enlarger exposure question?

stradibarrius · Feb 20, 2013

Last night was the first time I have tried printing in over a year. My makeshift darkroom was out of commission. When I tested my paper/dev combo for max black, I had to close the lens down to f/16.5 with a grade 4 contrast filter to get the time to around 15 seconds.
With Oriental Seagull FB I never did get a good time. With Ilford MGIV FB I was able to get some fairly good prints with the above set up.
Should I not be able to use f/8 and still have enough time to dodge or burn? 15 secs is fine but with the Oriental paper the time was going to be in the 5-8 sec. range...
Are my control elements time and f/stop?
Ideas about why the time was so short?

Denis P. · Feb 20, 2013

stradibarrius said:
1) Are my control elements time and f/stop?
2) Ideas about why the time was so short?

1) - yes, plus bulb (light source) output

2) see above, under 1) - perhaps your light source is too strong?
You did not say what kind of enlarger you are using (condenser, diffusor).
Perhaps you are missing a diffusor glass? Some enlargers have a diffusor glass plate between the light source (lamp) and the lens, which you might be missing.
Just an idea...

Then again, if you have used that enlarger before, you probably know how it is supposed to be used And the light source should not have become brigther during the year you haven't used it

ac12 · Feb 20, 2013

control elements: paper sensitivity, time, f-stop, light output, head height.

Light Output: One thing that you did not consider is the light bulb itself. My Durst M600 is a very bright enlarger, I went down from the original 150w bulb to a 75w bulb, and sometimes I want a 40w or lower bulb, for less light, to get a longer exposure time.
- You may want to change bulbs for different papers, higher wattage for a slow paper, lower wattage for a fast paper. But because bulb changing is a PIA, do this as the last option.

Head Height: Another is the height of the head of the enlarger above the baseboard. The closer it is, the higher the intensity of the light on the paper. The farther, less intensity on the paper. This applies to paper calibration and contact printing.

What I do not know, because I have not tried it is, with the same magnification, but with 2 different lenses 50mm and 80mm with the head at different heights to maintain the same image magnification, will the exposure be the same?

tkamiya · Feb 20, 2013

Don't be afraid to stop down more if you need to. Loss of sharpness due to refraction is not noticeable unless you are printing really really large (and at that point, the exposure time won't be so short anyway).

Also, check the wattage of your bulb. I *think* 75 watts is the lowest available for purpose made enlarger bulbs.

tkamiya · Feb 20, 2013

ac12 said:
What I do not know, because I have not tried it is, with the same magnification, but with 2 different lenses 50mm and 80mm with the head at different heights to maintain the same image magnification, will the exposure be the same?

I tried it. Yes.

henry finley · Feb 20, 2013

Print paper has been too fast for 30 years.

stradibarrius · Feb 20, 2013

My enlarger is an Omega Universal 4x5 variable condenser. Can I use a standard light bulb or does it have to be an enlarger bulb? I tried raising the head up to reduce the intensity but of course the image got much larger than the 8x10 paper. I'm not sure I understand how I could raise the head. The negative is 4x5 and I'm using a fujinon 135mm lens.

Konical · Feb 20, 2013

Good Evening, Barry,

Given the conditions described immediately above and without seeing the actual negative, I don't find the exposure time to be particularly unusual. My exposures from 4 x 5 with a condenser-head Beseler MCR-X are not too much different for typical 8 x 10 prints. Why be concerned about using ƒ11 or ƒ16? With LF (especially) or MF and a high-quality lens, I think you'd be hard-pressed to detect any difference in image quality whether you use ƒ8 or ƒ16. Most of my 8 x 10 prints from MF negatives are made at ƒ11; most from 4 x 5 are at ƒ16. The overall negative quality seems more important to me in most cases.

Konical

bdial · Feb 20, 2013

You should use an enlarger bulb, these have a denser coating to even out the light compared to standard "household" bulbs.
There are at least a couple of different wattage screw-base bulbs, you might want to try a lower wattage bulb to extend your times some.

ac12 · Feb 21, 2013

Raising the head was only for making density calibration prints and contact prints, not for printing the image. Because the image will get bigger as you raise the head, just as you found out.

Non-enlarger bulb is only for "the last option."
If you can use a standard enlarger bulb, use it. 75w seems to be the lowest wattage for enlarger bulbs. After that, use ND filters to reduce the intensity.

As for "the last option," that is for people like ME, who have a Durst L1000. The special enlarger bulb for that enlarger is no longer made, so we have to make do with whatever will work.

Why the fixation on f8?
As other have said, close the lens down as you need to. That is what the aperture control is there for.

stradibarrius · Feb 21, 2013

In the darkroom class I took a while back the teacher said we should always use f/8...I wondered why the manufactures put other apertures on the lens if they weren't to be used?

Konical · Feb 21, 2013

Good Morning, Barry,

There has long been "rule" that lenses tend to perform best a couple of clicks down from maximum aperture. That may well be correct in some (many? most?) cases, but I wonder if isn't also a holdover from decades ago when some lenses were less precisely constructed and/or there was more variablity from sample to sample. Clearly, a lot of lenses on old folding cameras have lenses which are rather poor wide open but respectable when stopped down somewhat. The problem with stopping down too much is that an extremely small aperture can cause diffraction which degrades an image. This is one reason that a lot of 50mm lenses on 35mm cameras have a minimum aperture of only ƒ16. On many large-format lenses, apertures down to ƒ45 or ƒ64 are not uncommon, and diffraction isn't much of a problem since the diameter of the opening is still large enough to minimize diffraction. Printing at ƒ8 with a 50mm enlarging lens makes some sense, although I haven't noticed any problem when I occasionally use ƒ11 or ƒ16. With the 135mm or 150mm enlarging lenses used for 4 x 5, an aperture of ƒ16 or even smaller still has an opening which is large enough to avoid any significant diffraction and allows a long enough exposure for dodging and burning.

Konical

stradibarrius · Feb 21, 2013

Thanks Konical! That is great information. At this point I'm not going to worry about it, I'm just going to print and enjoy. I checked the bulb and it is a ph212/150w so I think I'm going to change to a ph211/75w and that should help out and it is a simple solution.

enlarger exposure question?

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