Above vs Below the lens filters

hiroh · Jul 31, 2024

My new enlarger has slots for both above-the-lens and below-the-lens split grade filters. I don't have any filters yet, so I wanted to check if both positions give the same results and what the pros and cons of each are.

I prefer the ones in a plastic frame that go below the lens, simply because they seem easier to handle.

Thank you.

Paul Howell · Jul 31, 2024

The below the lens filters are handy when split contrast printing.

hiroh · Jul 31, 2024

Paul Howell said:
The below the lens filters are handy when split contrast printing.

Aren't they both for split grading?

mshchem · Jul 31, 2024

Paul Howell said:
The below the lens filters are handy when split contrast printing.

+1, below lens less chance of jiggle??? Maybe? I used above the negative acetate filters for years before I had colorheads, both work fine.

Mark J · Jul 31, 2024

It's a good question, and like mshchem I am wary of using the filter drawer above the lens in case of shifting the head on multiple exposures of a print. I have only recently been using filters on a Durst 138 condenser enlarger. There is no problem with sharpness when used below the lens ( up to 210mm at f/11 ) , there is a small amount of haze you can see in the filters, in the dark, when exposing, which in theory might affect contrast, but it's not stopped me from getting the contrast I want, in all areas of prints I'm doing so far .

Pieter12 · Jul 31, 2024

I would think the below the lens filters might degrade the projected image if they are not totally clean--no dust, no fingerprints, no scratches. I have been using above the lens filters on an Omega D5 for years, never had an issue.

pentaxuser · Jul 31, 2024

The below-the-lens filters are fíne but it has always seemed to me that a separate drawer above the lens tat you can open and close was better. I presume that such drawers are made to slide open and closed by the enlarger manufacturer such that there is very little if any chance of spoiling focus if you bellows adjustment knob is sufficiently stiff

They are certainly cheaper in Ilford's case as the filters are the same except that you do not need the paraphernalia under the lens to hold them

pentaxuser

Pieter12 · Jul 31, 2024

pentaxuser said:
The below-the-lens filters are fíne but it has always seemed to me that a separate drawer above the lens tat you can open and close was better. I presume that such drawers are made to slide open and closed by the enlarger manufacturer such that there is very little if any chance of spoiling focus if you bellows adjustment knob is sufficiently stiff

They are certainly cheaper in Ilford's case as the filters are the same except that you do not need the paraphernalia under the lens to hold them

pentaxuser

The D5 has a hinged door for the variable condenser where you can easily slip the filter in. You would really have to manhandle it to introduce vibration.

grahamp · Jul 31, 2024

I use below-lens filters when the colour head won't do the job - if I want the condenser head on the 4x5 (big filters I don't have), or I have the 8x10 conversion set up (huge filters I definitely don't have), or I need a true Grade 5.

When I was mostly doing 35mm/6x6 I used above lens filters on condenser heads.

There is less risk of vibration and displacement with below-lens mounting if you use more than one filter on a print.

As long as the filter is clean, using it below the lens is far less of a potential problem than alignment, focus, and even illumination.

pentaxuser · Jul 31, 2024

Pieter12 said:
The D5 has a hinged door for the variable condenser where you can easily slip the filter in. You would really have to manhandle it to introduce vibration.

Yes my impression was that most enlarger filter drawers are designed to allow insertion without danger of vibration to the extent of altering focus and also if removal of one filter and insertion of a second one is required such as in split grade printing but clearly opinion on this is divided

pentaxuser

Don_ih · Jul 31, 2024

hiroh said:
Aren't they both for split grading?

Contrast filters are for setting the contrast of the exposure on variable-contrast paper. The standard approach is to choose one and leave it in there for your print ("This negative will print best at Grade 3", for example.) Split-grade printing is a non-standard (but very useful) way to use the contrast filters ("I'll print at grade 0 for 14 seconds then at grade 5 for 6 seconds", for example.)

You don't want anything to move when you change filters.

The advantage of above the lens filters is that dust and scratches on the filter have zero impact on the projection.

However, the below lens filters also have no impact, unless they have dust specks the size of moths on them.

DREW WILEY · Jul 31, 2024

Depends on the quality of the filters. I only use excellent multicoated glass filters below the lens. Filters made of thin polyester sheeting, similar to heat-resistant lighting "gels" (but not gelatin at all) degrade the sharpness a little bit.
Above the negative stage, I don't use loose filters at all, because I have colorheads for that purpose. But for efficient split printing, or in conjunction with a cold light, below the lens filters can be convenient, especially if you have a swing-arm filter holder.

ic-racer · Jul 31, 2024

Use whatever is most convenient. I have used both above and below systems with similar results for both split and single-exposure multicontrast B&W work.

Currently I favor doing my base exposure as a single-exposure; combined filtration exposure. In addition to what I believe is a better work flow, it also avoids the risk of moving anything while swapping out filters.

laser · Jul 31, 2024

From an optical image point-of-view the best place for filters is between the light source and the negative. Omega D-5V enlargers can provide this in the Variable Condenser Drawer. It takes 6x6-inch filters.

mshchem · Jul 31, 2024

I used Beseler 4x5 filter drawer no trouble. It depends on the machine. Colorheads are great light sources, but twirling the dials can be a problem. I don't do a lot of split grade printing, but when I do I just punch in the setting on a controller, nice but it's going to go poof one day.

MattKing · Aug 1, 2024

Start with the below lens ones - they are slightly more convenient, particularly with split grade techniques.
When you have used them a lot, and therefore gained lots of experience, the filters will probably be due for replacement anyways, so you can revisit the question. You may very well decide then that a variable contrast light source is a better choice.
I would weigh the potential of very slightly better optical performance of above lens filters slightly differently if you were an experienced printer looking to eak out the last little bit of quality.

Patrick Robert James · Aug 1, 2024

Below the lens is just easier and you won’t be able to tell the difference.

xkaes · Aug 1, 2024

laser said:
From an optical image point-of-view the best place for filters is between the light source and the negative.

BINGO!!! -- but below the lens is easier to use. Pick your poison.

Doremus Scudder · Aug 1, 2024

Below-the-lens filters need to be of higher quality. Ilford makes two kinds, one for above and one for below the lens.

If you use other than Multigrade or VC filters (e.g., blue and green filters), make sure to get good optical quality filters for use below the lens.

After that, below-the-lens filters are more convenient.

Doremus

snusmumriken · Aug 1, 2024

I am very fussy about my prints, but after very careful study I really cannot see any difference between prints using below lens and above lens filters. The former are way more convenient.

RalphLambrecht · Aug 1, 2024

hiroh said:
My new enlarger has slots for both above-the-lens and below-the-lens split grade filters. I don't have any filters yet, so I wanted to check if both positions give the same results and what the pros and cons of each are.

I prefer the ones in a plastic frame that go below the lens, simply because they seem easier to handle.

Thank you.

As you said, the below-the-lens- filters are easier to handle with little shaking of the enlarger head. If kept clean. They are a good solution and are easy to replace if faded.

pentaxuser · Aug 2, 2024

Doremus Scudder said:
Below-the-lens filters need to be of higher quality. Ilford makes two kinds, one for above and one for below the lens.

Doremus

My understanding is that the actual filters are made of the same material so optically are the same in every respect except that below the lens ones need a platform to hold them under the lens and use a plastic frame

I believe Ilford has actually said this somewhere in its literature

pentaxuser

Doremus Scudder · Aug 3, 2024

pentaxuser said:
My understanding is that the actual filters are made of the same material so optically are the same in every respect except that below the lens ones need a platform to hold them under the lens and use a plastic frame

I believe Ilford has actually said this somewhere in its literature

pentaxuser

Very possible. That would mean that the above-the-lens filters were also of optical quality and could be used as below-the-lens-filters as well. I know that some use Rosco theater gels for VC filtration, which should go above the lens.

Best,

Doremus

MattKing · Aug 3, 2024

Traditionally, the above lens filters were made of acetate, while the below lens filters were gels.

DREW WILEY · Aug 3, 2024

I still recommend good glass filters below the lens. The Paleolithic custom might have understandably once been real Wratten gels, but those are a lot harder to keep clean and kink-free, and in this day and age, are likely to cost even more than glass.

But if you're just using the enlarger as a light source for a contact printing frame down below, you can get away with all kinds of filter materials beneath the lens.

Above vs Below the lens filters

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