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Negative warp


chris_autio

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It's been a while since I printed 35 mm negs. I usually just print medium and large format.

This particular negative would warp when using the condenser head. I figured it out after a couple 16 x 20s

ran thru the soup! I solved it by holding a red filter under lens until exposure began.

I could have used the filter swing but am wary of touching any part of enlarger during exposure. But this kept me from dodging an area in image. I could have used my cold light.

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This is one of the big advantages of a cold light, and part of why I switched many years ago. The other suggestion is to leave the enlarger on for a while so that the negative will warp to the maximum degree, focus and then quickly turn it off and load the paper and expose. If you prefer to use the red filter method, I suggest that you attach your enlarger to the wall at the top to maximize its stability. I did this with picture wire with my Omega D-2 and it made it a lot more stable at greater magnifications.
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I could have used the filter swing but am wary of touching any part of enlarger during exposure. But this kept me from dodging an area in image. I could have used my cold light.

Gee. How short was the exposure?

Surely the couple of seconds, or less, that it takes to fling aside a filter with one hand, wouldn't make much difference to using a dodging 'wand' in your other hand?

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Gee. How short was the exposure?

Surely the couple of seconds, or less, that it takes to fling aside a filter with one hand, wouldn't make much difference to using a dodging 'wand' in your other hand?

My exposures are anywhere from 35 to 70 sec at f/11 on a Schneider 150 lens when making 30 x 40 prints. I vascillate between the two heads often. My cold light head is damn dark. At one time I was thinking of setting up a strobe ! in the head. Hey, one small step... one giant leap for mankind.

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Many years ago I put a thermocouple on a neg in my Beseler and measured the temperature rise with and without heat absorbing glass (p/n #8042)- http://www.conradhoffman.com/heatabsorb.jpg

 

Negative pop is, IMO, strongly affected by how the carrier is made. Some of my old carriers were run through a process called "Timesaving", which is essentially a big belt sander. If they do this after the hole is punched, the edges get rounded. The result is the neg isn't supported right at the edge of the cutout and has a greater tendency to pop. Glass carriers solve the problem and replace it with the problem of dirt and spots.

 

We have such great technology now, but too late, as film use isn't what it used to be. I'd think an LED light source would solve the heat problems and be fully adjustable for paper filtration. I know Heiland makes one, but it's a bit pricy.

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"Glass carriers solve the problem and replace it with the problem of dirt and spots." For every stride there is a downside. I must have been through a couple of these, but my best strategy is to focus after a few seconds... and when printing, set my timer beyond the set time. It works. My 4 x 5 carrier has teeth to grip the negative. I bought an 40 watt LED bulb and it too WORKS! I have yet to compare it to the one you suggest, but it is most certainly cooler to the touch.
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  • 2 weeks later...

OK . . . Sometimes, problems get stuck in my head . . .

 

What enlarger are you using? Can the bulb be replaced or adapted to an off the shelf LED bulb? Even if you have to keep the condenser (you wouldn't have a diffuse source) you would eliminate the heat issue.

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OK . . . Sometimes, problems get stuck in my head . . .

 

What enlarger are you using? Can the bulb be replaced or adapted to an off the shelf LED bulb? Even if you have to keep the condenser (you wouldn't have a diffuse source) you would eliminate the heat issue.

Hi Ed, I replaced the 40 watt with a 75 watt LED. Still cool enough not to warp the negative. I have a Beseler 45, of which I can easily put a cool head on (which allows for a full-frame 4x5 to be printed. The condenser head vignettes each small corner enough to be a problem at times.) When choosing the LED, make certain there no identifying MARKS on the bulb.

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