Print exposure times too short

[Xícara de Café]

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Hello Forum,

I have a Leitz focomat 1c with a Schneider Componon-S 2.8/50. The lamp I'm using is a frosted  7 watt LED with a colour temperature of 4000K. I'm getting good results for my purposes but the exposure times I need to use are rather short to do dodging and burning. With split grade printing on 7"x9.5" FB paper my the times with the #5 filter are typically between 2 and 5 seconds and with the #0 filter, anywhere between 4 and 40 seconds but usually at the quicker end of the scale.

I always use f/8. To lengthen the times should I start closing down or try and find a lower wattage lamp?

Cheers,

Edited September 29, 2019 by Xícara de Café

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[jaapv]

Or put a yellow filter on the lens to reduce the light.

[Xícara de Café]

Thanks. I guess what I'm also asking is, can I expect a drop in quality if I stop down to f/11 or 16?

[jaapv]

Yes, you can expect a drop in quality. It won’t be dramatic. 

[M.Hilo]

That led bulb you use: in terms of watts, how does that compare to a 75watt opal enlarger bulb?

[Xícara de Café]

Hi, it doesn't give the equivalent wattage on the bulb, but I remember when I bought it that I was looking for something close to 75 watt equivalence and i think it was close if not the same. On the side of the lamp it has "TKL 700" printed. Perhaps this has something to do with Lumens? I think I wound up with a colour temperature of 4000K because all the other lamps at this brightness were either much cooler or much warmer. I've since found lamps online at 3000K, which I think was the temperature that I was originally looking for.

 

[Michael Hiles]

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I think you should get a 212 bulb (150 watts incandescent). That is what I use on my focomat 1c and my exposure times are in the 15-30 seconds at f8 or f5.6 (most of my efforts are split grade) for a roughly 7 x 11 paper. The 211 or 212 bulbs are what the enlarger was designed to use. Even illumination across the field. Your LED bulb might be useful if you were to make a 16x24 print, but even illumination might be a problem… Stopping down to f11 or f16 risks loss of sharpness due to diffraction at small apertures – avoid if possible.

Edited September 30, 2019 by Michael Hiles

[M.Hilo]

Michael is right. Also I use 150w bulbs with the Ic. My work prints are on 24x30cm paper and the image size is about 7x11 in. Exposure times run from 10 to 15 seconds, stopping down the f4.5 Focotar to f8.

If I were you I'd get both the 75w and 150w opal bulbs.

 

[Xícara de Café]

Thanks. I will try a incandescent. The 75w lamps are available here, at the wrong voltage for this city, but I'll get hold of a transformer. It is odd that I'm needing such short exposure times with this 7w LED. I don't suppose it could be the heat. Recently it has been over 30ºC indoors. Or perhaps the format of the bulb places the element too close to the condenser. I guess i won't know until I try the correct lamp. Thanks for the suggestions everyone.

[Michael Hiles]

Heat generated by enlarger lamps should not impact exposure times. But it might be bad for your enlarger lamp house. LED bulbs are quite efficient and I suspect that yours are generating lots of light. I would also be very surprised if the bulb is in the right place for even illumination. You should have a much better experience with a 211 or 212. They are designed to exactly work with your enlarger (one of the best ever made by anyone).

[M.Hilo]

11 hours ago, Xícara de Café said:

 Or perhaps the format of the bulb places the element too close to the condenser.

 

A regular enlarger bulb is about 11cm long, maybe the 75watt is a bit less. If your led bulb is longer, yes this could be part of the problem.

Besides a Focomat Ic I also have a Valoy II that is modified to do up tp 50x60cm. The bulb of the Valoy II sits closer to the negative and yes, exposure times are much shorter. I think the last time I switched between these enlargers 50x60cm was 70 seconds for the Focomat, and 45 seconds for the Valoy II.

Your Focomat: do you have the socket pulled up as much as possible?

Which voltage is used where you are?

[adan]

On 9/29/2019 at 8:08 AM, jaapv said:

Or put a yellow filter on the lens to reduce the light.

Not on vari-contrast paper - yellow light lowers the contrast (Xícara's #0 filter is already yellowish), and a yellow filter will diminish his #5 filter's higher contrast effect.

ND filter should work, though. Ideally in the light path above the negative, where it will have no effect on the optics. Gel or glass.

[jaapv]

That is true. However, I was never happy with the  vari-contrast system, preferring traditional papers.

[Xícara de Café]

On 10/1/2019 at 2:30 AM, M.Hilo said:

A regular enlarger bulb is about 11cm long, maybe the 75watt is a bit less. If your led bulb is longer, yes this could be part of the problem.

Just got a chance to measure it, it's about 11.4cm, so not far wrong.

On 10/1/2019 at 2:30 AM, M.Hilo said:

Your Focomat: do you have the socket pulled up as much as possible?

Aha! Thanks! No it wasn't, it was extended as low as it could go. I didn't know that this was adjustable. Should the lamp be pulled up as much as possible? 

On 10/1/2019 at 2:30 AM, M.Hilo said:

Which voltage is used where you are?

220V. The lamp is b-volt for 110/220V.

Edited October 2, 2019 by Xícara de Café

[BernardC]

On 10/1/2019 at 5:23 PM, adan said:

ND filter should work,

A #2 filter is effectively an ND (same contrast as unfiltered light), they are included in the set to provide consistent exposure times when switching between filters. You can try stacking one of those with your #0 and #5.

[250swb]

On 10/2/2019 at 3:56 PM, Xícara de Café said:

Should the lamp be pulled up as much as possible? 

 

Coupled with the correct bulb adjusting it up or down is how you fine tune your exposure times. I always preferred 'up' because it gave me a bit more time to dodge or burn smoothly.

[M.Hilo]

On 10/10/2019 at 8:57 AM, 250swb said:

Coupled with the correct bulb adjusting it up or down is how you fine tune your exposure times. I always preferred 'up' because it gave me a bit more time to dodge or burn smoothly.

As far as I know, the up and down movement of the bulb is mainly meant to achieve even illumination. However, it seems bringing it up gives the better even illumination. Of course you must also center the bulb as much as possible, with the three screws.

Getting longer exposure times when the socket and the bulb are up is nice in most cases.

You do this adjustment procedure in a total dark darkroom and I like to stop down the lens to f11 or even f16. Somehow it then is easier to see fall-off . . .

 

 

Edited October 11, 2019 by M.Hilo

[otto.f]

On 9/29/2019 at 11:29 PM, Xícara de Café said:

Thanks. I guess what I'm also asking is, can I expect a drop in quality if I stop down to f/11 or 16?

I work with a Heiland Splitgrade on a Beseler. It has LED-lamps too and sometimes I have to dim them because of too short exposure times (this is possible with the controller). I saw today that my Schneider Componon 2.5/50 needs a 0.2 harder Grade at F8.0 than at F5.6. So even at F8 the contrast of this lens is already going down and at F11 even more, 0.5. This is not what you should want. There is also a small focus-shift in this lens, so as long as there’s no alternative, you have to focus at F11 itself and not at 2.8

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[M.Hilo]

On 10/2/2019 at 4:56 PM, Xícara de Café said:

Just got a chance to measure it, it's about 11.4cm, so not far wrong.

Aha! Thanks! No it wasn't, it was extended as low as it could go. I didn't know that this was adjustable. Should the lamp be pulled up as much as possible? 

220V. The lamp is b-volt for 110/220V.

https://www.secondhanddarkroom.co.uk/product/lamp-75wnew/