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salihonba
2-Sep-2009, 17:03
Has anyone ever tried to use LCD monitor as a VC light source to make contact print?

Friend of mine make 8x10, and no darkroom, he used to make film scanned and viewed on monitor only, I told him he lost lots of detail on film, which scan can not capture, and advice him to make contact print, since there is no enlarger, why not use LCD as light source?

You got RGB to adjust, to change the color of light, to match the different grade of contrast needed.

Furthermore, if you need some dodging or burning in some area of the contact, you can adjust the light intensity on that area by software, to get a perfect contact in one shot, but I can foreseen that will need many further steps.

If you have these kind of experience, can you provide me the RGB value for each grade? I know that LCD differ from each other, but at least it is a start point to explore.......

Matthew Rolfe
3-Sep-2009, 07:01
I presume that you have a darkroom anyway, or you are planning to install one for making contact prints. Once you have set up a darkroom and installed all the necessary equipment to develop your prints, chemical trays etc, then you may as well go ahead and buy a cheap second hand enlarger to make contact prints from. Using an LCD monitor as a light source just seems a bit over complicated and awkward.

However, If you are up for the challenge then give it a go, good luck!

Matthew

salihonba
3-Sep-2009, 21:41
Thank you Matthew, but ironically, my friend use 8x10 in the reason to avoid installing an enlarger, or even a darkroom. He lives in H.K., a place where darkroom is a dream people can have but impossible to come true, too expensive the real estate.
Enlarger takes space, but trays are not, with large format film, and contact print only, that is the way my friend to deal with the environment around him.
So now back to the point, LCD monitor as a contact print light source is not bad if you treat if as a big flat light panel, light color can be precisely adjust through RGB value, and the light intensity also can be adjust, even you can control areas of light intensity, if you want to dodge or burn some part of image, and, these settings can be saved as a data file, for making consistent contact print, especially for those dodging and burning areas. If using VC paper,by changing color of parts area of LCD light source, split printing is feasible on contact print, but for enlarger-light-source contact print, is very tricky to get same effect.

These are the pro what we brainstormed and listed, and for the con, it will be involved with some skill of IT knowledge and image processing skill, and I think it is a way nobody (I presume?) ever tried before, not knowing how it works or not, all will be a blind-crossing-river process......

any idea or suggestion welcome, please don't leave us in dark.....

Daniel

BetterSense
3-Sep-2009, 21:46
way too complicated.

You just need some sort of controllable light source. Try a soup can with a 10W bulb in it, and a hole punched in the bottom, suspended over your negative. Heck, I used to make contact prints in my old apartment bathroom by turning the lights on and off real fast.

salihonba
3-Sep-2009, 21:59
way too complicated.

You just need some sort of controllable light source. Try a soup can with a 10W bulb in it, and a hole punched in the bottom, suspended over your negative. Heck, I used to make contact prints in my old apartment bathroom by turning the lights on and off real fast.

It sounds easy! do you control your paper grade? how to do it?

BetterSense
4-Sep-2009, 06:26
Ill ford multigrade filters. The 3x3 plain square ones are the cheapest. Or, you can come up with your own filters. I think you just need to vary the proportion of magenta and yellow light reaching the paper.

aduncanson
4-Sep-2009, 06:52
salihonba,

A knowledgeable member here has previously called attention to enlargers from this company. This contact printer uses a modulated CRT spot to dodge negatives while printing. It clearly is no solution for Hong Kong's real estate limitations, but it does prove your concept.

http://www.egoltronics.com/markv.html.

For contact printing an LCD display might work well, perhaps with suitable diffusion added. Similarly the Digital Light Projector chips commonly used in rear projection TVs would seem to serve as a modulated light source for enlarging.

Much of the same custom dodging capability is given by creating a (possibly enlarged) digital negative using a computer printer.

salihonba
4-Sep-2009, 16:59
thanks BetterSense, an elegant way to solve! I like this, and can be done immediately! for proper control the light on/off, I am thinking of a LED matrix, no heat, and can be a rectangular formation....., and no worry about on/off, always on, just block it when need it off.

salihonba
4-Sep-2009, 17:35
Thanks aduncanson, I read the link you provided, wow! it is really big! an industrial machine!
What I am thinking of the contact process need a LCD monitor and a thin piece of semi-matt glass like ground glass.
http://lh6.ggpht.com/_gvRcWa2LHhg/SqGvEytV2zI/AAAAAAAABvc/pWCRKqnlKrQ/s288/cp01.jpg
you scan your developed film in very rough resolution, say 72ppi, just for viewing on monitor, then decide paper grade and pick correspondent RGB values, and make some dodge and burn and grade change in part area, all in soft paintbrush, now this is the light source specifically for this film, it can be saved as a data file.
http://lh5.ggpht.com/_gvRcWa2LHhg/SqGvFLurHKI/AAAAAAAABvk/bG7YLn1LmmU/s800/cp02.jpg
Now is time for contact print, stack in order 1. monitor 2.light source data file open. 3 matt glass to diffuse pixel. 4.developed film. 5. Multigrade paper.
http://lh4.ggpht.com/_gvRcWa2LHhg/SqGvFu8gY1I/AAAAAAAABvs/lLvGJA1RxQ4/s800/cp03.jpg

that's the idea.
http://lh6.ggpht.com/_gvRcWa2LHhg/SqDCx_SeGQI/AAAAAAAABuo/t_GR6D3xYic/s288/taipei01.jpg

complicated? yes for first time, but think of the large format contact print, I mean really big, like 10x24 or something like that, a tailor made light source for it is worthy doing, especially for those difficult negatives.......

only in brain now.

CatSplat
4-Sep-2009, 18:44
Haha, I think the LCD lightsource is a really cool idea. Heck, you could lighten or darken areas of the screen as a form of dodging and burning if you put the screen close enough to the negative!

Flea77
4-Sep-2009, 19:05
Here is a different take on it. We strip old LCDs for the backlight for my bosses translucent arrowheads. You take out the backlight, the voltage inverter, and the power module (assuming an older LCD with a seperate brick power supply). This is all mounted in a wooden frame like a picture frame with a frosted piece of glass covering it. The electronics are mounted in a small project box (think Radio Shack) with a simple toggle switch.

The advantage here is that the whole thing is the size of a picture frame and about 1/2" to 3/4" thick. You could easily place this on the counter, place a negative on top, then paper (emusion down) on top of there, toggle the switch on for the correct time, then off, then develop. Very little room used, and no little LED power light on the front of the monitor, no monitor stand, no bezel in the way, no computer to run.

I have considered doing the exact same thing. Good luck!

Allan

salihonba
4-Sep-2009, 19:14
Here is a different take on it. We strip old LCDs for the backlight for my bosses translucent arrowheads. You take out the backlight, the voltage inverter, and the power module (assuming an older LCD with a seperate brick power supply). This is all mounted in a wooden frame like a picture frame with a frosted piece of glass covering it. The electronics are mounted in a small project box (think Radio Shack) with a simple toggle switch.

The advantage here is that the whole thing is the size of a picture frame and about 1/2" to 3/4" thick. You could easily place this on the counter, place a negative on top, then paper (emusion down) on top of there, toggle the switch on for the correct time, then off, then develop. Very little room used, and no little LED power light on the front of the monitor, no monitor stand, no bezel in the way, no computer to run.

I have considered doing the exact same thing. Good luck!

Allan

but what about the grade change? how to change the color of light?

Robert Hughes
5-Sep-2009, 10:10
For grade change you could consider buying some stage light gels like 1/4 blue, 1/4 orange, CTB (correct to blue) or CTO (correct to orange) for starters. Place those right over the LCD.

Flea77
5-Sep-2009, 18:59
but what about the grade change? how to change the color of light?

I actually would not change the color of the light. The reason I would do contacts (which may be very different from yours) is to judge how well the image was exposed, composed, focused, etc. None of that requires changing the light.

If however you wanted to do dodging and burning, etc, you could simply place the backlight assembly on top of a support of some kind (say a stack of books on each side) facing down, place the paper on the counter below it, then go to it. It would likely require a longer exposure though.

Allan

salihonba
5-Sep-2009, 20:11
Yes my goal is to build a system that for large format film that do contact print as final output, no enlargement, like those huge size film 20x24. So I am looking a way that can do all the techs that on enlarger.

And not only it copy all the tricks you can have on enlarger, most important part is, it records and plays your tricks again, and again.....

For enlarger, you got light path as space for dodging and burning, you got VC light source to change grade, or area splitting prints......

So in traditional way, you utilize all these tools and tricks in darkroom, struggling to make a perfect print, finally it came out, fit your standard, and now you want to make a second print, you have to do those process again!

explore a way to make a perfect print is an creative challenge, but do the same thing again and again, is a hard labor work.

But if we use LCD monitor as a light panel, and through color control, area intensity control, we can do all enlarger does, all these can be precisely set in digit, and the greatest part is, these setting (color, intensity) can be saved as a file (through image software).

I treat this as a tailored light source specifically for this film.

For the first perfect contact print, you need to play all the tricks, just like on enlarge, struggling to make a satisfying print, but after that, to make a second, third, of even years later you want to make the same print again, just use that light source file, it saves those tedious job for you.

Now is a digital era, but we insist on analog output because it is not replaceable, at least at this time, but we can take the advantage of digital tech, to make the creation process easier and consistent. traceable and has a record to discuss later.

biggerthebetter
1-Oct-2009, 06:54
I think Salihonba is right on track. The LCD is not just a light source (like the soup can with a 10 watt bulb suggestion), but also control colour (for contrast control) and all dodging and burning, so one cna have reproduceable results.

I shoot 8 x 10 now, and am shopping for 20 x 24, so this is EXACTLY why I stumbled on this thread. So I can contact print my negs, but in a very very consisten way. If I print one today, I want to get the exact same print 5 years from now. This is especailly needed if one use expensive processes like platinum printing.

Salinhomba, did you make one yet? I am very impressed.

by the way, I live in bangkok. I go to Hong Kong next week and if you live there would like to see if you have made on of these yet.

SAShruby
1-Oct-2009, 11:01
Why don't you go for LCD Big screen TV and a card with tv output? Then you can do 20x24 easy... Maybe little bit expensive but over the long run, effective