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Thread: Enlarging from 5x7 to 8x10 to 11x14

  1. #1

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    Enlarging from 5x7 to 8x10 to 11x14

    I have just started developing and enlarging my 4x5 B&W negatives. Last night I made a few test prints. I used 5x7 R.C. Glossy paper that came with my enlarger. I was able to make nice looking B&W prints after about 8 test prints, I would like to try making larger prints that are 8x10 and 11x14, my question is, how do I determine how much time I should add or what f stop I should go to, to print this size. Here is the technical information. Omega D-5 pro-lab 4x5 with a Nikon 135mm lens my exposure time was
    3 sec at f11 to make a 5x7 print.
    Thanks, Jacob

  2. #2
    Whatever David A. Goldfarb's Avatar
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    Re: Enlarging from 5x7 to 8x10 to 11x14

    5--8--11--16

    Recognize those numbers? Indeed, they're about the same as the f:stop series, so as long as you're using the same paper, each step in standard paper size requires one more stop of exposure, either by time or by aperture--at least as a starting point. You might find that as you enlarge, you need more contrast, and reciprocity could become an issue with very long printing exposures.
    Last edited by David A. Goldfarb; 10-Jul-2006 at 13:48.

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    Re: Enlarging from 5x7 to 8x10 to 11x14

    David,
    Sounds easy enough, I will give it a try.
    Thanks, Jacob

  4. #4

    Re: Enlarging from 5x7 to 8x10 to 11x14

    David'

    Thanks for your comment. It is so obvious that I ( and I suspect WE ) lose sight of this when going larger.


    Barry

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    Re: Enlarging from 5x7 to 8x10 to 11x14

    I'm not sure that simply doubling the exposure as you move from one standard paper size to the next is going to get you real close to a correct exposure. First, moving from 5x7 to 8x10 to 11x14 to 16x20 to 20x24 paper sizes obviously doesn't represent a doubling of the previous size. Second, the inverse square rule of light fall off, which tells us that the intensity of light doesn't decrease in direct proportion to increases in distance (or something like that) affects the new exposure on larger paper. Then there's the fact that as you move from one standard paper size to the next the printed image has to be changed to some extent (except when going from 8x10 to 16x20), which requires its own adjustment of the height of the enlarger head. Finally, some enlargers such as the Beseler MX series have canted center columns so that there isn't a direct correlation between changes in image magnification and changes in the distance the head travels on the center column.

    When I printed in the darkroom I used a book published by Kodak called "The Kodak Darkroom Guide" or something like that. It contained a little wheel that could be used to determine the correct exposure (or close to it) when going from one magnification to another. Once you knew the correct exposure at one magnification and knew the magnification factors involved in moving from one print size to another you could use the wheel to determine a more or less correct exposure for the new magnification. I don't know if Kodak still publishes that book but if not it should be readily available used. There must be other methods but that's the one I used and it worked pretty well.
    Brian Ellis
    Before you criticize someone, walk a mile in their shoes. That way when you do criticize them you'll be
    a mile away and you'll have their shoes.

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    Re: Enlarging from 5x7 to 8x10 to 11x14

    It's not exact, but the easy way (besides the Darkroom Dataguide that Brian recommends) is to compare the ratio of the area of the prints. 11x14=154. 5x7=35. 154 divided by 35= 4.4. Multiply this by the correct exposure time for a 5x7 print (3 seconds). 3 times 4.4= 13.2 seconds. So try 13 seconds. 8x10=80. 80/35=2.3. 2.3 times 3 equals 6.9, so try 7 seconds.
    Incidentally, those are awfully short times. There must be some way of cutting down the amount of light that your enlarger produces.
    Wilhelm (Sarasota)

  7. #7

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    Re: Enlarging from 5x7 to 8x10 to 11x14

    there is a rough calculation which is :

    T2 = ((W2/W1)^2) * T1

    where:

    T1 = time for smaller print
    T2 = time for bigger print
    W1 = long side of smaller print
    W2 = long side of bigger print

    It never works exactly, but will get you fairly close without changing fstop.

    more accurate is to measure the difference in height of the enlarger head and using the inverse square law you can calculate the difference in time.

    Also, if you have a spot meter, you could take a reading from a piece of white paper or baseboard at smaller enlargement size. Then move enlarger up and take another reading. Then convert the difference in stops to time.
    Last edited by robc; 10-Jul-2006 at 22:04.

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    Re: Enlarging from 5x7 to 8x10 to 11x14

    When you use a spot meter. If I took a reading of F11 with my exposure time of
    3 sec. for a 5x7, then increased the size to a 8x10 and took another reading of f8 would my new time be 6 sec. for exposure?

    Jacob

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    Re: Enlarging from 5x7 to 8x10 to 11x14

    Quote Originally Posted by Jfnphotography
    When you use a spot meter. If I took a reading of F11 with my exposure time of
    3 sec. for a 5x7, then increased the size to a 8x10 and took another reading of f8 would my new time be 6 sec. for exposure?

    Jacob
    That ones easy because its exactly one stop difference so its double the time, so 6 secs would be correct at the same enlarger fstop as your first print. Just make sure you take the two readings from the same angle and position/distance.

    What you really need is a formula for when its not exactly one stop. I've forgotten what the formula is. Will work it out and report back shortly, unless someone else chimes in with it in the mean time.

    People forget they have a handy lightmeter which they can use as an enlarger exposure meter if needs be.

    Keep a record of the exposure differences between the enlargement sizes because you can then just refer back to the difference for future prints. Infact, if you do it for all the different paper sizes you expect to use in one go, then you will have a handy look up table for future use. It may not be exact, but it will be pretty darn close.
    Often when changing print size, the print looks diifferent and you find that you also want to change print contrast or where the emphasis in the print is. Because of that, the times you calculate for the bigger print never seem to be exactly spot on.

  10. #10
    Donald Qualls's Avatar
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    Re: Enlarging from 5x7 to 8x10 to 11x14

    Hmmm. Maybe it's just me, but I usually just make a new test print when I change sizes -- I split filter, and test both filters on the same test exposure, so I need only one test print to get both exposure and contrast (at least to the stage of a good working print).

    Once you have this time, you can apply any dodging and burning as a percentage of the total working from your notes on the smaller print -- that way, if (for instance) you changed the lens aperture to keep the printing time reasonable when you changed magnfication, you don't add to the complexity of the task, or increase the likelihood of a miscalculation leading to one or more completely wasted prints. It's also pretty quick to do -- a couple minutes to make the test exposures, maximum five minutes souping the test print, and a minute or two under the inspection light picking the best area in the grid...
    If a contact print at arm's length is too small to see, you need a bigger camera. :D

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