Using filters under the enlarger lens

gone · Jun 21, 2016

My enlargers don't have filter drawers, but they do have those swing out red filters for focusing, which I don't use anyway. I was going to take the red filter out and lay my VC gel filters on top of that if I need filtration, but I read something on the web that suggested keeping the filter very close to the enlarging lens. I suppose I could simply hold the filter flush to the lens w/ my hand, but is there any disadvantage to having the filter an inch or two below the lens? I really don't want to open the neg carrier and lay the filter on top of the neg because these enlargers have glass carriers and the carriers themselves are a PITA to get in and out w/o shifting something.

The only thing I could think of is possibly diffraction if I have the filter too far from the lens, or possibly it might give an airspace for dust in the air? Possible focus shift? Just guessing here.

Dali · Jun 21, 2016

Not sure it is a good idea as you introduce in the optical path something which might not have the required optical features.

pentaxuser · Jun 21, 2016

If these are the proper "under the lens" filters then these filters do have the required optical features The Ilford supplied filter holder does no more or less than the red safety filter holder so no problem. Some red safety filter holders( Durst M605 is one example) can be moved both up and down the stem anyway but I wouldn't worry about this.

pentaxuser

RalphLambrecht · Jun 21, 2016

Dali said:
Not sure it is a good idea as you introduce in the optical path something which might not have the required optical features.

under-the-lens- filters are fine as long as they are clean but I never gave any thought to their distance to the lens;just used the Alford clip-on set,which makes it easy to swap filters without disturbing the set up.

JHG · Jun 21, 2016

The filter "carrier" on the Bessler Enlarger that I use is about 2 inches below the lens. Use that as a frame of reference.

tedr1 · Jun 21, 2016

Yes the Ilford below the lens setup is made specifically for use in the way you wish. I think it includes a method of attaching the filter holder to the barrel of the enlarging lens. Filters are in little frames that can be handled without touching the filter surface with the fingers.

Paul Howell · Jun 21, 2016

What enlarger do you have, I have a Omega D3, I slide 6X6 filter in over or under the adjustable condenser?

DREW WILEY · Jun 21, 2016

If you want high-quality results you need optical-grade filters under the lens, just like over a camera lens, preferably coated glass ones.

gone · Jun 21, 2016

They're old Federal enlargers. One is a condenser model, one a diffuser. I fixed them all up, good lenses, new bulbs, and I'm having a shoot out to decide which one to keep. The filters are the usual square Ilford Multigrade filters that would normally reside in a filter drawer, but these enlargers do not have a filter drawer.

Paul Howell · Jun 21, 2016

If you do split grade printing then you need to use the filter holder under the lens. As I dont split print, in addition the D3, I have a Federal Stowe Away diffusion model and put a 6X6 over the diffusion glass which I just leave in place until I want to change contrast, it is pain to pull the housing apart but works for me. Saying that most of the time I use Salvich graded FB paper, number 3 works well in the Stow Away.

pentaxuser · Jun 21, 2016

Paul Howell said:
If you do split grade printing then you need to use the filter holder under the lens.

Not sure what you mean by this. Surely you could still use a filter drawer above the lens or use a filter on the red safety holder or even hand-hold the filter if you chose to do so?

pentaxuser

Paul Howell · Jun 21, 2016

Federal Enlarges don't have filter drawers, yes if you remove the red filter you can set a VC filter on it, or use an under the lens filter holder, I just prefer to use VC filters over the lens.

DREW WILEY · Jun 21, 2016

For split printing all you need is one good glass deep blue filter (47), and one deep green one (58). A small investment. No need for a whole set of
optically inferior VC "gels", which never were meant for being used over a lens. But if "gels" are "good enough" for personal purposes, so be it.

mmerig · Jun 21, 2016

In Ctein's "Post Exposure, 2nd edition" he compared resolution with a filter below the lens (using modern thin ones and older cast-plastic ones) and no filter, and could not see any difference with either filter type or no filter. He could see 320 lp/mm in the center and more than 280 lp/mm at the corners, using a high-resolution target.

I have done informal tests with a grain focusing scope and could not see any differences either, nor a focus shift with a 150 mm lens at f5.6 (wide open).

Paul Howell · Jun 21, 2016

DREW WILEY said:
For split printing all you need is one good glass deep blue filter (47), and one deep green one (58). A small investment. No need for a whole set of
optically inferior VC "gels", which never were meant for being used over a lens. But if "gels" are "good enough" for personal purposes, so be it.

Under or over lens? Seems that gel type filter were designed to used above the lens in the filter drawer. I also have older Kodak and DuPont filters that designed to used under the lens, not glass but a heavier plastic.

Blighty · Jun 21, 2016

Paul Howell said:
If you do split grade printing then you need to use the filter holder under the lens.

Not so; I use above lens filters.

DREW WILEY · Jun 21, 2016

You gotta take the old literature within the context of its era. True gels (made from gelatin, not acetate or polyester) came in a great variety, but
have always been fragile and prone to fading. Thicker optical grade acrylic filters are relatively modern, but even more expensive. Unless you already own a set of these, it makes way more sense to buy good coated glass filters if you intend to put anything in front of the lens for enlargement (versus just using the enlarger as a light source for contact printing in a separate frame below). Somewhere along the line the term
"gel" got routinely applied to thin lighting gels, which need to be heat-tolerant but certainly not optically pure. These can also be used in a
filter drawer, ABOVE the negative. I hear argument about this all the time. Those who put acetate or polyester gels over a lens and say it works
perfectly fine might be correct in the sense it is perfectly fine for them, but not necessarily for the viewer! if it were me looking at the print, I'd
probably be constantly rubbing my reading glasses with a cleaning cloth, wondering why things look out of focus.

mmerig · Jun 22, 2016

DREW WILEY said:
Those who put acetate or polyester gels over a lens and say it works
perfectly fine might be correct in the sense it is perfectly fine for them, but not necessarily for the viewer! if it were me looking at the print, I'd
probably be constantly rubbing my reading glasses with a cleaning cloth, wondering why things look out of focus.

Please show an example where simply placing a modern VC "gel" filter (like Ilford's) under a lens, is noticeably out of focus compared to no filter. Thanks.

gone · Jun 22, 2016

Yes, I probably misspoke, in the words of politicians. These Multigrade Ilford filters are surely acrylic. OK, I'm just gonna pop out the red filter and lay the square filter on top of that swing out arm. Laying the filter on top of the diffusion glass is probably a better idea, but I need to get the filter in and out when doing test strips w/ different negs. For me, the simpler the better. Not doing split grade printing at this point, so that's not a factor. Thanks for the help.

I suspect that while things might conceivably appear out of focus w/ a filter over the lens if you looked through your grain focuser, you'd probably just be seeing diffusion of the light path and the neg would still be in proper focus? Just my guess. It males perfect sense that a filter made from optical glass would be of higher quality than an acrylic one, but I'm thinking that if the acrylic filter is of good quality, like these Ilfords, there shouldn't be a drop off on print quality. In any case, the Ilfords are what I have.

pdeeh · Jun 22, 2016

mmerig said:
Please show an example where simply placing a modern VC "gel" filter (like Ilford's) under a lens, is noticeably out of focus compared to no filter. Thanks.

you don't ask DREW WILEY for evidence.
You just have to accept that he is always right, about everything.

Jim Jones · Jun 22, 2016

When using a thick filter beneath the enlarging lens, focus should be checked with the filter in place. A filter in the optical path can shift focus by maybe 2/3 the thickness of the filter. Depth of focus on the easel is usually larger than this, but critical photographers may want to precisely center the focus on the paper surface.

Paul Howell · Jun 22, 2016

momus said:
Yes, I probably misspoke, in the words of politicians. These Multigrade Ilford filters are surely acrylic. OK, I'm just gonna pop out the red filter and lay the square filter on top of that swing out arm. Laying the filter on top of the diffusion glass is probably a better idea, but I need to get the filter in and out when doing test strips w/ different negs. For me, the simpler the better. Not doing split grade printing at this point, so that's not a factor. Thanks for the help.

I suspect that while things might conceivably appear out of focus w/ a filter over the lens if you looked through your grain focuser, you'd probably just be seeing diffusion of the light path and the neg would still be in proper focus? Just my guess. It males perfect sense that a filter made from optical glass would be of higher quality than an acrylic one, but I'm thinking that if the acrylic filter is of good quality, like these Ilfords, there shouldn't be a drop off on print quality. In any case, the Ilfords are what I have.

You can also look for Kodak Polycontrast filters and a filter holder that attaches the lens, just a little easier to use.

DREW WILEY · Jun 22, 2016

Evidence is what every serious printer knew all along until the era of web snarkism evolved, which seems to overrule both common sense
and basic laws of optics. What do you want - another silly scanned smudge to prove that everything looks the same, no matter how compromised your technique? Go look at some actual prints instead, seriously done.

pentaxuser · Jun 22, 2016

DREW WILEY said:
If you want high-quality results you need optical-grade filters under the lens, just like over a camera lens, preferably coated glass ones.

So if one has no filter drawer above the lens and has to use under-the-lens Ilford filters that person will experience a drop in quality?

Does this mean that Ilford sells its under-the-lens filters knowing that a drop in quality is inevitable? What should such a person do if he wants top quality instead of buying Ilford filters.

What do you do to replicate the 12 grades needed for VC paper?

Thanks

pentaxuser

DREW WILEY · Jun 22, 2016

What you need to realize is that what Ilford is doing by this is marketing a practical amateur solution for printing VC papers. I doubt that any pro lab
would ever contemplate something like plastic MG filters because this kind of thing is more easily and precisely accomplished in the light head itself.
Ordinary colorheads make life easy; and there have obviously been specialized heads invented too, with specific MG feedback circuitry. But if you wish, you can also learn split printing, which requires only two glass filters, a deep blue and deep green, which can be obtained in glass. The only
disadvantage of split printing, other than the initial learning curve, is that these kinds of filters are quite dense, so it might be difficult to see the
image during dodging and burning if you happen to have a weak light source. I don't even think about "grades" of paper. I can do any hypothetical grade or anything in between. I leave that "grade" talk where it belongs, when I use true graded papers. VC papers represent a continuum which you
can control all kinds of ways. Pick what is best for your style and your personal equipment. But anything that goes below a lens can obviously affect
the image. What quality of filter would you want over a fine camera lens to begin with? No difference.

Using filters under the enlarger lens

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