How to get longer exposure times

Kevin Kehler · Sep 18, 2008

I am using a Fujimoto G70 enlarger, with a diffuser head on Ilford Multigrade IV RC Satin or Pearl paper, developing in Ilford PQ Universal paper developer at 1:14 for 90 seconds. I am wanting to make some Fiber prints this weekend but am having a problem with getting more time under the enlarger in order to control dodging and burning. Even with the 80mm Leitz lens stopped down to F/22 (the lowest setting) and set at a height of 700mm+, I only have an exposure time of 9-11 seconds for most of my negatives, if I want to keep my blacks from blocking up. I diluted the developer to the max recommended by Ilford to add possible time but I am still finding I am trying to do 3-4 dodging actions in under 10 seconds. I recently read Adams The Print and he discusses 30-45 second exposures; I have also read in Black & White Photography magazine's Printer's Art section about longer exposures of similar length in some of their work.

If you have any suggestions, I would greatly appreciate any help possible. I use the Ilford developer because I have traditionally used Ilford products and it is the only one my camera store carries on a regular basis (4-6 week special order for anything else). Does the FB paper need a longer exposure compared to the RC paper and thus it is not a worry for my "fine" prints? Should I place the print in the developer for less time? Dilute the developer further? Will toning give me even more problems since it darkens the image more (and thus needs to be printed lighter)?

DWThomas · Sep 18, 2008

I dealt with a similar problem by picking up a 4x neutral density filter. My dumb luck, all three of my Nikkor enlarging lenses take the same thread. An additional bonus is that with the 4x on and an 5x5 test print, raising the enlarger for 10x10 and taking off the filter puts me right in the ballpark.

My limited experience is that shortening development time tends to produce uneven results; I try to get an exposure that I can develop fully.

DaveT

ic-racer · Sep 18, 2008

If you are using a color head you can go the the 'mixed filter' values for each grade (those contain both Y and M, which is like extra ND, as the paper is not sensitive to red).

If you are already doing that, you can get a ND filter from Rosco for less than $10 USD to put between the light source and the negative. If you don't have room or a filter tray, most enlarging lenses have filter threads on the front. You can put a glass ND filter there.

I don't think that enlarger has interchangeable mixing boxes, but if you have the opportunity to use a bigger mixing box the light output will go down also.

Anupam Basu · Sep 18, 2008

I agree that an ND should do the trick, but I'd also check if your negatives are too thin.

DeBone 75 · Sep 18, 2008

I put a dimmer switch on my Beseler 45 MX. The bulb is a 120 volt 200 watt. Works perfect.

Kevin Kehler · Sep 19, 2008

Never thought of a ND filter, wonderful idea. I also discovered a switch that reduces light output by 30% which should help. Thanks everyone!

srs5694 · Sep 19, 2008

Don't dimmers change the nature of the light spectrum (the balance of red, green, and blue light)? If so, using a dimmer might change the contrast of the print on VC papers. This isn't necessarily a problem, really (you can always use VC filters to adjust the contrast), but it's something you should be aware of, particularly if you might try changing the light output for different print attempts.

jmal · Sep 19, 2008

Yes, fiber paper is usually about a stop slower in my experience. Also, if you like Ilford warmtone paper (MGWT), it is about a stop slower than the neutral MGIV. The ND advice is good too.

Jmal

dancqu · Sep 20, 2008

A longer focal length lens also works. I've a 105mm
on while doing smaller prints from 6x4.5. More room
under the lens for focus and paper handling. Dan

fschifano · Sep 24, 2008

srs5694 said:
Don't dimmers change the nature of the light spectrum (the balance of red, green, and blue light)? If so, using a dimmer might change the contrast of the print on VC papers. This isn't necessarily a problem, really (you can always use VC filters to adjust the contrast), but it's something you should be aware of, particularly if you might try changing the light output for different print attempts.

Yes, a dimmer will change the color temperature of the light source. That's ok for graded papers, but it plays hell with variable contrast papers and filters. A given filter setting will not deliver the same results as an un-dimmed lamp. Exposure times and filter compensation factors will change in unexpected ways. It's not the best way to go. Neutral density filters are the best option. The only thing that changes is the intensity of the light. The color temperature is unaffected.

Nicholas Lindan · Sep 24, 2008

Try ND filters. Rosco 'e-color' filters are cheap and reasonably neutral in the blues and greens. http://www.rosco.com/uk/filters/ecolour.asp about 9/10ths the way down the page: #209-211 & 298, 299.

Available at B&H for $5.95 for a 21x24" sheet.

Claire Senft · Sep 24, 2008

Using a longer focal length lens will give you a longer distance between the negative and the easel. A longer lens will not change the exposure time. The exposure changes based upon magnification not distance.

dancqu · Sep 25, 2008

Claire Senft said:
A longer lens will not change the exposure time.
The exposure changes based upon magnification
not distance.

At same magnification a longer lens can project
a larger image. Given a same light source and it
being available over a greater area, the intensity
of the projected image must be less with the
longer focal lenght. Dan

Graham.b · Sep 25, 2008

Is not allways follow that the more glass that you put in front of the (longer length) the less light to get through. Would this not change the time or the spread of light.

2F/2F · Sep 25, 2008

What lamp do you have in the enlarger?

Are all the parts present in your diffusion head?

Is the diaphragm actually closing down to f/22, or is the collar just spinning without changing the aperture?

Are your negs well exposed?

I can't think of any reason other than those - too bright a lamp, missing diffusion, mechanical problems, or thin negs - why you would need to stop down to f/22 and/or add ND. I have never had to add ND, even in tiny RC prints.

My first thought and the most obvious cure would be to use a bulb that is more dim. KISS is worth a shot before buying lenses and filters.

DWThomas · Sep 25, 2008

Claire Senft said:
Using a longer focal length lens will give you a longer distance between the negative and the easel. A longer lens will not change the exposure time. The exposure changes based upon magnification not distance.

Having gone through this a year or two back, I'm with Claire. You're starting with a certain amount of light and projecting it to cover a certain area. If you project the same negative to the same image size, the lens focal length is not relevant. I actually checked the difference between an 80 and a 105 projected to the same image size on my Omega B-8, using an Ilford EM-10. There was less than a half stop difference. I suspect there are practical issues as to condensor optimization and the like that would account for that.

And that's when I bought an ND filter.

DaveT

John Koehrer · Sep 25, 2008

DWThomas said:
Having gone through this a year or two back, I'm with Claire. You're starting with a certain amount of light and projecting it to cover a certain area. If you project the same negative to the same image size, the lens focal length is not relevant. I actually checked the difference between an 80 and a 105 projected to the same image size on my Omega B-8, using an Ilford EM-10. There was less than a half stop difference. I suspect there are practical issues as to condensor optimization and the like that would account for that.

And that's when I bought an ND filter.

DaveT

So Physics and the inverse square law no longer apply? Isn't 1/2 stop difference between 80 & 105 for the same magnification about right?
Remember if you double the distance you need four times the light for the same exposure.

Nicholas Lindan · Sep 25, 2008

John Koehrer said:
So Physics and the inverse square law no longer apply? Remember if you double the distance you need four times the light for the same exposure.

The inverse square law only applies to a uniformly radiating point source. If you have a very long line source, where the length is much greater than the light to subject distance, the light diminishes with the simple inverse. If you have a very large plane source the light intensity remains constant with distance.

The reason for the inverse square law isn't that the light 'peters out' as it travels but that the area being illuminated gets bigger. Same amount of light - larger area - dimmer illumination.

The same optical relationships exist when taking pictures: the exposure in a camera does not change with the focal length of the lens. 'Bellows correction' is a factor of the magnification ratio: at 1:1 you need to open up 4 stops and it doesn't matter what the lens focal length is.

In an enlarger you have a fixed amount of light pouring through the negative. The lens takes all that light and puts it on the paper. It is the ratio of the area of the negative to the area of the image on the paper that sets the amount of exposure required. As the area of the image on the paper increases the light has to get spread around thinly and the image becomes dim.

Doubling the height of the enlarger, with any given lens, doubles the height and width of the image - making the area 4 times as big. Hence the term 'inverse square': you square the linear dimension change to get the change in area.

MattKing · Sep 25, 2008

A longer lens may have a smaller (in terms of f/stops) minimum aperture, so in that way it may help.

I too have the same problem with my Beseler 67 and colour head. I'd really like it if there was a lower wattage alternative to the standard halogen lamp.

Matt

pentaxuser · Sep 25, 2008

It seems that the OP hasn't responded since the 19th and its now the 25th so maybe he has found the solution but as it is a colour head and he is using multigrade paper, he is presumably already dialling in Yand M and still finding a problem with exposures that are too short. If he is and is using the smallest aperture and can get a smaller bulb but it's still a problem which seems incredible but so be it, then as another tactic, isn't it possible to dial in C to add neutral density to the correct Y and M for the grade that has been chosen?

pentaxuser

DeBone 75 · Sep 25, 2008

"Yes, a dimmer will change the color temperature of the light source. That's ok for graded papers, but it plays hell with variable contrast papers and filters. A given filter setting will not deliver the same results as an un-dimmed lamp. Exposure times and filter compensation factors will change in unexpected ways. It's not the best way to go."
I can't belive how many times someone on here tells me I can't or should not do what I do all the time with no problems. I often have the same trouble with some negatives or I just want longer to dodge and burn, so I just turn down the dimmer and it works just fine. I can't make that any clearer. Now of course if it is a color head then yes that may make a differance, but I don't no for sure. And yes I use VC paper.

MattKing · Sep 25, 2008

pentaxuser said:
It seems that the OP hasn't responded since the 19th and its now the 25th so maybe he has found the solution but as it is a colour head and he is using multigrade paper, he is presumably already dialling in Yand M and still finding a problem with exposures that are too short. If he is and is using the smallest aperture and can get a smaller bulb but it's still a problem which seems incredible but so be it, then as another tactic, isn't it possible to dial in C to add neutral density to the correct Y and M for the grade that has been chosen?

pentaxuser

Correct me if I'm wrong, but I believe that if you intend to add neutral density, you need to add equal amounts of Cyan, Magenta and Yellow. That works fine when you are printing using a set contrast level, but when you are trying to split grade print with maximum Yellow first, and then maximum Magenta next, it means that the filter settings are much more finicky (it is much easier to just turn the dials to either the minimum, or the maximum).

Matt

srs5694 · Sep 25, 2008

MattKing said:
Correct me if I'm wrong, but I believe that if you intend to add neutral density, you need to add equal amounts of Cyan, Magenta and Yellow.

That's correct, at least from a theoretical point of view. In fact, from an ideal theoretical point of view, cyan filtration won't change exposure or contrast for B&W papers, since cyan filtration removes red light, to which B&W papers are insensitive. I'm told that in practice, there can be small effects because the cyan filters block a small amount of green (and perhaps even blue) light. I don't know how important this effect is with most color enlargers and B&W papers. I know that with my Philips PCS150, which uses independent red, green, and blue lamps rather than a single light source with cyan, magenta, and yellow filters, the amount of red light has no effect that I can discern. I therefore print B&W with the red light turned off, to save the bulb. I suppose with a more conventional design it would probably make more sense to print with no cyan filtration, to improve image visibility. Adding equal amounts of magenta and yellow filtration should get pretty close to ND filtration, if that's what you want.

pentaxuser · Sep 26, 2008

MattKing said:
Correct me if I'm wrong, but I believe that if you intend to add neutral density, you need to add equal amounts of Cyan, Magenta and Yellow.
Matt

Matt I couldn't recall properly the correct procedure but if I have understood you correctly you are saying that if the print calls for grade 2 and this is say 30Y and 30M then you add say 10/20/30C to get a resonably long exposure time and then adjust the dual filtration. So add 10C and adjust 30Y and 30M to 40Y and 40M. Add 20C and adjust 30Y and 30M to 50Y and 50M etc.

It all sounded familiar once you had laid it out. I just mentioned it out of academic curiosity as I was surprised that no-one had come up with it as another option.

It should be "academic" as in the meaning of academic as "have no real application" in that I cannot believe that using the full range of stops, plus a lower wattage lamp and dual filtration cannot solve the problem. Likewise with split grade printing even at grade O, the addition of the amount of yellow recommended should add an appreciable time to the exposure and max magenta even more.

pentaxuser

How to get longer exposure times

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