How to prolong exposure time

jernejk · Mar 31, 2013

I use Adox and Foma papers at the moment and my exposure times are measured in seconds. The problem is worse when splitgrade printing, since times for high and low contrast exposure get really short, shorter than my timer's precision.

I don't want to stop my enlarger lens below 3 stops (f8 or f11, depends on the lens) to keep it sharp. The head is colour with 12v (halogen) lamp, so no way to tweak the source either.

What else could I do?

AgX · Mar 31, 2013

-) use a grey filter

-) use a double polarizer filter

-) use a bulb of lesser wattage

anikin · Mar 31, 2013

I have not noticed sharpness degradation from stopping down the enlarger. Try it, you may surprise yourself.

pdeeh · Mar 31, 2013

I asked a similar question recently and got the similar answers.
as a result bought a £1 stepping ring for the lens so I can use a a polariser I already own - it's made all the difference and I now have sensible exposure times for otherwise tricky negatives.

DWThomas · Mar 31, 2013

Faced with this sort of probem, I bought a two-stop neutral density filter. I have the good fortune that it fits all three of my enlarging lenses!

And like anikin, I also can't say I've noticed any issues with stopping down my enlarger more than commonly recommended.

jernejk · Mar 31, 2013

anikin said:
I have not noticed sharpness degradation from stopping down the enlarger. Try it, you may surprise yourself.

I will try, but on paper I should actually open it to 5.6 it seems http://www.coinimaging.com/nikon_el50-28n.html

jernejk · Mar 31, 2013

AgX said:
-) use a grey filter

I have tray for 7x7cm filters. Where could I get a ND gel filter?

cliveh · Mar 31, 2013

What size prints are you making? Are your negs very thin?

AgX · Mar 31, 2013

jernejk said:
AgX said:

-) use a grey filter

Click to expand...

I have tray for 7x7cm filters. Where could I get a ND gel filter?

Lee Filters offer a range of ND lighting-filters (for use above the negative) with densities from 0.15 up to 1.2. They also come in sheets.

For use below the lens you can use either their plate or foil camera-filters in sizes up to from 75x9omm up to 150x150mm in densities up to 0.9 .

jernejk · Mar 31, 2013

cliveh said:
What size prints are you making? Are your negs very thin?

I'm printing 6-10x enlarged 35mm film, I think it's of pretty normal density. The color head has a 100w halogen lamp, but the exact specifications are not given.

Anyway, I've been trying to figure something and it seems a layer of paper-towel tissue in the filter tray gives me an extra stop, two layers two stops...
Need to check the heat though.

cliveh · Mar 31, 2013

jernejk said:
I'm printing 6-10x enlarged 35mm film, I think it's of pretty normal density. The color head has a 100w halogen lamp, but the exact specifications are not given.

Anyway, I've been trying to figure something and it seems a layer of paper-towel tissue in the filter tray gives me an extra stop, two layers two stops...
Need to check the heat though.

Paper-towel tissue in the filter tray sounds like a fire starter and not ideal. Can't you use a smaller wattage bulb?

anikin · Mar 31, 2013

jernejk said:
I will try, but on paper I should actually open it to 5.6 it seems http://www.coinimaging.com/nikon_el50-28n.html

Well, sure, the MTF curves show you that highest resolution of the optics is at some F value. But honestly, the optics resolution is the least of your concerns when printing on the enlarger. The biggest factors that affect print sharpness are enlarger vibrations, head alignment and negative flatness/pop and you have to deal with these before worrying about lens diffraction. At least that was my experience.

jernejk · Mar 31, 2013

cliveh said:
Paper-towel tissue in the filter tray sounds like a fire starter and not ideal. Can't you use a smaller wattage bulb?

It's not ideal, but I don't think it's really hazardous. The enlarger is like this one http://www.flickr.com/photos/vegaluthier/4409261714/
The bulb is where you see the cooling slots on the head the tray is in the enlarger body. The head is actually a separate compartment and most heat stays there.

i need to check the bulb. There are no specs really, it has 5cm diameter and uses 12V. I'll try to find something after Easter holidays (the stores are closed). It would be cool to try LED actually.

Nicholas Lindan · Mar 31, 2013

Dialing in both yellow and magenta will add density.

You can also place an ND filter in the filter tray, above the negative or in a below-lens filter holder. The most cost-effective filters are from Rosco (or the Lee equivalent) http://www.bhphotovideo.com/c/product/163141-REG/Rosco_102302102124_E_Colour_210_6_Neutral.html A 0.6 will add 2 stops (4x) to the exposure time, a 0.9 OD will add 3 stops (8x) and a 1.2 will add 4 stops (16x).

ac12 · Mar 31, 2013

How LARGE are you printing?
If you are not printing a 35mm frame at larger than 11x14, and maybe larger than 16x20, don't worry about the "optimal" aperture of the lens. The practical side is, unless you use a magnifier and look at a very detailed image up close, you likely won't see the difference anyway.

To prove this theory, make a print at your expected print size at both the "optimal" aperture and at f/16 (the smallest aperture on the EL-Nikkor 50/2.8) and see if you can see a difference in the images. I would guess that you will not see a difference.

Also if you are doing that detailed work, you would have to use a glass carrier to make sure that the negative is FLAT and not bowed, and you would have to make sure that your enlarger is in alignment on all 3 planes (easel, negative, lens).

Light = heat.
That is why negatives sometimes pop/warp when you are printing them.

Louis Nargi · Mar 31, 2013

how about frosted glass.

noacronym · Mar 31, 2013

Louis Nargi said:
how about frosted glass.

Do not involve frosted glass in a condenser enlarger setup. They don't mix very well. Been there--done that.

jernejk · Apr 2, 2013

I explored my options today in a hardware shop. I came up with an idea to replace the current 12V setup with GU10 on plain 230V. This way I would get rid of the transformer which only takes space and adds complexity. It would also open a possibility to experiment with LED.

It seems the procedure to switch to GU10 is fairly simple. The GU10 bulbs fit nicely. See LED mounted in place of the original here: https://www.dropbox.com/s/qkt04xpjge5jq5d/20130402_194654.jpg

All i need to do to change to Gu10 is:
- replace current head cable with 230V + ground (easy as it's bridged to internal wires like this: https://www.dropbox.com/s/gkczjpu3v4uwpwp/20130402_200542.jpg
- replace existing connector in the head with GU10 one, but reuse internal cables
- ground the head

Any reasons why I shouldn't do it?
Also any reasons not to use LED? It has a lag before it turns one which could make timing non-linear at short times.. but other than that?

jernejk · Apr 3, 2013

The conversion is done https://www.dropbox.com/s/a4klnvmz6x3z946/20130403_121420.jpg

Haven't tried it yet, but it seems quite ok.

How to prolong exposure time

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