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Forum: Film Processing, Scanning, and Darkroom
01-15-2010, 09:01 AM
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Acquired some 10mm 660nm Led's. Those definately look different. Even if they are less brighter, the red tone is much purer and deeper. Will post a picture later.
Pictures posted. It was a real challenge to image this. When looking directly you can clearly see the colour difference in addition to brightness. In picture the brightness difference is only thing you get (but i was pleasantly surprised how well the RAW handled it).
In the pictures you see: Left - new 660nm LED's (wide angle), Right - old ~630nm LED's (narrow beam), in front a dot from laser pointer (probably 650nm). One, raw developed to emphasize the colour difference (interesting that increasing saturation actually clips both colours same, you need to decrease it and manipulate lightness curve).
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Forum: Film Processing, Scanning, and Darkroom
12-30-2009, 12:51 PM
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Lol, good one. I just thought if i'm about to do something, i shall do it so there is 100% confidence. Now i believe it is 100% safe to handle materials in the darkness achieved. Only have to check seal wear from time to time.
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Forum: Film Processing, Scanning, and Darkroom
12-30-2009, 08:03 AM
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So i did a partial sealing. The weather tape works very well. The only problem, it is very puffy and i can barely close the doors now.
Attached are 50mm f1.4 images at iso1600, 30 seconds.
First floor images are only with 40W ceiling bulb in adjacent room. All others are with additional 5W led flashlight moved around to flood the gaps. Some shots of the seals as well - i had to add some more after initial sealing, because first seals changed the way doors rest in frame, opening new gaps.
Now there is only the floor left. When i will get the chemicals, i might try the paper test and check my safe light as well.
I hope others find this useful as well.
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Forum: Film Processing, Scanning, and Darkroom
12-29-2009, 08:55 AM
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So back from home depot type shop.. as far as i could tell by flashlight, the brown type of weather seal blocks light. White lets it trough straightforward. Actually that's the only material i could find that can be used in such door frame sealing style.
As for the floor part (where there is no step-like structure), i could not find a directly usable material. Or one that could be used on the outside surface of doors, covering gaps. I figured i could cut bike inner tube flat and attach it to doors with two sided sticky tape.
Tho there was that brush like thing you can stick to the bottom of the doors, but it was nowhere near the required density.
I think i failed with the LED's. I made a small "lamp" of four 10mm "RED" LED's, but when comparing to my RED laser (that is either 635nm or 650nm) they seem a lot more orange. Maybe it is related to much higher monochromacity of laser? Since most 10mm red led spec's indicate 620-625-630 (or just 630) nm peak output.
My cokin red filter looks like it only makes them darker, not deeper red, but hard to tell because after short time with them, they make all colours seem a bit more green.
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Forum: Film Processing, Scanning, and Darkroom
12-28-2009, 03:15 PM
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I dont think my soviet paper will have such grading. They had one standard and one glass filter you could buy. There was no such choices. But probably those "grades" can be used with this paper. I'll just have to find their matching wavelengths, because that's how led's are "graded". (Just found out that grading is related to paper type not light colour..whoops).
This Thread seems to have a good explanation:
Beginner's Questions About Safelight
In short: it seems, like red light is good for all papers (Variable contrast and Graded - dont know what it means), but the amber is suitable only for Graded paper (sensitive to UV-Blue, VC - UV,Blue,Green). Amber is more pleasant to work under.
Now i just need to find what red is safe red. Here, a kodak PDF showing spectral transmission graphs and descriptions for various filters:
http://www.kodak.com/global/en/professional/support/techPubs/ti0845/ti0845.pdf
1,2 - RED, DARK RED: Starts cutoff at 700 nm, max density at 600nm.
RED - transmits up to 10% light. DARK RED ~7..8%.
Red led's usually produce light at 633, 660, 635 [nm] - last one being most common.
So i think it should be safe to use one.
Another thought is about perceived intensity. Since it has narrow spectrum, you need higher actual intensity for the light to look bright. But i believe it is the same for paper.
In attachment i've included picture of my paper packaging. There is only unreadable developing information and date of manufacture indicating that the paper is expired :D.
A Kodak paper response curve confirming what's written in that thread.
A Dark Red filter transmittance graph.
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Forum: Film Processing, Scanning, and Darkroom
12-28-2009, 01:58 PM
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Well the problem i see is that the led would probably work to some degree. That is, i would not get blown (how do you say it?) paper or have dense enough fogging to be obvious - even more if i'm doing this for a first time. I'd just think that that's the way it should be, or I've messed up something with the chemicals. Probably i could try to lit some sheet by direct light, so the uneven shape of led beam is visible, to see if it produces any effects. Unless the direct light would be so intense it would blow the whole frame.
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Forum: Film Processing, Scanning, and Darkroom
12-28-2009, 12:20 PM
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Thanks for all the useful advices. Currently it seems that there is no generic best solution and everyone does the best he can. So i shall se what materials are locally available and best suited for my case. Will report back when i finish.
Just a tiny off topic question. Can the RED led form optical mouse be used as a safe light. I've red people using rear bike led's and claiming them to be safe if not brought too close to paper or used for more than 10 minutes.
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Forum: Film Processing, Scanning, and Darkroom
12-26-2009, 05:55 PM
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So a closer look at the door revealed that the situation is even better for most edges except at floor. There is a double step-like structure.
Now i might take an ultra bright flash light and check some insulation/sealing materials at store, but i wonder where would be the best place to install them (depending on their shape of course).
Theoretically the more the best, but im afraid that extensive modification might not let the doors close.
Another problem is floor. There is no step-like structure at all. See illustration.
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Forum: Film Processing, Scanning, and Darkroom
12-25-2009, 07:18 PM
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Well, its not that spacy. Just a small shower/toilet - no tables or other accommodations. But its still cheaper than buying anything (like changing bag), already available, possibly more easy to change and probably most sutable for chemical work (sink, water, ventilation, tiles).
Btw, to reduce costs, can you use a DSLR for the light leak test - ISO1600, F1.4, few minutes, pointed at possible leak sources.
It seems that the only source are doors, still there is a theoretical chance that light might bounce in trough ventilation system, but it had to take long way trough grill, matte concrete walls and dimly lit attic and what not...
I plan on sticking that long tube like foamy thing (it seems to be called "Self adhesive weather seal") around the perimeter of doors, but im not sure how light proof it is. Something like this in a way like that (attached):
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Forum: Film Processing, Scanning, and Darkroom
12-25-2009, 01:56 AM
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Are there any special measures and materials available to seal a room completely off the light, or simple solid doors are enough.
The only room i could use for film processing basically has no direct source of stray light (windows, keyholes, doors with gap to frame) BUT....
After checking the room for 5 minutes staring in complete blackness, your eyes start to adapt and you see that the step-like door frame still is able to leak light.
If i pack the perimeter of doors with paper, i can start to see a fain fuzzy glow around the doors after 30 minutes.
How do you determine if the "darkness" level is enough for film processing.
Btw. some people have told me that you cannot work with B&W film under red light, because most current films are sensitive to it.
Is this true for B&W as well?
How do you make prints then, or is the paper still insensitive ?
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