if you're planning to do only B&W.
I haven't tested the extremes on the one that's available to me, but it's easer to use, since you can just dial in the contrast level without referring to a chart to use Y & M on a color head.

[markbau]

What is the difference between using a dichroic head with under the lens filters versus a dichroic color head with the built-in filters? I assumed dichroic head meant color dichroic head and thus brought an enlarger that is so named yet came with an empty box where the color filters are in the color head version.

Am I missing only a slight convenience by not having built-in color filters? Or is there more to it? I have seen this discussed in terms of condenser or cold head with under lens filters versus diffusion with built-in filters but not the case where both heads have diffusion light sources.

Putting a filter in the light path between the lens and the paper opens up the possibility of degrading image quality unless the filters are perfectly clean and free of any scratches. Personally I would never put a filter under the lens.

Mark

[RH Designs]

Putting a filter in the light path between the lens and the paper opens up the possibility of degrading image quality unless the filters are perfectly clean and free of any scratches. Personally I would never put a filter under the lens.

Mark

The Ilford filters are so thin and so far out of the plane of focus that their effect is invisible. I have never noticed any image degradation when using under-lens filters. Scratches might have an effect but a few specks of dust certainly don't.

[srs5694]

There was a recent thread here on APUG (sorry, I don't have a URL) about old under-lens filters degrading and causing flare, among other problems. I've no experience with this myself, though.

[Neal]

Dear Cymen,

Keep a set of under the lens filters around for the extreme cases, but the convenience of the built in filters is wonderful. Besides, you can free yourself from the concept of paper grades. If you want more or less contrast you just dial it in.

Neal Wydra