EXPOSURE TIME

[dieselvsb21]

I WAS TRYING TO ANSWER THIS BY LOOKING OVER ALL THE POSTS BUT WHILE IM STILL CHECKING I WILL ASK THIS.

IF I HAVE 2X 500WATT GARAGE TYPE CONTRUCTION LIGHTS FOCUSED ON MY SCREEN 24 INCHES ABOVE.

DOES 4-5 MINUTES SEEM LONG ENOUGH?????

GOING TO BE 1ST SCREEN .....1ST TIME......... 1ST TRY

[d fleming]

Unfiltered uv blacklight tubes for light source would be better and do a search for step wedge test to learn how to calculate exposure time. What emulsionare you using? Most come with info sheetes when shipped that will have a calculator for exposure time for the product.

[dieselvsb21]

IM USING THE DIAZO EMULSION W/SENSITIZER THAT CAME IN A SPEEDBALL STARTER KIT
IT SAY 20 MINUTES WITH A 250 WATT PHOTO BULB (WHICH I COULDNT FIND LOCALLY)
SO IF THE MATH WORKS OUT SHOULDNT 1000 WATT DO GOOD 4-5 MINUTES?????

[d fleming]

I would say you definitely need to do a step wedge test to determine proper exposure time with your light source. If your light source is adequate at all. The thing about light sources is the spectrum of uv light they emit. If it doesn't contain the proper spectrum of light to replicate the sun you can shoot all day with no results.

[dieselvsb21]

ok thank you very much......ive read about that test and really dont understand the process, so im going to scrap the 1000 watt idea and order the 250 photo bulb from amazon.....that way ill know that it is the right way.

[d fleming]

Check into your local lighting store and see hiw much a couple of unfiltered uv flourescents are. Cooler (temp)light and may be cheaper. For that matter what you have may work, I've just always either used metal halide or flourescent depending on the job. You can even use the sun for free. Step wedge test is a simple thing to do and will save you some time & $.
http://www.ulano.com/support/supportmenu.htm
Click on the step wedge test line and watch the vid.