Adding time to Burn & Dodge?

[romie]

Hello again:
Thanks for the helpfull info on my last thread. Enlargment Magnification Formula. The square root law does apply.
Anyway, if I have a exposure time of 00:15@ say f11 and I need more time for burning and dodging, what is the faxtor I should use to keep the f-stop the same but change (add) more time for burning and dodging? :roll:
Thanks - romie, Boston, MA,

[oriecat]

I don't think you'll find a factor for that. It's trial and error as far as I know. Or comparing work prints at different times and deciding which areas you like at which times, and then the differences have to be worked out.

[ksmattfish]

I want to help, but I am having a hard time understanding your questions.

If you get a good overall exposure at f/11 for 15 sec, but you need more time to complete burning and dodging then you will have to change the f/stop.

15 sec at f/11 = 8.5 sec at f/8 = 30 sec at f/16 = 1 min at f/22

If you want to stay at f/11 then you will have to et you dodging done during the 15 sec exposure, and you can add whatever burning needs to be done afterwards.

I saw your other post too. Ilford makes a handy print exposure meter that runs about $30. I have one and find it quite nice for adjusting time to compensate for additional contrast filters or increasing enlargement size.

[romie]

ksmattfish thanks for the info. Did you use the Ilford exposure meter to come up with the times or did you do the math in your head? If you did the math in your head how did you do it? I will look into the Ilford exposure meter!
I agree if I want to keek the f-ring at the same stop I will need to have all of my dodging and primary exposure done within that time of :15 sec. exposure.
romie - B.M. :cheer:

[ksmattfish]

Ummm, I did the math in my head. You need to learn about how light is measured in photography. It is measured in stops (or f/stops). A stop is a halving or doubling of the amount of light. You can increase your exposure by one stop by doubling the time OR by opening up the lens aperture 1 f/# (moving to a smaller f/#). If you did both of these things, then you would be increasing your exposure by two stops. To decrease your exposure by one stop you would cut your time in half OR close down the lens aperture by 1 f/# (moving to a higher F/#). If you did both of these things you would be decreasing your exposure by 2 stops.

How I got the figures I cited above is: if f/11 at 15 sec is a good exposure time, then if I close down the aperture 1 f/#, to f/16 (losing 1 stop of light), I must double the time to 30 sec (adding 1 stop of light) so that I'm getting the same exposure. Or you can do it the other way, open the lens up to f/8 and set the time for 7.5 sec. As long as you balance the changing of one setting with the other, then you have the same exposure.

I don't know if I'm explaining this well. You need an understanding of f/stops both when operating the camera, and in the darkroom. Remember, your enlarger basically works just like your camera when it comes to determining proper exposure. The lens has the same f/#s and you can think of the timer as a shutter, it's just that paper has a very, very slow ISO, so exposures are usually measured in seconds rather than split seconds.

Go out and find Henry Horenstein's "Black and White Photography; A Basic Manual". Henry will do a much better job of explaining than I do, plus there is lots of other good stuff in the book that you need to know.

[ksmattfish]

I screwed up on that original post, it should be 7.sec at f/8, not 8.5 sec (15 divided by 2 = 7.5, not 8.5)

[ksmattfish]

arrrgh! 7.5 I suck at typing

[ksmattfish]

The Ilford print exposure meter (EM10) isn't as fancy as a regular light meter. It just has an on/off switch, a dial, two red lghts, and a green light.

Once you have figured out a good exposure, but you are going to add contrast filters or raise the enlarger head, you measure the light from an area that is bright but still shows detail. Turn the dial until the green light comes on.

Adjust the enlarger as necessary, and then remeasure in the same place. Most likely you will now get a red light. Adjust the enlarger aperture until the green light comes on, and you should be pretty close to the same exposure as befoire.

[romie]

Hello ksmattfish & Friends of the Forum!
Hang in there with me friends, I know some of this stuff. I to have keyed in miss information. I will attempt to make clear my concerns as plain as I am able to. Stay with me; if you will. I think I will be learning as well as those that might not have a clue about where this thing might be going, including myself! That is what the FORUM IS ABOUT ? RIGHT!!!!
Strap on and let all of us injoy the Ride!
romie shep - B.M.
"Yours In THe Struggle"
:roll:

[motcon]

to increase exposure time you need to do one or a combination of the following:

- close down the aperture on your enlarger. if you are the optimal two stops down already, one more stop won't hurt much (unless you have a cruddy 3 element lens).

- you can use a nd filter under the lens. works well.

- you can tweak your in camera exposure and neg development process to produce denser negs

- i've had success by processing unexposed film and putting it in the neg carrier with the neg to be exposed

your milage may vary.