Using filters under the enlarger lens

[Patrick Robert James]

I have two enlargers, a Saunders 4550 with built in VCCE filtration, and a Leitz Focomat with which I use below the lens filters. Like Drew stated, you only need two. I use a 47 and a Green 13 though. It is nearly impossible to find a 58. After studying the Kodak transmission values, I realized that a Green 13 would work fine, as would a Yellow 8. I also put a UV filter over the condenser to eliminate any problems related to UV light.

If you do use a below the lens filter, regardless of the kind, focus through the highest contrast one. That said, every setup is a little different, so it may or may not matter.

Personally I don't like gels for filtering enlarging light. Even Ilford states they have to be replaced every so often because they fade. They are also really easy to scratch.

By the way, Drew (who might be prone to minor hyperbole) gets a lot of grief for some of the things he writes here, but in my experience most of what he states is true, some I can't have an opinion on since I don't have any experience with it, and rarely I think he is smokin' something. The point I am trying to make is you should probably listen to him if you want to make technically good prints. Just my opinion based on years of doing this stuff.

All that being said, use whatever works for you so you are happy with your prints. In the end it all really doesn't matter anyway. Just to prove my point, I saw some large prints of Elliot Erwit recently and they were pretty pathetic from a technical standpoint, but the museum didn't care.....

 

[mmerig]

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.

Not sure this is directed at me, but so far, I've seen evidence to the contrary of what you say (e.g., Ctein's test, which is hardly a smudge), so I was looking for something similar that would refute it, not just hearsay about serious printers.

Regarding optics and common sense, any defects in a sheet of plastic would be more apparent the closer it is to the plane of focus rather than further away, as in a filter drawer or below the lens (about the same distance on either side of the POF). If we are so worried about defects in plastic, we should only use optically perfect glass plates rather than film.

 

[DREW WILEY]

This is like asking which can run faster, a man or a horse. You don't need to read Aristotle; you just need to have been around horses. I suppose
everything is hearsay to someone who doesn't yet understand the inherent optical differences between one category of plastic from another; it has nothing to do with "defects". Fine. Learn the hard way or don't learn at all. It's your prints in question, not mine.

 

[Patrick Robert James]

If you use Ilford's filters under the lens I would say the difference is minimal at most. You would have a very hard time noticing it unless everything else was perfect which in most people's darkrooms isn't going to happen. If you decide to use Cinema filters then you would notice it.

As an interesting aside, I put a gel in a pinhole camera once and it imaged a pattern on the negative. It wasn't subtle either. Glass filters had no effect. Keep in mind pinhole cameras image everything. Optical systems like an enlarger only image at or near the plane of focus.

 

[DREW WILEY]

I've deliberately smudged gunk on gels below the lens to blend complexions. Photoshop in a jar. I've used odd old lenses to print with for a particular effect. But I know the difference and how to optimize sharpness and microtonality, which is far more frequently the name of the game.

 

[DREW WILEY]

(got interrupted)... My main objection to optical acrylic filters (not to be confused with thin pseuo-gels) is that they can be easily scratched or marred, and worse, are electrostatic, so tend to attract dust, esp with cooling fans etc in operation nearby. There are certain time I fine-tune light
for some kind of contact frame duping using certain flavors of these; but all my actual VC printing is either done with colorheads or split printing.
A couple of my colorheads are true RGB, so can control full split printing with colored light wholly above the neg carrier.

 

[M Carter]

I found camera filters (52mm) that match the colors of the contrast filters, just the far ends of the series, 00 and 5. I drop those into the red-filter holder when I'm worried that messing with the filter drawer could give me blur (Beseler 67 doing very large prints with the head up high). It's worked fine for me, and I like that the metal filter rings keep the filter glass off of surfaces.

 

[grahamp]

I'm with Drew about this - putting an extra two surfaces in the enlargement path after the negative is not going to improve resolution. There is also the potential for light loss from reflection. Worst to best: 'Over lens used under lens' (and assuming clean and in motion), purpose-made under lens, over lens in filter drawer (enlarger disturbance on some models), colour (most unable to reach G5) or VC head.

You have to accept the limits of your system too - a Beseler 5x4 condenser head needs a big filter; my old Durst F30 required that the negative carrier be disturbed to change filters above the lens.
A test for under lens use is easy to do - G2, no filter, G3, a sharp negative, full enlargement, center of the frame, and use a good magnifier.

 

[Bob Carnie]

My 2 cents- I would never use filters under lens other to soft focus effects

I quite like the Ilford filters for the simple fact that when split printing I have lots of selection of the starting filter for the low hit. Or if I want to start with a high filter I have options .

 

[DREW WILEY]

A lot has to do with the degree of magnification. For example, a minor loss of sharpness enlarging 8x10 film to a 16x20 print won't be apparent anywhere near as much as attempting something analogous with 6x7 cm roll film, for example. But my own philosophy is that little comprises add up to cumulative issues, and that you're really only as good as your weakest link, so why compromise to begin with?

 

[tedr1]

I hear the surplus wafer-fab houses do a nice line in precision optics, unbelievable resolution, floor mounted, comes with the clean room system thrown in

 

[RalphLambrecht]

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.

I'd go with the Alford clip-on set then! They work well and can be used with any enlarger.

 

[pentaxuser]

My 2 cents- I would never use filters under lens other to soft focus effects

I quite like the Ilford filters for the simple fact that when split printing I have lots of selection of the starting filter for the low hit. Or if I want to start with a high filter I have options .

I am confused about what you are saying here, Bob. It sounds as if you would not use under the lens filters for VC paper but then it sounds as if you like Ilford filters for VC paper.

Does this mean that Ilford over the lens filters are OK but not under the lens ones in your judgement i.e. no matter what Iford says, its under-the-lens filters represent an optical compromise that is best avoided as I think Drew Willey is also saying?

Thanks

pentaxuser

 

[grahamp]

Where possible, colour the light before it reaches the negative (VC head, colour head, above the lens filters). Anything after the negative (negative flatness, alignment, lens quality, below lens filters) has the potential to affect the print. Sharpness is only one criteria, though often the easiest to measure. Scatter from a filter can reduce contrast, and even effect exposure if the sticky finger prints are thick enough (!). The whole photographic process is one of reducing the quality as one goes from subject to negative to print. It's physics. But I am happy to do my bit to hold back the inevitable advance of entropy.

I have the luxury of a colour head, but the only G5 filter I have is an under-lens one, so I have to compromise if I really need a G5 (rare).

 

[Bob Carnie]

I use the filters above the lens and negative in a Condenser system using the filter drawer or I use dichroic filters above the negative stage with my Deveere and Durst Enlargers.
I believe filters between the lens and paper will compromise the image quality .

I use the filters made by Ilford in 1/2 grade steps from 00-5, but always over the negative stage unless I want to soften the image and I will use different devices below the lens, like a pictrol, nylon, gause, texture paper, and so forth.

I am confused about what you are saying here, Bob. It sounds as if you would not use under the lens filters for VC paper but then it sounds as if you like Ilford filters for VC paper.

Does this mean that Ilford over the lens filters are OK but not under the lens ones in your judgement i.e. no matter what Iford says, its under-the-lens filters represent an optical compromise that is best avoided as I think Drew Willey is also saying?

Thanks

pentaxuser

 

[pentaxuser]

Thanks for explanation Bob

pentaxuser

 

[eddie]

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

Did anyone ever make commercially available glass contrast filters sold as a set, as the Ilford/Kodak plastic sets were sold (1/2 stop increments)? I can't recall ever seeing them.

 

[DREW WILEY]

No, though optical grade CC filters were made in mild degrees of magenta and yellow. There would be no viable market for printing sets of them. Labs with serious budgets already had colorheads; and VC papers themselves weren't very good until relatively recently. Today there a wonderful VC papers to choose from. It's really a non-issue if you learn to split print.

 

[mmerig]

Hopefully, momus, (the original poster) has this figured out and has moved on. It never hurts to ask a question, but the answers can be painful. Sometimes on APUG, someone will ask a technical question, and the responses are typically so wide-ranging, with little or no evidence either way, that making a decision is as good as a coin-toss. One post even referenced a published test (Ctein's), but it was ignored as if it was wrong or irrelevant, rather than a point of departure for a decision. If it could be demonstrated as either wrong or irrelevant, it would be good to know. Ctein's book (Post Exposure, 2nd edition) is free, by the way, so quite accessible.

In this case, the question was essentially whether reasonable-quality plastic filters, used below the lens, could significantly degrade resolution. Because many enlargers out there don't have filter drawers, I suspect that lots of people use plastic filters under the lens, so there could be broad interest in the question.

Of course a filter can be held below the lens, and any added surface(s) below a lens will affect resolution, but the resolution issue, on a practical level, is unresolved by this series of posts. There are so many contradictions -- and not just the "does not affect resolution" versus "people will look at your print and say 'geeze, the printer must have had the filter under the lens, what an idiot'". For example, one concern is having two surfaces below the lens that could degrade resolution, yet glass is great, but plastic is terrible. Both have two surfaces, but that does not make them the same, of course, but are the differences important? Another is that using plastic (or anything else) under the lens is a compromise. Everything in photography is a compromise, but how much difference does a filter under the lens really make?

Information on the optical characteristics of plastic versus glass versus neither, could define the differences theoretically but that would take a lot of work and some dense mathematics.

Even theory needs to be tested empirically, so why not jump right to it? In the time it took me to write this post, anyone with a filter, an enlarger set-up, a grain focuser, and a piece of film can answer the question for themselves. Just focus on the grain, as usual, with and without the filter, and see how much difference there is. You can also move the filter up and down, vary the f-stops, change the enlargement ratio, see if you can adjust the knob to the expected focus shift (if you can, maybe your true talent lies in neurosurgery). Maybe put some goo on the filter, to see how fuzzy things can get. Have someone else do the tests with your set-up and see how repeatable they are. Or knock yourself out and make actual enlargements (keeping the contrast the same, by using a #2 filter and no filter and adjusting exposure, and using small sections of really big enlargements to keep the cost down) and show them to several people to compare.

With all these tests, is there a difference in the grain resolution? Is it within the realm of prints that you intend to make? If so, maybe a change is needed. Like buy #47 and 58 glass filters, thus compromising dodging and burning because of high filter density. Get another enlarger with a filter drawer, assuming that over the lens filters have less effect on resolution. Get a color or VC head, and forget filters and mess around with dials instead. But what if you like the look of a condenser-head enlargement? Just go with good'ol graded paper, but lose some steps in grades compared to the VC systems, and gain a lot of boxes of paper.

But the point is, the simple, quick test that does not cost anything but a few minutes will go a long ways to deciding on whether to use filters below the lens or not. It's an easy way to decide, if you trust your own eyes and brain more than APUG opinions. If there is a hard way that is somehow better, that would be good to know too.

 

[Bob Carnie]

Actually , when I first started printing I did these tests, and FWIW I concluded a filter in the light path below the lens will soften. Here is a simple test, for colour printers still using an enlarger. Brides Dresses were notorious for containing blue and we would use filters to clean the whites, but
if one over did it the pretty lace would soften to mush... do it a few times and let your eyes be the judge.

This is not Opinion but rather a proven Fact after printing a few thousand white dresses. I remember an older technician blasting a young technician (it could have been me) saying he had forgotten more about photography than I knew. I kind of get his point now .

 

[DREW WILEY]

Reminds me of office arguments. Some upstart MBA will come up with an idea and push it, and us old timers already knew the outcome of that tactic long before he was born. Yeah, we might have made the same mistake once ourselves! That's why we know. But it seems everyone has to learn the hard way. Not all web input is equal.

 

[MattKing]

The issue is really about magnitude.

Does the detrimental impact of using below lens filters exceed the detrimental impact of vibrations and other factors that may be induced by trying to use filters elsewhere in some smaller, lighter and more portable enlargers than those used by Drew Wiley and others with top-line equipment in permanent darkroom?

Particularly for those who use split-contrast printing.

Don't restrict tests to high-grade, professional enlargers when the users most interested in the results may be printing with a Beseler Printmaker 35.

 

[wiltw]

I have always heard the Kodak position about acetate vs. gelatin filters, but could never find an explanation of 'why not'.

"Gelatin filters are for use with image-forming light beams. Acetate filters are suitable for use only in non-image-forming beams."​

 

[mmerig]

Bob's test about the wedding-dress whites is not so simple or definitive, and not the same test that I described above as he implied (maybe Bob did that too, but it's not clear in his message). Loss of detail (mush) can be due to loss of contrast, or with whites especially, under exposure during printing either due to time or filtration. I am sure Bob knows this, but lost sight of the problem at hand. Doing the wrong test a thousand times just means you are wrong a thousand times. I've been there, done that, too.

Color printing and its nuances is not what this thread is about, which is using a filter below the lens, and if its optical characteristics affects resolution in b & w printing. A definitive way to see any differences is to look at magnified grain with the enlarger system, and if printing, keep the contrast and exposure consistent. This approach eliminates confounding effects due to differing contrast and exposure, especially if the negative is b & w.

Matt King points out, as I did, that magnitude is important. As well, Ctein reported resolution numbers that indicate magnitude, and if his numbers are valid, the effect of the filter is negligible. It's not like we are doing lithography for the latest Intel chip. It's photography at about 2 to 10 X for most people.

I started b & w printing around 1971, my dad was a professional photographer, mostly weddings, so when I helped him I saw plenty of white dresses. Although I mention this for the sake of old timers that deem long experience as paramount and lord it over people that do not agree with them, my experience does not matter in this situation. The test I suggest above is hardly a new idea -- it's direct observation that anyone can do, with 30 minutes or 30 years of experience, and decide for themselves. My own opinion on filter position be damned.

But I am beginning to think that some of the responses are merely to show off experience or equipment, or lend some mystique to b & w printing that is probably not there, rather than help an APUGer with his problem. So sad, but so be it.

There's a saying in academia (which I have been part of, so guilty as charged I guess): "The arguments are so fierce because the stakes are so low".

Lastly, I am not pushing under-the-lens filters, or that rigorous tests always rule the day. There is a rote aspect to photography technique, and preferences that are based more on gut feeling and comfort than anything else, and give the user more confidence. I get that.

Thanks for reading this far.

 

[pentaxuser]

I have always heard the Kodak position about acetate vs. gelatin filters, but could never find an explanation of 'why not'.

"Gelatin filters are for use with image-forming light beams. Acetate filters are suitable for use only in non-image-forming beams."​

Thanks. So anyone know into which of the two categories above that Ilford under-the-lens filters fall? Secondly and maybe equally importantly can anyone say with authority whether Ilford under and over the lens filters are made from different stuff?It was my understanding the filters were made of the same material. If this is the case then it doesn't of course automatically invalidate the claims that what is OK above the lens isn't OK below the lens but it does make you wonder why Ilford would sell stuff that is knowingly and demonstrably inferior at the risk of users then blaming Ilford.

I think it was Roger Hicks who used to say something along the lines of: Why is it in Ilford's interest to sell you material or give you information that they know is wrong?

I think that mmerig has made a valuable contribution in this thread

pentaxuser