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Printing- Exposure, aperture, burning, help with manipulating the 'basics'

Lorena M , Oct 18, 2010; 07:38 p.m.

Help.
So this is what I do not understand or, what i am having trouble understanding.
i usually work with a 2 filter.
Sometimes i use a 3 filter and decrease the exposure seconds (or that's what i've done).
I always do a test print, 3 second exposure, 1'' each strip, at f/8.
When the image looks right at 3 seconds or 6, i've been told to increase aperture number and multiple number. That is, if it's 3, and i move to f16, that should be a 12 second exposure.
Now my questions is the following:
When an image is too bright- do i increase exposure time and increase aperture number?
or
do i change filter number?

When an image is too dark, do i decrease exposure time and decrease or increase aperture number?
I'm very confused with how aperture on enlarger/filter/exposure seconds affects how light or dark an image can come out.
At the moment i am working with an image that i set at filter 2, aperture 8, and 12 seconds. Some spots are too dark and others too light. Some mirrors are pure white. I proceeded to burn and dodge, but i dunno if this is the right thing to do. I burned the mirrors for 6 seconds, and it's still too white. Should i do 9, 10, 11 seconds on the mirror?

-oh, i understand how increasing aperture number lets in hald the amount of light, so compensate by adding exposure seconds.

Responses

Lars Holtgrewe , Oct 18, 2010; 09:08 p.m.

A few pointers to help you on your way:

The aperture of the enlarging lens is largely used tocontrol the printing time. It works the same as your aperture in your camera; a larger aperture (smaller f-stop), the more light, a smaller aperture (larger f-stop), the less light. Generally most lenses will start to perform best stopped down 2 stops from wide open.

A good procedure to follow for making a starting test strip is this:

1. Set or insert a #2 filter and stop the lens down 2 stops from wide open, insert the negative and adjust the enlarger head height to project the approximate desired paper size
2. Place the test strip (I usually use ~1"x8" strips cut from an 8"x10" sheet) in an area that will allow you to see variations in time (light and dark values vary as little as possible). In a landscape, the horizon line is often a good place to put the test strip.
3. Expose the strip in intervals. Start with 5,10,15, etc. seconds.
4. Develop and stop for normal times, fix for 1 minute (30 seconds if RC paper).
If the entire strip is too light increase exposure time (10,20,30,...). If the entire strip is too dark decrease exposure time (1,2,3,...)
This is where the aperture of the lens can come into play. Often you will want to stop the lens down further to extend the printing time. Each full stop smaller is 2x the printing time. This would turn your (1,2,3,...) time into (2,4,6,...) and allow easier burning/dodging in the future.
5. Once you have a test strip that goes from too light to too dark, you have a test strip you can evaluate.
6. Find the time in which the highlights have just barely discernible details; this is your starting printing time.
7. Place a full sheet under the enlarger and expose at the time found from the test strip and evaluate. Ensure the highlights are correct and judge contrast.
8. Now you may adjust the contrast by changing the filter. If large changes in contrast are required you may need to change the exposure time. Do another test strip to find your highlights.
9. Only at this point may you consider dodging/burning. I will leave that topic for future discussion.

That will get you started, and to answer a few other questions as briefly as possible:

Exposure time determines overall how light/dark the image is. Contrast/filters determine the range of values from white to black (number of gray shades).

Check the negative to ensure there is anything to print in the mirrors before attempting to burn in. It is very possible those highlights were "blown out" and there will be nothing there to print. If it is an otherwise good negative, this could be hidden with minor amounts of spotting if the area is small. If it is a large area, and there is nothing there to print, abandon the negative.

Ian Gordon Bilson , Oct 20, 2010; 07:05 a.m.

Lorena : google "F stop printing". If you change the time of your exposure,and the aperture of your lens as well,you will never learn the way it works.
Start,as you did,by choosing an F/no for your lens :f 8 is good. Use your #2 filter =good. Test print for a good result. Too contrasty ?
OK :in the example you described,where the bright parts of your picture are too light,and the dark bits too dark,you will need to change your filter to something lower :start with 0.5.
If you change two things at once,you won't learn which made the difference.If you change one thing at a time,you will.
And,too much time,or light,will give you a darker picture,and the reverse will give you a lighter result.

Austin Luse , Oct 21, 2010; 01:09 a.m.

These two have given you some good things to think about. I have some things to add. Firstly, if your going from a number 2 to a number 3 filter, you shouldn't change anything else. With the majority of modern VC filters, the exposure time will not change with the changing of the filter. So no need to change the aperature. Also, after focusing, and setting the whole image up, put the lens on the aperature that you intend to make the final print with. Chances are that your enlarging lens stops down to f 16, in which case, stop the lens down to f 11 (or the next stop brighter from the dimmest setting). then make the test strip with the lens at this aperature (dont forget to put the filter in before making the test strip). Process the test strip normally, as in, for the full time for developer, and stop bath. You can put it into the fixer for 20 seconds if its an rc paper, and you dont intend to keep the test strip. Then evaluate.

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